Tores mailbox VIIC and VIIC/41 operation and technical details

[NZSnowman]

Simon,
exhaust air duct is on the port side of the boat. Forward 'b' valve is on the forward bulkhead, on the port side of hatch, near the upper edge of the door (with blue handle). The oxygen manifold is located in the aft starboard corner of engine room - over the clutch piston is visible water trap and manifold itself. Over the hatch to electric motor room are visible two thin lines - I believe they are lines to aft torpedo room and to forward part of the boat. There is also one large pressure gauge - I think it also belongs to this system. I was not able to locate aft 'b' valve.


--
Regards
Maciek

Thanks Maciek for the information.

Do you have any photo's of the exhaust air duct and the oxygen manifold, I don't seem to have any photo's of them

The oxygen line look like 10 mm? 

[NZSnowman]

Compartment ventilating and supply systems

I image we should look after the engine room crew

Let take that bad air away

[NZSnowman]

Tore, what is that small hull opening right next to the vent valve, is it a drain line?

http://www.360cities.net/image/submarine-u-995-machine-room#2.39,-64.09,48.4

[tore]

Simon.
Engineroom stand by and ready to get rid of that bad air. . I assume your question concerns the ventilationshaft drain as indicated on the photo below.
Tore

[SnakeDoc]

Hi Simon,


1. Forward 'b' valve.



2. Water trap and control manifold






The manifold itself is the same as in forward torpedo room:

Back to the two lines above the door to aft torpedo room - now I think, that one of them is oxygen supply line to air exhaust duct, second - maybe the line to aft torpdo room or to control room.


--
Regards
Maciek

[NZSnowman]

Thanks Maciek

[NZSnowman]

Tore, was the only way to get the dirty LO off the boat was a hand pump?

[falo]

"Yes , much have been changed and I don`t understand some of the changes, the flood gates are the fingerprints of the submarine. It would not make much of an extra to put in some floodgates, they have blanked off some floodgates instead as shown on your photo. On the other hand they have put up an extra wind deflector on the radar casing which never was there on any VIIC, that cost extra and they have removed the original exhaust outlet and put in a new instead, that cost extra as well. Why if funds are short?
Tore"
__________________

I think further on money is very scarce but I agree they picked the wrong priorities. But some changes has a explanation: The blanked floodgates should stop those visitors of the boat who would like to climb on the wooden deck by using the floodgates as a "ladder". This concerns for example floodgates nearby the entrance and exit.

Thanks for your attached photos with the comments.

Regards
falo

[tore]

Falo.
Good to hear it is a rational explanation for the blanked off floodgates. Somebody has economical responsibilities for follies moving around, that`s probably why you have a grid shutting off the access to the tower. It is easy to forget she is now a museum allowing people to crawl all over, but why did they make a hinged manholecover easy to open on the saddletank as shown on the photo below?
Tore

[falo]

"but why did the make a hinged manholecover easy to open on the saddletank as shown on the photo below?"

Tore, to be honest, I don't know and I have not an explanation for that. Again the manhole looks not very accurate. Maybe this hole stores the tools and paints for the preservation team? Just guessworking about that matter.
Regards
falo

[tore]

Simon.
Dirty luboiltank pump.
The dirty luboiltank has no direct connection to an electric driven pump and normally you are only able to empty the tank by handpump. However the tank was originally connected to the purifier having both suctionpump and dischargepump connected to the tank. As you know the purifier was removed on the later version of the VIIC and VIIC/41`s.
The port and starboard luboil systems were normally operated separately. Thus in case you had a massive contamination of the oil, like emulsification due to watercontamination (it could happen), you emptied the relevant systemtank by the fueloil transferpump and did not use the dirty oiltank.
Tore

[tore]

Simon.
Maybe the dirtyoil tank handpump system requires an explanation. I `ll take one of Falos fresh photos as a reference. The handpump has suction via 3 way cock A, either from port or stb. systemtanks and discharge to the hose connection via 3 way cock B. Cock B has a 3rd outlet to a funnel which goes to another 3 way cock C. Cock C has two more connections  to the suctionpipe of the pump and via the cock A either to the port or stb. systemtank and an another connection to the dirty oiltank. As there are no non return valves in the system you can either fill or empty the tanks via the hose connection.
Tore

[NZSnowman]

Dirty Engine Lubricating Oil

One more system added to U-1308

Piping = Violet - Blue - Violet

[tore]

Simon.
Seems to be OK. Some small details. As usual the wooden handle of the handpump is gone , may be you should put it in. There is a small suctionhose connection right underneath the suctioninlet of the pump. My uploadfolder is full so I cannot show much pictures I am trying to see if i`ll manage after deleting a few old photos. I am notifying Wink.
Tore

[tore]

Hi Wink!
Just a test of my uploadfolder.
It seems to work! thanks Wink.
Tore

[NZSnowman]

Hi Tore
 
You may have noted the number of engine room drawings has slow down. I been busy sorting out my Master’s Degree. I hope to get back to it soon.
 
Was hoping to finish the engine room this summer but that not going to happen

Simon

[tore]

Simon.
After all we are having fun with a hobby, your education is of course more important. In the meantime I have prepared some sketches which might put some light on further details particularly in the engineroom.
Tore

[tore]

Simon.
Just keep busy with you studies and look into this whenever it suits you. I have gone a bit further into the fuelracks and governors of the main engines as your drawings have a few items missing on this system. May be you shall have a better understanding if I try to explain the working of the system. I start with the port engine as you know the starboard is a bit different. The basic is that the engineer is the overruling factor when he place the fuelhandle in the required position. If he want a higher revs he moves the handle so the fuelcontrol rod moves towards aft, turning the fuelpump plungers and thus increase the fuelinjection. The rod push the governor servo levers as shown on the sketch below, which means the servo piston goes down to a new fixed position and the whole linkagesystem turns around the fulcrum point A. The linkage (C )pulls down the servo slide admitting oil pressure to the top of the piston and drain underneath. At this position the new required revs is obtained and it is left to the governor to keep the revs stable. As the increased revs cause the centrifugal forces to move the weigths out thereby moving a sleeve and the connecting rod coming out of the camshaftcasing goes upwards. The rod is connected to a lever having a turning point at the servo pedestal which means the other end goes down and pulls A down. A is no longer a fixed point ( it has been shifted to B) and the servolinkage turns on fulcrum B.
This means the slide linkage point C goes down and the slide shut of the oil to the top of the piston and a new equilibrium  at the new higher revs has been established. The governor and servo shall "hunt" around this revs as the load varies. The lowering of the revs follows the same pattern in the opposite way. Just remember you first move the fulcrum B and then the system obtain balance at the new revs. by moving fulcrum A. How you are going to incorporate this on your drawing is not easy but as you see there are a few things missing. The linkage from governor lever to A ( adjustable) and one of the  two adjusting screws on the linkarm from servopiston to fuel controlrod.   
Tore

[tore]

Simon.
Governor linkage starboard engine.
As we have previously discussed the starboard engine is a mirrorexecution of the port except a few items. The fuelpumps and the governors are the same. In order to have the plunger inspection ( adjustment) window towards the aisle, the fuel pumps on starboard engine are turned 180 degrees meaning the fuelrack is moved opposite to the port engine. Thus for increasing the revs the rack moves forward. The governor servo is  the same as on port and not turned, and the linkage has to be different from the port linkage. For increasing the revs the fuelcontrol rod is moved forward (opposite to port) and  connected to the servo piston  via a trunnionshaft with levers to be able to connect the servo piston rod B which is  towards the centerline of the engine, the lever lift the servopiston to a new required revs position. At the same time the slide ( C) is lifted allowing oil pressue(red) to bottom of the servopiston and the whole leversystem is turning around A as the fulcrum. The increased fuelinjection rises the revs, the governor weights centrifugal forces lift the governor shaft coming out of the camshaft casing exactly as on port engine. As the servoslide connection point C is on the same side as the the governor rod you don` t need a balance lever as on port system, but only a supportarm hinged to the pedestal which means  (C) goes up ( opposite port) now using B as a fulcrum and an equilibrium   is obtained at the new fixed point B matching the required revs. I fully realize it there are a lot of links and levers but hopefully my sketch below having dozens of arrows  rather helps to explain and not confuse the system.
Tore

[Capt Kremin]

Hi Tore,
 
Sorry to distract you a little bit, but I have a question, if you don't mind.
 
It concerns the pressure hull.
 
When you served in the Kaurawas the pressure hull painted? if so. how often?
 
Regards
 
Jon

[tore]

 Jon.
At the time of KNM Kaura the pressurehull was divided in two, the part which was submerged while the submarine was surfaced and thus having barnacles and seaweed growth like a conventional ship.However the saddle tanks were painted black right up to the casing and that was an antifouling painting, approximately each 6 months depending on the growth , resistance and thus speedreduction. Then you had a complete painting of the outside, both pressurehull and casing each 2 years. The ballasttanks and especially ballasttank no. 3 were painted inside with a yellow!! ( yellow submarine? ) anticorrosive  zinc chromate simultaneously or if needed during the 6 monthly inspection. The wooden deck was constantly inspected and painted dark by crew, more for airplanes than need for protection. In fact the German regulations said always to have a dark paint for the wooden deck on board in view of the airsurveillance. The fancy wooden look deckpainting  which some modellers are using is thus not correct, a more dull dark gray almost black, would be more appropriate.
Tore

[Capt Kremin]

Hi Tore
 
Thank you very much for you answer, you have solved a couple mysteries that I have been wondering about.
 
Regards
 
Jon

[NZSnowman]

Tore, after a long time and lots of hard work, I think I have added all the piping under the decking forward of the engine

[tore]

Simon.
No doubt it is a lot of hard work behind this drawing. To have a complete picture of all the systems in a sideview is almost impossible, but after having a quick look it seems you got almost everything in place. Well done.
Tore

[SG]

Tore i would like to ask you 2 questions about life in a type VII u-boat.
- Is it true that humidity and being wet were a constant issue? i mean how dry a crewmember would expect to be on a ordinary day? I've seen the scenes of Das Boot when people rushed back inside from the conning tower and the shower raining from the turret hatch was a constant matter. The film also shows food moulding. Was it all really like that or it used to happen only in long patrols or in particular circumstances, for example extremely bad weather?
- Diesel smell: confined to the engine room or soaking uniforms, berths, food?
thanks in advance
 

[tore]

SG.
First of all Das Boot gives an unprecedented image of the real life in a VIIC. Humidity was a problem. I never took my best uniform on board in spite we sometimes had to entertain guests and attend cocktailparties on fleetvisits abroad. All the stripes and buttons turned quickly green and the cloths got mouldy. For my own sake I solved the the problem in an illegal unconventional way by letting the first electrician installing a 40 watt bulb in my closet to keep my uniform dry. We never used the uniform at sea. This however was the fringe benefit of being the chief engineer and was of course never allowed to be installed for the rest of the crew. The lovely smell of diesel was not confined to the engineroom and I am afraid there was some concentration around my bunk and battledress not food,. Apart from a few drops of water coming from the upper hatch just after surfacing during normal weathercondition it was dry. However in bad weather water would come gushing down like crazy and we very often had to shut the hatch leaving the poor buggars on the bridge to the elements. A few times we had to dive to continue sometimes you could feel the swell at 50 meters.(North Sea). Moulding of the food (bread)happened only during weeks of patrolling  like our longest schnorcheling trip of 28 days.
Tore

[SG]

Thank you very much Tore! the installation of the 40 W bulb was really a great idea!   
Another question: Are the missions/patrols of KNM Kaura still classified? if not: what is the the most risky mission the Kaura has ever undertaken? 

[tore]

SG.
I don`t think anything is classified, more history. Risky missions are not usually planned, they just happens for various reasons. The first risky mission was probably the first dive after being mothballed for several years after WW2. During the first years of the cold war and NATO we thought it would be OK to introduce the 3 VII Cs in our submarinefleet. The VII Cs were stowed away in a Norwegian fjord with very limited drawings and instruction material. The German navy did not exist, thus no possible German info. Old submariners got the job to figure out the details and I am told the first tests were carried out in the harbour of Trondheim with the biggest available harbour crane hook secured to the hull prior to the test dive. Incident occurred and risky situations ,not mission, arise. I have experienced two. During a work up period with fairly fresh crew we should carry out a routine dive and some how the main dieselair inletvalve was not shut, luckily the inletvalve into the engineroom was, but the whole airduct from the conningtower to the engine room was filled with water app. 5 tonnes, creating an unintended deep crash dive which didn`t stop till we were well below 100 meters. A similar situation occurred during a testdive after an annual docking. You always have an accurate weight calculation prior to such a dive to be sure you have the right ballast. No 1 being the responsible officer made a mistake and at the dive we went down like an elevator. The CO very quickly took action and ordered to blow all the tanks but we were so heavy so it took quite some time before we stopped at record depth where we were "hanging" some nervewrecking seconds before we slowly started to climb to the surface. However surfacing by blowing air and not using hydroplanes at depths exceeding 100m creates a jet effect by the expanding air and you shoot out of the surface like a torpedo and hope no surface vessels are in the neighbourhood. Other wise I was in charge of the longest schnorchel research mission ever at that time in our navy. 28 days submerged which I wouldn`t put in the category risky.
Tore

[SG]

Amazing, am speechless and grateful for your willingness to share your 1st rate experience with us. By the way what was the record depth KNM Kaura ever reached? did the crew experience health problems secondary to reaching sudden depth during the uncontrolled crash dive followed by subsequent fast surfacing? I Imagine you tested silent running as well. Was it effective? was it double checked by surface units hunting for the Kaura?

[OldNoob]

Wow

[tore]

SG
KNM Kaura had a pressurehull damage in main ballasttank no 3, dents possibly by depthchargers. These dents were repaired by some extra frames but we were not 100% sure she could take the max designed diving depth. We never took her deeper that 125 meters in my time. We did not have any noticeable healthproblems due to incident like sudden uncontrolled crashdives. The procedure after such event was immediately to repeat the same thing, but off course under full control.
Silent running was a must. We had annually a test at the RN noise test station in Loch Goil near Bute Island, the submarine was semisubmerged and underwater microphones were surrounding the hull picking up each  possible noise we made. This was  the only time I was fully in charge of the sub. The CO and NO 1 were ashore watching the instruments and the engineers and electricians were starting and stopping each motor and component being a potential noisemaker. Each component had the noise registered and in the end you got a certificate for each component to be used under silent running condition. We got the exact picture of the noise we were making and it was indeed effective.
Tore

[SG]

A good amount of great information! thank you so much Tore

[tore]

U 995 and present days execution.
Falo is finishing off his excellent photos of present days U 995 revealing the details of the externals. Apart from the previous comments I have a few remarks to modelbuilders.
As the German U 995 she  never operated as a schnorchel uboat. The schnorchel was installed March/April 1945. As a museumsboat she is equipped with a hinge float schnorchelmast, the original installed mast had a ringfloat. The schnorchel exhaust deck pipe and valve has been removed. The compass casing forward of conningtower was of the old streamlined type not the present days. For an Uboat serving in the Arctic I am not sure she has the right colour and the steel forecastle and poop deck is painted in a light blue-gray colour deviating very much from the dark wooden deck. A dark casingdeck all over was very important in view of the air-surveillance. As mentioned before , a wind deflector is fitted on the radarcasing, on the original U 995 it was not. The wind deflector on the rest of the tower was smooth rounded, not as today execution.
Tore

[tore]

Following up my remarks on the colour of the wooden deck I post below a page containing a translated page of the instructions to the Uboat Commanders from the German high command revised 1943.
Tore

[42rocker]

A little of topic, but
A friend of mine translates and sells the M.Dv No. 906 - Geheim!  Handbuch für U-Bootskommandanten which is the manual in the above post. If you are interested in a copy see

http://www.germanmanuals.com/REmanuals.html

John does a good job on all of his manuals.

Thanks to everyone for such a great thread.

Later Tim

[SG]

Tore,
on this page there's a list of transmitters n receivers employed on u-boats:
http://www.uboatarchive.net/KTBNotesCommunications.htm
can you recall which ones (transmitter+receiver) among them were aboard the Kaura?
Had KNM Kaura the original german radio sets changed for some more updated post-war versions or still retained the original german radios?
Thanks a lot in advance and.. HAPPY EASTER!

[tore]

SG.
Sorry I have been off line for some 9 days and not able to respond. Unfortunately I don`t know anything about the radiotransmitter and receiver on the VIICs as it was not within my responsibility and usually the radiopeople wasn`t too happy to have any visitors. Generally our communication was fully intergrated in the Nato system and I should guess our equipment was adapted to that postwar system. During long voyages submerged we had to report at given hours by to a central Natostation Rugby by extreme longwave signals. We got signals as well from this station.

[SG]

No worries Tore, i've been logged off for a few days too. Thanks for the information anyway, although incomplete it's undoubtedly a great piece of information!
Cheers

[Don Prince]

Gentlemen,


I have been reading through the post on this site subject matter and I believe I can learn a great deal.  I may post questions later if you don't object to answering some basic questions about the Type VII C...


Kind regards,
Don_

[tore]

Don.
Shoot! Basic questions or not. I`ll be happy to answer if I can.
Tore

[Don Prince]

Hello Mr. Tore,


I am in the process of setting up the Skizzenbuch for the VIIC U-Boat in a 11 x 17 leather post binder.  I have the basic outline for the manual in MS Word.  However, I find it very difficult to read the schematics so graciously provided by Captain Jerry Mason on the uboatarchive.net web site.  It's almost impossible to determine pipe line colors on the black and white copies of the original German documents.  I don't know where I found Plate17 and Plate 27 that are a light tan color and you can see the color striping on the pipes.  In addition, you can tell that when a pipe crosses another that it is not a junction.  Does anyone know where the source for those documents came from and is it possible to get the full set.  I am only having "Staples" to print one copy for my own personal library and the leather post binder is very expensive ($230.00).


I understand the Negative Buoyancy Tank is vented internally through a muffler when it is being flooded in a surface maneuver.  Are there photos pointing to the control device (Valve) and the muffler in the control room?  I believe I would like to add photos of things like that to my Skizzenbuch. 


Regards,
Don_

[tore]

Don.
I am not sure I fully understand your questions correctly. However most of the systemsketches provided on the net derive from the instructionmanuals of U 570 captured by the British in Iceland September 1941, thus the system sketches are not always 100% up to date with the executions of late war VIICs. The drawings are pretty much the same as we used onboard. However  some sketches have been coloured and adjusted by different people (crew?) and some mistakes are introduced. Thus there are no sketch valid for all the VIICs allthough basically the principal  system are the same. I suggest you chose which " VIIC vintage" you would go for and we discuss each system separately and hopefully I can answer your questions. In order to make it a bit simpler I answere your first question in a separate post.
Tore

[tore]

Don.
Untertriebzelle system.
Yes, the venting mufflers and pipes  are fitted on the aft part of the attackperiscope casing. See photo below, a photo of the mufflers situated down in the bilge follows I just have to find it.
Tore

[tore]

Don.
I finally found one of  Falos execellent photos and put up a few arrows showing the system.
Tore

[Don Prince]

Hello Mr. Tore,
Thank you for the information and the photos...  The photo labeled Q Tank Muffler explains a lot and I have a few questions regarding that photo and Plate 7 from the Skizzenbuch.
The Negative Buoyancy Tank side of Plate 7
1.  There are 3 muffler (k) in the drawing on Plate 7
Q1 - Is there only 1 muffler as indicated in the Q Tank Muffler photo?
2.  Plate 7 shows 3 valves on the Negative Buoyancy vent line; a valve near each tank and one valve near the muffler (no glass viewing eye). 
However, the Q Tank Muffler Photo suggests there is a separate line from each Negative Buoyancy tank which has a valve and a glass viewing eye.  These two vent lines are joined at a “Y” connection and vent through the muffler into the internal pressure hull.
Q2.  Are my observations correct?
Q2-1.  On Plate 7, should the valve (h) going to the muffler (k) be a glass viewing eye instead of a valve?  This would make Plate 7 closer to the actual piping.  Unless there are actually 4 valves; 2 near the Negative Buoyancy tanks and 2 near the muffler?  The Plate 7 just doesn’t match the Q Tank Muffler photo… 
3.  The Q Tank Muffler photo has 4 valves and 4 glass viewing devices feeding into the one muffler.  I assume 2 lines for venting from Negative Buoyancy tanks and two lines for venting from the Regulating tanks and Bunkers. 

Q3.  Am I correct?

Q3-1.  Looking at the Q Tank Muffler photo  -  from left to right; which valve controls what?

Regards.
Don_

[Don Prince]

Hello Mr. Tore,


One of the photos you sent was of Plate 17 and the lines to blow the Negative Buoyancy Tank.  However, when I look at the 2 different Plate 17 prints that I have there is a difference.  There is an extra valve going to the Negative buoyancy tank???


I will attempt to upload the two images later...


Regards,
Don_

[Don Prince]

Here is the different Plate 17 with the extra valve at the Negative Buoyancy Tanks...


Opinion?


Regards,
Don_

[tore]

Hello Mr. Tore,
Thank you for the information and the photos...  The photo labeled Q Tank Muffler explains a lot and I have a few questions regarding that photo and Plate 7 from the Skizzenbuch.
The Negative Buoyancy Tank side of Plate 7
1.  There are 3 muffler (k) in the drawing on Plate 7
Q1 - Is there only 1 muffler as indicated in the Q Tank Muffler photo?
2.  Plate 7 shows 3 valves on the Negative Buoyancy vent line; a valve near each tank and one valve near the muffler (no glass viewing eye). 
However, the Q Tank Muffler Photo suggests there is a separate line from each Negative Buoyancy tank which has a valve and a glass viewing eye.  These two vent lines are joined at a “Y” connection and vent through the muffler into the internal pressure hull.
Q2.  Are my observations correct?
Q2-1.  On Plate 7, should the valve (h) going to the muffler (k) be a glass viewing eye instead of a valve?  This would make Plate 7 closer to the actual piping.  Unless there are actually 4 valves; 2 near the Negative Buoyancy tanks and 2 near the muffler?  The Plate 7 just doesn’t match the Q Tank Muffler photo… 
3.  The Q Tank Muffler photo has 4 valves and 4 glass viewing devices feeding into the one muffler.  I assume 2 lines for venting from Negative Buoyancy tanks and two lines for venting from the Regulating tanks and Bunkers. 

Q3.  Am I correct?

Q3-1.  Looking at the Q Tank Muffler photo  -  from left to right; which valve controls what?

Regards.
Don_

Don.
I am sorry to confuse you as I introduced the inboard venting and muffler for the FO regulating tanks 1 and 2 port and stb. This has nothing to do with the venting of the Untertriebtank. Thus a number of your questions are based on my mistake. I am afraid the venting of the Untertriebtank is  a bit more difficult to show on a photo, but as these tanks never are used for fuel there are no sightglasses, they have Kingstones and thus they have a pressure hullvalve ( valve near the tank). The Kingstones and vents are operated from the forward end of the CR and there is a common muffler  probably situated under the floorplates. I cannot recall the exact position of the Kingstones and inboard vent pipes, but have indicated on the photo were I believe they are. The Kingstones are operated by removable handles so you only see the valvestem. Back to the questions on the FO regelzelle. Contrary to the drawing the system is connected to one muffler. As to the sightglasses, only tanks which can carry fuel are equipped with sightglasses and the piping is slightly deviating from the drawing which is normal.  On the photo I have indicated my assumption of the system, if something is unclear just ask.
Tore

[tore]

Don.
Blowingsystem of the Q-tank (neg. Tauchzelle).
The two system plans 17 and 17b are indeed different. The plan 17 system is using a dualsystem, the inboard venting pipe act as a blowingpipe as well, connectionbranch marked Drueckluftanschluss (pressure airconnection).  The connection to the Q tank is via an ordinary hullvalve. The system 17b has a separate blowingair pipe no connection to a ventingpipe and is entering the Q tank via a checkvalve and an ordinary hullvalve, eg. two valves. Plan 17b is new to me, do you happen to know the year it was made? I have a feeling it could be later than  1941. It should be a drawing of the inboard venting from the same year which give an better explanation of the system.
Tore

[tore]

Don.
Further to my to days post I assume the arrangement for the Q tank venting-blowing on the U 995 is as follows. Your system 17b is a newer version of the plan 17 possibly introduced in 1943 and indeed installed on U 995. The piping is located forward part, port and starboard of the CR. On the photo below you`ll see the venting having a hullvalve and a second valve. On the photo of the stb hullvalve you `ll see they have exchanged the T handle with the inboard valvehandle a common thing on the museum U-995. The ventpipe on starboard goes up and cross over to port side  where it goes behind the electronic boxes and down to the muffler under the flooring. The port ventpipe goes down behind the the same boxes as well and joins the stb pipe prior to the muffler. Next to the ventpipe is the blowing air hullvalve, having a round handwheel with a ball. This valve has a checkvalve in the same housing as can been seen on the photo. To sum up, there are double hull ventingvalves on the ventingpipe,no connection to the blowingair pipe and a separate blowingpipe having a double hull valve of which one is a checkvalve.This should match very well with your systemsketch 17b and possibly for most of the VIICs built from 1943, so take your pick which vintage you`ll go for.

[tore]

Don.
In order to have a better overall picture I post two of Falos photos which shows the electronic boxes as well.
Tore

[Don Prince]

Hello Mr. Tore,


Thank you for all your time and effort in helping me understand the drawings.  If you don't mind; I believe I will use your method of overlaying actual photos on the Plate prints.  That's an excellent means to demonstrate a point and it will make my Skizzenbuck much more impressive to view...


Kind regards,
Don_

[tore]

Don.
I Guess the Q-tank system is not Complete without your indication of the Kingstones valvespindles which in some cases can be hard to localise. The Q-tank Kingstonespindles are the second spindles from forward bulkhead as shown on the photo below. As previously told the handles are cranks which are removed when not in use.
Tore

[SnakeDoc]

Hi Gentlemen,

Tore, I think, that the spindles you have marked on the photos are the drive shafts for the flood valves of the Tauchbunker 4. This topic was discussed here:
http://models.rokket.biz/index.php?topic=106.msg9585#msg9585

The valves you have marked are (in my opinion) for blowing Tauchbunker 4, getting fuel and sounding the tank.
Shaft drives of the Untertriebszelle flood valves are located further aft - near the attack periscope shaft (see the attached photos).

Regard to the hull valves of the Untertriebszelle - also see photo.
What do you think Tore?

--
Regards
Maciek

PS. Welcome to the forum, Don. You did not answer my email

[tore]

Don.
It is always good to have a watchdog like Maciek, particularly when you make a hasty conclusion like I did  in my eagerness to find a system matching you plate17b. Maciek is right, the Q tank is placed on both sides of frame 45 slightly ahead of the attack periscope casings centerline. Thanks for the correction Maciek, I was too quick. Maciek is introducing a solution to the Kingston which I believe is correct, further a blow/ venting solution which I am afraid would put your plan 17b on hold and back to good old plan 17.
You suggestion of the blowing/ venting of the Q tank seems to me to be correct Maciek. Some thoughts which backs up Macieks suggestion. Apart from the obvious placing of the Q, the use of same would indicate Macieks  arrangement suggestion is correct. Q is used as a quick diving tank which mostly is needed in emergency situations like crash dives avoiding ramming, collisions or depthcharging as such it has to be easy and quick to operate and placed close to the voicepipes. So I guess Macieks photo " untertriebzelle" is a good reference to use together with plan 17. As many times before together we find the correct solution
Tore

[Don Prince]

Gentlemen,


I really appreciate all the help in locating photos of the Negative Buoyancy Tank control devices in the control room.  I found a photo on the internet which looks to be the Kingston valve wheel on the other side of the control room.  It looks to be the round black wheel, am I correct?


Regards,
Don_

[tore]

 ;Don.
This time I have doublechecked with the frames you can be sure this is the wheel for the port Q-tank Kingstone, you see the both on my bad photo below. I am still curious to know from where you got the plan 17b.
Tore

[Don Prince]

Hello Mr. Tore,


I wish I had a clue as to where I downloaded that Plate 17 (I renamed it because I had other Plates from the uboatarchice.net).  [size=78%]Today I looking into the functionality of the Main Pump and The Trim Pump.[/size]
[/size]
[/size][size=78%]The main Pump -  The manual states it's a reversible pump...  However, I seem to get everything to function properly with the pump running in one direction by utilizing different valves to provide pressure or suction.  Am I missing something?  I will post a photo of the mail pump and could you point out how the pump is reversed and why?[/size]
[/size]
[/size][size=78%]The Trim Pump -  I believe I understand how it works.  I will post a photo of the pump and could you post a good photo of the Trim Controller.  [/size]

[Don Prince]

The Main Pump

[SnakeDoc]

Tore,

regarding to the "plan 17b" - I was able to find its origin - it comes from "U Bootskunde für U Boote Bauart VII C", which translated version is published on uboatarchive.net - which was issued on 15 July 1940.

"Skizzenbuch fur das Maschinenpersponal" coming from U-570 and published on uboatarchive.net, which contains "plan 17" - was issued March/April 1941.

I think, that this explains differences.



Tore, there is one more thing, that makes me wonder. On the "plan 17" are marked four Druckunterschiedmessers - pressure differential gauges for the regulating tanks Regelbunker 1 Bb/Stb and Regelzelle 2 Bb/Stb. They show pressure differences between the external sea water pressure and inside the tanks - what is useful when fine flooding and blowing regulating tanks. Their are also used for operations described in Tauchvorschrift ( http://uboatarchive.net/DivingRegulations.htm ) - paragraph 155, 163, 185

These four gauges are gathered on the control panel above the blowing ballast tank distributor (see photo - on both sides, in the middle - pressure gauge of the main blowing valve).

In the control room of U-995 are two more differential pressure gauges - near Untertriebszelle blowing lines' hull valves. These gauges are not drawn on the "plan 17", but are mentioned in the British report on HMS Graph (table on the page 39 - http://uboatarchive.net/U-570BritishReport.htm ). 

The purpose for these gauges I have found also in Tauchvorschrift - paragraphs 131 - 133.

Reading these paragraphs I'm wondering about "residual water check" (Restwasserprufen). It became obvious to me, that main problem while blowing Untertriebszelle is to stop blowing just before they are emptied - to avoid escaping of compressed air bubbles through the bottom flood valves. For this reason, the residual water check lines were applied. But I can not imagine how they worked. Could you put some light on this topic Tore?

--
Thanks, regards
Maciek

[SnakeDoc]

The main Pump -  The manual states it's a reversible pump...  However, I seem to get everything to function properly with the pump running in one direction by utilizing different valves to provide pressure or suction.  Am I missing something?  I will post a photo of the mail pump and could you point out how the pump is reversed and why?

Well, in the original text the term is: "selbstansaugende, umschaltbare 2-stufige Kreiselpumpe". I translated umschaltbare as reversible, but it rather should be switchable. Switchable - that means that pump's two stages can be connected parallel or in series - for great capacity and low head or low capacity and high head respectively. The switching took place by control valve.

The Trim Pump -  I believe I understand how it works.  I will post a photo of the pump and could you post a good photo of the Trim Controller.

I have attached photo of trim controller.

--
Regards
Maciek

[tore]

Maciek.
Thanks for you spotting of the source for plan 17b.
Your observation on the differential manometer is correct. I assume the following: The local placed differential manometers for the Q is required for a good monitoring of the diff pressure not exceeding 2 bar. being the max allowing diff pressure. The normal procedure for using Q is, if you have time, to open the Kingstons (and inboard venting) filling the tanks while surfaced, then you are about in excess of 4 tonnes heavier than normal surface condition. In the event of crashdiving, you open the normal ballastvents, this Q weight speeds up going through the surface and at about 10 meters the hydroplanes and trim of the submarine take over the further diving. Depending upon the diving angle, E-motorspeed (and depth) the order blow Q is given and Q is blown by a diffpressure below 2 bar. The water residue checksystem is a small pipe going down to the Kingstons and an internal cock in the CR ending into a small funnel, I believe you can see same on the photo of the port system. At the blowing of the Q the testcock is open and seawater is pressed out until the waterlevel is slightly above the Kingston openings, then the blowingair enter the residuewater testline before it reach the Kingston opening, air comes out of the testcock and the order stop blowing Q is given, and the Kingstons are shut. Sometimes both tanks are not emptied at the same time and you have to shut the blowing hull valve of the empty tank before the other, that is one of the reasons you have two separate "controlstations" for the Q. I have tried to make a sketch showing how I assume the system works. I hope I have understood your question correctly.
Tore

[tore]

The main Pump -  The manual states it's a reversible pump...  However, I seem to get everything to function properly with the pump running in one direction by utilizing different valves to provide pressure or suction.  Am I missing something?  I will post a photo of the mail pump and could you point out how the pump is reversed and why?

Well, in the original text the term is: "selbstansaugende, umschaltbare 2-stufige Kreiselpumpe". I translated umschaltbare as reversible, but it rather should be switchable. Switchable - that means that pump's two stages can be connected parallel or in series - for great capacity and low head or low capacity and high head respectively. The switching took place by control valve.

The Trim Pump -  I believe I understand how it works.  I will post a photo of the pump and could you post a good photo of the Trim Controller.

I have attached photo of trim controller.

--
Regards
Maciek

Maciek
Trimpump.
You are of course right. As a further comment to this pump, the trimcontroller was very much in use. Prior to shifting of some weighs inside the submarine you pumped water from forward to aft or the opposite. One of the most used order from the officer on watch was: pump 400 liter from aft to forward, then you knew it would be followed by : diving station!. It happened people were on their station before the latter order was given. The weightransfer was necessary as quite a few people lived in the fwd torpedocompartment and had their divingstations in the CR.
Tore

[tore]

Don.
I don`t know if you got the working of the "Trimschalter" OK so I made a sketch showing how it works in the trimpumping mode, ballastwater from forward tank to aft and the opposite. Please note that the trimpump is a piston pump, the airvessels can be clearly seen in the front, whereas  the main bilgepump is a two impellers centrifugal pump where the impellers can either be run in series or parallel as Macieck says.
Tore

[Don Prince]

Hello Maciek,


I looked at the photo closely and it looks like there are 5 pressure gauges (one under the red hand wheel) clustered around the main blowing valve.  Would that be a pressure gauge for each dive tank 1 through 5?

In addition, on your photo labeled "untertriebszelle gauges"  The large red hand-wheel is for one or both Negative Buoyancy tanks?  I don't see the same configuration on the other side...


Regards,
Don_

[SnakeDoc]

I looked at the photo closely and it looks like there are 5 pressure gauges (one under the red hand wheel) clustered around the main blowing valve.  Would that be a pressure gauge for each dive tank 1 through 5?

There are five gauges - the one on the top/in the middle is the pressure gauge in blowing distributor, the other four - two on each side are the pressure differential gaueges for Regelzelle Bb, Regelzelle Stb, Regelbunker Bb and Regelbunker Stb. See photo.

In addition, on your photo labeled "untertriebszelle gauges"  The large red hand-wheel is for one or both Negative Buoyancy tanks?  I don't see the same configuration on the other side...

The large red wheel is hand regulating valve for both tanks. See photo.

--
Regards
Maciek

[SnakeDoc]

Hi Tore,

thank you for your answer - that was exactly what I wanted to know.

The water residue checksystem is a small pipe going down to the Kingstons and an internal cock in the CR ending into a small funnel, I believe you can see same on the photo of the port system.

Are you thinking about this line? I have marked this with green color.
I also marked lines which (if I'm not mistaken) fed differential pressure gague for Untertriebszelle Bb. The red one connects with Untertriebszelle Bb, while the blue one - with outside sea.
Unfortunately I was not able to find good photo with some cock/valve visible, which would cut off the residual water check line from the negative tank.

--
Regards
Maciek

--
Regards
Maciek

[Don Prince]

Hello Meciek,


Would this drawing be correct?


Regards,
Don_

[tore]

Hi Tore,

thank you for your answer - that was exactly what I wanted to know.

The water residue checksystem is a small pipe going down to the Kingstons and an internal cock in the CR ending into a small funnel, I believe you can see same on the photo of the port system.

Are you thinking about this line? I have marked this with green color.
I also marked lines which (if I'm not mistaken) fed differential pressure gague for Untertriebszelle Bb. The red one connects with Untertriebszelle Bb, while the blue one - with outside sea.
Unfortunately I was not able to find good photo with some cock/valve visible, which would cut off the residual water check line from the negative tank.

--
Regards
Maciek

--
Regards
Maciek

Hi Maciek.
Yes your green line could be the residual water checkpipe. The checkvalve might be situated further up as indicated on my photo below. I am not sure about your assumption for the diff manometerpipes though. As you see from my photo it looks as if both  pipes goes only to the manometer.
Tore

[tore]

Hello Meciek,


Would this drawing be correct?


Regards,
Don_

Don.
I am not sure, as the  two systems blowing and venting is combined in one on board, this can be confusing as on plate 17 and 7 they are drawn as separate system see my photo below. The blowing system on plate 17 starts with the blowing valve (hand control valve) having air supply from the main distribution manifold. After this valve is the reliefvalve, a manometer connection and a drain. This is a standard package for all the airblowing system. After this system is a shut off valve. It seems to me as you have switched  the hand control valve to this shut off valve. When the drawing and the real world is not corresponding it is usually best to follow the real world. It is almost impossible to check the system locally based on the photos we have available, however we can not see any plain manometer, but clearly a differential manometer which we can assume is hooked up as on the visible port side, the reliefvalve is visible so that is OK. The shut off valve I cannot see but I am almost sure it is there together with the connection to what I would call the common venting/blowing pipe.
Tore

[Don Prince]

Hi Meciek,


Thanks for the quick response....  I did a little art work to enhance the previous photo.  Does it look OK?


Regards,
Don_

[tore]

Don
Not bad. If you follow the port ventpipe down it disappears behind a small steel cabinet right underneath i the pipe ends in a fairly large Box which I believe is the  venting muffler for the two Q tanks, see the bad photo below.
Tore

[tore]

Don.
As a final touch I should probably mention that I believe the external floodvalve for Q is  not a  Kingston, square flapvalve, as on the fuel/ ballast saddletanks 4 and 2, but rather a valve behind a large square grating next to the aft Kingston on ballasttanks 4 port and stb. On the photo below you can see what I assume, my first thoughts were that this grating was connected to the fuel compensatingsystem but I believe the above is a better theory, you can see the round valve outlet behind the grating. Thus I suggest you rename floodvalve driveshaft: Handwheel external floodvalve . As a curiosity I have found out that the flood area of these valves are 0.24 m3 and with Q fully blown you have a residue water in the tanks of 0,16m3, not much.
Tore

[SnakeDoc]

Hi Tore,

Yes your green line could be the residual water checkpipe. The checkvalve might be situated further up as indicated on my photo below. I am not sure about your assumption for the diff manometerpipes though. As you see from my photo it looks as if both  pipes goes only to the manometer.

Thanks for your answer, I think you are right. I did not recognize relief valve.

I am not sure, as the  two systems blowing and venting is combined in one on board, this can be confusing as on plate 17 and 7 they are drawn as separate system see my photo below. The blowing system on plate 17 starts with the blowing valve (hand control valve) having air supply from the main distribution manifold. After this valve is the reliefvalve, a manometer connection and a drain. This is a standard package for all the airblowing system. After this system is a shut off valve. It seems to me as you have switched  the hand control valve to this shut off valve. When the drawing and the real world is not corresponding it is usually best to follow the real world. It is almost impossible to check the system locally based on the photos we have available, however we can not see any plain manometer, but clearly a differential manometer which we can assume is hooked up as on the visible port side, the reliefvalve is visible so that is OK. The shut off valve I cannot see but I am almost sure it is there together with the connection to what I would call the common venting/blowing pipe.

Tore, do you think, that relief valve is on the port side? Could you point, what you call the common venting/blowing line?

As a final touch I should probably mention that I believe the external floodvalve for Q is  not a  Kingston, square flapvalve, as on the fuel/ ballast saddletanks 4 and 2, but rather a valve behind a large square grating next to the aft Kingston on ballasttanks 4 port and stb. On the photo below you can see what I assume, my first thoughts were that this grating was connected to the fuel compensatingsystem but I believe the above is a better theory, you can see the round valve outlet behind the grating. Thus I suggest you rename floodvalve driveshaft: Handwheel external floodvalve . As a curiosity I have found out that the flood area of these valves are 0.24 m3 and with Q fully blown you have a residue water in the tanks of 0,16m3, not much.

I think you are close with your assumptions. I believe that description of the negative tank's flood valves in the type IXC report can be helpful:

The negative tank flood valve is a mushroom valve opening outboard.  The valve disc is provided with a screw thread, and is raised or lowered by rotating the valve spindle which is threaded into the stem portion of the disc casting.  The spindle is fitted with a collar and ball bearings to serve as a carrier for the vent valve disc.  When turning the spindle, guides prevent the disc from turning.  The valve is operated by means of a hand crank from within the vessel.

http://uboatarchive.net/DesignStudiesTypeIXC.htm


--
Thanks, regards
Maciek

[Don Prince]

Gentlemen,


Just how many people were required to be in the Control Room on a dive?


1 - Captian
2 - Chief Engineer
3 - Navigator
4 - 2 x Plainsmen
5 - Rudderman
6 - 2 x Q tanks (Port & Stb)
7 - 2 x saddle tanks (D2) Port & stb
8 - 2 x saddle tanks (D4) Port & stb
9 - 1 control D1
10 - 1 control D3
11 - 1 control D5


I count 15 people; it sure looks crowded to me.  Then again, on a crash dive you have people attempting to get to the bow of the U-boat.  They sure could use a computer system with sequenced controlled servos to do all those manual functions!!!

[Don Prince]

Hello Mr. Tore and Maciek,


I read your comments about the Negative Buoyancy tank and the different valve system.  I made some changes to Mr. Tore's drawing.  What do you think?


Regards,
Don_

[Don Prince]

Hello Mr. Tore,


"the flood area of these valves are 0.24 m3 and with Q fully blown you have a residue water in the tanks of 0,16m3, not much."

Should the flooding area of the valves be 0.24 m2 (square meters and not cubic meters)?

Regards,
Don_

[tore]

Maciek.
Thanks for your finding of the description of the Q floodingvalve as executed an a IX C I think it could be approximately similar to a VIIC.
Normally you would have a reliefvalve close to each tank as a protection of the tank, so I Guess stb Q would be the same as port. Common venting/blowingline is simply the two crossover pipes on plate 7 and 17 merged in one pipe see photo below.
Tore

[tore]

 ;DHi Don.
You are of course right, the floodarea should be in m2 not m3, my old stiff finger hit the adjacent 3 without my notice.
Tore

[tore]

Don.
I Guess manning of the controlroom varies. On your list you have missed a few. The most important man would be the NO 1 the officer second in comand of the CO, CR engineer, a petty officer who amongst other jobs is in charge of the blowingdistribution panel, thus blowing the tanks, the trim/pumpman, the chief electrician and then the torpedo officer only to mention a few in addition to your list.
Tore

[SnakeDoc]

Hi Gentlemen,

the number of the crew in the Control Room (as well as in other rooms) were determined by so called Rollentafeln. They were divided into two parts: seemännisch (nautical) and technisch. Each part described function of the crew member in every condition (that means Klarmachen zum Tauchen, Friedens Tauchstation, Kriegsmarsch, Freiwache, Gefechtstation, Artillerie Gefechtstation, Boje über Board, Manöver). In Kriegsmarsch condition, during dive, in Control Room there are following persons:
- forward dive plane operator
- aft dive plane operator
- vent of ballast tank 5 operator
- negative tanks stb operator
- negative tanks port operator
- vent of ballast tank 3 stb operator (also ballast tanks 2 and 4 stb when used - they were fitted with common vent)
- vent of ballast tank 3 port operator (also ballast tanks 2 and 4 port when used - they were fitted with common vent)

As the ballast tank 1 according to regulations had to be vented as last one, the vent valve could be operated by one of persons mentioned before.
Also there were persons mentioned by Tore - commanding officer (or officer of the watch), chief engineer, torpedo officer.
I believe, that blowing distributor, trim station or pump operator roles were performed by some of persons listed above.

Generally, Tore has interesting experience from the Norwegian service of U-995.

- main rudder operator was in conning tower (rudder station in control room was kind of emergency one. Although Tore said some time ago, that when KMN Kaura  was in service, the common practice was to use control room station, as it was more convenient while snorkeling)

Generally, it seems, that in control room should be much about 10 people. For comparison - on type IXC U-Boats:

When surfaced, there are five persons in the control room.  At battle stations, there are ten.

http://uboatarchive.net/DesignStudiesTypeIXC.htm

--
Regards
Maciek

[tore]

Don.
Your adjustment of my system sketch seems to be fine to me. If you study the original German plates you`ll see on the system sketch a 90 degrees gearcone arrangement inside the Q tank, if we assume this is right we should add same, further you valveopening seems to be a bit to large, I believe each of the nearby MBT4 Kingstons has a flood area of 0,9m2 whereas the total Q floodvalve area is 0,24 m2 for a comparison. The red dot on the photo of the grating indicates the diameter of the floodvalve inlet.
Do you have any particular reason for introducing a U bend at the end of the checkpipe? You would of course get an earlier warning but you`ll leave more residual water in the tank, but you could obtain same with the length adjustment of the pipe.
Tore

[tore]

Don.
Manning of the CR.
Maciek gave a good information of the German manning regulation, my info was based on RN and Norwegian regulation. Basically Maciek reference to the German regulation are the same, manning varies with the type of diving stations f.i.. it is a big difference with a routine surfacing while the crew are sleeping and at a battlestation situation, so it varies. The system of splitting the  crew into navigational (deck) and technical crew is normal in most navies I think. Our system was based on the RN system as our navy fought in UK exile during WW2 and our submarines were English and training was done in UK. I my shelf was trained in UK. The big difference is that in the German navy the chief engineer was responsible for the trim, ballast calculation and in command of the hydroplanes etc. In the RN and many other navies including ours this job is done by the NO1, next in command of the CO.
The chief engineer is mostly stand by if something should go wrong and engineers would be required. During battlestation in our navy however, the chief engineer worked with the CO with distance bearing/ calculation. Down below is a picture with the CO on his knees at the navigation periscope and I calculating the distances during a dummy attack just to give you an idea.
When using the attack periscope the chief engineer was not in the tower but in the CR. At the attackperiscope the CO could get a lot of info directly, however we did not trust the German fruitmachine so the CE had to do some calculation passing messages up to the tower verbally. So you see Don, as so many times before, it is not a single answer to a simple question.

[SG]

It's good to see you at work  . Also, Great info Tore.

[tore]

Don.
Manning of the Control room.
May be a further explanation why it is a difference in the German and RN ( and other navies)  manning regulations. The VIICs was, as known to all of you, equipped with manually operated ballastvents operated by rods and levers that required a lot of People locally placed. The RN and many other navies operated boats having hydraulically (Oleo system) operated vents which were controlled  by one person, like the blowing of the tanks at one station, that saved a lot of personell, thus a reduction of the people in the CR. The CR engineer was responsible for both the HP airsystem and the hydraulic system and would take an experienced PO engineer to handle and maintain. He was indeed an important man.
Tore

[tore]

Hi SG
The photo was made by a paper making a report about life on board a submarine, we were warned on beforehand, that`s why I was wearing an uniform with even a white shirt. We newer wore this at sea, as previously told my favourite dress was a pink pyjamas often covered by a greasy battledress and mostly my uniformcap .
Tore

[Don Prince]

Hello Mr. Tore,


Would this be correct for the locations of the Q tank valve and drain funnel for testing an empty condition on the Stb. side?


Regards,
Don_

[NZSnowman]

Hi SG
The photo was made by a paper making a report about life on board a submarine, we were warned on beforehand, that`s why I was wearing an uniform with even a white shirt. We newer wore this at sea, as previously told my favourite dress was a pink pyjamas often covered by a greasy battledress and mostly my uniformcap .
Tore

WOW... I was starting to think that the RNoN had a very high standard of dress code on there submarine

[SG]

Tore, now you must show us a pic of you at  work in your (in)famous outfit !!!!   

[tore]

Don.
Residue watercheck Q stb.
Your picture (green oval) seems to me as being the possible relief valve of stb.Q, Your green pipe could be the part of the residue water check pipe ending up in the funnel, sometimes these small pipes are bended and twisted. The pipe looks a bit small. I have made a picture suggesting my ideas, the reliefvalve is a bit doubtful as I cannot see the reliefvalve of the HP air distribution manifold. If you would check further please note: There are two pipes going through the hull near the blow/vent hullpipe, these pipes join in a greasenipple for greasing the external floodvalve so you don`t get confused by these pipes.
Tore

[tore]

Simon and SG.
Oh you guys! Don't forget we were 46 men who shared 2 small handwashing basins with no facilities for washing clothes and we could be submerged for up to a month. The VIICs were not fit for a prolonged submerged time as schnorcheling, so you were wearing your clothes until you almost could throw them away rather than bringing them back home. Thank god I have no photo of my pink pyjamas, however I Guess I have a photo of us coming straight from the North Sea dress as we used to be. I`ll see if I can find the photo some day .
Tore 

[tore]

Don
Residue water check Q stb.
I have rechecked the available photos and have made an additional picture putting up my final findings. My assumptions are: Q reliefvalve OK.greasing pipes OK.Q blowing manometer is missing only bracket left, diff manometer OK.residuetest line funnel OK, residue hullvalve having round wheel marked and OK. some of the piping can be seen but missing all the way to the funnel. I have posted a photo with the additional info. Thus I guess the picture should be complete as I see it today. As we know the 4 blowing manifold diff manometers have a single common reference pipe to the sea, I believe the Q diffmanometers are hooked up to same as well, although not shown on any drawing.
Tore

[Don Prince]

Hello Mr. Tore,


I was reviewing Plate 16 and I don't understand why there is an extra set of mushroom vent valves towards the back of Dive Tank 2 (D2) in the saddle tank area.  I circled the valves in question in red.  Does it have something to do with diving since the valves are towards the back of the saddle tanks?


Regards,
Don_

[tore]

Don
The vents are the residual airvents which are needed for the aft saddle ballast tanks because you dive with a bow down angle. By doing that air is trapped in the aft part of the tank and you need to get rid of that air by extra vents. They are operated from the engine room. For the same reason you don`t have this arrangement for the fwd. saddle ballast tanks 4 port and starboard as here the mainvents are at the aft end of the tank.
Tore

[Don Prince]

Hello Mr. Tore,


This is a long multi-part question with reference to Plate 16 and Plate 17...


Is the Regulating and RFO tank 1 open to the Sea?  A while back I had the understanding that this tank had fuel oil floating on top of water and as the oil was used it was replaced with Sea water (a Self Regulation tank).  If so, then where is the opening for the sea water to enter the regulating and RFO tank 1?


It looks like there are 3 blowing distributor systems
1.  the Main Blowing Distributor (Plate 17)
2.  the Exhaust Blowing Distributor (Plate 16)
3.  the Emergency Blowing Manifold (Plate 16 and Plate 17)


Q1.  is this correct. where are they located in the control room
Q2.  it looks like the Exhaust Blowing Distributor only affects D1 through- D5
Q3.  It looks like the other 2 blowing distributors affect all tanks except Regulating Tank 2 because this tank has no flood valve and has to be pumped???


If there is a down U-boat and a diver hooks up the two lines in order to bring the U-boat to the surface, then all effort is for nothing if no one is conscious and able to open the Tide valves on D2, D3 and D4, and open the hull valves on ALL the other tanks???


Regards,
Don_

[tore]

Don.
This was indeed many questions which all cannot be answered with yes or no. I post my answers in different posts starting the compensating tanks 1 and 2.
The purpose of the compensating tanks is to compensate for the changing the weigths of the submarine. The weigth is changing all the time, extra people are coming on board, fuel, freshwater and provision are consumed etc. Thus you have to compensate this by taking water in and out of the compensating tanks fairly often. Both the comp. saddletanks 1 and 2 have no direct contact with the sea, filling and pumping is done by connection to the bilge pumping system both for filling ( fine flood) and  emptying by the bilge pumps, see plate 6.
In order to further increase the reserve FO capacity a part of the compensating tanks are made as FO. reservetanks, called 1 port and stb.. The tanks are not always used as such. When RFO compensating tanks 1 port and stb are used as fuel oil tanks , the connection to the bilge system is shut and the tanks are connected to the fueloil system. See plate 9. If you have questions to the plates 6 and 9 shoot.
Tore

[SnakeDoc]

Don,

Is the Regulating and RFO tank 1 open to the Sea?  A while back I had the understanding that this tank had fuel oil floating on top of water and as the oil was used it was replaced with Sea water (a Self Regulation tank).  If so, then where is the opening for the sea water to enter the regulating and RFO tank 1?

Regulating and FRO Tank 1 (Regebunker 1) was not self-compensated tank. It was pressure-proof, flooded and emptied by means of the flooding and drain manifold (Flut und Lenzverteiler).

It looks like there are 3 blowing distributor systems
1.  the Main Blowing Distributor (Plate 17)
2.  the Exhaust Blowing Distributor (Plate 16)
3.  the Emergency Blowing Manifold (Plate 16 and Plate 17)


Q1.  is this correct. where are they located in the control room
Q2.  it looks like the Exhaust Blowing Distributor only affects D1 through- D5
Q3.  It looks like the other 2 blowing distributors affect all tanks except Regulating Tank 2 because this tank has no flood valve and has to be pumped???

Only main blowing manifold (compressed air) is located in the Control Room - right to the aft diving plane operator station.

The exhaust blowing manifold is outside the pressure hull - (more or less) over the main blowing manifold. Through the pressure hull are passing valve spindles, and only hand wheels are available for operation in the control room. These are eight, small, red hand wheels at the control room ceiling, over the main blowing manifold.

The emergency blowing manifold would be also located outside the pressure hull - in front of the conning tower, in the magnetic compass casing. Would be - because in late-war front going U-Boats it was not fitted (U-995 was not equipped with that). In the HMS Graph report this manifold is mentioned, but from survivors interrogation reports seems, that this manifold was fitted only for the time of U-Boat crew training (that is, when the vessel operated on the relative shallow waters of the Gdansk Bay or similiar).
Here is short discussion: http://models.rokket.biz/index.php?topic=921.msg12001#msg12001

The exhaust blowing manifold indeed affects only ballast tanks.

If there is a down U-boat and a diver hooks up the two lines in order to bring the U-boat to the surface, then all effort is for nothing if no one is conscious and able to open the Tide valves on D2, D3 and D4, and open the hull valves on ALL the other tanks???

All blowing valves of the emergency blowing manifold were located external - so available for diver. The flood valves of the ballast tank 3 was almost never closed when U-Boat was at sea. If the buoyancy gained by blowing all three main ballast tanks was not sufficient to rise the boat, the other measures had to be taken.

To know, how emergency blowing manifold could like, you can sea this diagram:

http://dreadnoughtproject.org/plans/KM_Uboot_Type_II_1934//bergungsplan_100dpi.jpg

--
Regards
Maciek

[SnakeDoc]

Tore,

The chief engineer is mostly stand by if something should go wrong and engineers would be required. During battlestation in our navy however, the chief engineer worked with the CO with distance bearing/ calculation. Down below is a picture with the CO on his knees at the navigation periscope and I calculating the distances during a dummy attack just to give you an idea.
When using the attack periscope the chief engineer was not in the tower but in the CR. At the attackperiscope the CO could get a lot of info directly, however we did not trust the German fruitmachine so the CE had to do some calculation passing messages up to the tower verbally.

Could you say something closer about Norwegian experience with German fruit-machine and  Norwegian practice of torpedo fire control, please?

--
Thanks, regards
Maciek

[tore]

Don
I believe Maciek has answered the rest of your questions in agood way. I would only add to the compensating tanks post I forgot to mention the air/ venting  system which we have touched upon previously as seen on plate 7 and 17,( the system with the sightglasses and muffler at the aft part of the attackperiscope casing). I guess using the dicussion on the Q system would help to understand the sketches.
Tore

[tore]

Maciek.
Torpedo firing and the fruitmachine was not really under my responsibility, that was the torpedopeoples job, so I am afraid I cannot help you very much. I did only the manual calculation using graphs and tables after receiving the COs info of speed, bearing etc. We had a student on board from the technical university in Trondheim taking his master on this "computer" it was of course the prehistoric computertime, but  I am sorry I cannot contribute in any sensible way.
Tore

[SG]

The purpose of the compensating tanks is to compensate for the changing the weigths of the submarine. The weigth is changing all the time, extra people are coming on board, fuel, freshwater and provision are consumed etc. Thus you have to compensate this by taking water in and out of the compensating tanks fairly often.
 

Tore, does it mean that you had to weight all the provisions in advance, before embarking them? What about the crew? did you know the weight of every single men aboard or you just assumed a mean weight of, for instance 70 kg per crewmember? also, did you take in consideration the possible weight loss of the people aboard or it was ininfluential?
How often did you calculate the weight change of the submarine?
thanks

[Don Prince]

Hello Mr tore,


I now know exactly where that Plate 17 came from....  The manual "U-Bootskunde für U-Boote Bauart VII C, Stand vom 15.7.40." - this manual has an appendix in the back of the book where you will find Plate 16 and Plate 17...


5.  Anblaseleitungen, Notausblaseund Raumnotluftleitung


Translate to English?


Regards,
Don_

[Don Prince]

Hello Mr. Tore,


Plate 16 = I assume the 1 vent valve in the diesel room to vent the trapped residual air in both D2 tanks is located in the roof area.  Do you have a photo of this valve?  Are the venting lines going from the back end of the tanks to the valve located internal or external to the pressure hull?


Regards,
Don_

[SnakeDoc]

Tore,

Torpedo firing and the fruitmachine was not really under my responsibility, that was the torpedopeoples job, so I am afraid I cannot help you very much. I did only the manual calculation using graphs and tables after receiving the COs info of speed, bearing etc. We had a student on board from the technical university in Trondheim taking his master on this "computer" it was of course the prehistoric computertime, but  I am sorry I cannot contribute in any sensible way.

Thank you Tore for your answer. It would be interesting to take master on such piece of equipment (as well as reading such scientific description).


--
Thanks, regards
Maciek

[SnakeDoc]

Don,

Plate 16 = I assume the 1 vent valve in the diesel room to vent the trapped residual air in both D2 tanks is located in the roof area.  Do you have a photo of this valve?  Are the venting lines going from the back end of the tanks to the valve located internal or external to the pressure hull?

As the vent valve of the Tauchbunker 2 is located outside the pressure hull, it is hard to get photo. But if you mean the drive for this valve - one is located in the control room - on the aft bulkhead - over the hatch to the petty officers room - large red wheel on the stb side (the wheel on the port side is the drive for the Tauchtank 1). In the diesel engine room, to the driving shaft going from control room, the other wheels are attached, so the vent can be operated also from the diesel engine room.
See also here: http://models.rokket.biz/index.php?topic=106.msg13275#msg13275


--
Regards
Maciek

[tore]

SG.
A full control of the weigths in and out is necessary. This is particularly elaborate after major refitting, preparing for long patrols,provision,fuel, torpedoes taken on board and compensating for shooting same etc. In my days a rough estimation of each person would be 75 kgs today you would probably add another 10 kgs pr. person I guess . Not only the weights taken on board, but the salinity and temperature of the sea had to be taken into consideration. In addition to weights taken on board you had to know where it was stowed as the tilting moment has to be taken into consideration for the trim as well. The influences of these shifting of weigths was many times based on experiences rather than calculations. As mentioned before f.i. prior to sounding the alarm for diving stations you knew that 400 liters had to be shifted from aft to forward trimtank. You could of course compensate a lot by the hydroplanes and the movement of a single person or normal watchchanging would not require a trim changing you compensated by the hydroplanes. The need for  fairly extensive corrections  is why there are  elaborate systems of compensating- and trimtanks as you want to have an optimal boat for easy handling of hydroplanes. Tanks were sounded every day and adjustment was carried out accordingly.
Tore

[tore]

Don.
Residueventing MBT 2
I believe Maciek has answered in a good way. I can only add that the drive rod from the controlroom goes into the engineroom and ends up at frame 21 in a bevelgear where it goes through the through the pressure hull. I am posting a photo showing the arrangement.
Tore

[tore]

Don.
Further to my previous post I am sending a bad photo showing the enginroom hand wheel for the residue ventingvalve, the rod continues to the CR.
Tore

[SG]

Very interesting, Tore. Thank you very much!!

[Don Prince]

Thank you Mr. Tore,


That explains a lot and I'm very grateful for your patients and understanding.  It looks like you have answered many of my questions before and I do apologize for being such a bother.


Several years ago, I started building an OTW Radio Controlled model of a Type VII C U-Boat "U-96" which has a fiberglass hull and a brass deck and tower.  The kit came with 2 flat tower side sheets and the laser cut out deck sections.  I had to manufacture the rest of the tower components from brass plate and rods and assemble everything with a small soldering gas torch.  It took me about 2 years to complete the U-Boat structure, but I have not installed the water tight chamber along with the all the electronics (receiver, servos. dive system, speed controller, depth controller, and pitch controller, plus tons of other stuff).  To complete my U-96 project it would take well over $3,000 and lots of time.  When it is completed, U-96 will be capable running on the surface, or diving to a predetermined depth in a lake or pool.  Today, U-96 sets on a table in my library as a huge 84 inch long accurate display model.


Sometime next week, I will take some new photos of U-96 and post them on this web site.  Oddly enough, this is the Accurate Model Parts site...


Regards,
Don_

[Don Prince]

Hello Simon,


I was looking at your drawing new2u and now I see where you have configured in the D2 tanks residual vent valves b1 in your WorkingDrawingV03.  Could the d1 control valve wheels be in the ceiling of the diesel room?  That sounds like a Mr. Tore question, if he has not already address the issue.


My offer still stands...  Simon if you ever decide to publish a book with all your Type VIIc drawings, then I would be one of the first in line to purchase a copy.  Your work is that good!


Regards,
Don_

[tore]

Don.
Some time ago we discussed these valves see page 53 thru 55 in this thread. However I better sum up: The venting system of both the main venting MBT 2 and 4 as well as the residueventing MBT 2 have all fairly long external venting pipes which are controlled from the inside by common ventvalves for quick handling. The main venting of MBT 2 and 4  port and stb from CR and  the residueventing MBT 2 port and  stb from the CR and engineroom. This implies some external piping which might be susceptible to damages which could be fatal. To overcome this risk the system has valves close to each MBTs so you can shut off  each tank separately eliminating the external vent pipe. These valves should be operated from inside.  The valves are having spindles going through the pressurehull and ending up in a removable T bar on plate 6. The valves seems not to be fitted on the residue venting system and thus no valvespindles in the engineroom.  To make it even more complicated to you, the MBT 2 and 4 port and stb. have a 3rd valve in the ventduct outside the pressurehull, these are gatevalves and used for shutting off the tanks while used as fuel bunkertanks. The gatevalves are placed outside the pressurehull under the casing and are not operated from inside the pressurehull thus not valvewheels in the engineroom which is according to plan16.
Tore

[tore]

Don.
Emergency ventvalve MBT 4 port.
Further to my post this morning I show you a bad photo of what I believe could be the valvespindle of the port MBT4s emergency shut off valve for the ventline. I Guess it`s situated between frame 47 and 48 slightly aft of the navigation periscope. The starbord valve is hard to spot as on all the photos I have, a lot of stuff are in the way.The same goes for the valves of MBT2, you shall probably find the spindles in some of the upper small cabinets in the PO mess aft of the CR.
Tore

[SnakeDoc]

Hi Tore,

To make it even more complicated to you, the MBT 2 and 4 port and stb. have a 3rd valve in the ventduct outside the pressurehull, these are gatevalves and used for shutting off the tanks while used as fuel bunkertanks. The gatevalves are placed outside the pressurehull under the casing and are not operated from inside the pressurehull thus not valvewheels in the engineroom which is according to plan16.

Accidentally I have found something related with the gate valves. See this Deutsche Wochenschau: http://www.youtube.com/watch?v=aqdvK2ZtxoA , since 7:30. The reader says something like: Bei schwerer Wetter muß ein Tauchbunker aufgestellt werden. I think, that camera operator recorded operation of converting Tauchbunker from fuel tank to ballast tank mode, when the crew member opened gate valve on the venting duct.


--
Regards
Maciek

[tore]

Maciek.
Unbelievable what you are noticing. Indeed I guess the man on deck seems to open the gatevalve on fuel/ ballast tank 4 port. which means it is converted into a ballasttank by using a T bar on the valve from the casingdeck under bad wheather.
Tore 

[NZSnowman]

Great spotting Maciek!

It looks like I will need to update my drawing, from a hex shape to a square shape (7:37) peg on top of the valve 

Simon
 

[Don Prince]

Hi Simon,


It looks like the crewman is holding a "T" bar tool with a collar on the end of the shaft with a recessed square for fitting over the screw to unlock the access door (the tool)in the deck to the valve below.  the crewman also has a 2nd tool in his hand that looks like a double hook with a square cut-out to access the valve (The tool 2).  I'm not sure why it was designed like that?  Am I right on this?  (see photos)


Regards,
Don

[NZSnowman]

Don, yes on the 'square'. I will need to change my drawing from hex shape to a square shape

The hatch covers for these valves are different between the older and the newer style of decks of Type VII’s.
 
For the newer style of deck, the hatch cover for tank 1 valve is long/narrow because of the large lower Wintergarten (left of drawing) and tank 4 is just a key hole in the deck.

[Don Prince]

Hello Mr. Tore,


I must have been sleeping...  I totally missed the photo of the Q tank Kingston (now believed to be Mushroom) valve spindles in the photo.  I modified the photo so that I will not miss that again.


Is it normal for the valve wheel or handle not to be on the valve shaft?  I bet the Captain would really get up set if the crewman said they can't find the valve wheel during an crash dive and they can't express the Q tanks!!!


Regards,
Don_

[NZSnowman]

Hi Simon,


It looks like the crewman is holding a "T" bar tool with a collar on the end of the shaft with a recessed square for fitting over the screw to unlock the access door (the tool)in the deck to the valve below.  the crewman also has a 2nd tool in his hand that looks like a double hook with a square cut-out to access the valve (The tool 2).  I'm not sure why it was designed like that?  Am I right on this?  (see photos)


Regards,
Don

I also saw the 2nd tool and was wondering what its for

[tore]

Don.
The spindles which you have marked are the spindles for the MBTS 4 aft Kingstons. If you look at page 111 on this thread you`ll see Maciek correction and the special mushrom floodvalve fixed wheelhandle. This valve have a much smaller floodarea than the adjacent MBT4 Kingstons as discussed.
Tore 

[tore]

Don.
Valves and Kingstons spindle.
On the VIICs a number of valves end in a spindle without handle or wheels. You have several reasons for that. Spacesaving and preventing accidental opening of special important valves. It is normally used on valves not so frequent in operated. The CO don`t have to worry about the Q,  the floodvalve wheelhandle is always there.
Tore

[tore]

Simon and Don.
Nice to see you are back Simon. The strange tool you have noticed is a wheelclaw. The tool is used on wheelhandles on valves which are hard to open. You put one "claw" on the spoke and the other on the wheelrim thereby you get a rod giving you a better momentum for opening the valve.
Tore

[VIC20]

Hello Tore,


Simon pointed me to this great thread, I'm developing a Type VII simulation game.
It's amazing to read what kind of details you remember after many decades! I hope you could answer me some questions (unfortunately actually I have a lot of questions).


- I'm currently working on the simulation of the G.W. engine for my game.
The load is simulated with a simple calculation (propeller law) so it's like a test bed.
http://www.wolves-of-the-atlantic.com/downloads/Enginetest/Enginetest.html
(It will load the Unity plugin to play the simulation which is harmless. Ignore the bad graphics, it's just to give me a primitive visualization)


My biggest problem with the simulation is the acceleration of the engine itself because it's impossible for me to simulate the resistance caused by each part of the engine. I went with the power delivered to the shaft as basis of my simulation instead.
Basically the drag of the working propeller and the diameter and weight of the propeller and shaft are limiting the acceleration and revolutions per minute. The engine power itself is based on the amount of fuel per revolution (can be controlled with the slider).
It seems that the simulation matches the real world thing. But what about the time it takes to accelerate engine RPM? I have absolutely no idea how fast such an engine can accelerate to different RPMs.


- And the fuel consumption shown in the simulation, does it make any sense to you?


- Another question is the AK speed (highest continuous) which should be 470 RPM, was it really possible to run the engine at 470 RPM for longer times? And 490 RPM for something like half an hour?


- From what I've read on the Type VII manual I think the governor limits RPM to not exceed 490 RPM + 10% (which would be 539 RPM). How fast does this governor work? I think it pushes a kind of lever to limit the fuel inflow, does it have a "way" from 490 to 539 RPM or does it instantly limit fuel inflow?


- The manual says the engine can't be started with the supercharger clutched in. And the supercharger can't be clutched in below 390 RPM.
Also the fuel lever can't be moved to a higher position than something that would result in about 420 RPM unless the supercharger is clutched in. Now my really stupid question: do you have to declutch the supercharger when going from higher speed to below 390 RPM???


- What is the minimum RPM the engine can run at?


- do you remember the RPM (or loss of speed) when charging batteries (at the different drive modes)?


- Is it correct that you can engage the clutch of the diesel while the engine is running up to 350 RPM? What when you switch from diesel to E-Machines? The E-Machine operate at a maximum of 280-295 RPM, do you need to reduce the diesel RPM to below 300 RPM before you clutch in the E-machine or isn't it necessary (manual says the generator can work as a brake when propellors break through the water surface in bad weather).


- how long does it take to stop and start engines to reverse?


enough questions 


regards


Mark

[tore]

Mark.
Welcome to the thread, yes it is indeed a lot of interesting questions which I need a bit time to answer. Please be aware of the many alternative ways you can operate the engines. Singel engine, dual engine, engines declutched completely from shafting, clutched in E generators, clutched in propellers, run with different batterycharging , combination of propulsion and  batterycharging, various type of schnorchling etc. I`ll try go into  into your questions one by one if you have patience with a man going on 86. I`ll probably have a few answers ready by today.
Tore

[VIC20]

That's great thank you! I have a lot of patience after all the endless search on the internet before 

[tore]

Mark
The GW engine fuelinjection is controlled directly by the fuel handle on the maneuver stand, thus it is an immediately respond of the engine, a matter of 3-4 seconds from 0 to 350 rpm with engine disengaged from the shaft system. The governor is only maintaining the revs set manually by the fuelhandle and is controlled by centrifugal weights on a shaft driven from the camshaft drive. As the force for moving the fuelrack is not sufficient, there is a linkage from the governor to a slide on a hydraulic servomotor which moves the fuelrack according to the variation of torque to maintain the preset RPM, a detailed analyze of the system is discussed previously on this thread. The servomotor is a delaying element, but only at the variation of torque to maintain a preset revs. I would say a second or two. The variation of torque can be due to inertiaforces like clutching in generator/ E motor, tailshaft incl. propeller or resistance due to generator load or Emotor drive, torsional vibrations and propeller torque due to speed, waves and in shallow waters, depth under the keel etc.
The fuelconsumption for this engine would be between 157 g/bhp and 165 g/bhp, I should assume.
The max continuous rpm is 470, I guess you could run that for hours,  we usually were operating at 460. The overload rpm 490 was limited to a half hours run as far as I remember.
Increasing the rpm to 539 seems to be excessive, we never exceeded 490. By adjusting the linkages you could increase the revs beyond the preset values.
I assume you would have more questions on my answers, so just fire.
Tore

[tore]

Mark.
Supercharger GW engines.
The GW engine is basically a normal aspirated engine which had a booster(Roots blower) driven via a doublecone clutch from the camshaftdrive. At low load and rpm up to 350 rpm you clutched in the blower by moving a handle on the boardside of the engine at the maneuverstand, by doing that you shut off the normal aspirated air inlets and opened for the booster airduct from the blower thereby you increased the airsupply, the bmep and output of the engine by being able to inject more fuel.The interlocks on the fuelrack and the declutching of the blower was indeed executed as you mentioned.
You could run the engine  some 100-150 rpm I guess.
There are different battery chargingloads, starting by not cruising, only charging at very high loads when your batteries were low and very light, just topping up the batteries. As far as I remember the rpm varied with the load I can`t remember the revs. When cruising you put the chargingload according to the requirement of the speed and the timeneed for getting batteries fully charged ,up to the decision of the CO.
Tore

[tore]

Mark
Diesel engine clutch.
As the blowerclutch, the engineclutch was a double cone frictionclutch, the difference being the size and it was pneumatic/hydraulic operated. I guess you could engaged the clutch at 350 revs, but the wear and tear increases with the speed and inertia forces so we usually started with the clutch engaged. Engaging the clutch at relatively high speed created a lot of smoke allthough nobody knew about the asbestos danger, the smoke could be unpleasant in a confined space.
The starting procedure after surfacing was a bit cumbersome, you wanted to get the engine ready as soon as possible in order to exhaustblow the ballasttanks as you was semisurfaced and the  boat was in an unstable position. However you had always some seawater leakages in the exhaust system and some time these leakages could even fill the cylinders. In order to prevent waterstroke, you opened up all the indicator cocks and blow air through the cylinders to get all the water out. Then came the normal starting after shutting the indicatorcocks ,run the engine to some 100 rpm. by air before admitting fuel to the cylinders and ignition. It could take at least 3 minutes.
You question on maneuvering.
After 1942 I guess the GW VII Cs diesels were not direct reversible, the reversing mechanism was removed and the VII Cs were maneuvered by the E-motors only. Direct reversing of a diesel is slow, complicated (expensive), consumes air and is not necessary on a submarine. Most WW2 submarines were maneuvered by E motors. If this is not clear just put forward you questions.
Tore

[Don Prince]

Hello Mr. Tore,


If the crewman was using the wheel-claw tool to operate the gate-valve below deck, then in this instance the wheel-handles were present on the gate-valves.  Perhaps Simon's first drawing was correct after all...


Thanks for the answer about the Q tank missing hand-wheels...


Q tank question - the tank had its internal support structure modified with knee braces to provide support for external pressure.  However, this will not provide for increased internal pressure in the tanks.  This would be a good reason for monitoring the internal pressure of both Q tanks. 


I can think of only two reasons for Q tank to experience increased internal pressure of the magnitude required to burst the tank.


The mushroom valve at the bottom of Q tank were left open after an express.  Now, as the U-boat dives to a greater depth, the water pressure compresses the air in the tank and could causes the tank to burst.   I can see the same situation happening if the mushroom valve were leaking.  I don't believe the venting air pressure could ever cause this problem.


Diving question - as the U-boat goes to a greater depth the actual volume of the pressure hull decreases because of external pressure, and this changes the neutral buoyancy to a negative buoyancy.  Is anything done to adjust for the loss in buoyancy internally like pumping out water from Regulating tank 2?


Regards,
Don_

[SnakeDoc]

Don,

The mushroom valve at the bottom of Q tank were left open after an express.  Now, as the U-boat dives to a greater depth, the water pressure compresses the air in the tank and could causes the tank to burst.   I can see the same situation happening if the mushroom valve were leaking. 

This is not a case - when the flood valve of the negative buoyancy tank is left open or is not tight, the pressure inside the tank is always the same as outside - so there are no forces affecting the tank.

Diving question - as the U-boat goes to a greater depth the actual volume of the pressure hull decreases because of external pressure, and this changes the neutral buoyancy to a negative buoyancy.  Is anything done to adjust for the loss in buoyancy internally like pumping out water from Regulating tank 2?

     
181.  To proceed to great depths (more than 40 meters), the Engineering Officer gives the depth order and the depth changes in increments of 10 meters to all rooms verbally man to man.
         Because the boat loses volume at greater depth, it must be made lighter by timely pumping (for type VII boats approximately 1 ton per 100 meters).  It is appropriate to pump out a greater amount, because the boat will be heavier by the accumulating leak water anyway.

http://uboatarchive.net/DivingRegulations.htm

--
Regards
Maciek

[tore]

Don.
Maciek has answered your questions excellent. I can only add, apart from the depth, the variation in salinity and temperature influence the buoyancy of the boat as well. This can be significant fi. when you are submerged  in a fjord like the very deep Norwegian fjords particularly when the glaciers are melting and freshwater are in layers between the seawater can give you a bumpy ride. However you can compensate a lot by the hydroplanes, but in order to keep the margins you want to correct your buoyancy as much as possible.
Tore

[SnakeDoc]

Maciek has answered your questions excellent. I can only add, apart from the depth, the variation in salinity and temperature influence the buoyancy of the boat as well. This can be significant fi. when you are submerged  in a fjord like the very deep Norwegian fjords particularly when the glaciers are melting and freshwater are in layers between the seawater can give you a bumpy ride. However you can compensate a lot by the hydroplanes, but in order to keep the margins you want to correct your buoyancy as much as possible.

I would add to Tore statement, that although air compressed in the tanks is harmless to the boat construction, but it is highly undesirable due to volume changes along with depth, which results in the changes of buoyancy.
That's why the residual vent of the ballast tank 2 is so important, and that's why, the Germans had special maneuver after submergning the boat - so called durchpendeln. That means slightly trim the boat bow and aft, to remove residual air from ballast tank 1 and 5.

81.  If the flooding maneuver runs normally, the order follows:
         Commander:  "Bring boat to x tons positive buoyancy and put in balance".
         Engineering officer repeats the order.
     
         The boat is brought to a positive buoyancy of approximately 2 tons by flooding the regulating tanks on the orders of the Engineering Officer initially without consideration of the trim.  Now the boat becomes sensitive in longitudinal stability and is oscillated by means of small trim adjustments to purge the residual air from the ballast tanks.
     
         The boat is brought to the ordered buoyancy by further flooding the regulating tanks.  From 2 tons of positive buoyancy the Engineering Officer continually reports decreases in the remaining buoyancy.

http://uboatarchive.net/DivingRegulations.htm

--
Regards
Maciek

[VIC20]

The starting procedure after surfacing was a bit cumbersome, you wanted to get the engine ready as soon as possible in order to exhaustblow the ballasttanks as you was semisurfaced and the  boat was in an unstable position. However you had always some seawater leakages in the exhaust system and some time these leakages could even fill the cylinders. In order to prevent waterstroke, you opened up all the indicator cocks and blow air through the cylinders to get all the water out. Then came the normal starting after shutting the indicatorcocks ,run the engine to some 100 rpm. by air before admitting fuel to the cylinders and ignition. It could take at least 3 minutes.
You question on maneuvering.
After 1942 I guess the GW VII Cs diesels were not direct reversible, the reversing mechanism was removed and the VII Cs were maneuvered by the E-motors only. Direct reversing of a diesel is slow, complicated (expensive), consumes air and is not necessary on a submarine. Most WW2 submarines were maneuvered by E motors. If this is not clear just put forward you questions.
Tore

Thank you! Those two facts are completely new to me.


After surfacing in a dangerous war situation would they have taken the risk to start the engines without blowing possible water out of the engines first?
(OK, I just have to think what kind of situation this could be… possibly makes no sense at all, the only reason to surface while being in range of enemy vessels would be to show the white flag)
I guess the U-Boat can run on E-Machines during this procedure? (or isn't that a good idea without blowing ballast tanks first?)


Then I'll will allow usage of reversed diesel in the game only if the E-Machines are damaged.

I guess you could engaged the clutch at 350 revs, but the wear and tear increases with the speed and inertia forces so we usually started with the clutch engaged.

This makes sense with the information of the seawater leakage in the exhaust system after surfacing. And I think that also means usually E-Machines were shut off until the ballast tanks were blown? Otherwise the shaft would still run at something close to 290 RPM when the diesel is clutched in which is basically the same stress on the clutch just flipped.
So you switched from diesel to electric but usually avoided to switch from electric to diesel while running?






 

[tore]

Mark.
We had our ways and means if a quick start was important, in peacetime f.i.heavy weather. It would take an experienced engineer. Before blowing the tanks (by air)and the mainclutch was still disengaged, running on E motors, you opened the indicator cocks to drain as much water as possible, then carefully admitted air ( low pressure) to the cylinders turning the engine very,very slow to blow out the water all prior to surfacing, then you started the engine as soon as the diesel air inletvalve opened. The procedure would  create some overpressure in the boat and required a very experienced crew for correct timing.  You normally used the E-motors all the time to keep the boat into correct position while exhaustblowing the tanks. When the tanks were fully blown you reduced the E-motor revs and engaged the main clutch and run on diesel.  I think nobody would take the risk of starting the engine without a watercheck as a waterstroke would damage the engine beyond searepair.
Tore

[tore]

Mark.
If you allow the usage of a reversible diesel in your games the relevant boat has to be one of the pre 1943 types, you clearly see the difference of the engine as the direct reversible engine has a dominating vertical reversingcylinder at the maneuvering place forward of the engine see photo.
Tore

[VIC20]

Thanks Tore, it's an early VIIC in the first version of the game.

[SnakeDoc]

To complete Tore's detailed explanations - the German war-time description of G.W. Diesel engines gives following data:
fuel consumption during stationary trials:
overload (1/2 hour), 1612 HP, 494 RPM, 195,5 g/bhp
overload (2 hour), 1515 HP, 486 RPM, 190,2 g/bhp
full load, 1400 HP, 470 RPM, 190 g/bhp
3/4 load 1056 HP, 429 RPM, 187,4 g/bhp
1/2 load without blower, 702 HP, 375 RPM, 182,3 g/bhp
1/4 load without blower, 350 HP, 298 RPM, 197,5 g/bhp

standard revolutions: 470 RPM
highest revolutions: 515 RPM
lowest revolutions (with blower): 130 RPM
lowest revolutions (without blower): 100 RPM

--
Regards
Maciek

[VIC20]

Thanks,    I've just realized you are the one who translated the Type VII manual on Jerry's website to english and Don Prince seems to be the one who had the german original copy.


Any chance that I could I get a copy of the german original? It would be easier to read for me.


I'm currently a bit confused about the engine telegraph and correspondending RPM. Tore said they usual were operating on 460 RPM.
The manual says:



KF = 180.0
LF = 275.0
HF = 340.0
2xHF = 396.0
GF = 435.0
AK = 471.0
3xAK = 480.0


The british report on U570 wrote:



KF = 161.0
LF = 263.0
HF = 310.0
2xHF = 404.0
GF = 469.0
AK = 485.0


Any idea what's the reason for the difference?

[VIC20]

full load, 1400 HP, 470 RPM, 190 g/bhp

hehe, my confusion rises…

The 1400 HP at full load should be shaft horsepower (manual says 1400 SHP, 470 RPM at full load) but the fuel consumption is gramm per brake horsepower.
The manual says fuel consumption of the G.W. is 254 kg/h at full load (470 RPM, 1400 SHP) which is 0.181 gramm per SHP
I think consumption per bhp should be lower than per shp which makes the difference even worse. But actually I have no idea.

[Don Prince]

Hi Maciek,


Newton and Bernoulle and a bunch of other dead people would be ashamed of me because I ignored what my High School physics teacher (Marist Brother Matthew) taught me 55 years ago...  I was just in such a hurry to get that darn Q tank to burst and ignored the basic fluid mechanics that I had known for years...


Again, thanks for the physics re-fresher course...


Don_


PS - If anybody is doing he the math, I will be 73 on June 3rd

[tore]

Mark.
Reverting to my notes on waterleakages in the exhaust system I would emphasize filling the cylinders was really exceptional and has happen to me once, nevertheless the blow thru with open indicators was a routine after being submerged.
 Tore

[VIC20]

Mark.
Reverting to my notes on waterleakages in the exhaust system I would emphasize filling the cylinders was really exceptional and has happen to me once, nevertheless the blow thru with open indicators was a routine after being submerged.
 Tore

OK 


I've just found a website which says bhp and shp is identical? Is that true?

[tore]

Maciek, Mark.
Fuelconsumption, output.
The BHP is referring to the output measured at the enginemanufacturers testbed under controlled environment. BHP stand for Brake Horse Power and is referring to the testbed calibrated waterbrake which brakes the engine at various rpm in order to put up an output graph for the buyers approval according to the contract output. The other output designations like shp, is less accurate and I assume could be measured by a torque meter on the shaft at various places the output will then vary fi. if you have a liquid coupling after the engine and take readings after the thrustbearing, gearboxes etc. thus less specific designation.
Fuelconsumption is likewise measured on the testbed in close connection with the waterbrake for accurate output readings, temperature, barometric pressure etc. Then the most important detail, the reference fuel. Dieselfuel is not an accurate specification as you have many variations and I guess during WW2 it was a difference between the German diesel fuel and to days prime diesel quality called gasoil. For consumption measurement the lower calorific value is the most important, it can vary considerably like 42.000 MJ/kg to over 44.000 MJ/kg. So if you want to compare apples don't`introduce pears. So I assume without knowing the lower calorific value of the reference fuel you cannot compare the various fuel consumption figures.

[tore]

Mark.
Deviation on the engine telegraphs rpm.
We never used the engine telegraph designation and corresponding rpm which are put up in the lists you are referring to. I believe it is strange to have stages as 396 and 471 rpm. It looks to me as composed by somebody behind a writingdesk. Whatever order was given, you adjusted the engines to an approximate rpm level and the governor kept the engine at that level plus minus 3-5 rpm. We did not use these accurate figures as this was not a science issue. The CO passed on messages verbally if some unusual outputs would be necessary.
Tore   

[SnakeDoc]

Hi Mark,

full load, 1400 HP, 470 RPM, 190 g/bhp

hehe, my confusion rises…

The 1400 HP at full load should be shaft horsepower (manual says 1400 SHP, 470 RPM at full load) but the fuel consumption is gramm per brake horsepower.
The manual says fuel consumption of the G.W. is 254 kg/h at full load (470 RPM, 1400 SHP) which is 0.181 gramm per SHP
I think consumption per bhp should be lower than per shp which makes the difference even worse. But actually I have no idea.

it seems, that in the manual (that is U-Bootskunde fur U-Boote Bauart VIIC available on the uboatarchive.net) are given rounded values of the power
(1600 against 11612, 1515 against 1500 and 1400). I think, that rounded values are given for practical reasons, as the accurate value were measured
using waterbrake under test conditions (as Tore explained).

I have one note - in the original German documents, the power is nominated in the PSe units, that is equivalent of bhp. I was mistaken, translating it to the SHP as on the uboatarchive.net.

In hurry, I have given fuel consumption in the g/bhp, while in the original documents is given as g/PSe/h. I have attached the scan of the data table.
As a bonus - chart of the power and fuel consumption in the relation with the RPM.

--
Regards
Maciek

[SnakeDoc]

There are different battery chargingloads, starting by not cruising, only charging at very high loads when your batteries were low and very light, just topping up the batteries. As far as I remember the rpm varied with the load I can`t remember the revs. When cruising you put the chargingload according to the requirement of the speed and the timeneed for getting batteries fully charged ,up to the decision of the CO.

The RPM loss while charging you can roughly estimate using these documents. They are valid for cruising submerged (while snorkeling), but I do not have nothing better.

http://www.ubootwaffe.pl/images/okrety/instrukcje/chrapy/preliminary_snorkel_description1.jpg
http://www.ubootwaffe.pl/images/okrety/instrukcje/chrapy/preliminary_snorkel_description2.jpg

The starting procedure after surfacing was a bit cumbersome, you wanted to get the engine ready as soon as possible in order to exhaustblow the ballasttanks as you was semisurfaced and the  boat was in an unstable position. However you had always some seawater leakages in the exhaust system and some time these leakages could even fill the cylinders. In order to prevent waterstroke, you opened up all the indicator cocks and blow air through the cylinders to get all the water out. Then came the normal starting after shutting the indicatorcocks ,run the engine to some 100 rpm. by air before admitting fuel to the cylinders and ignition. It could take at least 3 minutes.

After surfacing in a dangerous war situation would they have taken the risk to start the engines without blowing possible water out of the engines first?
(OK, I just have to think what kind of situation this could be… possibly makes no sense at all, the only reason to surface while being in range of enemy vessels would be to show the white flag)
I guess the U-Boat can run on E-Machines during this procedure? (or isn't that a good idea without blowing ballast tanks first?)


Then I'll will allow usage of reversed diesel in the game only if the E-Machines are damaged.

I guess you could engaged the clutch at 350 revs, but the wear and tear increases with the speed and inertia forces so we usually started with the clutch engaged.

This makes sense with the information of the seawater leakage in the exhaust system after surfacing. And I think that also means usually E-Machines were shut off until the ballast tanks were blown? Otherwise the shaft would still run at something close to 290 RPM when the diesel is clutched in which is basically the same stress on the clutch just flipped.
So you switched from diesel to electric but usually avoided to switch from electric to diesel while running?

For the surfacing procedure (including exhaust diesel blowing) you can read here:
http://uboatarchive.net/DivingRegulations.htm
The corresponding paragraphs - 201 - 221 and 306 - 312.

--
Regards
Maciek

[VIC20]

Mark.
Deviation on the engine telegraphs rpm.
We never used the engine telegraph designation and corresponding rpm which are put up in the lists you are referring to. I believe it is strange to have stages as 396 and 471 rpm. It looks to me as composed by somebody behind a writingdesk. Whatever order was given, you adjusted the engines to an approximate rpm level and the governor kept the engine at that level plus minus 3-5 rpm. We did not use these accurate figures as this was not a science issue. The CO passed on messages verbally if some unusual outputs would be necessary.
Tore

That's extremely important info! 

[VIC20]

I have one note - in the original German documents, the power is nominated in the PSe units, that is equivalent of bhp. I was mistaken, translating it to the SHP as on the uboatarchive.net.

In hurry, I have given fuel consumption in the g/bhp, while in the original documents is given as g/PSe/h. I have attached the scan of the data table.
As a bonus - chart of the power and fuel consumption in the relation with the RPM.

That's exactly the kind of data that I need :-) I've made a crude interpolation from some data of the 9 cylinder machine of the IX before (which has same bore & stroke)


PSe (effektive Pferdestärke) is the power measured at the shaft of an engine (before the gears of a car) - wikipedia says PSe is like WPS (Wellen-PS) which is equal to SHP. After seeing this website I believe SHP and bhp are really the same http://www.engineeringtoolbox.com/horsepower-d_472.html
So I think you've made no mistake in your translation (but I gave up to study machine engineering after 3 days so I could be wrong and anything from the wiki is… well, we all know what I mean) also the whole PS thing is completely outdated so it's hard to google for it.


Your document with the graph seems to show PSe with auxiliary engines clutched in (angekuppelte Hilfsmaschinen) - the other document that is just a table is different and shows PSe without auxiliary engines.
You can also see that from the results - best to see at 375 RPM which is at 701 PSe on the table and at something like 715 PSe on the graph (both with supercharger).
It's great to have both because this could possibly make it easier for me to calculate the engine.
Where do you got those documents from?

[VIC20]

Tore, do you remember the impact of good and bad speeds (like hump and hollow in regard to the Froude number)? The slender shape of the hull combined with saddle tanks is pretty unusual. Do you remember if the resistance was clearly higher at bad Froude numbers so that you avoided those speeds?

[SG]

So if you want to compare apples don't`introduce pears.

 

[Don Prince]

Ruptured Negative Buoyancy Tanks (Q tank)
Let me try and make a fool of myself again...




http://www.uboatarchive.net/DivingRegulations.htm


33.  The pressure difference meters are to be monitored, particularly during expressing (danger of rupture with closed flood valve) and when the boat rises.  More than 2 atmospheres higher than outboard pressure is prohibited and must be equalized.[size=78%] [/size]
Equalization takes place after previous request to the Engineering Officer (for passing on to the conning tower) by complete opening of the "Vent negative buoyancy tank" valve, appropriately up to an internal pressure of 1.5 atmospheres (external pressure at periscope depth).


I can see two ways to rupture the Q tanks and the key element is the flood valve:
1.  Fail to close the Flood Valve until at depth
2.  Expressing at depth and then close the flood valve


Instance #1 - After expressing at 10 meters and failing to close the flood valve (bottom mushroom valve) will result in the Q tank's air being compressed.  This is not a problem for the tank at this point because the internal and external pressure are the same.  However, If the crewman closes the flood valve at 100 meters, now we have a problem!  As the boat rise with the closed flood valve, the outside pressure will decrease and the high internal pressure will stress the tank structure which was braced for external pressure.


Instance #2 - expressing the Q Tanks at a depth of 100 meters instead of 10 meters.  Again this is not a problem (same reason as above).  However, if the crewman closes the flood valve after expressing at depth, now we have same scenario with the compressed air in the Q tanks.  As the boat rises with the flood valve closed and decreasing external pressure, it is likely that the Q tanks will be ruptured because of the high internal pressure.


I sure hope I got it right this time...  If not, then I'll need another post high school lesson from Professor Maciek.


The manual says to monitor the pressure difference meter.  I assume that is the meter very close to the Q tank top vent valve (black and red wheel-handle).  Does this meter have a input line going to the inside top area of the Q tank, and a second input could be just a hole in the back of the meter to sample the internal hull pressure.


Regards,
Don_

[tore]

 Mark.
I cannot remember we had any problem which could be related to the Froude number. We had a small problem more related to revs of the shafting than the speed of the vessel. When running on E-motors we had no problem. Diesel running could create a minor problem as you had a complex shaftingsystem having masses at different length from the engine, like in/out of propellers and in and out of E-motors, thus you got different torsional vibration patterns creating stresses in the shafting, further I assume we got certain free moments which could excite hullvibrations. I wouldn`t say they created problems. The latter could anyhow be avoided by passsing the revs area quickly. The torsional vibrations in the shafting were diffcult to discover as no torsional meter was installed, however the engines were equipped with torsional vibrationdampers up front, but I doubt if that took care of all situations. I have seen a few photos of VIIC shafts breakages which clearly was due to torsional vibration stresses, but if these engines had been equipped with a torsional vibrationdamper I cannot tell. I personally believe the most serious rpm related problem would be pitting of the propeller. The late war VIICs were equipped with  special cast steelpropellers. At the root of the propellerblades we had serious pittings due to cavitation. Cavitation is a noise problem as well , however we never figured out which revs should be avoided. Sorry this may be a bit off the topics.
Tore

[tore]

Don.
I am not sure if your man violating every rule for operating theQ and common knowledge for a submariner would have a long career in the submarine service, using the Q as a compressor . However somehow the designers have taken such people into consideration. As we discussed previously each Q is fitted with a reliefvalve as well as differential manometers both are not shown on the pipediagram nor mention in the manuals I believe. The diff man is most probably connected to a common seapipe having direct connection to the sea on port side, serving the diff.manometers for the regulating tanks (4) and the Qs (2). The other pipes to the diff man. goes to each different tank, the pressure inside the submarine is irrelevant in this case it is  the  difference in pressure inside the Q and the sea which should be shown on the diffmanometer. When the inside pressure of the Q tanks exceed a safe level, the reliefvalve opens and the Q tank pressure is released, see photo below. This has happened not on my boat, but on another in my time. I guess your man would probably be offered a job as potatopeeler on the shore  submarinestation.
Tore

[VIC20]

BTW:

Tore, I know it's not perfect (and by far not as detailed as Simon's awesome drawings),
also it's still untextured and some stuff still missing…
and remember it's just for a mobile game.

What do you think of my command room model? 

[VIC20]

[tore]

Mark.
 I am impressed, very clean and easy to see the essentials. As you say some details are missing, but I guess you have everything necessary for the game-. I guess it is one of the earlier VIICs as you have not put in the schnorchel handle, however the radarmast is in place. I am not sure when same was fitted, Simon or Maciek would know.
Well done mark.
Tore

[VIC20]

Yes early VIIC but some things aren't like early VIIC, Simon showed me some things that won't belong there for early boats when I already had finished them. So actually I gave up on trying to make a command room for an early boat and will start the game with some generic interior. I have no idea what most of the things are anyway, I guess the radar mast is this one? If so then it does not belong to the boat the player will be able to use    …but well if someone asks then I can call this an early experimental totally secret upgrade for the boat which is currently not working 

[SnakeDoc]

Hi Mark,
well done -  very nice of model of control room.

Yes early VIIC but some things aren't like early VIIC, Simon showed me some things that won't belong there for early boats when I already had finished them. So actually I gave up on trying to make a command room for an early boat and will start the game with some generic interior. I have no idea what most of the things are anyway, I guess the radar mast is this one? If so then it does not belong to the boat the player will be able to use    …but well if someone asks then I can call this an early experimental totally secret upgrade for the boat which is currently not working 

Radar FuMO 30 entered the service in 1943. More informations you will find here:
http://www.ubootwaffe.pl/en/u-boats/equipment/radar-of-german-u-boats
Besides the mast, you will have to remove the electronic equipment box located between the navigator table and forward bulkhead of control room.


One interesting (but little known) detail would be the refrigerator unit, which consisted of two parts -  food chamber located in the forward part of the petty's officers room, in the stb corner (just behind the control room bulkhead) and the compressor unit , which was located in the control room - over the trim and drain manifold.
On U-995, in this place is some kind of metal basket, and in the petty's officers room is quite modern fridge.
Tore, do you remember, if the KMN Kaura was ever equipped with German refrigerator unit?


--
Regards
Maciek

[VIC20]

Radar FuMO 30 entered the service in 1943. More informations you will find here:
http://www.ubootwaffe.pl/en/u-boats/equipment/radar-of-german-u-boats
Besides the mast, you will have to remove the electronic equipment box located between the navigator table and forward bulkhead of control room.

It just takes way to much time to create the whole boat interior (for my first version), so I will go with the incorrect upgraded command room and with command room only in this version. I just had no good reference pictures of what was installed at the place of the FuMO30 before.  It's hard to find pictures of the older interiors.
And I guess the FuMO30 requires a newer conning tower… First version will be a reduced sim anyway - the later full version will support different U-Boat upgrades.


I'm already working on the game since 5 years and need to release or the people who are already waiting to play it will kill me one day   

[Don Prince]

This web site seems to have a good deal of information on the different HP ratings for ships...


http://www.scribd.com/doc/7174460/Basics-of-Ship-Resistance


Regards,
Don_

[Don Prince]

Hello Mr. Tore,


Thank you for the information on the pressure difference meter; it makes sense to compare the external sea water pressure against the Q tank internal pressure.


Besides my crewman who should be pealing potatoes on shore...  Are there  other ways to cause over pressure in the Q tank.  In any instance, it looks like the flood valve has to be closed.  Note*  I have been reading some articles and there looked to be quite a few problems with the Q tank flood valves leaking... 


I understand that there needs to be an automatic vent valve which will release gasses over a set pressure point.  At first it was hard to believe that the small relief valve and what looked to be a 3/8 inch line was large enough to handle the volume and pressure.  Especially when comparing it to the size if the pipe coming from Q tank to vent air into the hull through muffler.  That one looks to be about two inches in diameter.


Then. I guess reality sets in...  Q tank is 2 M3 on each side oh the U-boat.  Each side is equal to 70.6 FT3, or a little over 3 times the size of my 26 FT3 home refrigerator;  Q tank is NOT that darn big to begin with!  Both thanks combined only provide 4 metric tons of negative buoyancy.


The Type VIIC U-boat displaces 769 tons on the surface and 871 tons submerged...  It's amazing how much difference that 4 tons makes...


I apologize for all the trouble; I'm like a dog with a new chew toy and won't let go until I understand it!


Kind Regards,
Don_

[tore]

 Maciek.
Yes  I believe we had the german fridge. The door was right opposite to the officers and CPOs heads.
Tore

[tore]

Don.
The reliefvalve is not an automatic inboard vent and is not dimensioned as such, it is a reliefvalve which releases the max pressure and give a warning that something is wrong, more like a manometer pointing to the red part of the scale, telling you have to act immediately.
Volume of Q. I believe you should look into the way Q is meant to work, it is rather a help to get thru the surface in the first stage. When  you boat is on surface in areas where a crashdive could be necessary the tank is full,  ventvalve shut and floodvalve open. At the crashdive command you are app 4 tonnes heavier than normal, believe me for a submarine  it is substantial. Strange enough it is a certain inertia to get down thru the surface before the hydroplanes takes over, that`s where the Q helps. As soon as you have been thru that part, the hydroplanes and propeller takes completely over and are substantial more powerfull than Q. Then Q is not needed anymore and you should blow Q. This is usually at app. 10 meters for a VIIC I believe. Blowing at greater depth is waste of air and should be avoided apart from emergencies. Submerged the submarine is controlled by hydroplanes rudders and propellers and the submarine has the normal neutral buoyancy with Q empty. We never experience a leaking Q floodvalve.
Tore

[SnakeDoc]

Mark,

Radar FuMO 30 entered the service in 1943. More informations you will find here:
http://www.ubootwaffe.pl/en/u-boats/equipment/radar-of-german-u-boats
Besides the mast, you will have to remove the electronic equipment box located between the navigator table and forward bulkhead of control room.

It just takes way to much time to create the whole boat interior (for my first version), so I will go with the incorrect upgraded command room and with command room only in this version. I just had no good reference pictures of what was installed at the place of the FuMO30 before.  It's hard to find pictures of the older interiors.
And I guess the FuMO30 requires a newer conning tower… First version will be a reduced sim anyway - the later full version will support different U-Boat upgrades.


I'm already working on the game since 5 years and need to release or the people who are already waiting to play it will kill me one day   

Well, great work anyway. I'm also waiting for the release
Have you created all compartments? Could you paste some screen-shots?
What kind of software are you using?

--
Regads
Maciek

[VIC20]

Have you created all compartments? Could you paste some screen-shots?

No, only the command room. I want to build the whole interior for the later full version of the game which will also include at least Type IX. It just takes way too much time to build it. The main problem is there are no drawings that are of any use to build each tiny thing and when you build some parts too large or too small the whole then the whole thing won't fit at another position. It would be much easier to take a laptop and to build it while being inside U995 ;-)

This web site seems to have a good deal of information on the different HP ratings for ships...
http://www.scribd.com/doc/7174460/Basics-of-Ship-Resistance

Can't count the number of website about this stuff that I've visited during the last 3 weeks …but actually haven't seen this one before which is pretty amazing for me because I thought I've seen all the PDFs now     This is the first one that explains BHP and SHP in a good way






Tore, I guess you usually haven't accelerated the boat fast because of the fixed propeller pitch but what do you estimate would be a realistically looking time of acceleration to different (standard) speeds of the boat in seconds?

You said you could accelerate the declutched engine from 0 to 350 RPM in 3-4 seconds. Currently my simulated engine can go to 350 RPM in 7-8 seconds with propeller (ignoring the boats speed, like being fixed somehow)

Another thing I haven't understood yet   is the use of the supercharger. I still don't get if it was used below 390 RPM at all (once it was clutched in above 390 RPM)


Related to this: the document Maciek posted shows two RPM/Horsepower lines which would only make sense if the charger can be used below 390 RPM but even then it makes no sense because the manual says above 410 (or 420?) the engine can't be used without the supercharger. Can someone explain the two lines? My guess is it's just a theoretical interpolation for each line.
The fuel consumption shown makes sense to me as it does not show fuel consumption for RPMs of the uncharged engine above 420 and RPMs for the charged engine below 420.


I sometimes need more time to understand this stuff, my only real life experience with engines is a lawn mover and even this is 20 years ago. (I have no car, no driving license etc.)

[tore]

Mark.
I have not any figures on the acceleration subject so it has to be guesswork, may be Maciek has some. Anyhow as you rightly stated the VIICs have  fixed propellers, as such it has bad efficiency in some ranges. If the vessel is at 0 speed and should increase to say 17 knots, you start the engines and stir up a lot of water for the first 100 m. Then the propellers gradually improves and you increase the revs to max. and you might achieve 17 knots at some 300 m. So  a guesstimate of 400m to obtain full speed of 17 knots. Which means an acceleration from 0 to 17 knots or app 31,2 km/hours over 400m. This is a pure guesswork from my side and take it for that.
Your simulation of an engineacceleration 0-350 rpm on 7-8 seconds seems not to bad to me with all the components connected.
Roots blower.
I believe the Roots blower is not an ordinary supercharger but rather a booster which is needed for getting extra max. output. The difference being as an ordinary turbo supercharger takes the thermal waste energy from the exhaustgases and thus improve both the output and fuelconsumption, the Roots blower require energy which is taken directly from the engine via the camshaft drive. Thus it takes a higher specific fuelconsumption to boost the engines, but it was at that time a common way to get more output of the engines. MAN submarine engines had a first generation turbocharger called the Buchi system and utilized the thermal energy of the exhaustgases.
 Thus you did not want to run the Roots blower unnecessary as it took energy from the engines. The GW engines operated as normal aspirated engines up to 390- 400 rpm I Guess, then you had to make use of the Roots blowers to get more output. At lower revs like below 390 the blower did not contribute anything in fact it took only energy from the engines for doing nothing, moreover it is not an advantage to have two big rotating weights connected to the camshaft drive wear and tear, torsional vibration. etc. So it was definitely disconnected at lower revs like 390 rpm.
Tore

[VIC20]

Within 400 meters? Wow that seems fast. I'm upgrading the "engine" to the new data from Maciek's documents and I'm thrilled to see if my simulation automatically matches that later.

Your simulation of an engineacceleration 0-350 rpm on 7-8 seconds seems not to bad to me with all the components connected.

It's the result of an idealized calculation, I feared it would be too fast. "seems not to bad to me" is great because all I want to achieve is something that looks convincing at the end


Doh! I forgot that U 995 has the MAN engine.


BTW what about the basic colors? Are they correct in U995 today?
My current color setup looks like this:

[tore]

Mark.
Remember it is guesswork, having said that, the VIICs were reasonably fast on the surface compared to other conventional submarines as they had fairly high dieselengine output,for the tonnage. wolfpack tactic. Submerged, the speed wasn`t that great.
U 995 engine. I am afraid you have misunderstood me,  the U 995 has Krupp Germaniawerft engines and as such Roots blower. I Guess the white colours are OK however on the Laboe U 995 people have gone mad with red paint and practically every cock and switch has been painted red, it looks as if she got the measles. Don't forget they have put up fluorescentic lights for the visitors, the lightings were not that bright.
Tore

[tore]

I have been thinking on yesterdays acceleration estimates  and believe an increase in speed from 0 to 17 knots over 400 meters could be a bit too much, you should probably give it another 100- 150 meter thus the speedincrease over 500 to 550 meters. Still it is a guesstimate.
Tore

[VIC20]

Thanks again, still some steps to do here till I can test the acceleration speed.

[SnakeDoc]

Hi Gentlemen,

As the blowerclutch, the engineclutch was a double cone frictionclutch, the difference being the size and it was pneumatic/hydraulic operated. I guess you could engaged the clutch at 350 revs, but the wear and tear increases with the speed and inertia forces so we usually started with the clutch engaged. Engaging the clutch at relatively high speed created a lot of smoke allthough nobody knew about the asbestos danger, the smoke could be unpleasant in a confined space.

 Operating instructions state that the clutches should not be engaged when turning the shaft above 350 RPM.  They may be disengaged at any RPM.

The torsional vibrations in the shafting were diffcult to discover as no torsional meter was installed, however the engines were equipped with torsional vibrationdampers up front, but I doubt if that took care of all situations. I have seen a few photos of VIIC shafts breakages which clearly was due to torsional vibration stresses, but if these engines had been equipped with a torsional vibrationdamper I cannot tell.

The GW engines produced strong torsional vibrations in the crank shafts in the following RPM ranges: 260-290 and 360-450. The vibration dampers reduced them almost completely. The operating instructions say, that in case of damper failure, it must be removed (contrary to the MAN dampers, those in case of damage don't have to be removed) and the critical RPMs have to be passed over.

Some of the U-Boats were equipped with the Diesel Engine Torsional Vibration Indicator System. For the details see:
http://uboatarchive.net/DesignStudiesTypeIXC.htm
section S65, page 30.

--
Regards
Maciek

[tore]

Maciek.
It is always good to have a statement confirmed, you are an expert for finding written confirmations. The torsional vibration dampers varies in design, as your info on the GW and MAN engines mention. One is f.i.  mechanical, the other is hydraulical. I believe for the earlier boats they had a torsional vibration meter fitted. I cannot remember we had any. In the 1930 years it was not common to carry out relative complex torsional vibrations calculations for shaft systems, so I guess you had a torsionalmeter to monitor same. But as I said, there have been VIIC shaftbreakages due to torsional vibration stresses and may be they started to make more complex  torsional vibration calculations after that and installed a better tailormade vibration damper at a later stage. Just a theory from my side. The Rooths blower created torsional vibration as well and the drive had another mechanical vibration damper. After the war torsional vibration calculations became mandatory for all seagoing vessels and has to be submitted to the classification societies for approval. The barred rpm range varied considerably between a 6 cylinder and a 9 cylinder engine (IXC) as well as to which inertia masses you connected E-motors propeller etc. so you can not put up rpm valid for more than one cylinder- and mass configuration.
You mainclutch operatings instruction fit very well with my experience, but I would`t like to use 350 rpm as a standard. The wear would require frequent adjustments and even renewal of the friction layer.

[VIC20]

Just out of interest, what type of torpedoes have you used with Kaura?

[tore]

Mark
Torpedoes were a bit far away from my responsibility so I am afraid I cannot give you much info. We were training on using the LUT torpedoes but as the Germans had stored and left a huge amount of the ordinary "workhorse" torpedoes in  Norway, I believe some 1200, we were put up for using those. I cannot remember the the type no. I believe Maciek knows more on this than I do.
Tore

[Don Prince]

Hello Mr. Tore,


On Plate 17 there is a valve with a "T" as normal, and a line with a bubble in the end of it.  I can not find this valve in the symbol page?  Can you identify this valve and how it functions?


Photo attached....


Regards,
Don_

[tore]

Don.
I cannot remember the symbol so I have to try to figure out. The valve you have marked is the air blow stopvalve for the regulating tank 2 port. stb has the same. These  stopvalves are used for all the MBTs but then the housing contains a checkvalve as well.  Below is a photo of airblow hull stopvalve MBT 4 stb. For the regulating tanks I guess they look similar except the checkvalve is removed. I assume these valves  should be able to be locked open so may be the symbol indicate a lockingdevice.

[SnakeDoc]

Hi Gentlemen,


according to the Technisches Hilfsbuch für den Gebrauch in der Krietsmarine, this is symbol means plombierte Ventile, that is sealed valve. I must admit, that I don't understand, why sealing hull valve for blowing regulating tank. In case of Tauchbunker it is obvious - to prevent accidental blowing the fuel. It should be the same case for the regulating and reserve fuel tank 1 - but it is not.


--
Regards
Maciek

[tore]

Maciek.
I guess plombiert could mean the valve is locked in a position f.i. either open or shut. The valve arrangement is not only fitted on fuel ballasttanks but on several tanks having a blowing arrangement including MBT 3. I believe normally the ballast tanks blow valves were in a locked open position, for those to be carrying fuels the valves were locked in shut position in both cases the plombierung means locked in the position required. For reliefvalves f.i. we very often use the expression plombiert which actually mean putting a lead seal on the lock to the valve to ensure no unauthorized person change it. The authorized person can brake the seal and adjust the valve to any value. I don`t think the VIIC valves had a lead seal,  though but an ordinary lockingdevice to prevent any accidental change.
Tore

[VIC20]

A "plombiertes Ventil" should be a safety valve.


In Abhängigkeit von der Federauslegung kann der Ansprechdruck von Sicherheitsventilen in einem gewissen Bereich eingestellt werden. Der vorgegebene Ansprechdruck wird erreicht, indem über einen Gewindeeinsatz die Federvorspannung beeinflusst wird. Die Stellung der Vorspannung wird z. B. über eine Kontermutter gegen Lockern gesichert. Die Einstellverschraubung wird mit einer Haube verschlossen. Als Maßnahme gegen unbefugte Änderung der Einstellung wird diese Haube mit einer Plombe gesichert.

[tore]

Mark
Exactly!
Tore

[VIC20]

Currently my calculation gives a thrust force of 20,001.42 lbs (88,970.75 N) for a single propeller of the Type VII at 470 RPM, 1400HP and 17.7kn - does that sound OK?

[SnakeDoc]

Hi,

A "plombiertes Ventil" should be a safety valve.


In Abhängigkeit von der Federauslegung kann der Ansprechdruck von Sicherheitsventilen in einem gewissen Bereich eingestellt werden. Der vorgegebene Ansprechdruck wird erreicht, indem über einen Gewindeeinsatz die Federvorspannung beeinflusst wird. Die Stellung der Vorspannung wird z. B. über eine Kontermutter gegen Lockern gesichert. Die Einstellverschraubung wird mit einer Haube verschlossen. Als Maßnahme gegen unbefugte Änderung der Einstellung wird diese Haube mit einer Plombe gesichert.

Not any valve, secured with the seal? This part of text from Wikipedia describes (in my opinion) safety valve, whose overpressure setting is secured with the seal agaist accidental change.
--
Regards
Maciek

[SnakeDoc]

Currently my calculation gives a thrust force of 20,001.42 lbs (88,970.75 N) for a single propeller of the Type VII at 470 RPM, 1400HP and 17.7kn - does that sound OK?

Each main thrust bearing can transfer up to 10,000 kg (22046 lbs) of thrust. So it looks ok.


--
Regards
Maciek

[VIC20]

This part of text from Wikipedia describes (in my opinion) safety valve, whose overpressure setting is secured with the seal agaist accidental change.

Yes, that's what it describes. Sure, any valve could be sealed.

[VIC20]

Currently my calculation gives a thrust force of 20,001.42 lbs (88,970.75 N) for a single propeller of the Type VII at 470 RPM, 1400HP and 17.7kn - does that sound OK?

Each main thrust bearing can transfer up to 10,000 kg (22046 lbs) of thrust. So it looks ok.


--
Regards
Maciek

Thanks, this whole ship propulsion stuff is a lot like the thing with the chicken and the egg. Each time you find a way to calculate something you find out that you need another thing that might need the other etc. 

[SnakeDoc]

Currently my calculation gives a thrust force of 20,001.42 lbs (88,970.75 N) for a single propeller of the Type VII at 470 RPM, 1400HP and 17.7kn - does that sound OK?

Each main thrust bearing can transfer up to 10,000 kg (22046 lbs) of thrust. So it looks ok.

Thanks, this whole ship propulsion stuff is a lot like the thing with the chicken and the egg. Each time you find a way to calculate something you find out that you need another thing that might need the other etc. 

Can you briefly describe, how you calculated thrust force?


--
Regards
Maciek

[VIC20]

Can you briefly describe, how you calculated thrust force?

There are several ways that I've found how to do it… and I am not happy with any of them    - I'm searching since weeks for this stuff but haven't found anything better so far.


The most primitive is just a rule of thumb used by normal boat users:
For a good propeller the rule of thumb is:
HP * 20 = Thrust in LBS
would be:
1400 * 20 = 28000 lbs


well… I guess it's clear that this is nonsense


Next thing is the "pullard boll" (boat/propeller is fixed in the water and does not move)


thrust = 11.87 * (SHP * DiameterOfThePropellerInInches)^0.67 (power of 0.67)
would be:
11.87 * (1400 * 63.779527559124)^0.67 = 24631 lbs


Next estimation is (SI units):
(BrakePower * 0.5) / BoatSpeed*0.95    (0.5 is estimation of Propulsive Efficiency which is a bit low as it can be usually 0.5-0.7)
would be:
(1400*745.6998 * 0.5)  / (17.7 * 0.51444) = 57326 N or 12887 lbs


This is also nonsense because it uses the speed of the boat which is not correct, the correct calculation would use the speed of advance of the propeller


What I currently use is:

LBP (Lenght between perpendiculars at the water line) = 62.27 meters
B (Beam - I ignore the saddle tanks) = 4.7 meters
T (draugth) = 4.74 meters
Displacement = 769
Density (of Water) = 1025
StandardTon =  1016
RPM = 470
HP = 1400
VS = 17.7 kn (speed of the boat)


Volume = Displacement * (StandardTon/1000)*(1000/Density)
Blockcoefficient = Volume / (LBP*B*T)
PropulsiveEfficiency = 0.836 - (0.000165 * RPM *  Volume^1/6)      (An estimation by Henschke, 1965)
WaveFraction = (BlockCoefficient / 2) - 0.05        (Taylor)
VA = VS - (VS * WaveFraction)      (speed of advance of the propeller)
Watt = HP*745.69987158227
VA = VA * 0.5144444  (convert to meter per second)


Thrust Force = (Watt*PropulsiveEfficiency) / VA = 88970.76 N = 20001.42 lbs


usually you would also add the Coefficient of hull efficiency (close to 1) to the calculation…


HullEfficiency = 0.98


Thrust Force = (Watt*PropulsiveEfficiency) / HullEfficiency*VA = 90786.48 N = 20409.61 lbs

[Don Prince]

Gentlemen,


I'm have been looking at the valves for a few hours and I see the following:


D1 = HP hull valve + non-adjustable check valve
D2 = HP hull valve + non-adjustable check valve
D3 = HP hull valve
D4 = HP hull valve + non-adjustable check valve (per Mr. Tore's photo)
D5 = HP hull valve + non-adjustable check valve


My understanding of a non-adjustable check valve is the device will allow the medium (in this instance air) to flow in one direction.


My understanding of a hull valve is it is generally used in the full on or the full off state.


Then I reviewed the symbol section of the Skizzenbuch and seen a little ball on the valve wheel handle???  Could the drawing simply be indicating when there is a line with a ball on the end of it that this is a HP hull valve.  This is different form the valve handle on the Q Tanks...


See the drawing:


Regards,
Don_

[SnakeDoc]

Hi Don,

Then I reviewed the symbol section of the Skizzenbuch and seen a little ball on the valve wheel handle???  Could the drawing simply be indicating when there is a line with a ball on the end of it that this is a HP hull valve.  This is different form the valve handle on the Q Tanks...

You are on good track. In fact, all hull valves were fitted with the ball - I have marked them on the bottom part of attached drawing. But the symbol for such valve is quite different - see top part of attached drawing.

Generally - this ball is the part of identification system, which should allow distinction of various type of valves in poor light conditions.


Short description:

Further identification is provided at handwheels on valves.  Wheels for hull closures all have a large ball cast on the rim.  Valves for seawater lines are balanced cranks with straight handles.  For fuel oil, balanced cranks with tapered handles are provided.  Lub oil handles are five-sided.  Fresh water and hydraulic system valves are five-clover type.  Compressed air system valves are circular, with the rim slightly raised above the hub, with three spokes, and with an oval rim section.  The exhaust gas blow system valves also have three spokes, but the rim is greatly offset from the hub, and the rim is a flat oval.  Emergency vent valves have three spokes, a U-section rim and a hand grip.  Hand gear for vent valves has similar wheels with five spokes.  The main H.P. blow valve handwheel is a large flat wheel with five spokes.  The main H.P. blow valve handwheel is a large flat wheel with five spokes, and the main L.P. blow valve is similar, with three spokes.  Positions of cocks are indicated by grooves on the end of the square stern head.

http://uboatarchive.net/DesignStudiesTypeIXC.htm


--

Regards
Maciek

[SnakeDoc]

Mark,
thank you for your explanaintion.


--
Thanks, regards
Maciek

[tore]

Mark.
Sorry I have been traveling for a couple of days and have not been able to respond. I believe you have to get the modelbasin towing graphs in order to get an accurate input you for your game, it could exist some place in Germany. However the speed/ output relations have so many variables and would f.i. change according to the condition of the hull (fouling) often related to days at sea, weather and sea. If you want to vary the prevailing circumstances in your game, you need a lot of info which I doubt exist for a VIIC. I assume the designed max load of  the thrustbearing could give a clue if all conditions were ideal, calm sea, clean hull, draught and trim etc. which hardly exist,  as you mention thrust cannot generally be empirically  transferred into speed.
In the Uboat information effective July 15, 1940, translated by Maciek there is a table put up at page P 14, Section I General. where outputs related to dieselengine / E-motor revs are put up under two conditions A and B; I cannot find the definition for these conditions, but if we assume A is the optimal and B is the a realistic unfavourable condition, you should have the same rule of the thumb input as the crew would have, may be that would be the easiest way, remembering that the revs is not necessarily identical to the output of the engines, which f.i. could be overloaded at the revs stated.
Tore
   

[SnakeDoc]

Hi Tore,

In the Uboat information effective July 15, 1940, translated by Maciek there is a table put up at page P 14, Section I General. where outputs related to dieselengine / E-motor revs are put up under two conditions A and B; I cannot find the definition for these conditions, but if we assume A is the optimal and B is the a realistic unfavourable condition, you should have the same rule of the thumb input as the crew would have, may be that would be the easiest way, remembering that the revs is not necessarily identical to the output of the engines, which f.i. could be overloaded at the revs stated.

Trim condition A - Tauchbunker 2, Tauchbunker 4 and Regelbunker 1 empty.
Trim condition B - Tauchbunker 2, Tauchbunker 4 and Regelbunker 1 filled with fuel.

--
Regards
Maciek

[tore]

Maciek.
Thanks, you always are able to put up written facts.
Tore

[tore]

Don.
Hullvalves. Generally, as Maciek explained, the valve handle or wheel has a cast ball and is usually indicated as a dot or dots on the valvesign handle. The valve sign having a line and a circle I guess, as Maciek found out, is a "plombiert" valve, not necessarily a hullvalve, which I believe can be secured in a certain position. Technically this can be done in several ways f.i. like a counternut or counterhandle. The individual blowing valves are vital, but not always easy accessible and should be in a fixed secured position according to the CO order. Normally for the MBTs this would be in an open position. When MBT 2 and 4 are used as fuel tanks the valves should be secured shut. You shall find this arrangement on all MBTks including 1,3and 5 even if these tanks cannot carry fuel. In addition you shall find the same arrangement on the hullvalves for emergency airsupply and divers airconnection shown on the systemsketch but not allways installed on the VIICs.
Tore

[VIC20]

However the speed/ output relations have so many variables and would f.i. change according to the condition of the hull (fouling) often related to days at sea, weather and sea.

There is a rule of thumb for fouling and different sea routes. I need to get a convincing ideal state with calculations first. But even if my thrust calculation seems to be correct (all publications I've found use it) it seems to work for a static condition only (boat has reached maximum possible speed for this engine setting) and not while accelerating. 

[Don Prince]

Hello Mr. Tore,


Trim Condition B (main ballast tanks and main ballast and reserve fuel oil tanks filled with fuel oil increased load).

I have a lot of assumptions before the questions...  If my assumptions are totally wrong, then I need to be corrected.  I am in the learning process and definitely need guidance and will not take any offense...

With this additional weight, the boat is setting lower in the water.  This is verified by the Information Manual for the Type VIIC.  The turning radius is wider and slower because of the increased drag introduced by lowering the hull.

One would think that the boat would have no problem diving since it weigh was increased.  However, since D2, D3, and D4 are filled with fuel oil which weighs 13 percent less than water.  It looks almost impossible to get the boat to submerge.

D1             30.7 - M3              Trim Condition B
D2             22.6 - M3                      22.6 - M3
D3             47.75 - M3                   47.75 - M3
D4             26.6  - M3                     26.6  - M3
D5             25.15 - M3

Lets say 1 M3 = 1 metric ton

Total     =  152.8 tons                    96.95  - tons    (96. 8 *  13% less weight FO  =  12.6 - tons)
                  -12.6 tons
Total      =  140.2 - tons

They add about 5 tons of additional supplies, which even lowers the boat further and decreases surface performance even more.  With the supplies The total weight increases.

140.2 tons + 5 tons = 145.2 tons

In normal Trim Condition A the ballast weight would be 152.8 tons and it achieves neutral buoyancy and dives using the Regulating Tank 2 for adjustment.

Regulating Tank 2 has a total capacity of 15.2 M3 /tons
[/size]to be continued....

[Don Prince]

In Trim Condition B the weight is 145.2 tons,  or 7.6 tons less; my assumption is that the Regulating Tank 2 has the capacity to achieve neutral buoyancy and dive under these conditions.


[/size]If I haven't got things totally screwed up...

[/size]Q1.  Did the U-Boat you served on run in a Trim Condition B (fully loaded)?
[/size]Q2.  How did the weight effect the draft, generally how much lower was the boat in the water?
[/size]Q3.  With the fuel oil in the ballast tanks, did that change the handling characteristics when submerged?
[/size]Q4.  A basic fuel oil question - as fuel oil is consumed by the diesel engines is the depleted tank area pumped   with water at 87% to keep the boats weight in balance?  Tanks with compressed air would affect the boats weight and neutral buoyancy?
[/size]Q5.  Fuel oil floats on water; are the internal fuel oil storage tanks pumped with water as the oil is being taken from the tank?

[/size]Please feel free to add any additional wisdom,

[/size]Regards,
[/size]Don_

[/size]I don't know why i have the [size] [/size]

[SnakeDoc]

Don,

One would think that the boat would have no problem diving since it weigh was increased.  However, since D2, D3, and D4 are filled with fuel oil which weighs 13 percent less than water.  It looks almost impossible to get the boat to submerge.

Only D2 and D4 were used as fuel oil tanks. So weight difference between A and B trim condition would be only 6,4 ton

Q2.  How did the weight effect the draft, generally how much lower was the boat in the water?

The KTB for U-604's 1st patrol:

28 August, 1942, 04.20:
"During the pursuit, at the suggestion of the Engineering Officer, converted
main ballast and reserve fuel oil tanks 2 and 4 for use as ballast tanks. The
remaining fuel oil, 1 ton, was transferred from the ballast tanks to the regulating
and reserve fuel oil tank. At the same time the negative buoyancy tanks were blown.
Thereby gaining about 1 knot. With the high enemy speed of 16 knots these
measures were decisive."

http://uboatarchive.net/KTB604-1.htm

There is a book "U-Boat 977 The U-Boat that Escaped to Argentina", by
Heinz Schäffer, where is described a pursuit for a tanker, then it is said:

"All our blowers and compressors are screeching for all they're worth—we keep
on blowing our diving tanks every five minutes, for we have to keep as high
above the water-line as we can, since the higher we are the faster we go.
True, the increase in our speed's only fractional, but it is an increase."

(this description is not technically strict, but it shows the idea)

Q3.  With the fuel oil in the ballast tanks, did that change the handling characteristics when submerged?

There should be no difference.

Q4.  A basic fuel oil question - as fuel oil is consumed by the diesel engines is the depleted tank area pumped   with water at 87% to keep the boats weight in balance?  Tanks with compressed air would affect the boats weight and neutral buoyancy?

All fuel oil tanks (except regulating tank 1) are water-compensated. Regulating tank 1 - as filled with the fuel oil and air - would affect weight of the boat.

Q5.  Fuel oil floats on water; are the internal fuel oil storage tanks pumped with water as the oil is being taken from the tank?

Yes, internal tanks are also water-compensated. See the plate:
http://uboatarchive.net/U-570Plate10.htm

I don't know why i have the 

You are probably using some external editor, which uses its own tags, and then you copy and paste the text into the web browser.

--
Regards
Maciek

[SnakeDoc]

Q2.  How did the weight effect the draft, generally how much lower was the boat in the water?

It is generally hard to say without knowing the construction displacement and exact shape of the hull. But when I approximated the U-Boat hull by a cylinder and assuming the surface displacement of 769 ton, the change of draft between the condition A and B would be few centimetres.

--
Regards
Maciek