Author Topic: VIIC/41 - Schematices drawing  (Read 512471 times)

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Offline NZSnowman

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Re: VIIC/41 - Schematices drawing
« Reply #375 on: 19 Feb , 2010, 22:39 »
The 'mag' is at the foot of the fairwater (I must say I had to look up 'Fairwater' ;D) & the gryo is in the Control Room next to the Attack Periscope Shaft (below red outline).


Picture from U-995 http://www.uboataces.com/u995.shtml

Offline Pat

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Re: VIIC/41 - Schematices drawing
« Reply #376 on: 20 Feb , 2010, 22:24 »
I couldn't find 'fairwater' referring to subs, but isn't that the bulge in the front of the CT?  (At least when referring to the gyrocompass - there can be many fairwaters on a boat)  I'd thought the gyro was inside the fairwater but according to Snowman's pic, it's inside the control room.  Is one of them a repeater?

Yes, rokket, you're correct.  Magnetic north is not true north.  The difference between them is called "variation" and it changes depending on what part of the world you're in at the time.  Not only is it different because of geometry, but also there are large deposits of magnetic ore in some places of the world (there's a big hill in New Brusnwick, Canada for instance where the magnetism is enough to move a car) and there are also parts of the world (one I know of is east of the southern tip of Africa) where the magnetic compass is unreliable.

BTW, variation also changes with time, so that all nautical charts have a record on them of the year printed and the current rate and direction of variation.  You have to make a calculation by date and location both to offset the compass.

But the reason magnetic compasses are almost useless on steel-hulled boats is because of 'deviation', which is where the mass of metal on the boat throws off the compass even more.  There is a process called "swinging the compass", whereby you take the boat out to a known position that can be checked by triangulating shore references, and then go in a tight circle, all the while taking compass readings on a fixed point on shore and recording how it deviates from what it should be depending on what direction the boat is facing.   (and also taking into account the variation previously noted).

Even small bits of metal close enough to the compass can change it, like a battery driven watch or a pair of steel-framed eyeglasses in the case of hand-bearing compasses.  The engine of course is a huge mass of metal, but then also, there's more metal fore and aft of a compass then there is to either side, so the deviation changes accordingly.

Navigation is a very complex process (until GPS came along).  I did well to never be off more than 1/4 km on any trip I've been on, but then, I've never sailed more than 200 NM in any one direction either.


Offline Rokket

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Re: VIIC/41 - Schematices drawing
« Reply #377 on: 21 Feb , 2010, 00:54 »
Good Pic, NZ!  Good info, Pat. I wasn't sure if the variation was set for a time or not, but I do remember seeing dates or "changes XXX degper year" on some charts now that you mention it. Hey, great navigating, too!
Here's a link to a pic of a binnacle with small magnets either side to overcome the magnetic deviation:


I don't know how they compensate the small floaty mag compasses small boats use, but do know the bulby indicator is "backwards" in that the reading is made easier for the helmsman (heading N the "N" is at 6-o'clock, S at Noon, rather than other way, because often viewed from side/edge and not top-down). Interesting stuff.

"Fairwater" - I was being nitpicky, sorry. On a WWII sub (or at least in USN talk) it is the only real exposed part, the superstructure, the bridge.  Post-WWII it is called a "sail". Often it is incorrectly called "conning tower", and I have done it myself. But technically, the CT is ONLY the pressure-hull inside, not the outer superstructure.
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Offline Pat

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Re: VIIC/41 - Schematices drawing
« Reply #378 on: 21 Feb , 2010, 07:13 »
Ah, thanks for the correction on "conning tower" rocket.   :)  This forum is great for learning something new almost every time I log in.

Yeah, navigating across the water is a lot more complicated than on land.  True vs magnetic north, variation and deviation are just the beginning of the navigation courses I took and actually some of the easiest parts of it.  I still have 2 years to go to get the celestial nav part down, but since I've only sailed on the ocean within about 50 miles of the continent, I don't think I need those.  After all, even if I got lost, just head west and I'm bound to find N. America eventually, right?

BTW, the two balls in your pic are called "Flinder's balls" after Cap't Matthew Flinder, who was the one who invented the idea.  They're made of soft ferro-magnetic iron, and they're mounted on little slots in the arms ao they can be slid in and out.  You'll only find them on the binnacles of steel hilled ships, even in WWI torpedo destroyers, dreadnaughts, monitors, etc. (all these interesting types that we no longer have) so if you ever do a model of a tall ship, make sure you know what the hull was made of (or in the case of a ship like say, Cutty Sark, where the hull was wood but the frame was steel, so it would have had Flinder's balls).

Anyway, how they work is that as I'd mentioned before, in a steel hulled ship, there's more mass of metal lengthwise along the direction of the keep than there is athwartships, and that means the compass deviation is greater when the keel is lined up with magnetic north than when it's pointing east or west.  The Flinder's balls compensate for this by adding to the metal abeam of the compass, but they're placed much closer to the compass so even though small, their affect is greater.

Note also that the post in your binnacle picture is wood.  You don't get metal binnacles until more modern times when aluminum became sheap enough to make binnacles out of that.  I think some old ships might have had brass binnacles, but that would be a rarity.

My own boat haas an aluminum one but I made a teak covering for it to make it look reminiscent of the old style in your picture (only a LOT smaller!)

Oh yeah, the reading being backward in the binnacle you see would be specific to the design of that particular ship because of where the helmsman was expected to stand for whatever reason.  Some are backwards, most are regular.  Most mag compasses have different posts and markings on them to help read the direction from different positions around the compass, depending on where the helmsman is standing at the time.  On my own boat, the entire top is clear, like a snow globe, so I can read it from 360 degrees around.  About half the time, I wouldn't be standing directly behind because if the boat is heeling, it's just too uncomfortable so the helmsman might sit off in the corner to one side or the other where he has a backrest and cushions and better visibility forward around the mast.

Offline Rokket

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Re: VIIC/41 - Schematices drawing
« Reply #379 on: 22 Feb , 2010, 00:55 »
Flinders balls - I'm sure there were no jokes about that! Very cool. I never thought of the keel, but makes sense. Your teak cover sounds lovely Pat! You have to get some pix posted of all kinds of things!
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Offline Pat

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Re: VIIC/41 - Schematices drawing
« Reply #380 on: 23 Feb , 2010, 08:00 »
Yes, I'm sure there was a joke or two going around about Matt Flinder's balls.

Flinder's balls haven't disappeared on modern marine compasses either BTW.  They've just shrunk (again, I'm sure there are comments there too) and moved internally. If you take the cover off a modern compass, there are usually two small pieces of ferrous iron on slides that can be adjusted the same way as the big balls that the old tall ships sailors had on their binnacles.  (I just KNOW what's going through your mind now)

The modern ones are smaller I think because magnets can be smaller through better methods of making them with perhaps purer iron.

BTW, the teak sheathing on my binnacle (hey, no more jokes here please) aren't fastened on.  I didn't want to take the chance of interfering with the mechanisms inside the binnacle.  (The gearshift, throttle control, steering cables and compass lighting all go through a very narrow tube).  I drilled holes in the teak planks and then lashed them on with small line and covered the lashings with Turk's Head knots so that it looks fancy, but can be removed with a flick of a sharp knife if needed. 

Offline NZSnowman

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Re: VIIC/41 - Schematices drawing
« Reply #381 on: 24 Feb , 2010, 18:05 »
I couldn't find 'fairwater' referring to subs, but isn't that the bulge in the front of the CT?  (At least when referring to the gyrocompass - there can be many fairwaters on a boat)  I'd thought the gyro was inside the fairwater but according to Snowman's pic, it's inside the control room.  Is one of them a repeater?

Just come back from 4 days field work counting grasshoppers ;D It's what I study in the summer.

Pat, the bulge in the front of the CT is the magnetic compass, however, there is a second gyrocompass in the U-Boat but I am unsure where. 

Offline SnakeDoc

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Re: VIIC/41 - Schematices drawing
« Reply #382 on: 25 Feb , 2010, 06:02 »
however, there is a second gyrocompass in the U-Boat but I am unsure where. 

According to U-570 British Report
http://uboatarchive.net/U-570BritishReport.htm
and Type IXC Desing Study
http://uboatarchive.net/DesignStudiesTypeIXC.htm
on boats type VIIC and IXC were set of one magnetic compass and
one gyro compass (Anschutz type).

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Offline NZSnowman

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Re: VIIC/41 - Schematices drawing
« Reply #383 on: 26 Feb , 2010, 12:24 »
Hi Maciek

Thanks for the additional links :)

It does look like there is only one gyro-compass on the U-boats. I saw the gyro-compass labeled as "Master Gyro-compass" in Anatomy of the ship: The Type VII U-Boat by D. Westwood and I just assume there was a second one on U-boats.

Offline SnakeDoc

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Re: VIIC/41 - Schematices drawing
« Reply #384 on: 26 Feb , 2010, 15:56 »
Hello Simon

I saw the gyro-compass labeled as "Master Gyro-compass" in Anatomy of the ship: The Type VII U-Boat by D. Westwood and I just assume there was a second one on U-boats.

I have also met this term, but I think, it means something like "master gyro" and some number of slave repeaters.

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Offline NZSnowman

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Re: VIIC/41 - Schematices drawing
« Reply #385 on: 27 Feb , 2010, 12:13 »
Does anyone know if the keel of the Type VII is solid or made up of frames?

same for me, sure I've seen a pic. I THINK it's solid (or solid from big chunks) for weight.

Just a guess, but the standard material for ballast keels is lead.  They want the heaviest but cheapest material they can get to take up the least amount of space while lowering the centre of gravity so the boat rolls less.  It would definitely not be iron as that would corrode too quickly, and not likely steel because it isn't heavy enough and they need it more elsewhere.

If there are access hatches to the keel, that sounds like they might want to at least inspect it once in a while for corrosion and to clean out the limber holes so that any water will drain to a sump where it can be pumped out.  The limber holes on many ships often have a small chain running for and aft that could be pulled to drag out any gunk that got stuck in the holes, blocking the free flow of water.

Going back to the keel ballast question. Would the lead blocks be painted with anything, e.g. like anti-corrosion?

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Re: VIIC/41 - Schematices drawing
« Reply #386 on: 27 Feb , 2010, 12:51 »
Hi NZ,

I think painting with anti-corrosion is a good guess.

There is a mention in the overhaul papers of submarine Vesikko that

Offline Pat

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Re: VIIC/41 - Schematices drawing
« Reply #387 on: 27 Feb , 2010, 16:40 »
Simon, I don't know if there'd be any anti-corrosive coating on lead keel blocks or not.  My guess is not, because they're carried inside the steel of the keel so aren't exposed directly to water. 

The reason that the lead would be totally enclosed is because it's both very heavy, AND very soft.  You can't weld it to steel, since it melts at a much lower temp. and you can't bolt it either, since the boltholes would just wear away rapidly.  That means it any seam between steel and lead would quickly leak.

In my own boat, the lead is encased in fibreglass, and the only place it can be seen is through inspection ports on top.  I think some keels are through-bolted to outside of the hull, and the seam always seems to crack and let water in, making regular maintenance of the seam is a necessity.

Urpak's comment about scrubbing the ballast plates makes sense, in that lead does get powdery white on the outside and gets soft.  In fact, sailing ships before the invention of copper plating in the middle of the 18th century, were painted with a mixture of tallow and lead powder that made the underwater parts of the hull white (something to remember whenever making a model of a sailing ship.  You have to kow the date and location of the ship to determine what colour it would be below the waterline).

In a book I have, there's a colour plate of U-596, in Mediterranean camo, with the hull red below the waterline.  The saddletanks and the first what looks like 2 feet of the waterline are black or very dark grey, while below that is red.  Looks like the picture on Silent Hunter II.

I can't imagine that the KM didn't paint their steel hulls with anti0corrosive paint, which is that same dull red you often see the beams for bridges and buildings during construction.  The hull of Greif's Bismark is probably that colour below a dark band at the waterline. 

The dark grey of U-boat hulls would be an anti-fouling paint applied on top of the anti-corrosive paint.  It's the antifouling additives that make it turn dark after a few weeks immersion in water, it usually starts out a different colour, but of course, during wartime, they might also have used specif colours for camo reasons too.  The anti-fouling I use starts out a bright, copper colour when I first apply it, but about 2 weeks after launch, it looks about the same colour as a school blackboard that's been used a lot.

Offline NZSnowman

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Re: VIIC/41 - Schematices drawing
« Reply #388 on: 27 Feb , 2010, 19:51 »
Simon, I don't know if there'd be any anti-corrosive coating on lead keel blocks or not.  My guess is not, because they're carried inside the steel of the keel so aren't exposed directly to water. 

Two things:

I can not remember what it call but it happen when two different metal touch. Would this not happen with lead and steel ???

&....

I can not imagine the keels for the U-Boats were water poof :-\   

I can't imagine that the KM didn't paint their steel hulls with anti0corrosive paint, which is that same dull red you often see the beams for bridges and buildings during construction.  The hull of Greif's Bismark is probably that colour below a dark band at the waterline. 

I believe they painted anti-corrosive paint inside the saddle tanks.

Offline NZSnowman

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Re: VIIC/41 - Schematices drawing
« Reply #389 on: 28 Feb , 2010, 00:39 »
I was thinking, I imagine most or maybe all the ballast must be fore of the Engine Room :-\