Author Topic: VIIC/41 - Schematices drawing  (Read 512134 times)

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Offline NZSnowman

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Re: VIIC/41 - Schematices drawing
« Reply #615 on: 09 Oct , 2010, 20:06 »
I nearly finishing my research on the saddle tank hatches today. I apology to Dougie and Pat for misleading them about the differences in the shape of the hatches. http://models.rokket.biz/index.php?topic=124.msg6627#msg6627 As it has turn out that were are two different shapes hatches. There are five hatches along the saddle tank (Fig. 1).


Fig. 1. Hatch 1 to 5 - Stern to bow.

I am almost certain there is only one vent valve and this is Hatch 3 as illustrate in the plan below. Also there is no internal arms system to open this valve, you would need to be on the surface to open and closed it.

from uboatarchive.net http://www.uboatarchive.net/U-570Plate16.htm

Hatches
Hatch 1 access to Main ballast and reserve fuel oil tank 2
Hatch 2 access to reg. tanks and reserve fuel oil tank 1
Hatch 3 Vent valve for reg. tank 2
Hatch 4 access to Neg. buoyancy tank
Hatch 5 access to Main ballast and reserve fuel oil tank 4

By using the patches of the missing hatches on U-995 and counting the frames and was able to place the hatches in there correct locations. Below is a list of the real distance between the end of the stern to the centre of the hatch. If your model is 1:72 scale just divide the number by 72.

Distance
Hatch 1 27,750 mm
Hatch 2 30,250 mm
Hatch 3 33,750 mm
Hatch 4 35,275 mm
Hatch 5 37,350 mm

Size and shape
Hatch 1 about 60% sure on the shape and orientation, but should be 550mm by 400mm in size. I have not clear pictures of this hatch.
Hatch 2 not 100% sure on the shape or orientation but likely 550mm by 400mm in size. I have not clear pictures of this hatch.
Hatch 3 400mm - Circle
Hatch 4 400mm by 550mm in size.
Hatch 5 400mm by 550mm in size.

As yet I have seen no different between any VIIC
« Last Edit: 13 Jan , 2013, 10:55 by NZSnowman »

Offline Rokket

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Re: VIIC/41 - Schematices drawing
« Reply #616 on: 10 Oct , 2010, 00:57 »
Fig 4 is gold! See, there always seems to be a mix of round and oval - the Brit pic I was talking about pretty clearly shows round, and this is a mix. Interesting. Wish I had these a few yrs ago!
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Offline NZSnowman

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Re: VIIC/41 - Schematices drawing
« Reply #617 on: 10 Oct , 2010, 13:05 »
Yes you are total right about figure four being the key for the whole hatch system on the saddle tanks. You can clearly see the round shape of the vent valve and I can just make out an outline of the inner plate also. The picture also give me the idea about the smooth outer cover, as you could clearly see the bolts to fix the cover plate to, but so many photographs either show a smooth surface over the hatches or a hollow. Then I realise that there must be a smooth second cover.

Still love to get a good photograph of hatch 1 and 2 to be 100% sure about the shape and orientation to finish of the research. Does anyone have any pictures of the hatches on the saddle tanks?

It seem many of the solution of the unsolved puzzles left with U-Boats we found over the last few years have come from either one or two key photographs. 


Offline dougie47

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Re: VIIC/41 - Schematices drawing
« Reply #618 on: 10 Oct , 2010, 15:37 »
Hi Simon,

This is fantastic stuff, you've really taken this forward. I'll need a few days to digest properly and will get back to you.

Thanks,

Dougie

Offline dougie47

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Re: VIIC/41 - Schematices drawing
« Reply #619 on: 12 Oct , 2010, 13:26 »
Hi Simon,

Thanks for all your research on the vents/covers...very interesting! I was wrong about the orientation on 3 and 4 - I think you are right about number 3 being circular. I've had a chance to look at photos properly and it does look circular right enough.

I'm fairly certain that number 4 was also a circle. Could number 4 be a Vent valve for reg. tank 1?





In the above two photos, I think the green arrow points to #3, red to #4, blue to #5.

Notice also that #3 may be closer towards the centreline of the boat than #4 (the weld seam goes through #3 but not #4)?



#2 and #3 can be seen in the image above.



Sorry about the quality of the image above, from P15 of Wetzel's U 995 book. In this photo in Wetzel's book, #3 and #4 really do look circular, the rest look oval.

I used to think there were 5 covers, but it bothered me a bit because 5 seemed too many. I think 2 vents and 3 covers per side is more plausible.

The covers would be oval shaped as it allows for a crewman to fit through. The vents don't need to be oval, hence I presume the round shape. 

Cheers,

Dougie

Offline NZSnowman

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Re: VIIC/41 - Schematices drawing
« Reply #620 on: 12 Oct , 2010, 14:24 »

Vent valve; Hull opening (left), Inner hatch cover (middle) & Outer hatch cover (right).

Hull Opening: I have no idea that the valve look like under this hatch, however, the valve allows sea water in to the tank. I just used a frequent used valve on the boat and an open ended pipe.
Inner Hatch Cover: In the middle of this cover, you can see a smaller access hatch, I imagine it for quick access to the vent below :-\ Unsure what six pins do as seen in figure 4 of the previous posting. In the photograph below you can see what I believe is the under side of the outer hatch. There seem to be a rise support ridge on the base of this cover, perhaps the six pens lock into matching holes on base ???



Just was just about post my second part of my research then flash a warning

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Re: VIIC/41 - Schematices drawing
« Reply #621 on: 12 Oct , 2010, 20:51 »
Hi Simon great work with the saddle tanks, slowly everything comes together  ;D

Offline NZSnowman

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Re: VIIC/41 - Schematices drawing
« Reply #622 on: 13 Oct , 2010, 01:15 »
A update on the drawing, now includes the Saddle Tank Hatches



Key for Drawing
http://www.mediafire.com/?ign98y2vc981py8


Offline dougie47

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Re: VIIC/41 - Schematices drawing
« Reply #623 on: 13 Oct , 2010, 13:39 »
Hi Simon,

Yeah, I hate it when that warning comes up! I've had a quick look at your latest drawing. The size, location and shape all look really good to me.

That's a good colour photo you posted. I've never seen the hatch in the open position, as it is in the photo. Well spotted.

Keep up the good work.

Cheers,

Dougie


Offline NZSnowman

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Re: VIIC/41 - Schematices drawing
« Reply #624 on: 14 Oct , 2010, 15:07 »
Why did they change from bronze propellers to steel propellers from about January 1942 ???

Edit
Was it because of bronze shortage ???
« Last Edit: 14 Oct , 2010, 15:17 by NZSnowman »

Offline Pat

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Re: VIIC/41 - Schematices drawing
« Reply #625 on: 14 Oct , 2010, 21:41 »
I've spent a couple of hours looking for any advantages of stainless steel propellors over bronze and so far haven't found much.  It seems that bronze is a much better material for boat propellors than stainless steel, being cheaper, lighter, less brittle, easier to repair and having a lower friction coefficient.

So the only thing left that makes sense would be a shortage of bronze midway through the war.  Since England is known for large deposits of tin even since prehistoric times, it was likely a lack of tin that was the problem.  Tin is alloyed with copper to make bronze.

I can verify that bronze is better.  About 15 years ago, my propellor, which is bronze, got nicked by hitting a floating tire with a steel wheel inside.  I was able to get the propellor repaired quite easily.  I've been told that with similar damage to a stainless steel propellor it would have been a write-off.

If you're building a boat with a bronze propellor, the colour should be flat bronze, almost, but not quite oxidized to a pale green.  Think of the green of copper roofs but not so bright and mixed with a light brown.  Boat propellors do not go as dark as bronze statues but maintain a slight beige-orange-yellow hue in with the green.

If modelling a stainless steel propellor, it should be silver but shinier than a silver coin.  Almost, but not quite, mirror-like.  Think of the colour of a kitchen knife and almost as shiny.  Stainless steel props do not go flat unless in extremely sandy conditions.
« Last Edit: 14 Oct , 2010, 22:03 by Pat »

Offline NZSnowman

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Re: VIIC/41 - Schematices drawing
« Reply #626 on: 14 Oct , 2010, 22:12 »
Pat, do you think that late war u-boats had stainless steel or steel propellors ??? Or where the talk about steel propellors they always talking about stainless steel ???

Offline Greif

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Re: VIIC/41 - Schematices drawing
« Reply #627 on: 15 Oct , 2010, 02:14 »
Just wanted to say hi Simon!  Its been a while since my last post.  I had a very busy racing season in road cycling and did not get online much between the beginning of April and now.  You drawings are top notch as always.  How did the ski season go in NZ?

Ernest

Offline Pat

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Re: VIIC/41 - Schematices drawing
« Reply #628 on: 15 Oct , 2010, 07:02 »
Welcome back Ernest.  Nice to see you again.

Simon, I'm almost sure that whenever it says 'steel' for propellors, it means 'stainless steel'.

Regular steel is not desirable for ship's propellors because it quickly gets pitted from electrolysis and coated with rust.  This would particularly bad for submursibles because the way surface ships locate them is by acoustics (ASDIC for the Commonwealth, Sonar for the Americans).  Any pitting or rust buildup not only reduces the propellor efficiency, but it also causes cavitation - the formation of air bubbles that causes more propellor noise even at slow speeds.  (Cavitation is also the cause of the reduced efficiency, as the prop loses its driving power when it's turning through gas instead of water).

Also, marine organisms like barnacles will adhere to steel propellors but they can't stick to stainless steel or bronze.

Because of their speed through the water, propellors don't hold antifouling paint.  It just wears off in a matter of a couple hundred nautical miles.  The paint itself then also creates cavitation with the roughness between the worn and the unworn parts.  Usually the leading edge is where it polishes clean first.

Offline dougie47

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Re: VIIC/41 - Schematices drawing
« Reply #629 on: 20 Oct , 2010, 08:37 »
Hi Simon,

This photo might help with the treadplate on the lower part of the UZO-

http://cgi.ebay.de/Orig-Foto-U-Bootfahrer-U-Boot-635-Kapitan-Eckelmann-/380279884991?pt=Militaria&hash=item588a728cbf

Cheers,

Dougie