Type VIIb plans inconsistencies

[gerwalk]

A friend of mine is interested in converting the Revell 1/72 Type VIIc into a a VIIb. He is rather picky and he is colecting all the information he can and not take them as face value. One of the things he found is this section profiles from Heizewolf site:



I checked them with the ones published by Rössler and they are the very same (so, the reference is correct)

Now]http://www.subcommittee.com/forum/icon_cool.gif[/img]

[JWLaRue]

Pablo,

I do not recall ever

Pablo,

I do not recall ever seeing a "step" along the underside of the saddle tanks either. I'd have to check, but perhaps the location of those hull lines are where the valve openings are located......

Externally, the added frame section creates virtually no visible difference between a VIIB and VIIC.....except for the extra row of deck slots where the new hull frame was added. Spacing for the underside saddle tank valve openings appear to differ slightly as well (don't take that as verified).

As for tower differences, they changed throughout the war. E.g. adding Wintergartens, etc. The one thing that I can think of that clearly can denote a B from a C is how the engine air intakes were done. For example, some of the VIIBs had a single, teardrop shaped intake located right next to the aft periscope and inline with the centerline of the boat, while others had what is clearly recognizable as external air trunking along the outer, rear of the tower. These differences reflect the effort undertaken to make the boats more seaworthy in the North Atlantic (vs. the North Sea). The VIIC more or less standardized on the dual air intakes along the rear tower walls and not as external trunking.

-Jeff

[don prince]

Hi Gerwalk,

Reference Books:

"The Uboat: The

Hi Gerwalk,

Reference Books:

"The Uboat: The evolution and technical history of German submarines" and the German version "Geschichte des deutschen U-Bootbaus, band 1" written by Eberhard Rossler show the Frame Lines with a notch for both Type II and type VII. The book also has Frame Lines without the notch for both types as well. However, The fold out plan Tafel: Type VIIC (1944) - Generalplan 3 does show a notch where the frame member ends in the area of the Captain and Officers rooms. There is a line that extends from the lower dege of the frame notch to the outter hull. My only guess is that this is a piece of sheet metal to streamline the outter hull skin surface

Regards,
Don_

[gerwalk]

Thanks guys for the answers:
Jeff,

Thanks guys for the answers:
Jeff, I doubt the steps or notch are related to the tank valves: the separation goes all the way towards the bow and stern. Thanks for the comments on the differences on both classes.

I tend to agree with Don there must be a sheet of metal covering the gap.
I have the english version of "The Uboat: The evolution and technical history of German submarines". IIRC the VIIb frame lines plan shows the notch but not the one of the VIIc. The same happens with the IID and IIa plans. So, maybe that (notch) is the correct shape of the frames and they were covered whith a sheet of metal.

[hakkikt]

Warship Pictorial 27 has two

Warship Pictorial 27 has two photos of a Type VIIB in dry dock, supposedly U-99. The photos have been taken from the ground, and the lower edge of the saddle tanks is well visible. There is no step, but the lower saddle tank/hull border looks different between the two sets of vents, as if something additional were welded there.

I wont post a photo here for copyright issues, but if anyone is interested, send me a PM and I can mail you a scan, or at least a digital photograph of the page.

[JWLaRue]

The problem I'm having with

The problem I'm having with the explanation of the steps being covered with sheet metal is that we are looking at hull lines, not frames....which, as I understand it, means we should be looking at the final exterior form of the hull at the various points along the length of the hull......

Either way, it's good to see that the photo documentation shows no visible step.

-Jeff

[don prince]

Hi Jeff,

Rossler's books does list

Hi Jeff,

Rossler's books does list these drawings as Frame Lines....

Regards,
Don_

[JWLaRue]

Great discussion! Let's keep it

Great discussion! Let's keep it going!

This is most curious.....I took a close look at the planrolle done by Fritz Köhl and his plan 4 does not show that step.

Here's the whole drawing:



..and here is a close-up of the area in full-rez][/url]

I also took a look at my copy of Rössler's book (1989 Naval Institute Press edition).....and found within it 'both' variations of hull (or frame) lines, sort of......

From page 101, what might be a generic VII set of lines? Note the "step" both above and below the saddle tanks][/url]

From page 108, a VIIB (same as first posting)][/url]

...and from page 117, a VIIC][/url]

So a most curious question! I'd really like to find out if that "step" really means something as has been hypothesized or if it's some other artifact.

In the preface, Rössler notes that Fritz Köhl "redrew and retouched many U-boat plans which he made available for this book." So it is hard to tell the source for all drawings.

By the way, when I was asking about hull lines vs. frame lines, here is what I was thinking of in noting a difference between the two. This close-up of Köhl's plan 8 shows the frame detail..that is how the structure was actually built][/url]

Thoughts?

-Jeff

[don prince]

Hi Jeff,

Your last photo is

Hi Jeff,

Your last photo is the exact shot that is on the Type VIIC (1944) Generalplan 3 sheet that is included with the German book printed in 1996. That seems to be the only frame section that indicates the possibility of a notch. It does seem to have a piece of sheet metal that extends down to the hull.

Regards,
Don_

P. S. - I think that I may make it to the Sub Ragatta this year.

[JWLaRue]

Don,

Good spotting....but I still want

Don,

Good spotting....but I still want to better understand what these hull/frame lines are intended to represent then.

Either they are meant to show the outer hull form or to show some sort of construction details......but in either case I think we still have questions?

From a modeling perspective, I think we agree that the photo documentation shows no 'step' along the underside of the saddle tanks, yes?

Anyone have access to copies of the original bauwerft sheets?

If you are able to make it to the regatta, will you be able to bring your Type VII?

-Jeff

[boss subfixer]

Jeff,
After looking at what you

Jeff,
After looking at what you posted for plans here is my take on the difference between frame lines and hull lines.
The frame lines will give you the basic shape of the boat. Think about how Mylo and others have done their scratch builds, laying out the frames from the plans, assembling them in order and filling in between. This gives them the basic shape of the boat.
Hull lines give you more detail of how the boat is supposed to be shaped. Look at your plans for the type XXI and go to the conning tower. All those lines on the plan show how the conning tower is shaped with all the contours to get it to look correct and capture the hydro dynamics. If it weren't for hull lines we would be stuck looking at pictures and trying to get the various contours right on our models and the shipyard people would have the same problem trying to build what the designers wanted.
I have plans for modern nukes and the hull lines are referred to as mold lines . Maybe that term makes more sense to you.
My 2 cents, what do you think?
Don

[JWLaRue]

Hi Don,

I'm not sure I

Hi Don,

I'm not sure I understand the distinction you are making. Are you suggesting that the frame lines are not accurate representations of the outer surface of the hull, etc.? I could more easily understand that if we saw things like hull openings on those drawings. It's almost like it's a rough drawing and not meant to be accurate at the detail level.....

Even though the Köhl drawings are known for some inaccuracies, I'm reluctant to simply declare this one. I'm hoping that there is a reason for the differences.

-Jeff

[boss subfixer]

Jeff,

Are you suggesting that the

Jeff,

Are you suggesting that the frame lines are not accurate representations of the outer surface of the hull, etc.?

No not entirely. You can get a very good representation of the hull shape with just the frame lines.
But I could be confusing hull lines with water lines. I could get some info together tomorrow and look into it. I'm at work tonight so no access to my reference material.

It's almost like it's a rough drawing and not meant to be accurate at the detail level.....

This is more of what I'm trying to say. You can get a real good representation of the hull with frame lines just like Mylo did but if there were a hull detail that fell between frames ,maybe jutted out from the hull but it did not extend into the next frame line back, you may not get detailed enough information to replicate that area. It's hard to explain without looking at the plan and picking a specific detail to show you what I mean. If it would help I will do that. Again I may be confusing hull lines with waterlines.
Don

[gerwalk]

Very interesting discussion!
My friend asked

Very interesting discussion!
My friend asked me to post his comments:
1) Page 101 drawing could be a VIIA? (Gerwalk says: maybe not, because there is no external torp tube)

2) He has measured the height of the saddle tanks in relation with the hull and he found that in the VIIB drawing it is 5% larger than in the VIIC drawing. So: according to the drawings VIIb had higher saddle tanks than VIIC... If we cover this with a steel sheet the situation is even worst! And this is not what you can see in the photographs. (Gerwalk: I think we are seeing different sets of frames here... if you put them toghether they don't match at all: the C frames are taken from different parts of the boat than the B frames...)

3) If these are frame plans then the external steel sheets are not present (as it was discussed above) bu the in the drawings the width of the boat and the pressure hull are 6.18 / 4.7 m in the case of the VIIB which are correct... so: the drawings are taking the steel plates into consideration?
Even more: if in the drawings the external steel plates were absent then the union of the plates with the keel would distort the profile.

4) The shape of the bow of a VIIb is different from a VIIC. VIIB had a more "pointed" bow.
[/b]

[JWLaRue]

re: 1) Page 101 drawing

re: 1) Page 101 drawing could be a VIIA? (Gerwalk says: maybe not, because there is no external torp tube)

That is how I would interpret it as well....no aft external tube shown in the frame/hull lines would tend to say it's not a VII (i.e. "VIIA").

re: 4) The shape of the bow of a VIIb is different from a VIIC. VIIB had a more "pointed" bow.

If we're thinking about the same thing, early Type VIICs had the same bow as the VIIB. The Atlantik Bow is where the VIIC got that fatter looking bow......

-Jeff