Type VIIb plans inconsistencies

[JWLaRue]

Personally, I think that folks

Personally, I think that folks are placing too much emphasis on the drawings and not enough on the photographic evidence.

I would prefer to see actual original drawing and not re-creations......

Anyone have access to the originals?

-Jeff

[dougie995]

Hi Gonzalo,

Yes, the tanks in

Hi Gonzalo,

Yes, the tanks in the VIIB and VIIC plans are different. But are the plans authentic? Where did they originate from? I would agree with Jeff about period photographs. I’ve seen enough differences between U-boat photos and U-boat plans to always question the plans.

You MAY be right that the saddle tanks on VIIBs and VIICs were slightly different in shape but I can’t tell the difference in the photos. In the photos below, I’ve blanked off the drainage holes and tower. I’ve added a B for the front of the boat (bow) and an S for the rear of the boat (stern). Can you tell which boats are VIIBs and which are VIICs?













Have a good weekend,

Dougie

[dougie995]

Hello again gentlemen,

Me again. The

Hello again gentlemen,

Me again. The image below shows the VIIC Roessler plan overlaid upon the VIIB Roessler plan. The top and sides of the saddle tanks are in the same place. The big difference is at the bottom of the saddle tank – the VIIB tank comes much farther down than the VIIC plan. I’ve marked the bottom of the saddle tanks for both the B and the C –



The distance between the top of the saddle tank and the bottom of the keel was the same for VIIBs and VIICs. Let us call this distance A.

The distance between the top of the saddle tank and the bottom of the saddle tanks may or may not be different. Let us call this distance B.

If we measure A and B on various plans, then divide B by A, we arrive at a useful ratio. The ratio works out roughly as follows for the following plans –

Roessler VIIB front plan – 0.57
Roessler VIIC plan – 0.46
Kohl VIIC plan – 0.45
Revell VIIC kit – 0.48
VIIB side profile schematic (below) – 0.47



The image above is a schematic for a 1940-era VIIB such as U 99. This schematic may have come from a factory blueprint. It is the most authentic VIIB plan that I know of. I have added in colour the distances A and B to help explain them.

As can be seen from the ratios, they are all roughly the same (including for the VIIB side profile above). All except for the Roessler VIIB front plan.

In period photos there is a doubler (strengthening strip) just aft of the bottom torpedo door. The doubler is level with the top of this door. If we follow this doubler back along the hull we come to a weld seam that is at the same level. This weld seam leads back along the hull to a level that is just above the bottom of the saddle tank. So the top of the bottom torpedo door is just above the same level as the bottom of the saddle tank. This is exactly the same on photos of VIIBs and VIICs. So the bottom of the saddle tank appears to be in the same place on Cs and Bs in the photos.

Given these points, I would suggest that the Roessler VIIB front plan is probably inaccurate. Also that the height of the saddle tanks were the same on both VIIBs and VIICs.

Cheers guys,

Dougie

[gesalinas]

Hello Dougie and to all

Hello Dougie and to all people:

1) Saddle tanks belonging to VII B or VII C. It´s impossible to me to know which are from VII B or C. I have very few photos of hull in drydock in my books. All saddle tanks seems to be the same in your post here. And this is from you a very good point. Another way to see this problem.
2) I´m agree with your reasoning: I´ve measured the height of hull and saddle tanks in VII B drawings and VII C drawings. The Rossler VII B saddle tanks height it´s greater than VII C about 3 or 5 %. Also I´ve measured the breadth in VII B drawing at saddle tanks and at pressure hull and the proportion does match: 6.2/4.7 mts.
3) I wish to look the doubler (strengthening strip). The books I have not cover the whole bow because are few and small dark photos. But I understand your point. And I´m agree.
4) Remember that the step in VII B drawings also is in Type II drawing with saddle tanks. However I can´t find photos of type II with saddle tanks and the step. It´s a nightmare.
5) If you say that U 47 photo is not the U 47 (I believe that is correct), then ¿there isn´t drydock photo of U 47? It´s a pity.
6) I don´t understand the saddle tanks in U 31. ¿the bottom is open to the sea? The fuel could escape to sea. Also, the shape of this saddle tank it´s the same that VII B drawing which we can see at web page: http://www.heiszwolf.com/subs/plans/plans.html Another nightmare.
7) I´m agree that photos are decisive that any drawing. If you have seen many photos of VII B in drydock that don´t show the step, then I will accept the evidence.
The frames hull without saddle tanks on VII B drawing, according to photos; are very well, may be accurate.
9) I will return on monday, because tomorrow it´s sunday and the 3 friends goes to the bar to talk about World War II. The crazy guys of war. Also gossip about modelers. The three stooges. Shemp, Larry and Moe.

Thank you very much.

[JWLaRue]

6) I don´t understand the

6) I don´t understand the saddle tanks in U 31. ¿the bottom is open to the sea? The fuel could escape to sea.

Actually, it's not a problem since bunker fuel is a lighter density than sewater.....think oil slick from broken tankers.....

When the saddle tanks were used as fuel tanks, seawater filled the tanks as the fuel oil was used. This allowed the use of tankage that was not built/designed to withstand the pressures of operation while diving.

-Jeff

[dougie995]

Hi Gonzalo,

Yes, I haven’t seen

Hi Gonzalo,

Yes, I haven’t seen any photos showing the hull of U 47 in dry-dock. Still hunting for one, but I guess there isn’t one out there.

To answer your point 3, the two photos below show the doublers leading back. The first image is the VIIB U 54 and the second a VIIC. The red arrow shows the top of the bottom door. The blue arrow shows the doubler on the hull casing. The purple arrow shows the small weld seam running along the pressure hull.





Lastly, for the six photos I posted on the 25th, the third one down is the VIIB U 54. The rest are VIICs.

Jeff, I wonder if you can help on the subject of the 8 square vents on the bottom of the saddle tanks. On most dry-dock photos there are covers in place over the vents. I suppose the covers would have to be there otherwise the remaining fuel and water would just drain out onto the dry-dock floor!? But I also take it that when the boats were in the water these covers were moved into the open position, meaning the vents were open to the sea? So for our modelling purposes, a boat in dry-dock would have the cover in place (like the Revell model) and a boat in the water would have these vents completely open?

Thanks,

Dougie

[JWLaRue]

Dougie,

I believe that you are

Dougie,

I believe that you are referring to the flutklappen (tide vents)?

It's my understanding that you are correctly describing how these vents operate. I've also seen reference that states that these are screened openings as well.......though like you, I have yet to see any photo showing these vents in the open position.....

-Jeff

[dougie995]

Hi Jeff,

Ah, so that is

Hi Jeff,

Ah, so that is what they were called. Thanks. The photo below is one of the 5 dry-dock shots of U 99 in Steve Wiper’s Warship Pictorial book on VII U-Boats. By the way, the photos of U 99 in that book weren’t all taken at the same time (one shows U 99 with air trunks, the others show no trunks). In this photo the 8 flutklappen are open. I just hope they drained the fuel before opening them or someone would have been in trouble!



On the Revell model there are three raised squares on the bottom of the saddle tank, just as on U 995 (photo below). These are referred to as inlet hatches for the main dive tanks. One difference between Bs and Cs is that the VIIB schematic and U 99 photos show four inlets rather than the three on VIICs.



On the U 99 image above, the red arrows point to 4 squares on the piece that juts out at the keel (Westwood refers to this as the “ballast keel”). I think the inlet hatches are in the open position, resting on the “ballast keel.” I presume this explains what the “ballast keel” piece was for – to support the inlet hatches when they were in the open position. Would you agree?

Thanks mate,

Dougie

PS. Note that the “ballast keel” piece on the Revell model isn’t like it is on U 995. Another alteration required probably…

[JWLaRue]

Hi Dougie,

It's been my opinion

Hi Dougie,

It's been my opinion that those squares on the U-995 appear to be welded plate covering the actual ballast tank openings and were added to close up all the hull openings as part of turning the U-995 into a display memorial. Similar changes were made to the numerous U.S. fleetboats on display. However, now that you mention it, the triangualr shape of that keel section could be to allow the hatches to move downwards.......

Time to look for period photos of that area to be sure!

In either case, I agree that these openings were for the internal (hard) ballast tank located directly beneath the control room.

Speaking of "ballast keel", if the keel of the VII was built along similar lines as that if the Type IX, then the keel was a hollow box-like structure were ballast weights were added to trim the boat. Clearly not an operation that would have been done often!

-Jeff

[don prince]

Hi Dougie and All,

Thanks for

Hi Dougie and All,

Thanks for posting that photo of U-99... U-99 was a Type VIIB and there is no notch at the bottom of the saddle tanks in that photo. That is a great photo. Looking at my OTW TYpe VIIC and it looks the same. There are 2 sets of 4 inlets at the bottom of the saddle tanks, and there are 3 vent panels on each side of the keel for the main balast tank.

I wonder why the VIIC only had 3 vents and the VIIB had 4 vents on each side of the keel for the main ballast tank? One would think the VIIC would be slower to dive, but perhaps the port and starboard negative bouyancy tanks made up the difference for the VIIC.

FYI... David Westwood's book "The Type VII U-Boat" indicates the Type VIIB/C/D/F all had 4 vents on each side of the keel for the main ballast tank....

Regards,
Don_

[JWLaRue]

FYI... David Westwood's book "The

FYI... David Westwood's book "The Type VII U-Boat" indicates the Type VIIB/C/D/F all had 4 vents on each side of the keel for the main ballast tank....

Just another reason for us to continue to rely on the photographic evidence.....

-Jeff

[gesalinas]

Dougie: I have seen at

Dougie: I have seen at book Vom Original zum Modell uboot typ VII C a main cross section showing at ballast keel a hinged covers or plates that turns up and down (with doted curved line). The space in ballast keel is for allow open and close this "hatches". I guess of course.

[dougie995]

Thanks guys, this has been

Thanks guys, this has been a very interesting discussion.

Cheers,

Dougie