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Author Topic: Dimensional Drawings for P-40  (Read 8785 times)
Ivan
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« on: July 02, 2014, 01:44:47 AM »

Hello All,

This is my first post here.

I built a P-40E for Combat Flight Simulator many years ago based on the drawings by William Wylam.
Although the result LOOKS like a P-40E in my opinion, the lines don't look quite right when compared to photographs or even to many profiles I have seen. 

The Fuselage in front of the Fin looks to be a bit shallow and the entire assembly looks to be a touch too high.
I have gone back a couple times to compare the offsets of my wire frame model to the dimensions in the drawings and they line up pretty well.

Anyone have better dimensional drawings for the P-40?

Thanks.
- Ivan.
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Vince_M
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« Reply #1 on: July 02, 2014, 05:49:11 AM »

Hi Ivan and welcome...

The best drawings I have seen are from "Aircraft Archive" books which came out in the 1990s.
They are out of print but may be obtained on ebay sometimes.

Also, the factory drawings are available here at this website I believe!
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Ivan
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« Reply #2 on: July 02, 2014, 09:14:38 AM »

Thanks Vince_M,

I poked around a bit and found a PDF online of:

Aeroplane Special "Aviation Archive US Fighters of World War II"
ISBN 978-1-909786-22-6

Didn't find any dimensional drawings there though there are pretty good cutaways for all the US Fighters.

The best drawing I have found on this site is here, but although it seems closer to the shape I find in photographs, there are no dimensions to show where the Wylam drawings are in error:

http://www.p40warhawk.com/Art/Drawings/P-40E_3000.jpg

I also found detail drawings, but I am really looking for a more general schematic because it is the basic shape that is wroong with my model.

- Ivan.
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Vince_M
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« Reply #3 on: July 03, 2014, 12:55:51 AM »

I agree, the Wylam drawings are not accurate.
I'll look through my copy of Aircraft Archive as I believe there are cross sections of the P-40 fuselage.
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Ivan
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« Reply #4 on: July 03, 2014, 09:55:17 PM »

A cross section is actually not quite what I need.  A profile like Wylam's but with CORRECT dimensions is more like what I need.  I can guess from comparison with photographs, but that is hardly the most accurate way to do things.

I have also seen from various P-40 photographs that there is a distinct slope down from a peak behind the rear quarter windows that doesn't seem to be reflected in the Wylam drawing.

I will be going through drawings and photographs to see where the propeller centerline goes through the rudder because if I can locate the rudder reasonably precisely, all the rest of the pieces are constrained.  I have already gone through a LOT of drawings, but there doesn't appear to be a lot of consistency between them.  The Long Tail P-40s seem even worse in consistency of drawings.

Thanks.
- Ivan.
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Vince_M
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« Reply #5 on: July 03, 2014, 11:45:43 PM »

Ivan,
I understand better what you are looking for and I'll go back to the "Aircraft Archive" Fighters of WWII Vol. 1.  Those are the best dimensional drawings I have seen commercially available.
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Ivan
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« Reply #6 on: July 07, 2014, 09:57:49 AM »

I really should proof read what I type....

While my search was for "Aircraft Archive", My results gave "Aviation Archive" and I didn't even notice....
"Aircraft Archive" hasn't gotten me anywhere.

Here is a comparison of a Wire Frame of my model against a rather well known photograph from this site.
The photograph isn't exactly lined up, but it is pretty close.

Note that the forward fuselage up to the cockpit lines up pretty well.
The cowl fairing on the underside is noticeably too high at the aft end.
The base of the fin lines up.  The slope of the fin does not.
The top of the fin looks to be the correct height but the tip is too far back.
The bottom of the rudder does not line up nor does the tail wheel or the underside of the fuselage.

Without dimensions, I can only guess how far off my model is.
I hate guessing....

- Ivan.
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Vince_M
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« Reply #7 on: July 08, 2014, 09:18:23 PM »

Ivan,

Give me an email address and I will scan the pages you need from my book.

Vince
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Ivan
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« Reply #8 on: July 09, 2014, 04:13:31 AM »

Thanks Vince,

My email is
Ivan1GFP@yahoo.com

Since my last post, I found a few more large photographs of the P-40E and did the same thing with my wireframe overlay.
The funny thing is that the mismatches seem to happen at slightly different places which is probably due to the difficulty of finding a photograph that does not have some distortion the camera being too close to the object or slightly misaligned.

Out of curiosity and to see how bad the distortion was, I downloaded the Rudder tech drawing from here and resized it to match vertically with my best scaled photograph.  After making it semi transparent and adding it as an overlay to the photograph, the difference between the photograph to the drawing was not more than about two pixels at worst which works out to 0.04 feet.  A lot of it is probably due to the the my scaling of the drawing and photograph and the less than absolutely precise focus.  From this, I can tell he photograph is lined well enough because both vertical and horizontal dimensions match....

Unless you know exactly what you are looking for in the combined image, it looks like the rudder took a bunch of shotgun hits even at 1586 pixels wide.  At the size I would need to reduce the image to post here, it would be a blur which is why I am not posting it.

Thanks.
- Ivan.
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Ivan
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« Reply #9 on: July 12, 2014, 12:45:51 PM »

Hello All.

I finally found enough drawings to be able to locate major components fairly precisely on the longitudinal axis which is where the major problems were with my model.  The drawings are not completely useable for my purposes, but with a bit of conversion and combining information across different drawings, I should be able to arrive at a "reasonable" model of a short tail P-40.  These drawings don't seem to line up at all with the Wylam drawings which has to make you wonder how Wylam came up with all the precise dimensional labels.

- Ivan.
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Vince_M
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« Reply #10 on: July 13, 2014, 10:51:28 AM »

Sorry for the delay, it's been a crazy week.
I just sent the file.

Vince
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Ivan
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« Reply #11 on: July 14, 2014, 02:05:19 AM »

Hi Vince,

I downloaded your scan and also sent the best drawing I am working from back to you.
Hope you will find it interesting to see the discrepancies.

FWIW, I went back to the Wylam drawings and spent a fair amount of time looking them over.
I believe the following is true:

The BIGGEST problem that I can see is that Wylam apparently never figured out that the Fuselage Reference Line was considerably below the Thrust Center Line.  I believe the difference is 3.75 inch and explains some of the shape problems.
The front end of the aircraft is more or less correct vertically above the Engine Thrust Line, but a little off below.    Below the thrust line, the difference is less than can be explained by the 3.75 inch difference.  The Longitudinal measurements  seem to be about two inches short ahead of the cockpit which might explain why the overall length of the aircraft is listed at 31' 7".  The manuals state the measurement to be 31' 8.75" which I believe is the most reliable measurement.

Behind the cockpit, he extends the Thrust Line but I believe he then uses offsets from the FRL instead which would raise the tail significantly and reduce its depth.

What I don't understand is how with factory drawings, how the dimensions can become so confused because there are plenty of dimensions that simply don't make sense and can't be explained by a simple typo.

Can anyone shed some light on this issue?
Thanks.
- Ivan.
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Ivan
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« Reply #12 on: February 09, 2015, 05:03:36 AM »

I finally finished the P-40F (Short Tail).

In this I have run into a slight problem:

The P-40E appears to be 31.73 feet in length.
The P-40F appears to be 31.64 feet in length (31 feet 7 23/32 inches from the Pilot's Manual)
These numbers appear to match pretty well with the numbers in "America's Hundred Thousand" by Francis Dean.

The problem is that the P-40N and P-40L appear to be the same length which is surprising because it implies that the the length difference (presumably in the nose) for the short tail version does not carry over to the long tail version.
Either that is the case or the tail lengths are different which seems even less plausible.

Any idea what is the real story?

Also, does anyone know if the Engine Thrust Line between the Merlin and Allison P-40's is the same?  They look close, but in photographs, the Thrust Line seems slightly higher for the Merlin though perhaps it is just because of the missing Carb Scoop.

Thanks in Advance.
- Ivan.
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Ivan
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« Reply #13 on: February 09, 2015, 10:12:08 AM »

In looking over the large scale drawings here, it appears that the Thrust Line is consistent at 3.078 inches above the FRL.


- Ivan.
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