P-39 Airacobra armor

[fiftycal]

A while ago someone was talking about P-39 armor and i said i would get photos of the belly armor of one of my cobras, i forgot but ended up going to the hangar today, so here is the P-39 factory made belly armor for anyone interested.




in addition there was armor around the gearbox, front and rear windscreens, rear oil tank and occasionally behind the pilots seat.

 

[Ivan1GFP]

 

[Barrett]

Just got a review copy of Osprey's P39 v A6M in the Duel series by Mike Claringbold. 39s claimed c. 90 Zeros for 44 combat losses when MC computes 15 Zeros lost. Not unusual of course. I knew some of the SWP Airacobra guys—they were more interested in survival than claims.

 

[fiftycal]

this is factory made armor for a P-39F-2. only 27 were made, the holes in it are for cameras because they took all of the guns out and fitted cameras and armor

 

[fiftycal]

Just got a review copy of Osprey's P39 v A6M in the Duel series by Mike Claringbold. 39s claimed c. 90 Zeros for 44 combat losses when MC computes 15 Zeros lost. Not unusual of course. I knew some of the SWP Airacobra guys—they were more interested in survival than claims.

the cobra can almost out turn a zero at sea level but in png it was hot humid and high, very high mountains and the japs loved to come in over 20,000ft, the cobra power dropped off badly after 13k feet

 

[P-39 Expert]

A while ago someone was talking about P-39 armor and i said i would get photos of the belly armor of one of my cobras, i forgot but ended up going to the hangar today, so here is the P-39 factory made belly armor for anyone interested.

View attachment 500357
View attachment 500358

in addition there was armor around the gearbox, front and rear windscreens, rear oil tank and occasionally behind the pilots seat.

Wow. Any idea how much that piece weighed? Looks like about a half inch thick.

 

[fiftycal]

Wow. Any idea how much that piece weighed? Looks like about a half inch thick.

i can lift it, maybe 50 kg. i think its made to stop anything up to .308 on a deflection shot, not straight on.

the gearbox armor is steel, this is aluminum

 

[P-39 Expert]

i can lift it, maybe 50 kg. i think its made to stop anything up to .308 on a deflection shot, not straight on.

the gearbox armor is steel, this is aluminum

So, 50 kilos is about 110 pounds? Pretty substantial.
By the way, how many Cobras are in your hangar?

 

[Ivan1GFP]

this is factory made armor for a P-39F-2. only 27 were made, the holes in it are for cameras because they took all of the guns out and fitted cameras and armor

Hello FiftyCal,

That makes this a very very rare piece. Wow!

.......

This next question may be a bit off topic, but perhaps someone here might know:
I see that the Length of every production model of the P-39 / P-400 / Airacobra was 30 feet 2 inches.
Where was this a measurement from?
With the Aft end, it is pretty obvious it would be at the extreme end of the Rudder with the aircraft level, but in the Nose, is it at the end of the Spinner (my current guess) or to the Datum Line at Station Zero?

Thanks in advance.
- Ivan.

 

[fiftycal]

So, 50 kilos is about 110 pounds? Pretty substantial.
By the way, how many Cobras are in your hangar?

3 wrecks left, the rest were sold or parted out. only looking at completing one now, i was going to rebuild several but there is no market to justify the cost

 

[fiftycal]

Hello FiftyCal,

That makes this a very very rare piece. Wow!

.......

This next question may be a bit off topic, but perhaps someone here might know:
I see that the Length of every production model of the P-39 / P-400 / Airacobra was 30 feet 2 inches.
Where was this a measurement from?
With the Aft end, it is pretty obvious it would be at the extreme end of the Rudder with the aircraft level, but in the Nose, is it at the end of the Spinner (my current guess) or to the Datum Line at Station Zero?

Thanks in advance.
- Ivan.

i have seen different measurements between the P-39D1 with 20mm cannon and the D-2 with 37mm so i assume cannon tip to rudder? also i think some P-400's had a squared off rudder

 

[P-39 Expert]

i have seen different measurements between the P-39D1 with 20mm cannon and the D-2 with 37mm so i assume cannon tip to rudder? also i think some P-400's had a squared off rudder

One P-400 had the squared rudder. A couple of prototype P-39Es also had a squared fin/rudder.

 

[P-39 Expert]

3 wrecks left, the rest were sold or parted out. only looking at completing one now, i was going to rebuild several but there is no market to justify the cost

I get to see the P-39N in San Marcos fairly often. It still flies in airshows.

 

[fiftycal]

I get to see the P-39N in San Marcos fairly often. It still flies in airshows.

mine will fly.........in about 30 years lol, its missing something fairly important to allow it to fly....a dump truck full of cash

 

[Ivan1GFP]

i have seen different measurements between the P-39D1 with 20mm cannon and the D-2 with 37mm so i assume cannon tip to rudder? also i think some P-400's had a squared off rudder

Hello FiftyCal,

My understanding was that the measurement did not include the cannon at all.
The Airacobra Mk.I seems in some photographs to have a slightly narrower chord rudder but perhaps it is just the shape and not the chord. It is hard to confirm in a photograph.

My question is really whether the length was measured to the Spinner Tip or "Station 0" that is about 3 inches in front of the Spinner Tip and about 1.4 inches from the tip of the 37 mm cannon barrel.

By the way, are you certain that the P-39D-2 had a 37 mm cannon?
The Detail & Scale book, America's Hundred Thousand, and Warbird Tech all state that it had a 20 mm just like the D-1.
The Bell Model number 14A-1 would also suggest greater similarity to the D-1 than the Model 15 P-39D and P-39F.
Aircraft Profile book and Airacobra Advantage both state the cannon on D-2 was a 37 mm, but I have less faith in those books.
The D-2 was also built on a contract for Lend-Lease aircraft which I believe at the time would have meant for the British who preferred a 20 mm cannon.

Would you happen to know offhand the Tire sizes used by the Airacobra?
From photographs and drawings, I am estimating that the mains were 26 x 6.5 inch and the nose was 19 x 6 inch.

- Ivan.

 

[fiftycal]

Hello FiftyCal,

My understanding was that the measurement did not include the cannon at all.
The Airacobra Mk.I seems in some photographs to have a slightly narrower chord rudder but perhaps it is just the shape and not the chord. It is hard to confirm in a photograph.

My question is really whether the length was measured to the Spinner Tip or "Station 0" that is about 3 inches in front of the Spinner Tip and about 1.4 inches from the tip of the 37 mm cannon barrel.

By the way, are you certain that the P-39D-2 had a 37 mm cannon?
The Detail & Scale book, America's Hundred Thousand, and Warbird Tech all state that it had a 20 mm just like the D-1.
The Bell Model number 14A-1 would also suggest greater similarity to the D-1 than the Model 15 P-39D and P-39F.
Aircraft Profile book and Airacobra Advantage both state the cannon on D-2 was a 37 mm, but I have less faith in those books.
The D-2 was also built on a contract for Lend-Lease aircraft which I believe at the time would have meant for the British who preferred a 20 mm cannon.

Would you happen to know offhand the Tire sizes used by the Airacobra?
From photographs and drawings, I am estimating that the mains were 26 x 6.5 inch and the nose was 19 x 6 inch.

- Ivan.

Hi, the cobras were not all uniform. i have a early P-39D that had i think a 20mm judging by the ejection port size in the lower keel but it also had P-400 exhaust stacks, i also had a D-2 that did have a 37mm, i still have the mounts for it. they might have swapped and changed in theater as the 20mm was more accurate and in new guinea they used a ton of P-400's for parts. for example on woodlark island they left a lot of them in crates and only used a few parts.

26x6.5 mains is right, the nose wheels vary, im not sure of the early cobra sizes but the later Qs were 19 x 6 i think. i only have the later wheels

 

[Ivan1GFP]

Hi, the cobras were not all uniform. i have a early P-39D that had i think a 20mm judging by the ejection port size in the lower keel but it also had P-400 exhaust stacks, i also had a D-2 that did have a 37mm, i still have the mounts for it. they might have swapped and changed in theater as the 20mm was more accurate and in new guinea they used a ton of P-400's for parts. for example on woodlark island they left a lot of them in crates and only used a few parts.

26x6.5 mains is right, the nose wheels vary, im not sure of the early cobra sizes but the later Qs were 19 x 6 i think. i only have the later wheels

Thanks for confirming the Tire sizes. I have never been able to find a reference for that which is why I was working from photographs and drawings.

The D-2 with a 37 mm cannon really has me wondering though.
The 20 mm wasn't as highly regarded as the 37 mm for some reason and I find it strange that a substitution would be made in the field.
As I mentioned before, written sources don't tend to agree on whether the D-2 carried a 20 mm or a 37 mm.
America's Hundred Thousand even gives a weight breakdown of a D-2 armed with a 20 mm cannon.
There were only 180 aircraft produced for a single contract, so I would expect them to be uniform for armament.
Can you PM me the serial number for your D-2 for my notes?

Thanks.
- Ivan.

 

[fiftycal]

Thanks for confirming the Tire sizes. I have never been able to find a reference for that which is why I was working from photographs and drawings.

The D-2 with a 37 mm cannon really has me wondering though.
The 20 mm wasn't as highly regarded as the 37 mm for some reason and I find it strange that a substitution would be made in the field.
As I mentioned before, written sources don't tend to agree on whether the D-2 carried a 20 mm or a 37 mm.
America's Hundred Thousand even gives a weight breakdown of a D-2 armed with a 20 mm cannon.
There were only 180 aircraft produced for a single contract, so I would expect them to be uniform for armament.
Can you PM me the serial number for your D-2 for my notes?

Thanks.
- Ivan.

i sold the D2 not long ago, it was 41-38385 that shot down some aircraft before being shot down in new guinea.

the one im rebuilding is 41-6978 that was used by the naca to test self sealing tanks, then used in the war games as the enemy before being shipped to the pacific with the 12fs and crashing on vanuatu. im rebuilding it using the tail section of 41-7191 (P-39F) and some of the fwd fuselage of a P-39L that was recovered from a farm in washington usa (the farmer was hacking it up for scrap).

i have uploaded the latest wheel revision drawing if it helps

 

[P-39 Expert]

Thanks for confirming the Tire sizes. I have never been able to find a reference for that which is why I was working from photographs and drawings.

The D-2 with a 37 mm cannon really has me wondering though.
The 20 mm wasn't as highly regarded as the 37 mm for some reason and I find it strange that a substitution would be made in the field.
As I mentioned before, written sources don't tend to agree on whether the D-2 carried a 20 mm or a 37 mm.
America's Hundred Thousand even gives a weight breakdown of a D-2 armed with a 20 mm cannon.
There were only 180 aircraft produced for a single contract, so I would expect them to be uniform for armament.
Can you PM me the serial number for your D-2 for my notes?

Thanks.
- Ivan.

Some substitutions were made in the field. The early 37mm cannon was not as reliable as the 20mm and pilots would pull the 20mm from wrecks to substitute for the 37mm. The 37mm reliability went way up with the K (and subsequent) models which ducted more heated cockpit air to the gun bay which kept the open breech from freezing at altitude. The Russians considered the 37mm much more reliable than the (early) 20mm.
20mm went through some improvement also as it was considered reliable in the P-38.
But the D-2 came from the factory with the 37mm.

 

[Ivan1GFP]

Hello FiftyCal,
Thanks for the reference drawing for the nose wheel and the history of your airframes.
My apologies for hijacking your thread.

Hello P-39 Expert,
Thanks for the confirmation. I wonder though why there are different conclusions from different references.
I would have considered America's Hundred Thousand to be pretty reliable but for quite a few typps but discrepancy is far from a simple typo.

Gentlemen,
I have been trying to put together the references that I have in order to see how things fit together and am also attempting to build a 3D model. There is a LOT of reference material, but much of it seems contradictory at this point.
What should be a simple matter of overall length does not seem to be nearly so simple.
The typical length is listed as 30 feet 2 inches but does the measurement begin at the front of the Spinner or at the Fuselage reference which is 3 inches ahead of that? Dimensional drawings do not agree.
From scaling several high resolution drawings, I believe measurement from Spinner to Rudder is actually 29 feet 11 inches.

Another odd thing is that the Station diagram shows what appears to be the line between the Spinner and Nose as Station 15 1/16 inch. If this is the case, then "Station Zero" would be not quite to the tip of the Spinner instead of about 3 inches forward of it and there is a different reference line being used.
The problem with that interpretation is that last fuselage station would not match the Rudder Hinge Line but be about 6 inches behind it which makes no sense when compared to photographs and drawings.

- Ivan.