More proof that the P-39 rules! 😂 (1 Viewer)

[FLYBOYJ]

I read somewhere that the engines used on these aircraft did not have tight tolerances between the pistons and cylinder walls and most of that "black soot" was actually engine oil getting blown out from the exhaust valves. I've been trying to find the article that mentions this.

 

[FLYBOYJ]

In the original article;

 

[cammerjeff]

In the link I posted as the source, it talks about undersized pistons that allowed excessive oil blow by. I am not sure if the pistons were under bore size, or short skirt?

 

[FLYBOYJ]

In the link I posted as the source, it talks about undersized pistons that allowed excessive oil blow by. I am not sure if the pistons were under bore size, or short skirt?

Piston undersized per the article

 

[FLYBOYJ]

From the same article

 

[cammerjeff]

Looks like Revell even issues a Kit of the Cobra II

 

[Shortround6]

I kind of like the Tucker Special, weird but interesting.

Clipped the wings a little to much. Whatever he gained on the straights he lost on the turns.

 

[GrauGeist]

I read somewhere that the engines used on these aircraft did not have tight tolerances between the pistons and cylinder walls and most of that "black soot" was actually engine oil getting blown out from the exhaust valves. I've been trying to find the article that mentions this.

I figured it was running a rich fuel mixture, since it was a racer.

My '68 Chevell had a 502 big block running 12.5:1 compression with a Hillborn MFI that metered a rich air-fuel mixture, allowing it to run optimum at peak RPMs, but when it was at idle or lower RPMs, it was a smokey bastard.

 

[Shortround6]

A weight table for the Cobra II shows 1488lbs of fuel and 747lbs of water/alcohol mix.
There was some very heavy liquid consumption during the race. They not only stuck a 25 gallon P-63 water tank in the wing, they stuck a 75 gallon tank in the nose.
They also stuck a fuel tank in the rear of the fuselage in addition to putting thin wall bladders in place of the normal fuel cells.

 

[fubar57]

Surprised it didn't tumble its way around the course

​

 

[Shortround6]

Well, they got rid of the nose armor and that made everything OK !

 

[GregP]

Makes me wonder really hard how it handled since the 4-blade prop represents an increase in vertical surface area forward of CG without a corresponding increase in vertical surface area aft of CG. There was more than one P-39 that didn't handle at all well with a 4-bladed prop.

 

[Shortround6]

some of the racers had metal covered rudders and elevators.
I have no idea if that helped or hurt the control response but it should have cut a bit of the drag.
The Book "Cobra" by Birch Matthews has got full page weight comparisons for the 1946 Cobra II, the 1946 Tucker Special and the 1946 Lilly racer.
What they are not telling you is the change in the CG.
The Cobra II had 478.8lbs taken out of the empty weight, but they added 527.5lbs to the useful load (Fuel, oil and water/alcohol) and that was after they got rid of the guns, ammo gun, sight, oxygen equipment, 109lbs worth of radio (they left 20lbs), flare pistol, armor plate and armor glass.

I wouldn't even want to begin to guess how theses flew compared to the service aircraft.

 

[GrauGeist]

I'm assuming they got rid of the heater, too...

 

[GregP]

and the nose armor ...

 

[BlackSheep]

I always liked this shot of the 2 P-39 air racers on the Bell Flight line
View attachment 672663

source Cobra II Archives - This Day in Aviation

They actually look pretty sleek in civvies

 

[Big Jake]

They were old school, with crank handles.
Only thing missing was wind-wings and an AM radio in the dash with a chrome bezel and knobs!

Those that had ADF systems had AM radio set

 

[NevadaK]

Oh, and you could order top stitched hand tooled leather seats and steering wheel cover as a premium.

 

[GrauGeist]

Let us not forget the fuzzy dice hanging from the rear-view mirror and the plastic Jesus on the dash...

 

[Shortround6]

Let us not forget the fuzzy dice hanging from the rear-view mirror and the plastic Jesus on the dash...

It is 1941-42. Plastic is rare.
But a bakelite Jesus just sounds strange