P-39 Racer

[Idaho_cowpony]

Good-day folks,

One of the questions that often turns in my head, is the age-old question of the suitability of the P-39 for pylon racing.

The quick facts that stand out to me are; the great success of 'Cobra II' during the Cleveland era. And Mr. Carroll's ambition to develop a pylon racer out of that derelict P-39, rather then his expensive, and fast Signal Sea Fury.

The Sea Fury... what was wrong with it as a pylon racer to begin with? We know now, after history, not a whole lot. The wing is right, and the airplane does well on the course. Race #87 was the pioneer of racing Sea Furies, and also, of course, was only powered by the sleeve valve Centaurus. However, with that said. It's an airplane that from the factory is almost 90mph faster than the P-39.

So why... Why does Carroll... Why does Slovak.. why choose the P-39??

Personally I'm a believer. I think had projects like 'Cobra III', and 'Mr Mennen' been devised in today's modern world of air racing, with the things that have been learned up til this point, the aircraft could have been developed to be very capable of competitive speeds. (even by today's standards)

The aircraft is going to way significantly less than a Mustang. And have less frontal area, if I assume correctly.

PIREPS say that a properly configured P-39 handles extremely well. The room in the nose for an ADI tank, and other goodies would seem to be a positive feature. Also, the potential of aft CG would seem a plus, in regards to drag and overall co-efficiency.

So.. Let's talk this out, again, for a bit.. I want to hear the best reasons from the critics, of why the P-39 wouldn't do well. And also the opinions of believers like myself, who are optimistic about it's capabilities.

Roll on... and Happy Holidays!

- Joseph

[Big_Jim]

Re: P-39 Racer

The wing on the P-39 sucks so you are kind of speed-limited there. But the airframe is so light and tiny, you get a pretty good horsepower to weight ratio, even with an Allison.

Cobra I and II had that big paddle blade prop, and if you read any of the accounts of Tex Johnston running in 1946 he was very respectful of flying the airplane in the race. I know from talking to him in person before he passed away that Cobra II was more than a handful...though you wouldn't know it to watch him.

Cobra III tried the big 4-blade prop too. My opinion and several others who were there that day feel that the prop set up some ungodly vibrations, and with the clipped wings was very unstable. Carroll just did not have the experience to recognize what was going on, as if I recall he had less than two hundred hours total flight time in his book. Scared the hell out of him and probably realized he was over his head and couldn't control it.

When Mira tried running with a similar 4-blade propeller he made a couple of test flights with it and said it took all of his airmanship to keep it going straight and level and was happy to get it back into the pattern and on the ground. The went to Reno with a stock 3 blade in '72, but for the next couple of years actually tested a big 3-blade paddle prop, which was still apparently a handful. They finally gave up on it and Mira sold the plane.

Doug Fisher did a really good story on the Cobra racers in Air Classics last year which included an extensive interview with Slovak and in no uncertain terms he says that big 4-blade was evil, and gave a lot of props to the three guys who flew Cobra II from '46-48 for being able to handle it.

I think if you were going to run a modified P-39 as a racer you'd have to put a much bigger tail and rudder on it just to keep it going in a straight line...as well as only making left-hand turns. Ever.

[Propellerhead]

Re: P-39 Racer

I think if you were going to run a modified P-39 as a racer you'd have to put a much bigger tail and rudder on it just to keep it going in a straight line...as well as only making left-hand turns. Ever.

So in other words, run a P-63.

[Idaho_cowpony]

Re: P-39 Racer

Yes, I'm well aware of the ill effects of the other propeller setups. My Ideas would lean toward a lengthened fuselage, taller vertical stabilizer, modified wing airfoil. If she can qualify ahead of all the Corsairs in '48...

In 2011 Mr. Odegaard qualified the big Corsair at 380. I would imagine conservatively. What would we have expected from Cobra II at Reno, in it's historic form? Maybe 400? So we could maybe assume she would have been a top 3 contender, right into the 70's. Surely begs ones interest.

[V1670]

Re: P-39 Racer

Paging Mr. Hinton; Mr. Steve Hinton to the white courtesy phone please.

If I remember correctly, his first run on the pylons was in a P-63. And (I believe) it was an F-model with the taller tail.
He'd be in my opinion, the best source for info on why/why not a Cobra-racer. Also, refer to the Allison/Merlin motor thread elsewhere on this forum.

[Big_Jim]

Re: P-39 Racer

The best explanation as to why the P-39 isn't and won't make a good racer in the modern era is in the book Cobra! by Birch Matthews. It has a really good couple of chapters on the racing Airacobras and King Cobras.

[IcePaq]

Re: P-39 Racer

I'm guessing the higher horsepower put to the prop through a long shaft might have caused issues that would have taken a lot of experimentation and engineering to fix.

It's also possible that the mass of the gun connected to the gearcase had a positive effect on quelling vibrations and removing said gun may have caused the vibrations.

More than likely, higher mass of the gearcase would have helped when they went to a heavier prop.

Also notice the single U-joint shaft which proved vibration prone in cars and hasn't been used in many decades.



Without gun.

[B29FE177]

Re: P-39 Racer

The center bearing on the P-39/P-63 drive shaft is not a universal joint. It is just a support bearing. The shaft assy. is two piece and is rigged with NO angle. One side of this support has a spline, the other side is flanged. I, at one time when we had Mr. Mennen, found and bought 5 center bearings and 10 shaft sections to keep them from being scrapped. I sold them for what I paid and they were donated to the CAF. The drive shaft in the P-39/63 always comes up in conversation of the aircraft but I know of no problems attributed this assembly.
A true universal joint MUST run at an angle or it will vibrate.

[Idaho_cowpony]

Re: P-39 Racer

Thank-you for the solid information!

If I were to bring up one draw-back of the P-39, in regards to racing, it would have to be the wing. However, with that said, what types of airfoil modifications could be done, to help alleviate that?

- Joseph

[B29FE177]

Re: P-39 Racer

The question keeps arising as to's why Mira Slovak's P-39 Mr. Mennen could be or was not a successful race plane. It could've been, were it not for an overzealous FAA lawyer, a retired ex-FAA egotist and a Continental Airline's Vice President. The aircraft itself was not the problem it was a people problem!

Now that's out of the way let's get to the mechanics of the airplane itself. In 1972 after the airplane's return to Dick Martin's facility at Van Nuys a new 40 gallon tank was installed in the nose for ADI and spray bar fluid. At the same time, bearcat brakes and wheels were installed. The paddle bladed three blade prop had returned from the prop shop and was installed at that time. Dick Martin was moving his operation from Van Nuys to Palomar airport so Mr. Mennen was flown down there with no problems. Once it Palomar, Mira was contacted by another Continental Airlines Capt., Ted Janczarek to do a flight test article on the aircraft for Sport Flying magazine. That article was published in the January and February 1974 issues of that magazine. Mira gave Ted a cockpit checkout and Ted made two trips around the pattern with no problems of instability. It should be noted that Ted flew right-hand patterns which had been virtually impossible with the paddle bladed four blade prop. Ted then proceeded to deliver the airplane to Oxnard California. During the latter part of that flight the propeller began to malfunction by trying to overspeed. Ted was able to continue to Oxnard where he landed successfully. The toothpick three blade prop was reinstalled and Ted finished his flight test article for the magazine. Mira then flew the airplane to Santa Paula where was put in his hanger. So, as you can see the airplane with the paddle bladed three blade prop was completely controllable. Big Jim in his thread leaves the impression that the airplane craft was still unstable with the paddle bladed three blade prop and that is why it got parked and later sold. That was completely untrue! Mira was busy trying to pay for lawyers to fight the Reno violation, doing airshows in his Lunak glider and Bucker Jungmann. During one of those shows at Mojave I approach Mira about taking the P–39 to Torrance where I could work on it on my weekends. He quickly agreed. We made plans to take the airplane, with the repaired paddle bladed three blade prop, to the Cape May air races. We were going to approach Skip Cooley, who built the engine, and Bill Yoak, who worked for Dick Martin during the rebuild to assist me at the races. At that time we felt we had a viable race plane.

It was on the ferry flight from Santa Paula to Torrance that the retired FAA inspector, Jim Dewey filed as I recall seven violations against Mira's flight leaving Santa Paula. They were so ridiculous the FAA advised him to drop his allegations, which he did. However, the allegations were somehow turned over to our illustrious VP who threatened Mira's job unless he got rid of the aircraft. That, is why Mr. Mennen no longer raced and any other allegations are completely false!

[B29FE177]

Re: P-39 Racer

Now that I've hopefully answered some questions about the P-39, Mr. Mennen, I will try to make some comments about a P-39 as a race plane and its potential for winning. In the early 1970s we figured Mr. Mennen could do it. Remember, in 1972 when we tried to run at Reno, Gunther Balz won at something like 417 mph. Think how many years and cubic dollars it is taken for highly modified airplanes like Strega and Voodoo to still not average 500 mph during a race. We had a saying at Bonneville "the faster you go, the harder it is to go faster".

Then we get into the P-63 question. It was longer, had a better airfoil and in the case of the F model, a larger vertical stabilizer. Sandberg tried for many years before he gave up on his P-63. Larry havens put a lot of modifications in his but it wound up in the Pacific Ocean after an engine failure. It was no "ball of fire" at San Diego, however it was freshly done and may have had better results later.

Another thought came to my mind about Cobra III. It is my understanding that Mike Carroll was really more interested in the prop driven speed record than circle racing. Had we gotten Mr. Mennen to its potential I know Mira's interest would have been running at Reno but being an old dry lakes and Bonneville racer I would have wanted to go for the prop driven speed record. Neither of us got our wish.

The P 39 question is rather moot. There are too few and are too valuable to modify as race planes. If we still had Mr. Mennen and unlimited finances I would put it in a hangar were I would look at it lovingly and buy the Strega operation from Tiger. Remember, I stipulated unlimited finances.

Would you believe our effort with Mr. Mennen occurred 40 years ago. When I try to get up from my desk after writing this, I WILL BELIEVE IT!!!

Don Vance

[Idaho_cowpony]

Re: P-39 Racer

Mr. Vance,

Wow! Such valuable information! Thank-you very much.

My dad was fresh out of High School, and 17 years old, when he first made the jaunt to Stead for the races It was 1972, and his biggest motivation to attend was to see Mira's 'Mennon'. He was sure disappointed that the Cobra was unable to participate.

What could have been? Well, at the very least, sure is fun to think about.

Best,
- Joseph

[Lockheed Bob]

Re: P-39 Racer

Air Race Fans have to remember when Alvin"Tex" Johnson won the Thompson Trophy race in 1946 in the P39 it was a 30 mile course for 10 laps(300 Miles). Thats when they really raced.

[B29FE177]

Re: P-39 Racer

Idaho_Cowpony,

I'm glad your dad got to see Mr. Mennen. Most people had never seen a P-39 fly. At that time, Mr. Mennen was the only one flying in the world. That was the only reason Mira agreed to open the show on Saturday and Sunday. Big mistake!

The only laugh we got that weekend was the big bold headline in the Reno newspaper "SLOVAK SCRATCHED". Under that, in much smaller print was "So and so qualifies at XXX". I can't remember who it was.

You have to realize that Mira was quite a hero in Reno as the 1964 winner and for driving Harrah's gold Cup boat.

[Idaho_cowpony]

Re: P-39 Racer

...Mira was quite a hero in Reno...

Still is!