patterndreamer

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Hey guys,

I just saw a p-39 today and i was wondering. Has anyone attempted to put the engine in the scale location on these birds? Its an interesting set-up but albiet difficult to accomplish.

patternd

khodges

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Sure would be a technical challenge, from a modelling standpoint. Engine was actually behind the c/g, but the 20mm cannon in front balanced it out.

wascamp

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K, actually the P39 mounted a 37 mm M4 cannon and 2 M2 .50 cal MG's. A recent restoration of a P-63 Kingcobra required the ammo cans from the original setup be filled with lead to offset the removal of the original guns. I would think that cooling would be a huge problem as the original was liquid cooled. The new RCV four stroke would fit in the cowl but I think even that one needs air and the real plane has no intake whatsoever in the nose. Electric is an option but even they need to exaust heat.

patterndreamer

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Yeah it was just a thought. you could do it, but only on a very large one then you'd need to work out the cooling issue.

patternd

grbaker

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Years ago, there was an article in Model Aviation about a guy that built a Top Flite P-39 with the glow engine in the scale location. He had a marine head on it and he circulated water from a tank through the head and back to the tank. Since there was no flight report in the article, I assumed that he had not flow it.

khodges

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Thanks for the correection, 20 mm didn't sound right when I said it, and the hole in the prop hub sure looks a lot bigger. The -63 has a air scoop just behind the canopy that would work for intake of cooling air, the problem is where to let the warm air out. (I wonder if you made the exhaust headers "functional" as warm air outlets would they be enough). I've always liked these planes, and even though they weren't the success the -51's and -47's etc. were, it was a cool idea to put the engine "in back". If I were a pilot, though, I think I might worry that the engine would squish me if I crashed and otherwise survived the impact.

When I was about 7 or 8 years old (about 1961-62), my Dad bought me a control line Cox P-63 with an .049. We managed to fly it once, and then my dad stuck his finger in the prop, broke the prop, never flew it or ran it again.

patterndreamer

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i looked it up and there was no more risk in the p-39 and 63 in a crash than any other conventional plane. Maybe you could do something with a 63 it might be worth getting one and trying it out to see if it works.

patternd

badger41

Patterndreamer,
Back when the Toledo show was at the hockey arena, Roger Brennan entered a 1/5 scale p-63 in the "pinball scheme" with a rear-mounted os.91 with gear drive and liquid cooling,and drive shaft and scale 3 blade prop . It won best of show that year I think. An engineering marvel.
tom

rrudytoo

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Actually, the P-39 was available with either the 20mm or the 37mm cannon. Some years back I read a book entitled "Nanette" which was the unofficial name of the author's P-39 that he flew during WWII in New Guinea. Sadly, I can't recall the author's name. Anyway, he made reference to the two cannon types used in the Airacobra and its "effects" on the pilot while firing. These "effects" were felt in the crotch area with the 37mm gun firing slowly but with a pronounced "effect". The 20mm fired more rapidly but without the degree of "effect". I laughed outloud when I read the author's comment that, "I was a 20mm man, myself".

As for mid-mounting the engine, consider that the Moki does not use nitro in its fuel and, therefore, runs relatively cool hence, avoiding the over-heating problem provided that some measures of air flow are provided. These measures may be openings around the exhaust manifolds, the carb air inlet behind the canopy, the intakes built into the wing leading edges and the shutters located under the fuselage between the flaps. Another option, though admittedly not all that appealing, would be the use of a diesel powerplant. Diesels love heat and are reliable to a fault! Unfortunately, they're messy and smelly.

Just my 2 centavos.

Al

patterndreamer

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Yeah i thought about diesel, but then there is that lack of scale appeal when you go that route. I'm just wondering what widely avalible powerplant would work for this. maybe one of those RCV-91CD's? not the honeycomb one but the shorter one.

patternd

khodges

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I read Yeager's autobiography a few years ago; I remember him talking about he and his cohorts flying P-39's out at Muroc (now Edwards AFB) and seeing who could fly the lowest while following the "roads". They would later drive out those roads and find prop marks in the dirt[sm=stupid.gif]

rrudytoo

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Prop marks in the dirt!! And I think about some of the silly stuff I got reamed for. Life just isn't fair!

I read that book, too and, remember Yeager describing the "tree trimming" incident. What did we learn in shop class? The proper tool for the proper job? A P-39 tree trimmer. Just what every young man needs in his tool box! God bless Chuck Yeager.

Al

patterndreamer

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There would be a scale manuveur that would get you thrown out of a contest.

patternd

rctrax

A couple years ago I was down to the AMA muesium and they had on display a P-39 scale model that had a scale mounted mid engine. I don't know if it was successful or not but it was a fantastic piece of work

patterndreamer

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I wish i could see that model and indeed find out if it flew, and if not why.

patternd

britbrat

That was a good book -- I read it as well!

The 20 mm version was actually a P-400, an export varient of the P-39. It was sometimes called a "P-40 with a zero on its tail". Although the author referred to her as a P-39, Nanette was actually a P-400. Both versions were called Aircobra's.