Author Topic: Aircobra (P-39) teaser (Read 3875 times)

Pat Johnston · « **on:** March 15, 2012, 07:46:10 AM »

Bill Little mentioned last month that I needed an Aircobra for the Warbird Stable. Here is the outline. Good numbers. Great TVC, wing area in the low 560 inch range, for a 40-46. Should be a cutie. After doing it, the outlines are rather pleasing to the stunt eye. The wing has just a little more leading edge sweep than the P-40, but the shapes are close in a lot of the main components. Plans should be complete in another week or so.
Pat Johnston
Warbird Design Studio
Skunk Works

Dennis Moritz · « **Reply #1 on:** March 15, 2012, 08:47:36 AM »

Do you think vertical CG will be an issue? Are you planning to handle this with dihedral? I am not a fan of dihedral in CL planes. I know folks have a difference of opinion on this.

Bill Little · « **Reply #2 on:** March 15, 2012, 10:37:16 AM »

It looks great, Pat! Perfect for the OS .46LA. Should do really well!

Bill

Balsa Butcher · « **Reply #3 on:** March 15, 2012, 10:58:37 AM »

I like it Pat. Previously the most scale like stunt P-39 was by Walt Pyron, updated in FM by Bob Hunt. That one was a little smaller and had a side mount engine (but is classic legal). My issue with Airacobras has always been the canopy. A cut-down Sig WW-II canopy is close but not quite there. Easy to go from a P-39 to a P-63. Maybe show both on same plan? My guess is that it would be pretty much just a change in the rudder/vert stab.

proparc · « **Reply #4 on:** March 15, 2012, 11:00:17 AM »

Seems pretty close. I'd push back the canopy.

Tom Strom · « **Reply #5 on:** March 15, 2012, 12:36:25 PM »

OK Pat. Now you got my attention. Have always loved the lines of that aircraft. When you get one built, don't hesitate to send it to Tony and I to play with!!!!

Tom

Bill Little · « **Reply #6 on:** March 15, 2012, 12:39:55 PM »

Quote from: Tom Strom on March 15, 2012, 12:36:25 PM

OK Pat. Now you got my attention. Have always loved the lines of that aircraft. When you get one built, don't hesitate to send it to Tony and I to play with!!!!

Tom

Hi Tom,

You just need to volunteer to build the prototype for Pat! You can do a build thread here and get a great model to boot!

BIG Bear
RNMM/AMM

Peter Grabenstein · « **Reply #7 on:** March 15, 2012, 01:17:00 PM »

Oooops,

here is Christoph Holtermann´s Aircobra P39 with OS LA46.

http://www.fesselflug.eu/html/cobra_von_christoph_holtermann.html

cheers Peter

dennis lipsett · « **Reply #8 on:** March 15, 2012, 02:01:48 PM »

If I remember correctly Walter Umland had produced a P-39 form one of the fameous classic era designers.

Dennis

Steve Helmick · « **Reply #9 on:** March 15, 2012, 02:32:35 PM »

Quote from: proparc on March 15, 2012, 11:00:17 AM

Seems pretty close. I'd push back the canopy.

I agree! The rear deck is too long, making it look "funny". I also vote for the P-63, tho I believe the horiz. tail is also shaped differently. But both look very cool!

Steve

Balsa Butcher · « **Reply #10 on:** March 15, 2012, 03:01:20 PM »

Walter's excellent kit was of the Bill Simons P-39. Although an excellent stunter it was not as scale like as Walt Pyrons design and as undoubtedly Pat's will be.

wwwarbird · « **Reply #11 on:** March 15, 2012, 09:30:17 PM »

Quote from: proparc on March 15, 2012, 11:00:17 AM

Seems pretty close. I'd push back the canopy.

I definitely agree with moving the canopy back a bit and also showing the P-63 fin/rudder as a build option.

Pat Johnston · « **Reply #12 on:** March 16, 2012, 08:08:38 AM »

Good input from all you guys. I slid the canopy back about 1/3". Better that way.
I did do the plans for Walter's P-39 he kitted some years ago. I really didn't care for the use of solid blocks which were to be carved and hollowed. My version has formed sheeting over formers. It should be very light. Target weight in the low 40 ounce range with good wood selection. I'm projecting the ribs right now. The root will be a little thicker (18%) than the tip (16%). Of course, the world famous front end ellipse, transitioning to the trailing edge. With the roundish tips, the result will be a low drag tip for (theoretically) better wind turbulence control. Dihedral is a must with the wing as low as it is. Starting to shape up.
Tom, If you want to be the official Prototype builder, I can cut you the first kit.
Pat Johnston
Skunk Works

RDJeff · « **Reply #13 on:** March 16, 2012, 09:36:44 AM »

One of my all time favorite planes! I'm talking about the full scale ones. It's a shame they didn't perform as well as their looks would indicate. They flew them up here in their thousands, painted red stars on them, and then handed them over to Russian pilots who often exchanged good vodka and caviar for real nylon stockings. Once in a while, one will turn up in the woods around town, guns loaded and everything.

Douglas Ames · « **Reply #14 on:** March 16, 2012, 06:01:39 PM »

Looks good, but I'd drop the thrust line a little and change the ogive of the nacelle (3-blade prop or taller gear?)

- a little more curve on the top and less on the bottom.

Push the flaps outboard and make the T/E fillets larger. Canopy looks OK to me?

I realize stunt #'s aren't always scale. Trying not to be critical, just constructive. I'd buy one!

phil c · « **Reply #15 on:** March 16, 2012, 07:59:02 PM »

Now if you can just figure out how to mount the retracts. WW-II birds look just kinda silly stunting with the grear hanging out.

proparc · « **Reply #16 on:** March 16, 2012, 08:53:45 PM »

Quote from: phil c on March 16, 2012, 07:59:02 PM

Now if you can just figure out how to mount the retracts. WW-II birds look just kinda silly stunting with the grear hanging out.

You know, the one plane that really solves that problem,the ME 109 just doesn't get any love in stunt. You can fuselage mount the landing gear, and it stills looks scale. But, there one problem, the plane is as UGLY as hell!!

I bet a lot of WWII ME 109 pilots got off easy because, the hot looking Mustangs would engage them, and feel sorry for them because of their bu# ugly looks.

Or maybe they thought, why waste good bullets, when all we have to do is wait for them to crash and burn on ground handling.

wwwarbird · « **Reply #17 on:** March 16, 2012, 09:20:36 PM »

Quote from: Pat Johnston on March 16, 2012, 08:08:38 AM

Good input from all you guys. I slid the canopy back about 1/3". Better that way.

A third of an inch? If that's the case, it still needs to come back quite a bit more.

qaz049 · « **Reply #18 on:** March 16, 2012, 10:37:01 PM »

Quote from: RDJeff on March 16, 2012, 09:36:44 AM

One of my all time favorite planes! I'm talking about the full scale ones. It's a shame they didn't perform as well as their looks would indicate. They flew them up here in their thousands, painted red stars on them, and then handed them over to Russian pilots who often exchanged good vodka and caviar for real nylon stockings. Once in a while, one will turn up in the woods around town, guns loaded and everything.

Same in Australia.

This example crashlanded on a beach on Cape York (Northern Queensland) while escorting replacement aircraft flying North to Port Morseby in New Guinea. It sat on a beach from 1942 to the mid 1970's when it was recovered with ammunition intact. It later came to light that this particular aircraft had taken part in the defence of Port Moresby and had shot down three Japanese bombers.

Ray

wwwarbird · « **Reply #19 on:** March 17, 2012, 10:33:52 PM »

Just another thought here Pat. Off hand, I don't know how a guy would design the nose structure, but this design really would look better with side mounted engine. This would keep the P-39's sleek nose outline from the profile view looking better. Studying the plans for the older Walt Pyron designed P-39 might help with some ideas.

This is a kit offering that I would seriously consider. I've always wanted to do a "Tipsy Miss" P-63 Reno Racer and this could easily be transformed into one.

Please keep us posted as the drawings evolve Pat.