Go Back  RCU Forums > RC Airplanes > RC Warbirds and Warplanes
Reload this Page >

1/5 scale Bell P-39 Aircobra...

Notices
RC Warbirds and Warplanes Discuss rc warbirds and warplanes in this forum.

1/5 scale Bell P-39 Aircobra...

Old 01-04-2006, 07:16 PM
  #1  
Darrell B.
Senior Member
Thread Starter
 
Darrell B.'s Avatar
 
Join Date: Dec 2003
Location: Rogers, AR
Posts: 403
Likes: 0
Received 0 Likes on 0 Posts
Default 1/5 scale Bell P-39 Aircobra...

Well I finally have had some time to start my new project and thought that I would post a couple of pictires. I am building Jim Pepino's 1/5 scale Bell P-39 Aircobra. It will have an 80.5 inch wing span. I am uncertain of the AUW at this time, but I will weigh things as they progress and let you all know. Here are a couple of beginning pictures of the fuselage construction. I chose to cut out the parts my self so it is taking a little extra time. So far things seem to be working out quite well, and the plans look top notch. I hope that I don't regret saying that.,
Attached Thumbnails Click image for larger version

Name:	Ge96102.jpg
Views:	243
Size:	63.3 KB
ID:	381094   Click image for larger version

Name:	Pk30443.jpg
Views:	268
Size:	50.7 KB
ID:	381095  
Old 01-04-2006, 10:02 PM
  #2  
Darrell B.
Senior Member
Thread Starter
 
Darrell B.'s Avatar
 
Join Date: Dec 2003
Location: Rogers, AR
Posts: 403
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 1/5 scale Bell P-39 Aircobra...

Sorry for the slow start!

Here are a few more pictures of my fuselage build on the P-39.
Attached Thumbnails Click image for larger version

Name:	Tr49228.jpg
Views:	226
Size:	48.3 KB
ID:	381215  
Old 01-04-2006, 10:06 PM
  #3  
Darrell B.
Senior Member
Thread Starter
 
Darrell B.'s Avatar
 
Join Date: Dec 2003
Location: Rogers, AR
Posts: 403
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 1/5 scale Bell P-39 Aircobra...

more!
Attached Thumbnails Click image for larger version

Name:	Lj21611.jpg
Views:	206
Size:	53.9 KB
ID:	381217   Click image for larger version

Name:	Up48512.jpg
Views:	186
Size:	55.0 KB
ID:	381218  
Old 01-05-2006, 12:15 AM
  #4  
rrudytoo
Senior Member
My Feedback: (27)
 
rrudytoo's Avatar
 
Join Date: Dec 2002
Location: Simpsonville, SC
Posts: 823
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 1/5 scale Bell P-39 Aircobra...

Hey Darrell,

Now here's a refreshing change of pace! I've seen this plan offered but shyed away due to some unknowns. Mainly, I don't know anyone who built a design by Jim Pepino nor do I know where to get things like the canopy and fiberglass parts. Is there a current list of suppliers for these parts supplied on the plans?

What do you plan to power your Airacobra with? Will you be using the Robart retracts for the Palmer P-63 or is there another set available? Any thoughts of putting the engine in the original, mid-ship position?

Good luck, Darrell, and I'll follow along with your build.

Al
Old 01-05-2006, 08:18 AM
  #5  
Darrell B.
Senior Member
Thread Starter
 
Darrell B.'s Avatar
 
Join Date: Dec 2003
Location: Rogers, AR
Posts: 403
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 1/5 scale Bell P-39 Aircobra...

Al,

Let's see if I can answer your questions;

We have a couple of guys in our club that build off of Pepino's plans. One of them is building a Waco right now , and after looking at his plans, that was what pushed me over the fence to order these. They all seem to be nice airplanes. So far, it seems to be build very nicely, but not over built.

The suppliers listed on the plans are all out of business. These were drawn back in the early 90's. I talked with Craig at Fiberglas Specialties, and I am trying to make an origional cowl, worthy of copying, and he said that he would make me a fiberglass one. There isn't a canope available, but the plans do give instructions on how to build one.
The bigest challenge for me is going to be the engine exhausts and the air scoop on the top.

Robart makes a set of retracts that they just call P-39. They are close, but I am working with them to come up with a set that will fit into the plane better, and hopefully look more scale. Keep your fingers crossed, and we'll see.

I have thought about looking at building this with the engine in the origional mid engine configuration, but there are some huge cooling issues. I just don't know right now about this, and which motor to power it with. There are several out there, and more comming that will fly this airplane quite easily.

I would appreciate any and all comments about ths airplane, or my techniques, or suggestions on any issues discussed here. Thansk for your interest?

Best Regards,
Darrell
Old 01-05-2006, 08:29 AM
  #6  
a65l
My Feedback: (17)
 
a65l's Avatar
 
Join Date: Dec 2003
Location: va veach, VA
Posts: 2,005
Likes: 0
Received 6 Likes on 4 Posts
Default RE: 1/5 scale Bell P-39 Aircobra...

I beleive the Robart retracts for the P-39 are for the Top Flite kit, and would probablly be too small for yours.

Please keep the pictures coming.... I'm getting motivated to start a build project.....

Andy
Old 01-05-2006, 09:05 AM
  #7  
Darrell B.
Senior Member
Thread Starter
 
Darrell B.'s Avatar
 
Join Date: Dec 2003
Location: Rogers, AR
Posts: 403
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 1/5 scale Bell P-39 Aircobra...

Andy,

Here is a link to the ones that I'm using. They are supposed to fit the Consolidated P-39. The part number is #P-39.

http://www.robart.com/retracts/Custom.aspx

The only problem with them is that the nose gear strut is 1/2 inch to long. They are working with me to make one shorter for my application.

Watch out, or you will catch the building bug!!!

Good Luck,
Darrell
Old 01-06-2006, 12:51 AM
  #8  
rrudytoo
Senior Member
My Feedback: (27)
 
rrudytoo's Avatar
 
Join Date: Dec 2002
Location: Simpsonville, SC
Posts: 823
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 1/5 scale Bell P-39 Aircobra...

Darrell,

I didn't know about the Robart part# P-39 retracts. Those are PERFECT! As for the canopy and, possibly, the exhaust manifolds, those could be made by vacuum forming. I haven't tried that process yet but it seems easy enough once a suitable mold is made.

I bought a set of exhaust manifolds for a Ziroli Stuka from a fellow who made a master from balsa wood and then made the mold from a kit purchased from Micro Mark. The resulting resin manifolds are beautiful to look at with simulated welds cast in. Trust me, this will be the last of your concerns!

Not too long ago there was a guy who was featured in RCM for scratch building a 1/5th scale P-63 with a mid-mount engine. I talked with him over the phone and learned that he used a Moki 2.10 for power. This made real sense as a Moki uses no nitro and alcohol burns relatively cool. He utilized the original dorsal carb intake and the cooling ducts in the wing roots to bring in cool air and vented the heated air via space between the simulated exhaust manifolds and the fuselage walls in addition to the doors (shutters) under the fuselage utilized by the full-scale P-39 and P-63 to control engine temperature. He claimed that he never had an over-heating condition with this configuration.

He said that the Moki made more than enough power and that he flew his plane at half throttle most of the time. Full throttle brought the plane well beyond scale flight speeds due to the streamlining of the Airacobra and he cautioned that the plane did not scrub off speed quickly.

He used a shaft from the Moki's crankshaft to the prop drive washer that was made using tool steel. His weak link was the Woodruff key in this shaft. He said that the Moki was prone to "kicking" during starting and that the hard "kicks" were sufficient to shear the key and damage the shaft. (I'm guessing here but I think he may have used a collar to act as a union between the drive shaft and the Moki's crankshaft.)

I might be willing to give this combination a try. The only area I would deviate in would be in a threaded connection from the drive shaft to the engine's crankshaft. I have a Moki 1.80 sitting around waiting for something to do. Who knows?

Enough of my verbage. I'm excited to see your progress, Darrell. Keep up the great work!

Al
Old 01-06-2006, 01:49 AM
  #9  
Canuck1
Senior Member
 
Canuck1's Avatar
 
Join Date: Jul 2002
Location: Edmonton, AB,
Posts: 1,845
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 1/5 scale Bell P-39 Aircobra...

Good luck with your project. Keep the pics coming.

Craig.
Old 01-06-2006, 08:31 AM
  #10  
TLH101
My Feedback: (90)
 
TLH101's Avatar
 
Join Date: Dec 2001
Location: Elephant Butte, N.M.
Posts: 6,707
Likes: 0
Received 2 Likes on 2 Posts
Default RE: 1/5 scale Bell P-39 Aircobra...

Hey guys, keep in mind the Consoladated P-39 is much larger than the Pepino. I have a Consoladated, and had a Pepino kit. When you look at the Robart gear, be sure to check out the drawings listed on the site see if they will fit. The problem with the P-39 is the nose wheel retracts partially into the leading edge of the wing, and if you get too long a strut, it will be a big problem. Also, if you try to make the main gear retact "scale" toward the rear of the wing, you will have a problem with getting the wheel inside the thinner portion of the wing, due to the gear needing to rotate about 15 degrees. I dont thing that rotation is built into the Robart gear, or any other for that matter.
Old 01-06-2006, 08:55 AM
  #11  
grbaker
My Feedback: (29)
 
grbaker's Avatar
 
Join Date: Dec 2001
Location: La Porte TX
Posts: 3,561
Received 25 Likes on 18 Posts
Default RE: 1/5 scale Bell P-39 Aircobra...

Great project! It's my favorite warbird.

Once I get some other projects out of my way, I'll refurbish my DCM 1/5 scale P-39C. Powered by a 3W60 with Spring Air retracts and Lyte Flight struts. Pic in my gallery.

BTW - I'll go with a different exhaust system when I rebuild it. That muffler is just too ugly. Anyone had any luck using canisters inside the fuse like the 3D guys use?
Old 01-06-2006, 09:16 AM
  #12  
Darrell B.
Senior Member
Thread Starter
 
Darrell B.'s Avatar
 
Join Date: Dec 2003
Location: Rogers, AR
Posts: 403
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 1/5 scale Bell P-39 Aircobra...

Terry,

I have been e-mailing with Gary at Robart and we have come up with what I think is the solution to both of these issues. First off, I am having the front strut made half an inch shorter than the Consolidated to just barely clear the #4 former. I couldn't justify cutting it since it is the one that the wing plugs into. I am also going to mount the retract assembly a little flatter than Pepino had his, and half an inch lower to account for the loss of strut length when the nose gear is extended.

For the mains, we came up with using the retract bodies for the Midwest AT6. They have a 9 degree angle built into them that when mounted facing backwards will move the wheels back some when retracted, no rotation required. I will mount them in the scale location, right behind the main wing spar, and then when the wheels extend or retract there won't be any change in the CG. I think that this was the best solution to this issue.

Anyway, I have them on order, and should be hearing something on them in the next week or so. The P-39 struts are not stock so they have to work them into their regular production schedule. I'm not sure how Robart does it, but if they are like most cottage industries. they have a regular routine, but it is easy, interesting, and sometimes fun to work special projects into their shcedule to break up the monotony.

I spent a couple of hours with Craig at Fiberglass Specialties the other day. Craig is a great guy, and realy gave me a good tour of his facility. If I can ever get a plug made for the cowl on this bird, he is going to make a mold for it. I'm really hoping to get started on this soon. This is why I built the fuselage first. I have since started working on the horizontal stab, and will post a couple of pictures as soon as I get something to look at. Ok here is one to tease you with.

Best Regards,
Darrell
Attached Thumbnails Click image for larger version

Name:	Jh17129.jpg
Views:	193
Size:	39.4 KB
ID:	382068  
Old 01-06-2006, 10:12 AM
  #13  
TLH101
My Feedback: (90)
 
TLH101's Avatar
 
Join Date: Dec 2001
Location: Elephant Butte, N.M.
Posts: 6,707
Likes: 0
Received 2 Likes on 2 Posts
Default RE: 1/5 scale Bell P-39 Aircobra...

Darrell,
I think you may be onto something there. I have a set of the Robart T-6 gear from a Midwest Texan I am restoring, and a set of Pepino's plans, so I took some shots that may help you out. Looks like you will need slightly longer struts that a yoke for larger wheels, and a set of 85degree blocks on the gear, but other wise it should work. The wont be swept quite to the scale location when retracted, but will be pretty darn close. Also, since the legs are positioned away from the air cylinder when retracted, you can the have struts made with scale scissor location.
Feel free to use these pics as needed, and send to Robart if you want.
Terry
Attached Thumbnails Click image for larger version

Name:	Om33342.jpg
Views:	176
Size:	76.3 KB
ID:	382080   Click image for larger version

Name:	Ql32991.jpg
Views:	152
Size:	80.2 KB
ID:	382081   Click image for larger version

Name:	Vb73958.jpg
Views:	174
Size:	78.0 KB
ID:	382082   Click image for larger version

Name:	Pj17615.jpg
Views:	151
Size:	75.1 KB
ID:	382083   Click image for larger version

Name:	Gr93233.jpg
Views:	170
Size:	77.6 KB
ID:	382084   Click image for larger version

Name:	Oe57014.jpg
Views:	164
Size:	78.3 KB
ID:	382085  
Old 01-06-2006, 10:27 AM
  #14  
Darrell B.
Senior Member
Thread Starter
 
Darrell B.'s Avatar
 
Join Date: Dec 2003
Location: Rogers, AR
Posts: 403
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 1/5 scale Bell P-39 Aircobra...

Terry,

All I can say is WOW!!

Your pictures just confirmed all of my calculations, and I am very confident that my setup will fit almost perfectly into this application.

Thanks for the great photos.

Darrell
Old 01-06-2006, 12:15 PM
  #15  
rrudytoo
Senior Member
My Feedback: (27)
 
rrudytoo's Avatar
 
Join Date: Dec 2002
Location: Simpsonville, SC
Posts: 823
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 1/5 scale Bell P-39 Aircobra...

Darrell,

There is a build of the Dan Palmer P-63 by "nitetruck" on rcsb. He is using Robart gear made for the Palmer design which is a 1/5th scale, 92" span Kingcobra. Nitetruck tackled and solved the main gear rotation dilemma and describes and illustrates his method on the rcsb site. Go to Palmer Plans, P-63 Kingcobra and click on page 7 of his post. He has done some excellent work that should apply directly to your project.

I must say that I'm amazed that Robart did not mention their P-63 gear to you. The retracts in question are Robart part number "P63PKC" and there is no difference in price between this set and that intended for the Consolidated kit. To the best of my knowledge, the only difference between the gear used on the full-scale P-39 and P-63 was the position of the scissors link on the nose gear strut.

Good work, Darrell. This will be a most interesting series of posts and informational exchange.

Al
Old 01-06-2006, 12:55 PM
  #16  
Scar
My Feedback: (3)
 
Scar's Avatar
 
Join Date: Oct 2002
Location: Peoria Hts, Il. IL
Posts: 3,120
Likes: 0
Received 2 Likes on 2 Posts
Default RE: 1/5 scale Bell P-39 Aircobra...

Excellent posts, folks. I, for one, really appreciate the original poster sharing his work, and the helpful posts from you other posters.

Kudos!
Dave Olson
Old 01-06-2006, 04:35 PM
  #17  
Darrell B.
Senior Member
Thread Starter
 
Darrell B.'s Avatar
 
Join Date: Dec 2003
Location: Rogers, AR
Posts: 403
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 1/5 scale Bell P-39 Aircobra...

Ok guys, here is a serious question. I'm building the horizontal stab and the profile of the fuselage shows a normal airfoil for this, but the pieces that he is having me cut makes it a much more flat airfoil with the thickest part right at the hinge line for the elevator. I with I had a picture to show you, but it is not very rounded on the leading edge, and then a very gradual airfoil back to the main spar in front of the elevator hinge line. Here is a picture, I hope it helps!
Attached Thumbnails Click image for larger version

Name:	Da83264.jpg
Views:	143
Size:	3.5 KB
ID:	382260  
Old 01-06-2006, 09:31 PM
  #18  
Veltro
My Feedback: (1)
 
Veltro's Avatar
 
Join Date: Aug 2002
Location: Ventura, CA
Posts: 430
Likes: 0
Received 1 Like on 1 Post
Default RE: 1/5 scale Bell P-39 Aircobra...

Glad to see this thread! Keep the posts coming. This plane has been on my short list for years. I believe Robinaire did the nose strut for the one that flew at Top Gun a few years ago. It was build from this plan. Lee is a member of this site so hopefully he will join in.

Here is your source for exhaust stacks. Good stuff! I have the stacks (and all the other bits) for my P-40B and the quality is first rate. Can't argue with the prices, either.

http://www.rcfinaltouch.com/


- Jay
Old 01-07-2006, 09:19 AM
  #19  
Darrell B.
Senior Member
Thread Starter
 
Darrell B.'s Avatar
 
Join Date: Dec 2003
Location: Rogers, AR
Posts: 403
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 1/5 scale Bell P-39 Aircobra...

Good morning to everyone. I thought that I would post a couple of pictures and ask a question. In his plans, Pepino uses torque rods like you would use on ailerons to control the elevators. This allows for a split elevator running on two servos. I like this setup but was wondering if anyone has seen a better way to accomplish this. Is there any hardware out there already that works for this, or am I trying to reinvent the wheel.
Thanks for all of your comments.

Good Luck in your projects,
Darrell
Attached Thumbnails Click image for larger version

Name:	Ec88387.jpg
Views:	165
Size:	54.9 KB
ID:	382669   Click image for larger version

Name:	To45227.jpg
Views:	148
Size:	44.9 KB
ID:	382670   Click image for larger version

Name:	Ay73390.jpg
Views:	178
Size:	52.2 KB
ID:	382671  
Old 01-07-2006, 10:07 AM
  #20  
rrudytoo
Senior Member
My Feedback: (27)
 
rrudytoo's Avatar
 
Join Date: Dec 2002
Location: Simpsonville, SC
Posts: 823
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 1/5 scale Bell P-39 Aircobra...

Your call, Darrell. I deviate from plans all the time and I doubt if I am alone in doing so. We each have our own preferences for doings things a certain way and that is part of what makes this hobby so interesting.

As I see it, you have three options of handling the elevator controls: two servos, one servo with a split pushrod or adopting a common connector between the two elevator halves and using a single servo. Remember that your plans were done some years back and the output of today's servos is considerably stronger than they were when your plans were drawn. Having said that, I personally prefer the redundancy of a back-up servo just in case.

Keep posting your pictures. I'm really enjoying this!

Al
Old 01-07-2006, 01:03 PM
  #21  
TLH101
My Feedback: (90)
 
TLH101's Avatar
 
Join Date: Dec 2001
Location: Elephant Butte, N.M.
Posts: 6,707
Likes: 0
Received 2 Likes on 2 Posts
Default RE: 1/5 scale Bell P-39 Aircobra...

The main reason he has split the horn is because of the swept trailing edge. You cannot use a sinlgle piece, as it will bind when it rotates. The way it is designed lends it's self to the use of 2 servos quite nicely. 2 standards will work well. Another thing to keep in mind on a P-39, is the long nose, so tail end weight is not as bad as most other warbirds.
Old 01-07-2006, 08:01 PM
  #22  
Checkmate
Member
 
Join Date: Jul 2002
Location: Painted Post, NY
Posts: 49
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 1/5 scale Bell P-39 Aircobra...

My father built one of these a few years ago. Powered by a Moki 1.8 (plenty of power). Century jet main retracts and a robart nose retract. Weighed about 23 pounds and flys great!

Old 01-07-2006, 11:54 PM
  #23  
rrudytoo
Senior Member
My Feedback: (27)
 
rrudytoo's Avatar
 
Join Date: Dec 2002
Location: Simpsonville, SC
Posts: 823
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 1/5 scale Bell P-39 Aircobra...

Good catch, Terry. I didn't notice the swept spars.

Al
Old 01-08-2006, 08:51 AM
  #24  
Darrell B.
Senior Member
Thread Starter
 
Darrell B.'s Avatar
 
Join Date: Dec 2003
Location: Rogers, AR
Posts: 403
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 1/5 scale Bell P-39 Aircobra...

Thanks everyone, I like the redundancy 0f the dual elevator servos. I haven't had any issues with my other big birds, but you never know!

I saw where DuBro makes a torque rod system using 4-40 wire. Would this be heaby enough, or would you go to the next larger size? I am also looking at using some welding rod, and silver soldering the flat pieces for the control arms on, then making the bends for the pieces that go into the elevators.

Yes this plane is going to be nose heavy buy quite a bit! I have looked at putting the motor into the "scale location", but I can't figure out a good, light, drive shaft to use. If I put the crank shaft on the thrust line, the drive shaft wants to be right where I would place all of my electronics.

I'm still scratching my head over that one. Hmmmmmmmm!!

What kind of glue is everyone useing to join sheeting onto their ribs, spars, formers, etc.?

Best Ragards,
Darrell
Old 01-08-2006, 09:32 AM
  #25  
rrudytoo
Senior Member
My Feedback: (27)
 
rrudytoo's Avatar
 
Join Date: Dec 2002
Location: Simpsonville, SC
Posts: 823
Likes: 0
Received 0 Likes on 0 Posts
Default RE: 1/5 scale Bell P-39 Aircobra...

Darrell,

Welding rod would certainly be strong enough but would'n't that be rather heavy? An alternative would be either arrow shafts (my personal favorite) or carbon fiber shafts. Both have more than enough strength at a fraction of the weight.

As for the dual servos on the elevator, I, unfortunately, experienced the failure of a solo elevator servo on a final approach. Let's just say it wasn't pretty. Dual servos here would be a real plus.

As for the mid-mounted engine location, yes, a bit of engineering would definitely be in order. And the one who perfects it will be a hero to all who desire a scale P-39 or P-63, that's for sure! The driveshaft location is why I considered the use of the prop reduction unit in the nose per the full-scale aircraft. More engineering. For the purist or scale competitor, this would be a wonderful challenge. But for most of us, this would be an exercise in frustration when all we really want is a knockout plane to fly on the weekends.

Back to the building board, Darrell. Post those pictures!

Al

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell or Share My Personal Information -

Copyright © 2023 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.