Yellow Aircraft P-38 rebirth, and conversion - RC Groups
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Oct 29, 2014, 08:39 PM
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Yellow Aircraft P-38 rebirth, and conversion


I've been working on this plane for about a year now, and if I could stay focused, it would already be done. It's much closer to completion than it looks.

I got this from a gentleman in Alabama after an unfortunate crash on the maiden flight. The left DA-50 died on the very first circuit.
Luckily the club members who retrieved the plane did an amazing job collectiong all the pieces, and made it soooo much easier to glue it all back together

This is an electric conversion, but I made some changes inside, so I'll start with the rebuild, which encompasses most of the conversion

I'll let the pictures do the talking over the next few days, to get up to date with were it is now, and you guys can motivate me to finish it!

Jon Koppisch flies Al Ayler's RC scale P-38 Lightning model (0 min 40 sec)

Al Ayler's scale RC P-38 Lightning — flown by Jon Koppisch — loses one engine and crashes. (0 min 30 sec)

Al Ayler's RC twin-engine P-38 Lightning after the crash... (1 min 0 sec)
Last edited by 70 ragtop; Oct 29, 2014 at 09:04 PM.
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Oct 29, 2014, 08:44 PM
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Jon was nice enough to cut the damaged booms in half and ship it by bus to CT. This is how it came out of the box. Figured I was going to have to make a bunch of parts out of foam, but was very happy to see that most of the pieces were there. Just started taping them in place
Last edited by 70 ragtop; Oct 29, 2014 at 11:01 PM.
Oct 29, 2014, 08:50 PM
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Taping parts together as it comes out of the box
Oct 29, 2014, 09:01 PM
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As all the seams were popped, and almost all the wood inside was broken, it had to come apart. Learned very quickly not to CA anything at this point

Came up with idea to use a hot glue gun, and glue wood on the outside. The wood acts like a crutch holding the broken pieces together. By using hot glue, vs CA if something's not aligned quit right, heat it up with a heat gun, and adjust.
As the puzzle went together, I heated it up and adjusted many times to get it straight
Last edited by 70 ragtop; Oct 29, 2014 at 11:01 PM.
Oct 29, 2014, 09:29 PM
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Repairs start


Plane needed to be secured while repairs were made. A solid door filled the bill. Jigs were made from pink foam, and the plane was slowly glued to the foam/table using the same hot glue

The booms were pretty bad. They cracked at the radiator exhaust openings in the crash. During the next couple years, it sat leaning against a wall, so what was still attached twisted.

Used heat guns and some 3/4 pine strips to get everything into alignment and held in place
Last edited by 70 ragtop; Oct 29, 2014 at 11:02 PM.
Oct 29, 2014, 10:11 PM
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Made first repair to lower right boom. Since its a polyester resin, just used autobody resin I had. Was not happy as resin was too think, and dryed too fast.

Purchased 435 resin from US composites for $11, with MUCH better results. Dry times were a little longer, and it was much thinner, so layups were easier, with less resin build up

Also bought styrene, which is used as a thinner for polyester resin, but only had to use it when laying carbon tow in the fuse. Made it a little easier to make sure resin penetrated all the way thru the carobn before starting to kick
http://www.uscomposites.com/polyesters.html

Panel lines and colors were a huge help getting everything aligned. Once everything fit together properly, and was staraight, bottom half of fuse was firmly secured to the jig( foam cradles glued to door panel).

Shortly after these pictures were taken, moved the plane out to the garage, and stared the fiberglass repairs. I sanded the inside with a combination of hand sanding and a 2" air sander. The damaged areas were sanded almost paper thin, and the area around the damage was tapered out. The whole area was sanded down making the skin thinner.

Laid small pieces of glass in the damaged areas, increasing the size with each layer, filling in what was sanded out. Large pieces were then laid in, which tied all the smaller repairs together.

At this point laid in some carbon in pod area for added strength and rigidity
Oct 29, 2014, 10:59 PM
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Replacing the wood


Repaired the to top half, same as the bottom. Cleaned up the front side of the basement, added another bench, and some lights.

Time to replace the broken wood. The wood, as it came from Yellow, was very heavy. Wanted to try and loose a little weight, without loosing any strength.

I did a bunch of materials tests with different number of layers, and weight carbon, on different core materials. VERY impressive results, and while I wanted to use skinned foam core with carbon fiber spar cap top and bottom, I couldn't find a suitable material, without spending $$ thru the composites houses
Ended up using 1/8 a/c ply wrapped in carbon fiber, and in the end, probably better off. The area under the wing sockets has multiple layers of carbon that are tapered inboard, and tie into the caps. The front spar has carbon spar caps added. A nice fillet of carbon tow helps make sure they're going no were

Completed assy is about half the weight of the original, and small scale tests showed its stronger (couldn't break it, broke the 1/4 ply). Should be fine
Oct 30, 2014, 03:34 AM
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Wow you are doing an excellent job on this basket case, your patience is amazing.

Be worth it in the end as it will be an amazing looking plane
Oct 30, 2014, 02:44 PM
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Thanks, was on a roll for a while, and just got busy with other things.

Can't find any pictures, but once all the repairs were done on bottom half, ran carbon tow front to back. You can see it wrapping up on the sides of the horizonal stab

The elevator was damaged, and it was more work than it was worth, so just made a built up replacement. Where the booms transitioned into horizontal had a bit of crush damage, and a bunch of cracks. The elevator pivot blocks had also been knocked loose.

Center of horizontal stab was solid, so only opened up the ends for repairs.
Oct 30, 2014, 02:54 PM
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Back half glued/glassed back together


The boom halves had twisted, so it took a bit of persuasion to get them to fit right, and have nice round contour at the seam, without being wavy

Rear spar glued in place. Took the opportunity to replace the goop on the flag hinge block, and pivot blocks with something a little stronger.

Starting to look at battery locations
Last edited by 70 ragtop; Nov 01, 2014 at 10:01 PM.
Oct 30, 2014, 03:08 PM
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Motor boxes/battery locations


I knew from the start this was going to be built as an electric. Would have had to build a bunch of strength, and weight back into the plane to support gas worthy firewalls.

That combined with looking for battery location lead to the motor box idea, Motor boxes will tie into the front spar with a front support, vs conventional firewalls.
Plane is going to be silver, and the insides of both cowls will be OD. Looking at panel, and paint lines, decided the OD green portion of the cowling would be a removal hatch to access batteries right behind each motor

Next project was getting the right alignment. Yellow has you fit the cowls to the plane, and use them to locate the engines. Obviously not going to work in this case. Charles at Yellow was very helpful, and provided engine angles.

Made a jig from 1/2" ply to hold the motors in the correct locations, with the right angles. At this point, was using Tacon 160s. Was then just a matter of making the motor boxes to go in between motors, and front spar

The battery bay in the motor boxes can hold a Gens Ace 5300 10S pack, or a 4000 12S pack. There is also battery space in the nose...but we'll get to that
Oct 30, 2014, 04:09 PM
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Fitting moter boxes


Motor boxes attach to a very beefy part of the front spar. Added a 1/4 ply mounting block which makes it easy to install boxes once fuse halves are glass back together. Will leave motor boxes off to allow access thru firewall openings to reseam the fuse
Once boxes are glued together, they are quite strong. Firewall on is two layers of 1/8 that fit inside the box, and one layer that sits flush. Plenty of gluing area
Oct 30, 2014, 04:14 PM
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Reseaming the fusealuge


With most everything fit, time to reseam fuse. Used Hysol along seams I can't reach, like the tailing edge of the wing. Once initial joining was done, taped the remaining seams with glass tape


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