I am in the middle of rebuilding / re-covering the wing on my 11 yr old Alpha trainer. The single servo is going away and there will be one servo per aileron. I have fixed a couple of pieces of cracked sheeting, like from when my cellphone dropped out of my pocket and on the wing, causing a fairly large temporary repair. I have used a small paintbrush to apply water to a number of "dents" in different places on the sheeting and leading edge, and using my covering iron on a fairly high heat, pressed the dents out. (The same technique works on dining room and living room furniture). So far I have been very successful in rejuvenating the wood and making some minor repairs. I have one problem, probably a question of technique. - How do you make balsa filler stick? I can press it in place, but when I try to smooth it out, it just rolls out and feels like dried dough. I have stirred the stuff up, maybe I should thin it?

Thin it out with a little bit of water.

Ken

Maybe after 11 years you should renovate your instructor or try a different one

Terry

It has rained here for 17 days straight. I figured I would put in some more "serious" service work on that old trainer. I have flown it every year since new. The torque rods had over 1/4 in of play in them, and a couple of pieces of covering were starting to buzz. I understand that having the covering come off may be a bad thing, so I figured I would strip the wing and redo some stuff.
I added about 1/2 oz of water, that got me a thick toothpaste kind of consistency. It still doesn't want to stick well. Do you wet the wood where you want it to go? It does stick somewhat better, maybe I am expecting too much?

what/how are you trying to apply the filler???

Ken

If you get some light weight spackle and thin it to milkshake consistency, it will stick to dry balsa sheeting just fine. The drawback is waiting for it to dry.
If I'm in more of a hurry, I use Bondo lightweight formula auto body filler and apply it with credit cards. The key is to work it as thinly as possible and figure that 2 or 3 skim coats beats doing a lot of sanding.

I am almost done recovering an 18 year old Royal 40T ARF trainer. I removed the old stick-on covering and the plastic wing tips and tail caps. Rebuilt the fuselage at the tail, added a mount for a video and still camera, and landing and position lights. I used light spackle to fill. The spackle can be difficult to get to stick as well and if you just add some pressure while you gently smooth it across keeping the putty knife flat it will usually stay down. Once it is dry it stays in place well even during sanding, and has not come off yet.

I was putting the filler on with a popsicle stick, then using a bondo spreader, and a small putty knife to try to smooth it out. I think as noted, I have the best luck keeping the tool flat or nearly flat on the surface, using some pressure. It will stay, I think I was trying to feather it with the tool like you would on a car, and it would roll up the trailing edge of the tool.
I hadn't thought of using the Bondo, I have that and some spot putty I used for my Thunderbolt when I made the cowl.
Thanks!

It sands so easy you really don't need to feather it, just sand lightly when its dry and it turns out great.

I find that damping the wood where you are going to use the spackle and it will stick better without curling up. Works for me.

One coat of very thinned nitrate dope to encapsulate/bind all the dust and crud stuck in the balsa grain should do it.

The only thing that sticks to dust/dirt is more dust/dirt...and nitrate dope