I built a plane last summer that was a sheeted fuse and the wing was solid balsa carved from a piece of 3/8" stock and a piece of tapered stock.

I took my time and it came out really nice using Monokote. I tacked, stretched and sealed the edges, leaving an air escape, then shrunk the film with a heat gun. Finally I sealed the air escape. This left a covering secured at the edges but not tacked down hard all over. Not a single wrinkle, and smooth as a baby's b*tt. I was pretty proud. Next day I threw it in the truck and hit the flying field after work.

Even on the mild day that we had, the temp changes in the truck caused it to look like a flying prune. (Especially the wing) Boy was I bummed. Took it home and shrunk out the wrinkles but this time, because it was all sealed it caused bubbles. After a lot of work I managed to get most of them out. But now I'm finding any temp change repeats the problem. It happens almost entirely on the wing since it is sealed with film on both sides- the fuse is fine since the sheeting is uncovered on the inside of course and I'm sure that allows it to 'breathe'. I ended up heating and pressing the film hard to the balsa but that helps very little and gives less than a smooth appearance.

I know everybody has their favorite covering and a woodpecker would help on the fuse, but would appreciate feedback on technique, brand of covering, or similar experiences covering a solid, foam, or sheeted wing.

The problem is actually in the way you applied it, in my opinion... Monokote is great stuff, but it does take some practice to be able to apply it well. Anyway, basically the mistake you made was "shrinking" it down to get it to fit... You actually want to "stretch" it out to get it to fit... Once the edges are sealed you should never have to heat the middle to get it to shrink to fit... Monokote will shrink with heat, but the problem is, it also stretches with heat. But in general it wants to return to it's "original" size as it fluxes through temp changes... What you need to do when you apply it is to tack one corner down, then warm the entire sheet a bit with a heat gun (unless your working in a very warm workshop to begin with), and then stretch it as much as you can to the opposite corner and tack it there... Then heat a bit again and stretch to another corner, then repeat and get the last one... Then keep it slightly warm as you work on stretching and sealing at various points around the edges until it's almost completly sealed... Then warm it up pretty good with a hole for the air to escape.. Then seal the last part... After that, let the whole thing cool and it will be tight as a drum and stay that way... Basically you "stretched" the monokote out, so that once it cools it shrinks a bit and pulls itself tight... Through temperature changes, it will try to return to it's "original" size which is smaller than what it is in it's tight stage... therefore it will always stay tight...

Have you used an iron on it Mike?

Hey MinnFlyer,
I did go over it with an iron to finally nail it down after I got tired of returning to the shop to reshrink. I was not real happy with the finish though, and even still the problem persisted to some degree. I didnt use any surface treatment on the balsa however, as I had not originally planned on fastening it over the entire surface.

Just to clarify, I did stretch the covering tightly in all directions when applying the film and was pretty tight and had no wrinkles before the final shrink. It was not 'drum' tight but was as good as I could get it by hand. The technique I used was out of one of those expert "How To" books commonly found in the back of MAN.

I like rusirius suggestion of working in a very warm shop. I will be conscious of that in the future.

Anybody with other thoughts?

Something a lot of people take for granted is not wiping the wing with a Tack Cloth. Just brushing the wood or blowing it off isn't good enough. You really need to remove the fine dust or the covering will stick to the dust, and not to the wing (Or Fuse, stab, etc).