I'm at the point of sheeting in the Fuse on my Decathlon. I have to bend 3/32" x 3" Balsa Sheeting to make the round edge in front of the windshield. It says may need to wet the sheeting with Ammonia / Water to get it to bend without cracking. Is that just Rubbing Alcohol and Water. If not what should I use???
Trevor

No, it's not rubbing alcohol.

It's AMMONIA, just like the instructions said.

Why does ammonia work? I don't know. It just does. Mix it 50/50 with warm or even hot water. Spray it on until the outer surface of the wood is wet. Let it soak in for a minute or two. Spray it again and let it soak in. Then bend it around the curve and use thin CA to attach it to the formers.

bucket,

Unless you have a really hard piece of balsa, you probably won't need ammonia, especially for 3/32" sheet. just soak your piece in a pan of warm/hot water for 20 minutes or so, then wipe it off and try it around the formers. It should bend around just fine. If not, then soak it a litle longer. As rcPilot said, use thin CA to glue it down. This is one of those areas where CA really works better than other glues. Just don't get in a hurry and you'll get a nice job. That's another reason for using just water. With ammonia you'll WANT to hurry to get away from the smell! Good luck.

papermache

Where would you even get ammonia from?

The grocery store.

Don

I even use Windex when there's no straight ammonia in the house. It works just as good (but it can yellow the balsa).

David

I have read that ammonia works by softening the 'lignin' in wood. But I've also read that balsa has no lignin, so I don't know what to believe. Last year I was building an old timer and had to put a forward sweep in a 1" trailing edge. Wound up boiling it in straight water for 20 minutes, worked great. Jim

I have always used windex. Windex comes with amonia in it. Look for the original blue windex.

Unless your balsa is quarter grain (in which case you should save it for som other application) or if you want to bend it around a very small radius ammonia is not usually needed. The trick is not to soak the balsa, but rather to wet it on the "outside" surface. Because the wet side will swell, the balsa sheet will bend in a radius. In some severe cases I helped the process allong by heating the wet side with an iron. Wing torsion boxes and rear-fuselage turtledecks are a piece of cake using this very simple method.

I'm with Red B. I take a wet rag (get the water as hot as you can stand to hold) and rub gently on the "outside" of the piece to bend, lay it in place and start working it to conform. Don't hurry, and as you keep putting slight pressure on the piece, continue to moisten the outside with the wet rag. It will conform nicely . The top of the Decathlon boot cowl is a pretty gradual curve, but be careful as you get to where the top drops off to become the side, this much sharper bend will take a while to conform. Ammonia isn't really needed as much as patience is.

Balsa does have lignin (the 'cement' that holds the cells together), but much less than other woods.

Wood density and thickness determines the level of saturation and amount of ammonia and heat I use (as well as the extremity of the curvature to conform to). I wouldn't use a tack hammer to frame a house or a fire hose to water a house plant. Some say the overuse of ammonia weakens the wood. I don't know if it does or not but I do know that most powered planes are structurally overdesigned anyway so I don't worry about it. If the wood buckles while conforming you'd be better served to start with another piece of wood.