This is a great idea Paul! I can’t quite make out from the photo whether or not the incisions are on the outside or inside of the radius. Do you find it works better one way or the other?
rubbing alcohol will soften balsa ALOT. You can laminate up to 1/8" balsa very easily with wood glue or CA. Laminated balsa is VERY STRONG. I make curved wingtips, tail sections, and canopys for airplanes using this method all the time. Look at the plane in my avitar. The whole top of the fusalage and the curved black canopy is all laminated balsa. Just use thin sheets and several layers. That canopy has very compound curves in it in more than one plane. I can wrap a sheet of balsa around a pencil if I want to…
Check out the pic. The whole top of the fusalage and engine cowling is laminated balsa around multi-plane curves.
I’m just getting involved in some different wood-construction techniques, and that is quite insightful for both balsa-railed sandwich boards and some glassless wood-skinned boards that we’re working on. We’ve done steam-bending successfully (That was Pierre’s part, actually) but we were definitely looking for a dry method.
Out of curiosity, why inside, Bill? Will the slices propagate through (crack) if the strip is bent outside? Ideally, I would think that outside would give the most flexibility, as the segments wouldn’t bind on each other.
In case it is useful to anyone reading this, there is also a technique used by commercial fabricators of balsa products that are used for boat and airplane part molding (Baltek, et al) where a scrim of glass or similar cloth is bonded to the balsa sheet with a flexible adhesive. The balsa is then sliced both vertically and horizontally, producing a piece that can be draped in 3 dimensions. With this technique the balsa becomes little more than core, with the laminate supplying most or all of the stability and strength.
Paul that is nothing more than the same thing luthiers do to make and shape kerfing for stringed musical instruments. except that you are putting the kerfing on the out side.
The main ideas for having it on the inside of the curve are;
The smooth surface is on the outside, where it shows. Better appearance and all-
With the kerfs or in this case cuts, there’s material cut or at least separated, so when you bend 'em the slots or cuts come together along that smaller circumference.
What’s more, the outside grain isn’t in tension quite so much and it’s less likely to fail.
