Delayed response here, I've been very busy.
I want to add to the recent discussion about aircraft plywood. This is coming both from my own experience and a page in the Aircraft Spruce and Specialty catalog. Aircraft Spruce caters to aircraft home builders and restorers and have a website at www.aircraftspruce.com. They send free copies of their catalog. I'm not connected with them but have dealt with them from time to time.
Aircraft plywood may or may not be lighter than other plywood, depending on the type of wood it made from. It's made in a hot press and subject to extremely high standards: quality of plies, absence of voids, quality of adhesives (example - the adhesives are subjected to shear strength tests immediately after being immersed in boiling water for three hours). It's expensive, which may not be that big a deal for a small project. Because it is expensive it is often available in small quantities, usually 1/4, 1/2 and full sheets. A full sheet is four by eight feet.
The most common certified material is made with birch or African mahogany exterior plies over basswood or poplar cores. The birch is heavier and stronger than the mahogany. The material is available with ninety degree or forty-five degree plies, and thicknesses of 1/16 to 1/4 inch (roughly 1.5 to 6.5 mm).
Basswood plywood is avalable which is lighter but not as strong. It is usually not used for structural applications in aircraft but might work well for a lightweight camera. The Basswood plywood comes only with 90 degree plys.
Finnish birch plywood is often called aircraft plywood. You find this stuff in small quantities with very high markups in hobby shops. It is also relatively widely available from craft supliers and other kinds of outlets. It is all birch and made to high standards, and is about 20% heavier than the poplar core material. People building homebuilt aircraft often use it instead of the certified material, but it can't be used to repair a certificated production aircraft. This stuff is available as thin as 1/64 inch (0.4mm) up to 6mm (about 1/4 inch) and usually comes in about one metre by one meter square sheets (4 by 4 ft). The stuff in the Aircraft Spruce catalog is 3 ply up to 3mm (1/8) thick and five ply for larger thicknesses although I've seen 1.5 mm (1/16 in) five ply material before.
These materials work well without splintering if you work carefully with sharp tools. Whether it looks good is up to the eye of the beholder.
This is oriented towards the US but the same or similar materials are available elsewhere.
Jerry Henneman
near Seattle
