Howard: Yes, I did come across some notes on the internet while checking the facts in my post on gluing, saying the Australia had banned the use of Aerolite. However, both Aerolite and Aerodux are widely available in the UK for use on wooden aircraft. Notes from the LAA (used to be the PFA) indicate that they are happy with Aerolite, Aerodux or some of the expoxies that are more common in the US for wooden aircraft structures.
In a similar vein I’ve dug out a research paper from my files by the UK Building Research Establishment on the loss of strength with time of glued joints. The basic summary is that all glued joints lose strength over time, but that resorcinol and phenol based resins are better than urea based glues. Oddly enough, for close fitting joints, casein was generally better than urea and phenol resins, especially in the wet!
John: I agree, it is always essential to sand plywood before gluing. I also thought it was to do with clearing the crushed fibre ends. According to the LAA though, it’s mainly to remove the waxy press release agents. Either way, if you don’t do it, you’ll get a weak joint, and a self-dis-assembly kit.
Regards,
Andrew