Aluminum layering and expansion concern

[StanDahl]

If I want to do something like this, can the aluminum be attached to a wood frame, or does it have to be riveted together and floated over the frame and only attached at the edges? Is there a chance that uneven expansion rates will tear the skin apart?

[aggie79]

I believe I'm correct in saying that most Airstream aluminum skins are buck-riveted to steel frames, and that steel and aluminum have different rates of thermal expansion.

I don't have compound curves, but on my teardrop I have lap joints in the aluminum on the roof. I used screws (and sealant) to fasten the lap joints to my roof spars. So far no leaks. My aluminum does have some oil-canning when it is really hot - over 95 degrees - but everything stays tight.

Whether you rivet your aluminum sheets together and float them over framing or you rivet or screw your aluminum to framing, you are make holes in the skin and increasing the chances for moisture intrusion.

[angib]

Wasn't the 'traditional' way to build a trailer to nail (or screw) aluminium sheets to a wood frame? It was certainly used in Britain up until the 1960s.

[Wobbly Wheels]

To cite a more extreme example of thermal expansion and fasteners, I've done a few plexi hatches on boats. You HAVE to oversize pilot holes by 50% or the plastic will spider crack around the holes over time. Just a thought, but if one were to plead ignorance and just oversize the screw holes a bit, it ought to be smooth sailing. A decent polysulfide sealant like SikaFlex LOT 291 will be more than capable of dealing with any movement.