Been thinking of making new aluminium doors, bonnet and bootlid for my Cobra just because (and they might be lighter than the current glass fibre ones).

Thinking of vacuum bagging two or three three thin (0.5mm or less) skins of annealed Al sheets over the current body parts glued together with thin epoxy or even contact advesive then riveted to a light tubular frame.

Is this daft or might it well work?

May well be a simple way to make an all Al body if it works, and how cool would that be.

You will need to make each sheet smaller than the last if you want them to fit inside each other. Also, if you bend the metal over the existing door, it will be larger all round so may not fit in the gap. In theory though, you should be able to laminate aluminium provided you clean it well enough, and abrade it preferably, and use the right glue.

My first thought would be if it was quick, light and cheap then others would of tried.

whack and outside the box, interesting!

I think it might work on GRP doors like my Cobra's because they won't dent under vacuum loading like steel ones will because they are very stiff - I think it will be worth a try - also laminating in itself tends to stiffen things nicely and de-stresses the moulding so they should need minimal supporting structures to retain their shape.

Unless anyone can point out something I haven't thought of, maybe I will try it as it shouldn't cost too much money, time and effort to try and won't damage the existing doors if I am careful.. Will spend more time thinking it through.

If the doors have a double curvature they will not conform. If single then will be OK. I would suspect there would be little difference in panel strength between three thin laminated ally skins and one equal thickness thick one. Two skins with a uniform few of millimetres of foam between them would be several times stronger.

I agree there will be little difference in strength but think there will be much less spring back or in other words better shape retention in the "moulded" laminated parts than in a single moulded sheet after release from the mould.

Just thinking further I suppose I should drill lots of small holes in the lower sheets to stop air bubbles and uneven glue spread.

[Edited on 12/8/11 by Ivan]

If you are expecting vacuum to pull ally into a shape you have no chance, i use a 99.8% vacuum pump for veneering wood and it will only allow bending along the grain of the wood which bends very easily.
the only way to do it would be to shape the panels properly using an english wheel etc and then bond them, however laminating adds strength only when using disimilar material, or materials with weakness ie- when laminating wood you alternate the grain direction because is is stronger along the grain. alluminim onto alluminium if bonded properly will behave exactly as a solid sheet of similar thickness would behave so you will have wasted your time.

so, if you want alluminium panles then the best way to do it would be to shape it properly then bond the skins to a frame.
i have competition car composites book at home which has a strength comparison chart for different materials but i cant remember where allumium was, either between or below carbon and fibreglass but im sure there isnt much in it in terms weight saving. ill take a look when i get home tonight.