Shaping aluminium - dolly/buck

[Tigercubrider]

i have a fibreglass seat/tank unit with no aluminium tank.
I have bought a slightly larger aluminium tank (second hand) that I intend to cut/ bash and fit
Once it s the correct shape/size I will get a welder to tig it together.

The first plan was to try to make a wooden buck that fits inside the fibreglass, and once it's right, form the alloy over that. I shelved the idea

Then I lined the unit with tinfoil and molded the inside with modrock (plaster bandage) and now have a 3D shaped replica of the desired shape. The plan was to measure and copy dimensions

Recently on face book a guy showed how he shaped a "negative" impression in a home made concrete block. He then used it to shape his metal. My tank design will be a sort of teardrop so in theory the shape is doable. I'd add rebar and odds and sods for strength

I am quite keen on this?

Fourth option... a tree has recently fallen nearby. (Oak) I could "borrow" a log and hack it about with a chainsaw and belt sander, making a buck from solid green wood.

Am I bonkers?

 

[Burnerman]

Ye gods!
I think you could get the shape you need by using a bossing mallet and a leather sand bag, but bear in mind that aluminium needs to be annealed just like other non ferrous metals.
John

 

[conny]

If you can lay your hands on an oak log stick it in the post, I'll have it.