[Tidahapah]

When I planked my boat in 95 we used a 10" dia steel pipe and built a fire under the bottom end (which was caped) and the pipe filled with water and the addition of a little linseed oil.
These planks were 4 x 1 3/4" and up to 25" long.
Once they had boiled / steamed for an hour or 2 we took them out using hessian sacks and then clamped the planks in place and nailed and clinched them.
This has to be done whilst the planks are still relatively hot hence the potato sacks.

The timber was spotted gum an Australian eucalypt hardwood.
Benn