I used to use aircraft grade plywood in 1/8" for skin and frames and 1/4" for engine rails and transom on gasser boats,but with it's price increase and shipping costs I haven't been building for a while.I used to buy from Aircraft Spruce as you can get 24" x 48" where as the other companies mostly have 12" x 48" and sometimes you can't get too many parts on a piece that size and have waste.I like to get parts laid in really close to each other to avoid excess waste.I've found 1/8" and 1/4" birch 3 ply plywood at a local building center at a good price for a 4'x8' sheet.It's got a nice sanded surface on one side,but would have to be sealed really good.
They also have sheets of a white plywood that one sheets bends width wise and the other sheet bends length wise .This stuff can be bent in a circle.I've tried lauan plywood but it doesn't bend too easily before it starts cracking,plus it splinters on the edges.