ORIGINAL: Mikeup
I got mine in Depron ( 6mm ). I laid 1/32 ply on the top for strenght. The bottom of sponsons has 1/32 ply and the bottom of tub is also 1/32 ply. I used thinned epoxy on the ply for waterproofing. I have no water rudder but made an airrudder and used piano wire from servo to airrudder.. I haven't had it out as the hot weather , storms and rain and now moss. Always something. I sand the depron and used latex house paint which they say doesn't eat foam, wait and see.
The foam sponsons are only there for pictures. My final sponsons will be made of plywood. Probably 1/8" or 3/16" for the sides and aft parts with 1/32" for the skin on the bottom. My work area was inundated with sun so I quit working on it for awhile.. All I really have left to do is finish the radio box up front and make the sponsons and tub supports to get the control cables laid out.
This boat is water only. I think its an injustice to run a hydro on land. I'll be happy with 50mph on the water but I wont know for awhile. I think I'm on-par with coming in under-weight.