-I'm planning on building a boat pulled WIG biplane with plans to
convert it to an engine powered monoplane.
-For the boat towed biplane the top wing will be a high lift airfoil
designed for a 25mph stall.
-The mono wing design will be designed for a 35mph stall with the
engine on the wing/shoulder of fuselage in pusher configuration. For
the low power (50-65hp) the structure will have to be light, the wing
and tail will be built just strong enough to survive the turbulence of
flying in ground effect, while the fuselage will hopefully be strong
enough to survive the water.
-Ground effect turbulence can cause the plane to pitch up so may want
the CG a little more forward than normal along with a good sized
stabilizer and longish tail boom.
-I don't want to waste time on reinventing the wheel with structural
design/stress analysis. I plan on using common proven design
construction using typical weight targets for structural components.
Aerodynamically I plan to just copy proven designed airplanes using
typical dimensions.
-I wonder how narrow I can make the fuselage (2-3') and still have
good planeing
-Do I need a keel (I plan to have the rudder in the water to help with
control) and splash rails to keep spray out of prop
-no dihedral in wings, the top wing will be like a parasol so should
have good lateral stability without dihedral.
-For construction materials I plan on using: a solid plywood or box
spar, fibreglass fuselage, Aluminium sheet metal ribs, plastic tarp
covering
-I considered only using ailerons and elevator since only want to do
gentle turns but thought that full 3-axis controls are probably a
better way to go.

Brock