plywood vs strip planking

[jfblouin]

I need to understand what is the pro and con about using plywood or strip planking for the bottom of a planing hull.

In a 6,7m deep V 30 knots planing boat project, I study 2 options:

1- 15 mm thick white cedar strip planking (density 335 Kg/m3)
2- 16 mm thick fir exterior plywood (density about 600 Kg/m3)

All thoses will be encapsulate in Epoxy with fiberglass Bi-axe and Woven each side.

I need about 25 m2 of flat and straight panel application in the boat. The rest of the boat will be in strip planking. So the difference of weight is 125 Kg vs 240 Kg, a difference of 115 Kg on a 1200 Kg boat.

What are stiffnest, elasticity, resistance and solidity of thoses two ?
Can I reduce the tickness of plywood ?

[Raggi_Thor]

Strip planking has (practically) no strengt or stiffnes in the transverse direction, so you need some glass or veneer on both sides or some laminated frames inside and glass/veneer utside to make it stiff in that direction. The outside and inside should balance each other.
Plywood is probably stiff enough in the transverse direction, but may (probably) need some longitudinal stringers.

Plywood is normally lighter thatn strip planking, so I think you can reduce the plywood or increase the strip planking thickness.

Take a look at Nexus Marine, they build light and strong plywood boats.

[Raggi_Thor]

These pictures will give you an idea:
http://www.nexusmarine.com/chinook_interiors.html