how to get diameter wooden propeller for gasoline engine 7hp = 208cc

i use single engine for cricri mc 15 aircraft

hp 7 = 208cc
rpm 2600
ration 8.5:1
max power 7.0 hp 5.1 kw
max torque 14.0N.m
chord length wing : 53
and what if used belt drive 1/2 to increased rpm to 5200 what is propeller used