RCGF 30CC-Twin Operator's Manual page 10

Drill and Install the Propeller
The easiest way to drill the propeller to fit the hub is to use a drill guide. If you do not
have a drill guide, you can use the following method to drill your propeller. Most
propellers within the recommended size range have a 0.393" [10mm] center hole pre-
drilled. If your propeller has this predrilled hole, move on to step 3. If not, start with step 1.