Drag if empty space between motor and propeller

Hello, I have a 63100 motor with custom shaft (like 65161 flipsky shaft), on which I put a folding propeller from EML Store. Does the empty space between the propeller and the motor generates a significant drag that should be corrected with a 3D part ?

This setup is for a foil drive assist,



Yes you would be better off filling that space up with a spacer that tapers down to your propeller

I’d probably print something to go there, no idea of the efficiency gains but I’m sure there would be some. Let us know if you test it!