I'm driving a propeller, rather than a fan, although the engine and prop is only fitted to a test stand at the moment, just to check it's reliability.

The prop is a two blade, 62" Powerfin carbon fibre one and the reduction ratio is 2.38:1, using a polyvee belt to try and damp some of the torsional pulses from the V twin.

The reduction drive works well and the combination seems both quiet and reasonably powerful. I've not done a proper thrust test yet as I haven't got enough hours on the engine to run it flat out for a few minutes.