Sonex told me a about a year ago that 60" diameter is their limit. Measuring from the plans, that looks to give about 9" of clearance without any deflection of the gear. Does anyone currently sell 60" propellers for the Rotax on a Sonex?
I played around with JavaProp to design optimal propellers for the ~2300rpm Rotax and estimated you get ~8% more thrust at Vy when you step up from 60" to 68". The differences in cruise is much smaller, so I imagine you could be happy with the smaller diameter.
Gary's longer landing gear seems like a good idea to me, something I'd strongly consider for larger propellers.
14 cfr 23.925 says:
(a) Ground clearance. There must be a clearance of at least seven inches (for each airplane with nose wheel landing gear) or nine inches (for each airplane with tail wheel landing gear) between each propeller and the ground with the landing gear statically deflected and in the level, normal takeoff, or taxing attitude, whichever is most critical. In addition, for each airplane with conventional landing gear struts using fluid or mechanical means for absorbing landing shocks, there must be positive clearance between the propeller and the ground in the level takeoff attitude with the critical tire completely deflated and the corresponding landing gear strut bottomed. Positive clearance for airplanes using leaf spring struts is shown with a deflection correspondingto 1.5g.
Posted: Thu Jun 22, 2017 11:17 am