Jim Sower wrote:

I would guess toward the lower end (15:1) as an initial guess.  I do believe that a freewheeling prop should give a HUGE improvement in glide range over a windmilling prop driving the engine.  Look at the force/power required to spin your engine at the windmill rpm through the PSRU.  Then look at the tiny force/power required to spin the prop alone if it is freewheeling.  Now, with that differential in power required figure out how much force (drag) it takes to equal that power at glide airspeed.  The difference could nearly be like having the belly board down.  The difference between engine at idle and engine dead IS like having the belly board down.

Hard to verify.  Nobody has much experience with freewheeling prop.  What few data points there are might be suspect on account of the guy too real busy flying to get good data.

How many people COULD test that condition? ... Jim S.

The guy that sold me my engine was planning on it.  He has the whole clutch assembly in there.  Told me that I could put in a lever and disengage the prop for starting.  Too bad it all has to come out for CG reasons.