"I was told that I needed 52x56 or 52x59 by Culverprops. My KR will have a revmaster 2100D. I have a Avid mark IV now with a revmaster 2100D with a 60x28 and will turn 3000 static"
(Does the Avid have a PSRU?) Each prop maker has their own ideas and ways of measuring pitch (and differences in planforms of course) so they're usually not directly comparable in any exact way - unless you have special templates and tools and know what you are doing and even then there's voodoo involved. My point is that a Culver 52 x 56 is quite probably not exactly the same as a Sterba 52 x 56 in pitch or a Sensenich 52 x 56, or a Prince 52 x 56, etc. In any case Culver sounds full of bologna with their suggestion of a 52 x 59. I see on their website they do a lot of re-drive installations so perhaps with a PSRU a 52 x 59 makes sense . . . dunno. In my own experience, 52 x 56 is the most you want to go with a cruise prop on a direct-drive Revmaster 2100D with the KR airframe. Anything coarser and it would overload the engine's capacity to turn it at WOT. WOT would bog down your engine and it would be what is called "over propped.". With my GP 2180 and Sterba 52 x 56 I get 2800+ at the beginning of the takeoff roll and close to 3200 plus or minus at high altitude cruise. Even with this very-much-a-cruise-prop, my KR gets off the ground quickly and initially climbs fully loaded at 1000 FPM at 85 MPH. In warm weather I have to keep the nose down for cooling so 500 FPM is more the norm. My coarsely-pitched blades aren't turning as fast as a finer pitched prop would, but the mass flow is similar since the blades are taking bigger bites. The coarse prop really comes into its own when cruising up high in thinner air. It all depends on how you intend to use your plane. If you need to get in and out of a short grass field like Mark does, you might want a flatter prop like a 52 x 52. I put my Sterba 52 x 52 back on the plane a while back and while it does allow me to turn 3600 RPM WOT and renders a top speed of 170 or so at 2000 feet, oil and CHT temps go very high very quickly thanks to the increased friction heat at the higher RPM's. The difference in heat production between 3100-3200 and 3600 is dramatic. I could mitigate the heat build up by putting a Revmaster oil cooler on and using plenums on the cylinders but for the kind of flying I do everything is fine as is. My objective (one of them anyway) in using coarsely pitched props is to pull power from the engine using manifold pressure as opposed to RPM. This avoids wasting power through friction losses that come with higher RPM's and also avoids the destructive effects of the byproduct of that increased friction - heat - while at the same time allowing me to run the engine efficiently at WOT. How are you going to use your KR and what is your environment? Those are the key question in choosing a prop. Mike KSEE ____________________________________________________________ Do THIS before eating carbs (every time) 1 EASY tip to increase fat-burning, lower blood sugar & decrease fat storage http://thirdpartyoffers.juno.com/TGL3141/530e6557d5de36557373est03vuc
