I've had a lot of distractions from flying the last six months so am just now, these last three weeks, getting my new Sterba 52 x 56 on and settled in. I've flown it twice at low altitudes - once for fifteen minutes and tonight for twenty. I'm getting the prop bolts/new wood used to each other before taking the plane on a high altitude cross country. At lower altitudes, 3.5 and below, I'm seeing at 3000 RPM the same speeds or better that I was seeing at 3200-3250 with the Sterba 52 x 52. Oil temp is running lower too as is GPH. This is the second time I've been surprised at how much heat is generated from the wasted friction of higher RPM's. I'm seeing the usual 1000-1100 rate of climb (weather here is still cold) at 90 instead of 80. Acceleration on the runway does suffer some from what I've been used to with the flatter-pitched Sterba but the rewards* once in the air are well worth the loss.
* Rewards: lower fuel flow, lower oil temps, lower noise, faster speed. Comparing the new prop to the Prince 52 x 54 P-tip, once level at 3.5 and 3000 RPM I'm getting a little better performance - that's an initial impression based on two short flights, so that's not conclusive. However, that P-tip I'm afraid doesn't do anything except create drag. I took the Prince off and had it factory refinished after running into a little rain Gathering before last. The urethane leading edges on the Sterba hold up very well in rain I know from past encounters. I understand Prince has gone to a steel-embedded-in-composite leading edge in his most recent models. That should work. His previous extra cost "leading edge protection" sure didn't. The story will be told when I get it up around 9K and higher - cross country cruising altitudes. The added pitch really comes into its own up where the air is thinner. My cross-country at 9 - 11 thousand at 3000-3100 RPM has been an average of 147 MPH with the Prince. (I need some aerodynamic clean-up but that's another matter.) Based on the low-altitude performance I'm seeing, I'm very much expecting to see a higher average cruise number at the same altitudes and RPM's as when I had the Prince on. More later on this subject. ************ I often read postings re prop pitch numbers in the 40's. If one is flying a KR out of a short grass field with obstructions I guess a high-turning prop is necessary but really, we spend most of our time cruising so it's always made sense to me to have a prop optimized for that. Going for a climb prop is a mistake in most cases in my opinion. At 52 x 56 I've got more pitch than you generally hear about with a 2180 and even another inch wouldn't hurt. I'm seeing 3100 at full throttle and my full throttle RPM goal is 3000. I may try a 52 x 57 someday. My rate of climb is still at 1000 plus or minus (depending on weight and outside temps) even with this coarsely pitched prop and on hot days the lower oil temp due to the slower turning engine will be most welcome. Mike KSEE ____________________________________________________________ Groupon Official Site 1 ridiculously huge coupon a day. Get 50-90% off your city's best! http://thirdpartyoffers.juno.com/TGL3141/4da69280cc6625da60st04vuc
