> "This setup reportedly yields about 80 HP (according to the article), and right now I rate my 2100D about 70 HP (bone stock except for MOFOCO 041 heads). More importantly than HP ratings however, I'm curious to see how these changes affect my climbout performance, and also my static RPM on takeoff. I will certainly be able to tell if it runs significantly more powerful than before."
I think Steve rated his 2180 engines at 76 hp @ 3400. When you're comparing your static RPM and climbout performance - the coarser pitch of course will reduce your static RPM. I went from a 54" to 56" pitch . . . actually I started with 52 x 52 which is what the plane came with. With the 52" I'm thinking I had 3500 with full throttle, maybe a little more in cruise . . . certainly a lot more RPM than I wanted - having read Hoover's work and knowing just how wasteful it is to turn the engine that fast. Higher internal friction, higher heat, higher stresses. Going from the Sterba 52 to a Prince 54" pitch (same diameter) my takeoff RPM dropped to about 2800, which is what it is now with the 52 x 56" Sterba. Keep in mind when comparing things that even though the prop is turning fewer revs, each swipe of the blade cuts a thicker chunk of air and sends it backwards in the form of thrust. I was surprised how little runway and climb performance I lost in going to a coarser pitch. The coarsely-pitched prop really comes into its own once you reach cruise when you let momentum build, unloading the prop and allowing it to turn at it's natural WOT RPM. In my case, both with the Prince and the new Sterba, revs top out at 3100 - 3200 (biased toward the lower figure) which, because of mach tip speed/drag and a couple other factors is just where I want it. I like going high where the air is thinner so the coarser blades taking bigger bites of the thinner air is, to my lights, the most efficient use of my engine and prop and plane. The Sterba 52 x 56 stresses the engine right to the edge of it being overpropped. To explain that better, when adding throttle for takeoff, the engine won't take full throttle until I'm moving along at 30 MPH or so, just enough to unload the prop a little. It's very happy at WOT from that point on, both for climb and for cruise. Unless it's a hot day I'll leave the throttle at WOT from takeoff to cruise. Altitude reduces power for me automatically. On hot days however, full of fuel and travelling, I step climb it with reduced power to keep oil temp reasonable and just being nice to the engine. My baffling is a mess and needs re-doing but since I've gotten to know this engine so well I allow for things like that in the way I operate it. I sent the original 52 x 52" back to Ed Sterba for refinishing. It had been on the plane 20 years or more and still looked fine. No nicks to speak of. The urethane leading edges had slightly worn over the years and I thought it would be interesting to see if he could actually add some pitch to this prop. He said he tried but when I put it back on the plane I could tell no difference. It did look brand new however after his re-finish job. He didn't charge me anything for restoring the urethane and otherwise finishing off the prop to look like new. That prop got sent to Ken Cottle, the plane's builder. He wanted it for his KR, one of the three KR's that Sam Bailey built. https://1drv.ms/u/s!Au6bGVdsjGkwgzvfFeSwpd6cU1HR?e=2WSI9M or https://tinyurl.com/yau83nd6 Mike Stirewalt KSEE ____________________________________________________________ Sponsored by https://www.newser.com/?utm_source=part&utm_medium=uol&utm_campaign=rss_taglines_more Health Insurers Score Big Payday at Supreme Court http://thirdpartyoffers.juno.com/TGL3141/5ea72d49e1b0f2d49604fst04vuc1 Popular Heartburn Drug Is Latest Hope on Virus http://thirdpartyoffers.juno.com/TGL3141/5ea72d4a10e2c2d49604fst04vuc2 They Went for a 'Gorgeous' Hike. The Next Day, Singer Fell Ill http://thirdpartyoffers.juno.com/TGL3141/5ea72d4a343292d49604fst04vuc3 _______________________________________________ Search the KRnet Archives at https://www.mail-archive.com/krnet@list.krnet.org/. Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options. To UNsubscribe from KRnet, send a message to krnet-le...@list.krnet.org
