I'll also add on to what Mark has said. I'm considering an in flight adjustable prop but after careful consideration I decided not to go with the IVO because of the way it performs it's task. The IVO in flight adjustable prop varies the pitch by warping the blade. The base of the blade is fixed and a rod runs up the middle of the blade to the tip, which is twisted as the pitch is varied. This never did sit well with me as I felt that the prop would already be under enough stress during operation without twisting the blades on top of it. Also I was never convinced that merely twisting the blade by the tips would provide an efficient use of the blade as a whole. Food for thought. Pete.
Mark Langford wrote: > The thing about ground adjustable props is that they are not the magic > bullet that one might think. The blades still have a fixed amount of twist > in them, and simply rotating the blades around in their sockets doesn't > really change the "washout" on the blades from root to tip, it simply > rotates them around to get the most effective part of the blade correct. > It's for that reason that a correctly optimized fixed pitch blade will be > more efficient than a ground adjustable prop where the blades are simply > rotated. Another problem with that kind of prop is that all (two or three) > blades have to be set at exactly the same angle, or you'll get more or less > bite from one of them, leading to an aerodynamic imbalance in the way the > blade pulls, which will lead to an oscillating bending load on the end of > the crank, which makes it more likely to fatigue and break. > > My advice would be to check the "KR-info" list at > http://www.krnet.org/kr-info.html , where there's a pretty comprehensive > list of KRs, their engines, and their props. Many of these have been > optimized through trial and error, and are certainly a good starting point. > My advice would be to start with a choice that is known to work well (a used > prop would be best), and fly the thing for while refining the aerodynamics > of the plane (adding wheel pants other other such stuff). Then after > learning whether you want better climb speed or better top speed, lower or > higher rpm, or whatever, start worrying about getting the prop perfect. > > I've heard too many disparaging stories about the IVO over the years, many > of which are in the CorvAircraft archives at > http://www.maddyhome.com/corvairsrch/index.jsp . Just put IVO in the > keyword box. > > Speaking of the "KR-info" list at http://www.krnet.org/kr-info.html , I only > got one update last time I asked, and I know there are more planes that > could stand to have their performance data updated, so send them on... > > Mark Langford, Huntsville, AL > mail: N56ML "at" hiwaay.net > website: www.N56ML.com > > > _______________________________________ > Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp > to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net > please see other KRnet info at http://www.krnet.org/info.html > ------------------------------------------------------------------------ > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 8.5.339 / Virus Database: 270.12.44/2140 - Release Date: 05/28/09 > 18:09:00 > >
