Chopping prop
I don't know if this pertains to the prop you are considering, but it is interesting even if not. There is a Lancair builder at my place of work who is running an 0-320 and a Hartzell C/S who shared this info with me. It seems that the shop who built up the prop for him does some experimenting with a sacraficial prop to get the numbers right and then they will cut the blades to the optimum lenght on the ones they intend to sell for homebuilders. When I called them they had not done sacraficial testing on a prop for RV's yet, and didn't seem to think that they would without a wealty customer willing to foot the bill. Apparently there are more folks with Lancairs willing to pay for this kind of testing than us RV'ers.
Anyway, as I understand it...For the 0-320 Van's sells props with "C" blades which are most effiecient at lower airspeeds than the RV's are routinely flying. These blades were designed many years ago when GA airplanes simply didn't put up these kinds of numbers. Later, Hartzell apparently developed a "D" blade prop for use on the Beech Baron that was the same propeller with a different twist built in. It is apparently the same blade just twisted different and longer. With the twist built into this prop the thrust goes up by up to 200lbs. It seems that the blades have different zones, or steps which are doing the work at various speeds and attitudes. The "D" optimizes the section of the prop working at speeds around 200mph or so. Simply put, this shop finds "D" blades that cannot be certified because of various reasons and overhauls them, installs them on a hub that they have overhauled, and they are cut down to the desired length. On Lancairs and Glassairs they are increasing cruise by 15knots over the straight "C" blades! The speed is optimized also by shortening the props length up to a point, and then it hurts performance. As the prop gets shorter up to this point the speed goes up, and climb performance goes down. It's all a trade off. Anyway, I called to see if my "C" blades could be twisted to make them "D's" and they can, but it is a one way trip. Maybe when the day comes to overhaul the prop I'll have it done.
Anyway, I don't know where you would go to learn about the production planes that use which version of Hartzell and why that one is used, but it appears that there is a lot of science behind the selection. There is probably variants of this concept for each engines designed prop from Hartzell. Maybe a call to Hartzell could point you in the right direction.
Regards,
Bryan
