Any info on various prop sizes and performance with this engine. I will be using a stock muffler on a GP Phantom.

Kirknik:

I have tried 3 different props. I don't have RPM data, but I have measured static thrust.
The APC 13X9 prop will pull 10.2lbs. static thrust.
The APC 14X6 prop will pull 9.6lbs. static thrust.
The APC 15X6 prop will pull 9.2lbs. static thrust.
The 13X9 will give you faster rev's and more overall speed, but does not give much braking, i.e. faster landings. It also will not idle very low.
The 15X6 is slow to rev and gives to much braking.
The 14X6 seems to be the best overall prop for the flying that I do, i.e. good idle,good power and good performance.

How did you figure out your static thrust measurements? Just curious. I hooked a digi fish scale up to the firewall and ran it WOT a little rich with a 15x6 Pro Zinger and was getting readings in the mid 10lb range. It was also on grass so there is alot more drag. For me this is a real world #. Not like using a thrust program. I picked up an APC 15x6 and have a 15x4W on order that I want to try out. Seems to me that the Pro Z spools up pretty quick. Ooh, I am also using a Slimline Pitts muffler. I haven't tried with the stock muff. Sounds to me that I should try the 14x6 too!!!

I also use a digital fish scale. I have a engine stand with ball bearing slides. The OS web site recommends a 13X9 or 13X10 prop for the .91FX The 13X9 APC revs quick and pulls hard, but does not want to idle slow. I have my .91 on a .60 size Cermark Sukhoi and with the 13X9 it is FAST!!! It also has unlimited vertical and pulls out of a hover with authority. With the 13X9 add the high idle speed with very little prop braking and you end up with some very fast landings. I will try to attach a pic of my engine stand.

Ooh, OK. I have mine on a AW 60/90 EDGE and need it to slow down good. I like flying it more slowly. Thanks for the info.

p.s. Nice Bike!!