V. Sharp

I have a Global Ultimate bipe with an O.S. .70 (non-pump) on it. What would be the correct Prop for this combination? I have tried a Master Airscrew 13X8, and it seems to be a little too much prop. Any suggestions?
Thanks!

carrellh

13x8 is a lot of prop for that engine. I had to send a 70 Surpass to Hobby Services for repair. They test ran it on 10% nitro with APC 11x8 prop and said it peaked at about 11700 rpm. My engine is going on an Astro Hog and it needs power versus speed. I will not be using an 8 pitch prop. Several people have told me that a 13x6 is a good prop for the engine on a big slow plane; others say 12x6 or 13x5 would be better. I have a lot of props so when I'm ready to fly my Hog I'll try the ones that have been suggested and see which ones give me around 11000 rpm or a little less.

V. Sharp

Thanks, CARRELLH for your info. I thought the engine was lugging at idle with a 13X8. The next time out (if it ever quits raining in KY) I will try a 12X6, and I have some 13X4W APC's that I use on a OS .60 powered U-Can-Do. I prefer the power, and don't need a lot of speed. (I have a Pattern plane for that!). I WILL check the max RPM before I fly anything.

Thanks, again

Vaughan Sharp