I have found this site to be very instructive. I am not an rv owner but when I grow up someday I will have one. I currently fly a rans s-16 with an io-320. I have been struggling with low rpm since the day I purchased it. I have gone through all the "engine" stuff to make sure all that is ok (see post in traditional engines). I understand the effects of elevation. Using the standard 3% loss per 1000 feet of elevation puts my 160 hp engine at 127 hp at my base altitude.
Here's the quick and dirty. The plane came with a sterba 68-74 prop. The engine at sea level would only get 2500 rpm. I flew it home to Wyoming where my airport elevation is 7200 feet. The best rpm I could get was about 2450 straight and level full throttle at my elevation. I ordered a new prop from Ed sterba that is a 68-70. I tried that prop and could only get 2500 rpm full throttle s&l. I contacted ed and he offered to re pitch for free. I sent him the 68-74 and he re pitched it to a 68-64. I was expecting to gain a lot of rpm with the 64 pitch. I tried that prop and gained zero rpm increase. I fly at 10,000 feet a lot and need the rpm.
So here are my questions:
Is the sterba prop my problem? (Design, pitch, airfoil)
How does elevation affect rpm?
Should I be pitching for a 125 hp engine?
I can buy a Catto prop off a o-290 for a good price, just wondering if that the way I should lean?
Here's the quick and dirty. The plane came with a sterba 68-74 prop. The engine at sea level would only get 2500 rpm. I flew it home to Wyoming where my airport elevation is 7200 feet. The best rpm I could get was about 2450 straight and level full throttle at my elevation. I ordered a new prop from Ed sterba that is a 68-70. I tried that prop and could only get 2500 rpm full throttle s&l. I contacted ed and he offered to re pitch for free. I sent him the 68-74 and he re pitched it to a 68-64. I was expecting to gain a lot of rpm with the 64 pitch. I tried that prop and gained zero rpm increase. I fly at 10,000 feet a lot and need the rpm.
So here are my questions:
Is the sterba prop my problem? (Design, pitch, airfoil)
How does elevation affect rpm?
Should I be pitching for a 125 hp engine?
I can buy a Catto prop off a o-290 for a good price, just wondering if that the way I should lean?