Prop selection AND effects
 

Everybody you talk to has an opinion regarding what prop (size, pitch and manufacturer) is best on a particular engine. Some people will even have enough knowledge to tell you that one prop may work great on plane A but not as well on plane B depending on your flying style. Those opinions are always useful to get a starting point. The big problem most of us have is the price of props. It is just too expensive to play with different props to see if one is better than the other. However, I have run across something that I can't explain. I have a BMEAircraft 27% Pitts Challenger that I have been flying for about a year with an Evolution 58GX. I have 'played' with as many props as I could afford and I have seen some major differences I would like somebody to explain to me.

The NX 24x8 wood prop seems to fit my setup perfectly. The plane has more than enough power to do short takeoffs, will slow down and become very docile and smooth for landings, has unlimited veritical, and will twist, turn and tumble with the best biplane available. BUT - if I switch to a 24x10, the plane becomes a different monster. It is twitchy, won't maintain level flight (always dropping or climbing), remains twitchy even when slowed down ... and is just a nasty plane to fly. I have tried multiple 24x10s (NX, TBM, Evolution, Biela) and multiple 24x8s (NX, TBM, PT, Biela) and I see the same flight characteristics with all of the 24x10s ... so it is not just one prop or one manufacturer

Now I understand that the 10" pitch is wanting the plane to fly faster than the 8" pitch does at the same rpm. But I can see/feel this "nastiness" throughout the rpm range. How does the pitch difference effect the plane SOOO much?

Honestly, if I had to fly this plane on a 24x10, I'd get rid of it ... but on the 24x8 it is my favorite sky ripper. I wonder how many people have gotten rid of a plane because it handled terrible .. and they only needed a different prop?

RE: Prop selection AND effects
 

[quote]ORIGINAL: bonedaddy41

Everybody you talk to has an opinion regarding what prop (size, pitch and manufacturer) is best on a particular engine. Some people will even have enough knowledge to tell you that one prop may work great on plane A but not as well on plane B depending on your flying style. Those opinions are always useful to get a starting point. The big problem most of us have is the price of props. It is just too expensive to play with different props to see if one is better than the other. However, I have run across something that I can't explain. I have a BMEAircraft 27% Pitts Challenger that I have been flying for about a year with an Evolution 58GX. I have 'played' with as many props as I could afford and I have seen some major differences I would like somebody to explain to me.

The NX 24x8 wood prop seems to fit my setup perfectly. The plane has more than enough power to do short takeoffs, will slow down and become very docile and smooth for landings, has unlimited veritical, and will twist, turn and tumble with the best biplane available. BUT - if I switch to a 24x10, the plane becomes a different monster. It is twitchy, won't maintain level flight (always dropping or climbing), remains twitchy even when slowed down ... and is just a nasty plane to fly. I have tried multiple 24x10s (NX, TBM, Evolution, Biela) and multiple 24x8s (NX, TBM, PT, Biela) and I see the same flight characteristics with all of the 24x10s ... so it is not just one prop or one manufacturer

Now I understand that the 10" pitch is wanting the plane to fly faster than the 8" pitch does at the same rpm. But I can see/feel this "nastiness" throughout the rpm range. How does the pitch difference effect the plane SOOO much?

Honestly, if I had to fly this plane on a 24x10, I'd get rid of it ... but on the 24x8 it is my favorite sky ripper. I wonder how many people have gotten rid of a plane because it handled terrible .. and they only needed a different prop?
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Hi. I have been thinking the same thing. The props for my plane can run from about $65- 105 each so I can't have one of every pitch rang in my flight box.
But I found this adjustable pitch prop hub and as soon as they get the hub made for my engin I all over it. Take a look and see what you think.

http://www.soloprops.com/

RE: Prop selection AND effects
 

Torque effect on the 10 pitch is much greater. Have you tried a 22X8? What rpms are you turning with the 24X8? How do you like the Evo motor?

RE: Prop selection AND effects
 

Yep. Torgue was my only answer. It is just hard for me to believe that torque differences between a 24x8 and 24x10 change the plane's flight characteristics so much. I could accept it easier if it was a drastic change in prop size.

I run a 22x8 on my Evolution 45GX. A 22x8 would be way too small for the 58. Most people are running 24x10 or larger on these engines .. even up to 26x10. The 24x8 is borderline on being too small. I have been thinking about trying a 25x8 .... but haven't yet because TBM doesn't have any in stock. I haven't tached it in quite some time ... but I think I was getting around 67-6800 with the 24x8 and 64-6500 with the 24x10.

I have not owned any gas engines except the Evolutions (a 58 and two 45s) so I cannot compare them to anything else ... except by people I fly with having DAs, Brisons and 3Ws. To me, the Evolution is a great engine. Easy to start, easy to tune, dependable, and LOTS of power. The 45s are a bit on the weak side as far as design strength is concerned. I am yet to see one hit the ground that the cylinder wasn't broken where the muffler mounts ... and the X bar mount bent or broken. The 58 on the other hand seems to be VERY durable. I blew a base gasket on the 58 after about 5 gallons and Horizon replaced it. I think for the price (same as DA50), the 58 is a great engine. However, the 45 costs the same as the 58 ... so that is a bit expensive .. although it has the same power as other manufacturer's 50-52cc engines.