stunthanger.com
Engine basics => Engine set up tips => Topic started by: Joe Messinger on September 16, 2006, 10:56:08 AM
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Hello,
I know that many of the top fliers use 3 blade props on their stunt planes. Being that I've only been back at c/l (from the 60's) for a few years now, as always, I'm curious as to the reason(s) for such things.
Perhaps someone could explain the advantages of a 3 blade prop. More thrust? Downhill braking?
Also, is there a point in the weight of a plane that those above that point perform better with a 3 blade? I do remember using 3's on 1/2 A planes.
I know 3 blades are more expensive and I haven't seen very many offered by different prop makers. Carbon fiber 3's are what I've mostly seen on the competition planes and those are pretty pricey.
Would there be any advantage to using a 3 blade on a sport/competition plane such as a Cardinal or Score? How about a Vector 40?
Thanks in advance for any information and opinions.
Joe
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Sometimes it's just a matter of engine size and available prop clearance. I've been told that a 3blade has a different corner feel.
My own experience on a couple planes was that I could control the corner exit better with a 3 blade.
Walter
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Hello,
I know that many of the top fliers use 3 blade props on their stunt planes. Being that I've only been back at c/l (from the 60's) for a few years now, as always, I'm curious as to the reason(s) for such things.
Perhaps someone could explain the advantages of a 3 blade prop. More thrust? Downhill braking?
Also, is there a point in the weight of a plane that those above that point perform better with a 3 blade? I do remember using 3's on 1/2 A planes.
I know 3 blades are more expensive and I haven't seen very many offered by different prop makers. Carbon fiber 3's are what I've mostly seen on the competition planes and those are pretty pricey.
Would there be any advantage to using a 3 blade on a sport/competition plane such as a Cardinal or Score? How about a Vector 40?
Thanks in advance for any information and opinions.
Joe
HI Joe
Yes many times there is a very big difference in performance, typically the 3 blades have less precession , than 2 blades, they load the engine better sometimes and are quieter. Other times they wind up less in the wind and also give a more constant speed to the model. You also can use more blade area without having more ground clearance
This is not always the case, as there is no magic to just bolting on a prop, and you can at other times make the 2 blades work just as well or better. It s just another important tool we have to make the planes performance much better.
Regards
Randy
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The biggest thing is that the 3 blade runs smoother. Each prop blade hits its max angle of attack once per revolution(P effect). On a two blade prop one blades hits max and the other hits min at the same time, twisting the prop sideways. The difference is pretty noticeable on most planes.
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Could anyone recommend a 3 blade composite prop for a S.T. .51 on a Score?
Maybe an APC 3 blade?
Thanks,
Joe
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I don't know anything about APC's, I ran a Bolly 9.5x 6.25, 3blade on a ST.46, with excellant results, saw people run the very same propellor
on ST.60's, might work on the .51.
Walter
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Could anyone recommend a 3 blade composite prop for a S.T. .51 on a Score?
Maybe an APC 3 blade?
Thanks,
Joe
The BOLLY 12 x 6.5n or 11.5 x 6.5 3 blades work very well on that engine
Regards
Randy
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I noticed that the new plane I'm flying had a slight hunting problem. Hmm, that it's accurate. It would groove fine for a lap or two but if it hit a disturbance (turbulence, wind, whatever), it would hunt around a bit for maybe a half lap before it settled back into a groove. I changed from a Bolly 11.25x4 (pitched to about 4.25) two blade to an 11x4N Bolly three blade. The problem went away and the corners are still quite good.
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I agree with Randy's Bolly 3 blade suggestions.
But I was running a 4-3/4 pitch (repitched 12-4) Bolly 3 blade on my ST 51 trimmed to just under 12", on my USA-1. Had an awesome run, and pulled great in all the right spots. It was running a 4-2, but more like a PA in rpm.
Bill <><
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What's going on here? I use a 12 X 4 N Bolly cut down to 11 1/4 on my Aero Tiger .36?????
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What's going on here? I use a 12 X 4 N Bolly cut down to 11 1/4 on my Aero Tiger .36?????
Hi Ward,
I liked the smaller disc area of the cut down prop. And it worked real good.........
I haven't tried an 11 1/4 3 blade on my Aero Tiger 36.
Bill <><