Prop question
01-24-2004, 04:23 PM
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Prop question
I fly a GWS Zero and a GWS Spitfire with a Himaxx 2025-5300 on an APC 10x7 prop with an 8 cell 1amp HeCell pack. My dad thinks he's a genious and wanted me to experiment with different props. He doesn't think any of the electric props are sturdy enough and bought a master airscrew 10x6 regular black edition. I have apc 10x7 prop that i use when I fly it is .5 ounces and the master airscrew is 1 ounce. The extra weight should draw a lot more amps correct? Also he said to leighten the master airscrew he is going to drill holes in the prop close the the hole where the com shaft goes threw. Is my dad wrong or does he have a good idea? because I don't want to fry my month old brushless motor and Castle Creations 25amp speed control.
01-25-2004, 06:40 PM
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RE: Prop question
Scott, no your not going to fry your setup with that prop. Having said that, both of those props are fairly heavy for that model.
The GWS props, although fragile, are better suited for your setup. Rotating mass on a small model has a more pronounced effect, than it does on larger models, as does concentricity and balance. In other words, it's good to have a nice light prop which is well balanced.
If your father is an Aerodynamics Phd, you might consider his arguments, but small model airplane props act differently from their larger brothers and are usually contoured differently than than their gas powered brothers, beacause they are designed for different operating speeds. The most efficient props on the market today are only effective at a particular speed range. The Graupner CAM props, some of the best, are only about 60% effecient, and only through a narrow RPM range. Full sized planes have a prop efficeincy in the 90 % range. The good news is that electric props are cheap, and experimenting will be the only way you you will ever know for sure.
Craig.
The GWS props, although fragile, are better suited for your setup. Rotating mass on a small model has a more pronounced effect, than it does on larger models, as does concentricity and balance. In other words, it's good to have a nice light prop which is well balanced.
If your father is an Aerodynamics Phd, you might consider his arguments, but small model airplane props act differently from their larger brothers and are usually contoured differently than than their gas powered brothers, beacause they are designed for different operating speeds. The most efficient props on the market today are only effective at a particular speed range. The Graupner CAM props, some of the best, are only about 60% effecient, and only through a narrow RPM range. Full sized planes have a prop efficeincy in the 90 % range. The good news is that electric props are cheap, and experimenting will be the only way you you will ever know for sure.
Craig.
01-26-2004, 12:57 PM
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RE: Prop question
Hi Scott -
I wouldn't hesitate to use the MA 11x6 prop with that setup. I have noticed that the Graupner nylon props I use have a much wider blade area than their APC electric equivalents, and seem to have a lot more bite. You're also going down in pitch which should give you a much more authoritative pull.
I wouldn't worry about the extra prop weight, except to re-check your center of gravity. The extra weight should only put more load on the motor while you're spinning it up to speed.
I would not, however, drill holes anywhere, in any prop - that just sounds like a recipe to throw a blade off! If the weight is a great concern, look into the MA Scimitar in that size - it's sort of in-between an electric and glow prop (and they just look darn cool). I think the weight would fall somewhere in between, too.
Dan.
I wouldn't hesitate to use the MA 11x6 prop with that setup. I have noticed that the Graupner nylon props I use have a much wider blade area than their APC electric equivalents, and seem to have a lot more bite. You're also going down in pitch which should give you a much more authoritative pull.
I wouldn't worry about the extra prop weight, except to re-check your center of gravity. The extra weight should only put more load on the motor while you're spinning it up to speed.
I would not, however, drill holes anywhere, in any prop - that just sounds like a recipe to throw a blade off! If the weight is a great concern, look into the MA Scimitar in that size - it's sort of in-between an electric and glow prop (and they just look darn cool). I think the weight would fall somewhere in between, too.
Dan.
