Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

Laser Arrow Big prop or Small prop

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Old 10-27-2002, 10:49 PM
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Default Laser Arrow Big prop or Small prop

I'm going to pick up one of these next week. I'll probably do it as an electric for the winter. Maybe switch to glow when the weather warms up.

Anyway, I can go with a small fast prop or a big slower prop. And I'm wondering what size prop would be best for this airframe.

I can go with a smaller direct drive prop. Let's say an 8*5 at around 16k. I could go smaller of course. But to go bigger I need to gear the motor.

If I gear I can go much bigger. For example, how about a 10*10 at around 8 to 9k.

I can fool around with different props when it's built. Really the only thing I need to decide now is direct drive (8*5 or maybe 6*6) or geared. Maybe 10*10 or there abouts

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Old 10-27-2002, 11:52 PM
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Default Laser Arrow Big prop or Small prop

Have no clue about electrics but my Arrow likes a 9x8 and a 9x7 worked well also with glow. Not sure of the Rossi .45 piped rpm but it's screaming pretty good!
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Old 10-28-2002, 01:12 AM
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Default Laser Arrow Big prop or Small prop

Thanks Flipster-

This isn't so much a question on electrics as it is a modeling science question. Maybe like , if the HP stays the same, what would the Arrow be happier with. A smaller fast reving prop or a large slower turning prop.

Maybe it's a question of balancing thrust and prop speed against model drag.

With a 7*7 prop I can get, lets say, a pitch speed of 115 and 53 ozs of thrust. The RPM would be about 17k.

But if I use a large prop, 12*12, I'd get a pitch speed of 80 MPH but 75 ozs of thrust. In this case the RPM is a little less than 7K.

The power (HP) is about the same. I'm guessing the answer depends on how much drag the airframe has. How does the plane glide power off? Will the fact that I can pretty much hide the motor for less drag factor in.

Right now I'm leaning toward a large, maybe 10*10 prop. If I was looking at summer and not winter I'd just go glow. But I can only take so much cold. With the electric version, if I'm outside for an hour I'd probably be flying 45 minutes.

Ya know, I could probably build a plane in the time I spent on the boards this weekend.
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Old 10-28-2002, 01:20 PM
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Default Laser Arrow Big prop or Small prop

Don't plan on a glide with no power, it stops flying pretty quick. I set up on the field when I first started flying this plane and killed the engine and ended up in the corn because it didn't float like a regular airplane. Not sure if this is a delta thing because this is my first. My Arrow is light and anyone that picks it up at the field is shocked, so it's not that it is heavy.
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Old 10-28-2002, 01:46 PM
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Default Laser Arrow Big prop or Small prop

I think deltas lose altitiude more than traditional planes during turns. But should glide OK. So I guess that's the answer. The model must have fairly high drag. Big prop it is then.


Thanks a lot Flipper. That's waht I needed to know.

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