prop thrust calculation
09-30-2002, 12:37 AM
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prop thrust calculation
I am new to electrics and have been looking into converting a traditional balsa 10-size kit to electrics. The specifications weight is 800gm and the wing loading about 17 oz/lb.
Most electric motor give their power out specs in number of rpm/volt, or total watt. Let's say I put a 8x4 prop on a direct drive and spinning at 12000 rpm, how do I calculate the total thust in oz?
If I want to get this plane to do reasonable aerobatics, what would be the idea power/weight ratio?
Thanks guys
Chris
Most electric motor give their power out specs in number of rpm/volt, or total watt. Let's say I put a 8x4 prop on a direct drive and spinning at 12000 rpm, how do I calculate the total thust in oz?
If I want to get this plane to do reasonable aerobatics, what would be the idea power/weight ratio?
Thanks guys
Chris
09-30-2002, 12:01 PM
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09-30-2002, 04:08 PM
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prop thrust calculation
The simplest way to go is MotoCalc. Use their 30-day trial, then buy it.
You can't really calculate static thrust for "an 8x4 prop spinning 12000 RPM." Every brand of prop will be different, and they vary so much that there isn't even a good middle-of-the-road estimate; you'll either be sorely disappointed or overwhelmed. Besides, that's not how you calculate e-power anyway.
When calculating power requirements for electrics, you go by a number of Watts per unit mass. For reasonably aerobatic performance, 80 W/lb, or ~175 W/Kg should be your minimum starting point. You won't get unlimited vertical or hovering, but you'll have reasonable vertical and the ability to do most other aerobatics.
If you figure you can build the plane, completely outfitted with battery and gear, and keep it at 800g, then you'll want a power system that'll put out 140-150 Watts.
You can't really calculate static thrust for "an 8x4 prop spinning 12000 RPM." Every brand of prop will be different, and they vary so much that there isn't even a good middle-of-the-road estimate; you'll either be sorely disappointed or overwhelmed. Besides, that's not how you calculate e-power anyway.
When calculating power requirements for electrics, you go by a number of Watts per unit mass. For reasonably aerobatic performance, 80 W/lb, or ~175 W/Kg should be your minimum starting point. You won't get unlimited vertical or hovering, but you'll have reasonable vertical and the ability to do most other aerobatics.
If you figure you can build the plane, completely outfitted with battery and gear, and keep it at 800g, then you'll want a power system that'll put out 140-150 Watts.
