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Brian Taylor Me109E
- soloslogger
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Martin, 3 of my models are BT designs, F6F-3 (64", converted from BT's -5), a Spitfire Mk1A (69"), and an 81" Mosquito. All are electric. They are set up for about 150 W/lb. All three use Turnigy motors from Hobby King. All are direct drive outrunners. The F6F-3 and Spitfire Mk1A use the same motor, Turnigy 50-65 270 KV. On these two props both 17" dia. APC's, the Mk1A has a 12 pitch, the Hellcat a 10. Both fighters weigh 10-11 lbs at take-off. Both use the same size batteries, 6 cell 5000 mah. ESC's are 80-85 A. Both are BEC equipped.
The Spitfire goes through about 14 amps ave, the F6F-3 about 20 for typical 8 minute flights. Both these amperage estimates are based on charge-back. Both planes could fly for substantially longer periods.
Mike
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- soloslogger
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Mike
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- alan cantwell
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i have 2 sides
no you dont,
yes i do,
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i have 2 sides
no you dont,
yes i do,
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- Klipkopwildlife
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- I'm supposed to be retired!
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- soloslogger
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Mike
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- Garry Pollard
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Garry
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- Klipkopwildlife
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- Eric
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It's when you have the throttle wide open, and the plane is still reversing down the field, that you need to worry!
Technically, it is an interesting topic, but the limiting factor will always be the ability of the nut holding the transmitter!
if you are calm and collected when all about you are going berserk - you've missed something important!
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- Garry Pollard
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Klipkopwildlife wrote: Isn't it funny, we fly RC but we really don't have very much idea how fast they're going! Let's say that max speed will be 70mph, that's 70/60 miles per minute = 1.167mpm. Change that to feet 1.167 x 5280 = 6160'/min times 12 to inches = 6160 x 12 = 73,920"/min now divide by our maximum available rpm 73,920 / 6049 = 12.2" pitch
Dont you just hate a smarty pants
Garry
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- Klipkopwildlife
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Note that this setup of 2 x 4s Lipos in series weighs a total of 1,593g for 176W/lb using a 20 x 8 prop. Note the massive static thrust of over 7Kg! However I think the maximum available speed might be a little low.
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- Quorneng
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As planes get bigger the engines (or motors) rev slower for a given power level so the pitch to diameter ratio tends to be higher rather than lower.
So far an aerodynamically slippery Bf109 my guess would be a pitch of at least 75% of the diameter so with that sort of ratio identify the biggest prop the motor can safely swing within its maximum current limit.
I happen to know the Fokker Triplane had a 8' 7" diam x 7' 6" pitch prop.
I will now go back to cutting some Depron!
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- Klipkopwildlife
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Note that you only have 2.5Kg of thrust when stationary, a drive line weight of 1.45Kg and only 70W/lb!
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