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watts per pound and flight time


Old 03-20-2006, 11:29 PM
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Default watts per pound and flight time

Ok i plan on converting a Sig Lt-40 to electric it should weigh in at about 6lbs 10 oz ready to fly I will be useing an e-bay 600 wat motor and tower pro 60 amp esc the batteries I pln on useing are Maxxamps 2s2p 3000 ma batteries 2 in series should be 14.8 volts any Ideas with what prop to start with and how long of flight time I shold get? Any one with a realistic suggestion on watts per pound ratio I see some places saying 50 is enough for trainners will others are saying 100 for the same plane Thanks for any help
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Old 03-21-2006, 05:06 PM
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Default RE: watts per pound and flight time


i cant help you with the flight times but heres a link to a bunch of info about thhose motors and ESC's hope it helps you

link= http://www.rcgroups.com/forums/showthread.php?t=431127

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Old 04-01-2006, 04:44 PM
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Default RE: watts per pound and flight time

50 watts per pound for basic flying
75 watts per pound for some mild aerobatics
100 watts per pund for advanced aerobatics, pattern and a little 3D

150 for good 3D

These are based on brused motors. Brushless will give you a 50% better delivery to the prop for each watt of input.

If you are a glow pilot then you will want a brushless motor that will give you at least 75 watts per pound, minimum as glow pilots are typically flying over powered planes wheras electric pilots often fly on lower power to weight radios for normal sport flying. Just a tendancy. It has nothing to do with the technology.

Your 600 watt motor, if brushed, will be fine. If brushelss, it should be quite spirited in your 6pound, 10 ounce plane.

As for the pack, at 14 volts you will need to push about 45 amps into that motor to hit your watt expectations. The MFG should provide prop recommendtiaons.

For a 3000 mah pack you will need a MINIMUM rating of 15 C to hit your 45 amp level but you will be pushing the pack right to the edge. A 20 C pack would be better, and a 4000 mah pack at 15 C would be better.

A 3000 mah pack = 3 amp hour pack = 60 minutes at a 3 amp draw
If you pull 30 amps you will get 1/10 hour or 6 minutes.
You are planning to pull 45 amps so you should fly for about 4 minutes at full throttle. if you fly more at 1/2 throttle, then you can expect about 7 minutes.

Don't let those packs get below 3V. Make sure you have an ESC that has a LVC of at least 2.75V. Once you cut the motor off you will bounce back above 3V. At 2.5 V most lipo packs will degrade badly and may never fully take a charge again.

Hope that helped.
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