Thread: Discussion HK EPO Parjet, ARF
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Old Dec 24, 2012, 07:58 AM
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222 km/hr Parkjet flyer
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Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
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Quote:
Originally Posted by TheCure View Post
I just measured my newer un-maidened parkjet. Its got a 4200kv 2627 outrunner motor, 50a esc, 4.1x4.1 prop, running on a 4s 1300 nano.
I read about 1100g pull, 58a max @836watts. I think it weighs around 350g.

Am i going go have problem hand launching it?? Can i get by without a bungie if i apply liberal throttle to launch?
Its not power that's the real problem ... its prop diameter + power that is ...

Think of it like this ... the prop is a flywheel. The bigger the diameter and rpm - the greater the flywheel effect ... Laws of motion dictate that for each action - there is an equal and opposite reaction.
This mean we reach a point where the force turning the prop also wants to turn the model. Usually called Torque Roll.

The trick is to find the limit of throttle that will allow model to launch without torquing into the ground. Some try to counter with offest aileron - forget it - torque roll occurs BEFORE model is flying, aileron offset only works when surfaces have airflow ... so yes ... reduced throttle on launch and power up as she flies ...

Better still get a catapult bungee !

Nigel
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