Well, I guess that answers your question from your Email. All in all, it's fairly easy to calculate given all the parameters. The most important part of this is getting the weights right, which always means a little research. Pretty much all of the vendors list such parameters.. weight of each item in the process, including the airframe, motor, prop, battery, esc, servos, and so on. Just add them up and work through it as Opjose did and you will come up with a solution for that combination.

Just remember that making a change, increasing the battery capacity, for instance, adds weight and the whole thing needs to be re-done again to make sure you remain within the 'envelope' for that particular type of flying and for that airframe.

I don't want to oversimply this and insult your intelligence, but, here is the basic math for watts, amps, and volts:

Ohm's law (algebra) [:@] :

Volts X Amps = Watts

Watts/Volts = Amps

Watts/amps = Volts

Easier stated, multiply volts x amps you get watts. 11.1 Volts - three cell LiPo multiplied by 20 Amps drawn = 222 Watts

222 Watts divided by 11.1 Volts = 20 Amps

And so on.


For OpJose's prop calculation, that comes already done for you. Ask him where he got the info.. it's on a web site somewhere.
CGr.