Originally Posted by The Don
A 3900 KV motor is not intended for direct drive props. That high of KV used in a 70mm EDF will be about 1000 watts and that is direct drive but with a 2.75" diameter rotor so trying to swing a 6" prop is wasting power
Likely true. And unimportant, since I only do it rarely and then only to get out of trouble and/or watch the beastie climb like a scared cat.
This motor calc (link below) is a nice way to virtually test setups with buying and frying parts or wasting money and time in the process. You can get about 5 lbs thrust pretty easy with motors in the 1200 range and more at 1500KV on 4S with an 9x4.5 APCE prop. This is the way to go if you want o boost power on this model.
Here is another one:
Thank you, Don! Those sound VERY useful! I'll have a look when I get time, hopefully this weekend.
I assume they estimate static thrust only? Or do they also try to estimate thrust with airspeed?