Help! Fastest Airframe for 6 inch prop?!

Mr Man

Elite member
I've got multiple different pitch options, a spinner, lots of different motors and esc's, and want to be able to fit a 1500mah 4s lipo. Pusher or tractor is fine. Looking for fastest speed possible with foamboard.

Thank You!
 

clolsonus

Well-known member
Just a random thought. You can compute a theoretical max speed if you know your prop pitch and max rpm. You can't probably know the exact max rpm -- like in a climb vs a dive, but you could make some estimations and ball park the theoretical speed. The important thing to remember is the aircraft simply can't out-fly it's own propeller! So to go faster you can reduce the prop diameter so that the motor can spin at a higher RPM, you can increase voltage to spin the motor faster, and you can increase the blade pitch so you move forward further for every revolution.

But the two things you want to do is make the prop go around faster and move forward further for each revolution. But nothing is for free and everything is interrelated. Drag increases with the square of velocity and that is fighting hard against every small speed improvement you might try to make ... so reducing drag will help you get closer to the theoretical max your power system can deliver.

And of course all these factors and many others interrelate and affect each other. Also I've never actually tried to make a plane go really fast, I've usually been trying for increased endurance (bigger battery, lighter wing loading, cruise with fewer amp draws). There are certainly people here that are much smarter than me on the topic of go faster.
 

Mr Man

Elite member
I’m using what I believe is a 70mm edf motor, used it with a 6x4.5 prop on 4s and barely got warm.