seebass7400

I just got finished with my first build!!! A Precision Areobatics Katana Mini It was awsome!!!!! I can only hope its not blowing 15mph..... Oh and 95 degrees to go along with it!

Im running a Hacker A30-28 with a Hacker X7 30amp ESC, FP 2170 3 cell 25c with an 11x5.5 prop.

My Question is..... While testing a plane with an amp meter does the plane tend to run higher amperage due to holding it down? I ran 31.5 amps for about 45 secs. and shut her down.

My thought was, while flying, the plane would never come under that type of drag......? Any truth to that?


Thanks for any and all the info


Carlos

mrasmm

I would tend to think the same thing, although I don't really know. The best way to find out would be with a watt meter, but maybe someone else has some experience that way.

soarhead-RCU

I have read on other forums that slow flyer props un-load about 10 to 15 per-cent from static draw to flight draw. Seems like that would be about right to me!! People used to say that the old geared 400s that drew 10 amps static would unload to 8.5 to 9 amps in the air depending on the airframe of the plane and how sleek it was.....
Happy flying
Bob

seebass7400

thanks for the responses guys!

That 10-15% unload rate would that apply to a "E" Prop also?


Carlos

otrcman

Carlos,

Yes, the current draw will be less as soon as you are in forward flight. The reason is because the angle of attack (and thus load) on your prop is at its greatest when you are standing still. As the airplane picks up speed, the angle of attack of the prop blades is reduced, the motor RPM rises, and the current draw goes down. On the other hand, if you are hanging on the prop (hovering) then you can expect to see the full static current draw.

Exactly how much the current will go down on your airplane, with your motor, and with your prop is highly variable. You can expect the the current will go down more if your airplane goes fast and if your prop has a relatively low pitch. On any one flight your current draw will vary with every phase of flight. Pulling into a loop, for instance, will draw more current as you slow down in the first half of the loop, and then less current as you speed up diving through the second half of the loop.

It sounds like your static current draw is perhaps 5% over the max rating for the speed control. Unless you are doing a lot of hovering, your current should drop at least 5% in flight. And probably a lot more than that. If your airplane is somewhat over-powered, you may find yourself flying at partial power most of the time.

If you want to get a better idea of how much your exact motor/prop combination will unload, try this experiment: Hold your model (without the wing) out the window of your car while somebody else drives at 20 to 30 mph. Monitor the current with the motor running. You will probably be surprised at the current drop off with speed. If you do the experiment, post the results for others to see.

Dick

seebass7400

Thanks Dick,

I will try that and see. I will post my findings by tomarrow. Hanging out with my girls today

But once again thaks!

Carlos