Yaw Problem with my Quadplane VTOL

Hey Guys,

i did some testflights with my new quadplane test platform.

transitions are smooth, flyes nice as plane.

I only have very slugish yaw performance in qhover, so i had a look at thelogs: https://www.dropbox.com/sh/vzbc46ju5ldrbth/AADcCTUMRX5v5fYyWdtOP27_a?dl=0

 (second log is the more interesting, first one was with the wing cam, bad cg and not balanced...)

looked at the pwm out of the quad motors while in qloiter.

almost saturated ;/

3691329847?profile=original

interesting is also that motor rc out 5 and 6 have lower means. i think thats my yaw problem. so motor 1 and 2 are turning slower... what to do mechanicaly about that?

any advice?

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Replies

  • thanks for the response!

    to the "turn all motors point" you are right, but i rather would just turn the two motors working more ;)

    the CG of the plane is also the "middle" of my motor cg, so no problem there, they should have equal load.

    i think its fine if i fix the yaw thing than i have some more power margin.

    the problem for me is now what direction to turn the motors ;/

    Also maybe somebody else can have a look at the logs?

  • There are many possible reasons but the two very common ones.

    One is that your motors axies are not absolute parallel. Any small tilt of any motor will introduce additional torque, which the other motors have compensate that. But if you tilt all of them a little bit in the proper direction ( that they generate a torque around the vertical axis as they are already generate as reaction from the drag of the propeller) then you can increase the yaw response significantly, by practical no loss of lift.

    Another is the distances of the motors from the CG. On a fixed wing (with nearly rectangular wing shape) the CG should be at the 1/4 t line (1/4 from the leading edge of the wing of its cord the profile cord length). If you have the motors mounted in the same distance from that point than they should be have equal loads.

    In any case I would use one more cell or bigger propellers or motors with a higher kv. Since you don't have much reserve a gust (with that big wing) can be dangerous for your vehicle.

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