QuadPlane Nose Dipping When Yawing

ArduCopter
1

Hi all, we are trying to build a quadplane with the RVJET flying wing kit.
Pitch and roll works okay, but when we gave a slightly larger yaw the nose would dip and unbalance the plane.

Check:

  1. CG line is at the correct location
  2. Motors are symmetrical
  3. Tried moving CG line further back, doesn’t help

Does anyone know what to do?
Thanks!

Video: https://www.youtube.com/watch?v=ipZxB-uEYDc&feature=youtu.be
Log: https://drive.google.com/file/d/1LFWBN59LyRROPiEwPPj6B_AiQUynn2Br/view?usp=sharing

2

I have an RVJET Quadplane and I found that wing flex was an issue until I stiffened things up.
It does not look like you have an issue at slow yaw rates, only when you quickly yaw it.
So my bet is frame flex.