B-Wing Mk.1 [continued]

Quick clip showing bobbing:

Quick clip showing bobbing (0 min 55 sec)

Okay, here are some things I tried to remove that bobbing:

1) Change CG. Moved it way forward, way back, not much difference in the 'bobbing' behavior

2) Extend elevons. I thought perhaps the elevons were being blanked out at higher angles of attack as the flow separates/KF airfoil vortex sheds from behind the step. However, this seemed to make the behavior WORSE

3) Stiffen control linkages. This involved moving control horns to top, increasing torque and resolution of servo by adjusting linkage position, firming up the elevon hinge, etc. Didn't make much difference

4) Fly upsdide down.

And #4 is what made the difference. The wing flew a bit better upside down! For some reason, my KFm-2 wing wants to become a KFm-1 wing... and under loading (hard turns etc) this tendency flairs up and causes the bobbing behavior seen in the video.

Why does this happen??

Honestly I'm not sure, and being an aerospace engineer, it is killing me not being able to figure it out Sometimes when I am flying straight and level a gust of wind will come and make the plane take a hard nose dive... which means that in 'level' flight the wing is on the verge of creating 'negative lift', or swapping the high and low pressure regions of the wing... very odd, haven't seen that before.


All in all, it was a great learning experience (although frustrating) and revealed some good and bad points of the current wing design. I am now moving forward with B-Wing mk.2, which will be essentially the same plane but with a KFm-4 airfoil and slightly different winglet design to reduce nose-in on landing. Assuming that plane is successful, we will move forward iteratively to make the design even smaller and more agile while still carrying my Caddx Turtle v2 FPV pod I am working on

I have these wings designed in Fusion360 and setup parametrically, so all I have to do is change my input for wing sweep, wing span, chord, etc etc. and the design automatically updates with the new parameters. Pretty nifty If there is some interest, I will create a post/video about this in the future and share how I set it up, and perhaps even share my design files.


More to come soon on the B-Wing mk.2

https://www.instagram.com/highlydistracted/