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View Full Version : Yaw unstable at racing speed even at D:100 What the hell man?



brooksbot75
29th March 2016, 10:14 PM
So I've finally gotten my DIY quad built and flying...and crashing. Finally getting better at flying my backyard course but trying to practice up for doing my first stunts, I'm finding when I dive to pick up speed, when I level out, the slightest bit of cross wind will send it spinning to one side or the other. I can sometime keep it under control but it take full yaw stick and sucks all the momentum out of the speed run and kills the attempted loop or wingover. I've been jacking all the PIDs up and down hoping to get control of it but even with D at 100, it just makes it harder to turn it myself but the wind just slaps it around and does unspeakable things to it. Is this a normal thing for racing quads?
Acro naze32 full FC, DYS BE1806 motors, Mini 16A BLHeli ESCs(one always seems to delay in syncing up with the rest of them on arming even after many ESC calibrations), Gemfan 5030 props(same yaw drift problem with 3 blade props).

QuadroBro
30th March 2016, 03:19 AM
TOO MUCH D?

elmattbo
31st March 2016, 03:09 AM
Post a pic of the airframe? You can get some weird aerodynamic effects. This is what happened to my qav250 with aeroguards fitted.
https://youtu.be/dsEc_rh7irw

xjet
1st April 2016, 03:28 AM
Yep, if you have too much side-area in front of the CG then you can get a "shuttle-cock" effect where it wants to spin around and fly backwards. Another affect of too much side-area is that when the model yaws, the prop on the front motor towards which the quad is yawing can cavitate and lose lift because it is operating in the low-pressure vortex generated by the body.

In short... some seriously weird stuff can happen!

elmattbo
1st April 2016, 04:02 AM
Yep that pretty much sums it up! Lumenier were a bit coy about all this. First of all they quickly added a disclaimer to the sale of the aeroguard saying that it can cause aerodynamic issues. Then for later qav designs they had a much shorter side section and I've not heard of any issues with that. It was pretty alarming given I was just learning at the time!

CongoSavanne
2nd April 2016, 09:33 AM
TOO MUCH D?
Dewd... never too much D.

QuadroBro
2nd April 2016, 11:41 AM
Dewd... never too much D.
that's what she said.