First Batbone V-tail build! Stick scaling issue?

[d4ddyo]

My first Batbone V-tail build. Flys amazing but i'm still fine tuning it. can't get it to fly perfect just yet.

My setup:
KK2 board
3s 5000mAH Lipo
30 mAh iPeaka ESC
Cobra C-2213/18 Brushless Motor, Kv=1350

9x47 Gemfan up front
8x45 Gemfan in the back

I setup the KK2 just like David did on his bat bone video except I left the stick scaling on KK2 on channel 3 and 4 for throttle at 120. In the video he does a full throttle test and his v-tail tips backwards which is why he sets it down to 100 because of equal sized props on this one.

I'm confused. Lower the stick scaling on throttle on the tail motors will increase the throttle to the rear?

In my case the rear is set to 120... my V-tail on a hover tends to drift forward. I'm all calibrated and zero'd out. Do i have to increase the throttle scaling on this to level it out?

I can use a bit of trim but i don't think this is the solution.

 

[Craftydan]

ok, to get the terminolgy straight (there's a lot of terms to get confused) stick scaling is the rate adjustment at the board to "how much left is a command from the stick going to yield" -- for the entire craft. Think of it very much like a rate on the radio.

I believe what you're refering to is the "mix", which is how much of a correction/input gets divided out to which motor.

IIRC, from the video, he did a throttle punch from hover and felt the tail lift faster than the rest of the copter. he then went into the mix and lowered the throttle mixture to the rear motors -- his throttle went to max and the rear two motors got more thrust, collectively, than the front two, so drop them in the mix.

Now a level hover is an entirely different issue . . . and you've stumbled on a idiosyncracy of the batbone-Vtail layout. In a true V-tail (we'll skip the Atail vs. Vtail purist argument) , the angle of the motor mounts are parllel to each other and alligned with the centerline of the craft. In the batbone, they're alligned with their individual boom.

Look carefully -- you're rear motors aren't just canted slightly outward . . . they're canted slightly forward as well. this will *ALWAYS* give you an unopposed forward thrust component if the deck is level, so in a level hover, you'll drift forward with the thrust kicking off the back.

So what can you do about it? easiest, you can change your level. trim works just fine for this, or lift the front two booms and re-run your ACC cal. Hardest, you can build a better mount that leans them straight out left/right. In this case, I won't say either solution is far superior, but either will work.

 

[Tieman]

... my V-tail on a hover tends to drift forward. I'm all calibrated and zero'd out. Do i have to increase the throttle scaling on this to level it out?

I can use a bit of trim but i don't think this is the solution.

Trim does not help until you correct angles of back motors.

You can do something similar to my V-tail as it is described in my post:

View attachment 24169

http://forum.flitetest.com/showthread.php?9535-Batbone-MultiWii-V-Tail

 

[Craftydan]

Trim won't help the craft stop drifting forward when the frame is level . . . but the craft will stop drifting forward if you trim/calibrate it to lean back a little in self-level mode.