I am looking into purchasing a V-Tail quadcopter from HERE and was wanted some feedback on the following points as I'm pretty new to copters... been flying RC helis for years but wanted to try something new...
I want to use this copter for FPV but also have the added benefit of GPS and Mission planner plus the thing just looks cool... any advice is much appreciated!!
Thank you in advance.
Answers as I know them...
A & B) Yes, and yes. The more angle that you have the more stable it will feel with less roll. With the arms angled in you will have easier roll axis and less stable.
C) Kind of the same answer here as for A & B. The wider your angle the less roll that you will have.
D) It all depends on where you want your center of gravity to be. If you want it more up front then you will want longer tail booms compared to the front booms... you want the center of gravity to be more towards the back... shorter. I will tell you this, the tails will NOT add as much lift as the front.
Best bet is to build it (with out motors), put all your gizmos on it, and find out where you want your CG to be. (Pro-tip - don't make your front end to heavy)
Hope that this helps answer your questions... I'm a little tired right now so I may have just rambled...
Just got a quick clip but managed to do some flying with my Vtail 500 and pixhawk. Will do a better one sooner or later. Was a bit windy / some gusts and this was just a fresh flash of 3.2-RC2 and recalibrated accel but no tuning whatsoever. It did have a tendency to want to shoot high up in the sky once airborne in stabilize, switching to alt hold helped. Tested rotation and tilting left / right / forward / backward. Everything worked.
Thanks Tom. I can easily calculate the proper CG with my CAD, so i do not worry to much about that.
I was just wondering if there is a "defacto standard" how a V-Tail-Setup should optimally look like and which works best with the V-Tail mixer implemented in APM.
There are many varaints of building quads (standard, dat-cat sytle, spider style ...) and from all those variants the standard quad always works the best because of it's clean symetries. More or less my question could have been: "Is there a standard V-Tail design? If yes... how does it look like?"
Thank you so much!
Sorry that it took me this long to get back,
The long/short of it is that there is no standardized way to build a V-tail as far as APM is concerned. The only thing that you have to limit yourself with is the angle in which your tail rotors sit. As long and the angle is correct then you can just make minor adjustments to the PID settings to get the proper yaw.
I just finished building a PVC V-Tail (my first ever quad of any kind) and it hovers fine with stock PID's, Im running AC3.2 - I think the latest non-beta build.
However, Im having big time yaw issues.
When ever I give it anything more that very slight yaw control inputs, it wants to pitch nose down and roll opposite to the yaw input. It can be pretty dramatic.
One thing that may be adding to my problem is I didnt keep to the motor angles of the Hunter V-Tail. My rear motors are tipped at +- 40 deg, but much further apart than the Hunter. The quad is also heavy and under powered. It takes about 70% throttle to hover.
I'm a raw newbie so I have no clue how to tune this. Any tips on where to start?
Well no tips but can verify what your seeing I guess.
I have a lynxmotion vtail 500 but i modified it (added longer legs). I was trying to fly it after extending the legs and adding a gopro / gimbal. I could take off and hover a bit but not maintain hover. I guess the overall weight was just too much with the gimbal and camera. I removed them and then was able to take off and hover pretty well. I couldn't get too crazy because was just testing in the backyard, will take it to the park on a less windy day. Anyways....
When I first flew it my rotate was opposite so I reversed it in my transmitter to fix that problem. Today when I tried the yaw I saw something similar to what you saw, it would yaw the wrong way and also just kinda act erratic. I'm thinking I can solve the opposite problem again by reversing the yaw in the transmitter but it also acted really erratic so not sure about that. I'm thinking maybe there is an issue with the default vtail configuration.
I was able to to take off and hover several times, forward, backward and side to side motion acted as expected, only when I tried yaw did it act really erratic. I'm only on the default vtail configuration without any tuning as well. Depending on the weather / wind the next couple days I'll try to take it to the park for a more in depth test and maybe make a video so people with more experience can chime in. Overall besides the yaw issue my vtail was working pretty well without tuning, I just had an issue maintaining altitude some times, it would start dipping down and I would try throttle up but it would still descend, some times even touching down for a second before firing back up. Might have been gps related since I have trees around the backyard, but again not sure, pretty new to all this myself.
Thanks for the feedback Tim.
Mine yaws in the correct directions. Its just the adverse roll and pitch down that is the issue.
I flew again today and tried some random changes to the PID's. I did managed to get the pitching slightly better, but the adverse roll is at least as bad and possibly worse. It feels less stable and seems to want to over shoot on corrections now.
Im afraid to try auto tune because I dont dare do any yaw inputs for corrections. Need to get this at least somewhat better first. I'll keep playing with it for now.
I will try to get a video as well.
Tim - was your vtail flying ok prior to your mods?
Im wondering if its going to be necessary to build a new frame that follows the expected motor layout/angles more closely in order to fly a vtail.
You know I actually only flew it once. The short legs was an issue with the rear props hitting into the grass which prompted me to get it up higher. The first time I flew it I had to swap the 2 and 4 motor connections to get it to fly right but it seems they fixed that issue because I'm now using the regular quad x motor config. Really I don't think I tried yaw at all that first time, I went to the park and it shot up in the air after takeoff and I brought it back with just the right stick controls iirc which means no yaw.
It's short because I was just shooting with my cell phone for take off but this is that first time.
Ok, thanks for the info!
Well, I gave up trying to tune my adverse roll issue and built a new frame that more closely matches the motor layout of the Hunter V-Tail. I also lightened in up so its not as under powered as it was.
Ive only done a couple of very short test hovers but its working much much better!
It would be nice if there was some way to adjust parameters in MP to allow for different motor layout angles when they dont match the Hunter V-Tail exactly.