Chris,
The tail seems pretty good, i have a slight kick when i take off, maybe 6 -8 ". But other than that it doesent wag at all or ossicilate. Stays put in flight even with quick collective stabs, so im thinking more P gain wont help the swing on takeoff? I dunno, advice would be appreciated.
Tim
Nope. The P gain wonāt help it. Just trim the tail mechanically to stop it from doing that. Iāve never seen where a Pixhawk or a Futaba GY401 tail lock gyro would give a perfectly smooth takeoff without mechanically trimming the tail so it can take off without snapping one way or the other before the gyro āgrabsā it. When I first got my 700 nitro I flew it with no gyros at all and thatās the way you set it up so you donāt have to fight it with a no-gyro chopper.
I know Alignās manuals say to set the slider to the mid position on the tail rotor shaft, but thatās a bunch of hooey if you ask me. I always trim 'em.
I wouldnāt worry about it. Concentrate on getting it tuned. If you see some weird behavior at that point then we will investigate further.
As for the Dowels I would recommend either shortening them or taking them off for your tuning. My concern is that they could start coupling with the vibration. I just donāt like how long they are. If you want to widen your stance, you can certainly make them a foot to maybe a foot and a half wider than the main landing gear.
Chris,
The tail is indeed set at center. The previous FBL operated better that way. For whatever reason, when i added in a few degrees of counter pitch the tail would wag very slowly in a hover and stops were bouncing in one direction. The developer of the system recommended I center the blades and it worked. Now with my ar7200BX, that liked a cpl degrees of pitch, my ar7210bx wgich was the pro version liked the tail centered. Dunno, i just go with whatever works and ill just add the pitch in for the Pixhawk. Other than the kick it seems to hold quite well.
I was suprised to see how fast ot yawed sfter seeing the slow response on the bench. Once again this all boils down to me being unfamiliar with the system and its little nuances.
As to the Align manual, i have no idea. Admittedly i never used it when building. After a few Align models they start just kind of falling together, if I get one of the new Trex 760X models they are coming out with i might read the manual as they changed a significant amount of parts this trip, but in my experience Align has just been selling the same kits with some āupgradeā parts for a few years now.
Tim
Bill,
I am going to go ahead and just take them out of the equation. I agree they are quite long and could be coupling and adding to any issues. I only had them in case it did some crazy things, but now that ive seen what to expect im perfectly fine with losing them and thereby taking them out of the equation for further tuning.
Tim
I use 40 deadzone and some yaw expo in my radio for flying Pixhawk because I donāt like the fast yaw rate it has in Stabilize/Acro/Alt Hold. I like scale flight characteristics. My expo in the radio doesnāt affect it for auto flight as it uses the yaw accel values set for the benefit of the autopilot. And neither does it affect it for doing autorotations where anti-torque is reversed from normal powered flight. So thatās what I use, but everybody has different liking.
Personally, I have never bought a new helicopter. I keep an eye on craigslist and whenever I see an old unwanted flybar I go snap it up. Just got a Thunder Tiger Raptor 90 nitro for only $325 thatās almost new. The owner bought it and found out it was harder to fly than he thought so he put in the garage for a few years and then finally decided to get rid of it. The piston crown is still shiny and doesnāt even have any carbon on it. 
Chris,
Ive bought a few new and a few used helicopters. Ive had mixed luck with used, especially online sales through RCgroups or Helifreak. I bought the trex 700v2 used and although im sure the previous owner thought he did a good job setting it up and maintaining it, i had to go through and replace every bearing, swap all the gears for helical and install some of the Align āupgradeā parts. 
ive also gotten another used heli that was like new and looked as though itād been flown once.
I do have that opportunity to pick up an Align trex 700 flybar with an YS .91 engine and tuned pipe, align 5 volt servos beast x fbl and a spektrum ar8000 receiver for $700. I dobt know if thats a good deal for a used flybar heli? Ive seen it before at the field and it looks good and seemed to run well. Ill have to do some more research before i jump on it as i have no experience with newer nitro helis or flybar trex. My last heli before getting back into them a few years ago was a Kyosho concept 30, since then its been all electric. I do love the smell if nitro though! 
Tim
I donāt know, I guess that all depends on how bad you want it, and how bad the previous owner wants to get rid of it. I got this one for $325 and itās virtually new - doesnāt have more than 2 hours on it. It has a YS90, came with a new in the box Futaba GY-1 governor, Corbin blades, and Futaba S9452ās on the cyclic. It has a 1qt fuel tank and the YS90 burns less than an ounce/hr at 75-80% power, so it can easily fly for a half hour with reserve.
Iām going to remove the carbon torque tube drive and put a belt in it using a Raptor 30 85t gear and Align 700 Nitro belt and tail assy. And put my Pixhawk Mini on it running AC3.5
So the way I look at it, nobody wants flybars anymore. I do and can go on craigslist these days and just about pick out the one I want and get it for little of nothing. I donāt fly 'em stock anyway because nobody builds what I want, and theyāre set up for 3D. So I rebuild it custom for a scale or UAV heli. And have a new helicopter for 1/3 the price, and is way better for what I want than anything I can buy off the shelf.
Iām not actually a big fan of nitro engines. They got a lot power in a compact package. But the fuel is $30/gallon and theyāre really cranky and hard starting in cooler weather. And they run really hot in hot weather. Iām going to convert this one to a gasser with a Echo SRM-280 weed whipper engine in it. Bought the whole weed whipper on craigslist for $100 just to steal the engine and clutch off it for my helicopter. Custom make a hub with a shaft for the pinion gear and Iāll be in business. Then Iāll sell the YS90 to one of the airplane guys at the RC club for more than I paid for the weed whipper
so i took the dowels off and left the settings as they were. not good. Had to add a bunch of tail pitch to get it to not spin on takeoff. Worst though was the fast ossilations the moment it got airborne. Had to set it down some quickā¦ i would have thought the 6ā dowels would have had the opposite effect and added to the ossicilation. Guess not.
Tim
Wow. Not good. I guess that kind of males sense. The dowels added inertia to the aircraft which caused lower frequencies. When you removed the inertia of the dowel the aircraft behaves differently which includes higher frequencies and more feedback to the servos. Hopefully everything is ok. Since it seems that you are bound to have instability issues, make the FILT params for pitch and roll equal to 4. That shoukd help but wonāt eliminate the problem. Back off on the p gains and ease into them again. The good new is that when you hang the camera on it, the extra weight and inertia may allow you to increase your p gains a little more.
Also when you start seeing the oscillations again, send me the log or figure out the frequency of oscillation.
Bill,
I set pitch and roll at 4 for the filter. Ill test fly it afain and see if that helps.
Thanks,
Tim
It should help some. I would recommend backing off of your P gains to maybe 0.08 or 0.09. It will still give you some stabilization but hopefully keep from having bad oscillations. Then you can increase the P gain until you see them again
Bill,
That helped alot! Ill get the logs off the pixhawk.
Tim
I have the P gain at .068 AND the I gain at .12 and it doesent feel terrible. Even if I have the P gain lower it still feels locked in? Iāll upload the logs from this evenings tuning flights and Iām sure that will tell more of the story.
Tim
2017-05-17 17-59-43.bin (758.4 KB)
2017-05-17 18-09-05.bin (2.8 MB)
2017-05-17 18-20-21.bin (2.0 MB)
Bill, Chris,
This is the response I received when I posed the question about whether the internal dampening of the Pixhawk 2.1 was defeated if mounted sideways as I have it mounted.
Obviously this makes me wonder about a few things? Could this possibly be some of my problem?
Thanks,
Tim
proficnc
1h
Iām not sure if defeated is correct, but it was most definitely not designed to be mounted this way.
As such, there is no real data to say if it can or cannot function correctly this way.
Sorry for the vague answer, but I would prefer you made a right angle bracket to mount it correctly.
Phil
So I am looking at the RateP and Rate PDes and graphed out the lines are nothing like each other? Should these lines not somewhat mirror each other? Or am I looking at this the wrong way? Uggh, so much to learnā¦ My only PID tuning experience was from Black box logs in Clean flight and with that I just looked to the the amplitude of the graph drawn as a whole and looked for repeating patters that would be oscillations. In the case of me looking at my own logs, all I see is a repeating pattern so it makes me wonder just how messed up everything is? Or are repeating patterns a normal thing in Pixhawk logs and iām just reading into it too much?
Using your method I see a lot of repeating waves with 4-5 peaks per second, so thatās 4-5hz?
Thanks for all the help guys!
Tim
Oh and another quick thing, when I give a quick jab in the pitch axis, the tail wants to bob up and down once or twice. Its kind of a bounce, not an ossicilation, its like a rubber band effect. The roll axis is much less prevalent concerning that behavior. This is after the filter of 4hz and with I gain .12 and P @.068.
Tim