wag

[Bikersurgeon]

did some more hovering tonight and not nervous at all this time...so I had a chance to really look at the heli in hover, and there is indeed a low amplitude tail wag...maybe 1 inch total wag with a 1 second frequency. Dialed my gear endpoint down a few points at a time and really only noticed a slight improvement even when the point was set to 15 (which is about 10% real gain). should I move my servo arm ball in a hole? Thanks.

[Bob O]

Ideally you would want to set your gain for no wag at the highest HS you plan to fly in. This way you get the best tail holding power when you demand the most from your heli. As you fly at a lower HS, chances are that even without changing your gain, the gyro will still hold the tail.

You don't need much holding power in a hover, and generally if you're just hovering, you won't be doing that at a high HS. So if you set a gain just short of wag for hovering, as soon as you hit Stunt mode, the higher HS will induce a wag.

However, if you're just breaking in an engine and running a rich mixture, this can cause vibes that could result in a wag or other tail issues. But if you really want to find out where your highest gain is, you need to get it well into a high gain. In other words, don't just adjust it a few points at a time. Rather jack it up like 20 points. This way when the tail wags, you'll know it! Then you can back it off until the wag is gone.

Is the engine broken in?

As far as moving the ball on the servo arm, what distance is it at right now? I think the manual calls for somewhere around 13mm. It can't hurt to experiment here. If you move the ball in one hole, make sure to redo the limits in the gyro so you get full travel at the pitch slider. If you end up moving the ball back out to it's original position after moving it in, again make sure to redo the limits in the gyro so you don't bind things up.

[Bikersurgeon]

Thanks a million bob! very helpful...the ball is currently at 14mm from center...I agree, manual says set it at 13mm. Moving it in 1 hole on the arm I have will put it at 11mm from center. On further analysis I think you may have hit on something...no the engine isn't broken in, and is running rich, and thus vibey. My wiring isn't perfectly routed yet either (although I was careful to isolate the gyro wire)...the wag seems to be irregular...a bit more pronounced at times and almost gone at other times...I wonder if vibes might cause such an irregularity versus an out of tune gyro which might be more regular in it's wag. If it won't hurt to move the ball in a hole I think I'll do that just to see what happens, but expect I'll move it back out a hole (to original 14mm), make sure vibes are minimized, and wait for final tuning of a broken in engine...it is, after all, very stable/controlled, even with the slight wag. Thanks again!

[Bob O]

If it's just a simple case of gain being too high, the tail should give a constant wag. If it comes and goes, chances are there's something else to blame. Or a high gain coupled with something else.

14mm is pretty far out there. I'd go ahead and move it in one hole. Expect that you'll have to increase your gain quite a bit as a result. You might also try a different servo horn that has something between 11 and 14mm. You might also consider using a servo wheel and drill a custom hole at the precise distance you want it. Check this link on where to locate the ball on the servo horn:

http://www.spartan-rc.com/resources/...80&category=20

I've always used gain value as an indicator of whether or not the ball could be in a better position for best performance. Talking Gyro Sense now, I've always aimed for a value around 80 to 85. If I got wag prior to 80, I would move the ball inward. If I didn't get wag until 90 or higher, I would move the ball outward.

Depending upon the servo, tail blades, head speed/tail rotor speed, the recommendations in the manual seem to be fairly close if not right on.

ADDED:

In the end, gain value is relative. If you get the performance you need out of your particular setup, that's all that matters. There's no need to dial anything in for absolute perfection, just make it so it works for YOU.

[Bikersurgeon]

Thanks for the reply...awesome info! And I wonder..you mention head speed being a tail affecting factor....I have now ordered an optical tachometer. Someone commented that my head speed sounded too fast in that youtube hover video. I downloaded an android app called heliheadspeed...it's an acoustic tach...unsure of it's accuracy but thought it better than nothing till the optic one gets here. It showed a head speed between 2250 and 2400 rpm (it bounces around). I dialed down my midrange throttle curve a bit until it read between 1800-1900rpm. THAT is when I started noticing the wag. I'm going to take your advice and use a servo wheel and put the ball exactly 13mm out like the book says, set my gain back to 30% and start over. New problem though: wind gusts to 40mph today too bad there isn't a wind speed curve on my radio.

higher head speed=higher tail speed=higher frequency wag=less noticible to me, especially since it was dusk, and I was focused on simply not crashing lol.

[Bob O]

That was my comment on your video. Remember, tail rotor speed and main rotor speed are tied together. As you raise or lower the HS, the tail speed will follow.

If your tail started wagging after you reduced the HS, then it's not a gain induced wag. Could be a head wobble caused by low HS and hard dampers, or vibes from a rich mixture.

The HeliTach app for the iPhone is accurate on an electric heli for sure, as I tested it when it first came out. I've read where it also works on nitro birds but haven't tried that out.

Heading to work, I'll catch up with you later! Sorry about the high winds.

[Bikersurgeon]

LOL well hey there, sheepdog. I tried to leave a reply but couldn't figure out how to log back on till last night lol. Don't have too much fun at work, man.

[Bikersurgeon]

perfect day...sunny, 57 degrees, light winds. pulled out ALL the helis and flew them...no crashes ! Again noticed the irregular slight wag in the x50 tail. got the raptor 30 up and the SAME irregular wag was there....the raptor is not tuned rich but the x50 is. But guess what...since I am FINALLY able to fly in the DAYlight, I noticed that both the 30 and the 50 have blade tracking that is off by what appears to be about 1/2 inch in hover. I assume this could cause erratic tail behavior? It will be corrected soon. Anyone have an opinion on that "pull the blades back and check tips for tracking" (I can only vaguely remember the posts) vs tracking tape methods for adjusting?

[Bob O]

1/2 inch is A LOT, definitely need to correct that on your next flight. I personally don't use that method of folding the blades back, which can only be accurate IMO if the swash is perfectly level. If you don't know if your swash is perfectly level, I wouldn't use that method.

I've always set zero degrees pitch at mid stick of course, but one blade grip at a time and from the same side. I also use a bevel box, and when I had a flybar heli, I used a flybar lock. When I got each blade at zero degrees, I never had to adjust for tracking during flight.

What I mean by doing tracking one blade at a time is this; let's say you're seated at a table with your heli in front of you tail left/ nose right. I strap the bevel box to the top of the blade grip, and with the blade grip pointing toward me at an exact 90 degrees to the tail boom, I adjust the linkage for zero degrees. Then I rotate the head 180 degrees so the other blade grip is facing me, strap the bevel box to this blade grip and adjust for zero degrees.

If this is done accurately on the bench and your blades are balanced, the blades should track perfectly in the air. Of course you can do it with either side facing you, or the nose of the heli. It's sort of hard to do with the tail facing you.

Use what ever method is best for you. Once you get the blades tracking properly, the heli will smooth out nicely.

[Bikersurgeon]

Awesome! Thanks! Going to take your advice....I am color blind lol.

[Bob O]

Bevel Box. I really like this gadget, but you have to have a flat spot on the blade grip in order to use it properly like in the pic.

With a digital pitch gauge, you can't be bothered with it being off by a few tenths of a degree between blades. With it just sitting there, the tenths reading jumps around on it's own....LOL!!

Also, when I help track blades on other helis at the field, I don't use tape of any kind. I can normally see which blade is off just by eye-balling zero pitch and making an adjustment on the bench.

What I do then is mark a blade or blade grip and make initial adjustments to that blade only. If the adjustment resulted in tracking getting better, then I know I was adjusting the blade in the proper direction. If the tracking got worse, I adjust that same blade in the other direction, or put that blade back to where it was and make an adjustment to the other blade.

[tr911]

I purchased two bubble levels at lowes and they fit perfectly into the blade grips without the blades. You just have to make sure your heli is level.

[Bikersurgeon]

Changed (corrected) the servo/bellcrank/link swash geometry to true 90 degrees, rezeroed everything, and hovered in the floodlights last night....best I could tell the blades were IN TRACK...and the irregular wagging was GONE....floats like a butterfly ! can't wait for sunday though...there is no substitute for sunshine. Thanks for all the helps.

[Bob O]

Excellent!!! There's nothing else quite like a smooth running/flying heli.

[Bob O]

Biker,

Just curious as to what you ended up with. Did you drill a custom hole at 13mm?

[Bikersurgeon]

No, I ended up putting it back in the original hole (I believe that was 14mm out) after you (correctly) diagnosed this as a non gain issue...I had looked in the quark instructions too and it suggested, for larger nitros, to use 13-16mm holes, so I figured 14 put me back in the "near middle" of that range. I sure hope this thing looks as perfect in the sunshine sunday as it did last night!

[Bob O]

14mm sounds perfect then.