Tail wag please help!

[MrEmail]

Okay Atom 7HV flyers I have got an issue which I have a hard time solving.

I have been flying the 7HV with no problems but after a crash I have got a tail wag which is always there and I cannot get it to go away.

First things first setup is the following

Cyclic servo's Savox SG 2271
Tail Servo Futaba BLS 256
Motor X-era 4530-500
ESC YGE-120HV (Custom Cooler NO electric fan)
FBL: blue mini-v-bar / beastx
power: 2s lipo through skookum power bus
Flight packs: 2x 6s5300 Gens Ace
Bldes: Edge 693 SE
Tail Blades: Tried KBDD 104 / Edge 105 / Edge 115

Crash Reconstruction
It went in through a stupid mistake not to hot glue the servo connectors through the power bus (I think, because after the crash the cyclic signal wire was out a bit and I had no real control over the cyclic servo's)

The landing was not real hard because I hit TH and the heli went down gently but landed on the tail and then tilted forward and tipped over.

Visible Damage
The damage that I saw was this:
- tail hub
- 1 main blade had a dent
- Canopy
- Tail fin
- Tail blade grips

Repairs
I replaced the following parts in random order because I replaced more parts to fix the issue.
- tail hub
- Main blades
- Tail blade grips
- Tail fin
- bearing in belt tensioner because it was locked (replaced later and already an issue on intial build)
- tail pully (replaced later)
- tail shaft (replaced later)
- Tail blade link (1 side only the one which broke when pusing over ball link on reassemble)

Flight charistics
So I replaced different things and I went with the heli too MR Smooth to make him look at it to make sure everything runs as smooth as silk and so it does. So on spool up the heli shows no signs of wag and is completely still. But when in hover and in flight the wag begins. I tried different tail gain settings but the wag remains. The rotor head is completely locked in with almost 100% cyclic gain in the v-bar. The only way to remove the wag is to set the tail gain to rate mode. Then it has no wag and almost no drift (this means I set the length of the tail rod correct).

I also tried to set the I-gain of the v-bar to 30% and then it almost has no wag but this is not the way because you remove the HH option from the FBL unit. I also tried a beastx but had the exact same results.

Hope you guys can help because I am almost out of options here.

Thanx in advance.

[EricW]

Now you got me wondering who is Mr.Smooth, i must know him...
Obvious maybe...you checked the tightness of all links?
Some can be pretty tight and cause this.

[Ah Clem]

Belcom and Myrseth have pointed this out, several times, but it is easy to miss-did the tail grip thrust bearings get re-assembled in the correct order?

[myrseth]

+1 ahclem probably the most reoccuring issue is reassembly with thrust bearrings wrong. Most did it and cursed for many hours over it

[MrEmail]

Well I checked the tightness of all the links and this all goes very smooth.

I also checked how to bearings are ordered in the tail grips but I will check this again. But the other question is if the bearings are in the wrong order how is it possible that the tail performs well in rate mode.

[DannyvG]

try lubricating the tailshaft. Friction between slider and tailshaft can cause this (or friction in other places but the design creates friction between shaft and slider that you dont feel in the bench) behavior especially when the difference is showing with and without Integrator action.

[MrEmail]

Originally Posted by djamgils

try lubricating the tailshaft. Friction between slider and tailshaft can cause this (or friction in other places but the design creates friction between shaft and slider that you dont feel in the bench) behavior especially when the difference is showing with and without Integrator action.

Thanks for the tip but this is one thing I always do. I use sillicon spray to lubricate it all so things go smooth. The funny thing is, it's more smooth now then before the crash.

[DannyvG]

hmm ok.
Have you tried with and without governor, what governor are you using?

[MrEmail]

I am currently using the YGE governor without active freewheel.

[Vinger]

Tail servo might be damaged. Rate mode on VBar? If you have set it in rate mode then the servo does not work so hard, so try another one.

[MrEmail]

Tested the servo and checked the bearings but no luck the issue still remains....

[dunkonu23]

Try looking at the tail hub. If it wiggles any on the tail output shaft, you will have tail problems.

Scott

[weedwacker]

Someone here has said that the vbar sensors have been wonky after crashes. Do you have access to another stab?

[Raynman]

I had a vibration/wag on my 7HV - I knew it was coming from the tail, I replaced all the probablys and possibles - Still issue not solved - I decided to Swap out a NEW tail hub with another NEW tail hub ........ Problem solved / NO vibration or tail wag ....... After inspection, I could a slight flawse in the (new) tail hub ...... So Happy I sorted the issue

[BakedMopar]

Originally Posted by Raynman

I had a vibration/wag on my 7HV - I knew it was coming from the tail, I replaced all the probablys and possibles - Still issue not solved - I decided to Swap out a NEW tail hub with another NEW tail hub ........ Problem solved / NO vibration or tail wag ....... After inspection, I could a slight flawse in the (new) tail hub ...... So Happy I sorted the issue

Raynman I've had run into that some time ago except I could actually see it bent so I never even put it on. I've also bent a hub and broke a tail grip by accidentally hitting the tail during transport.

[MrEmail]

Well yesterday i flew with a new tail hub but it was no succes either. I taught it did a little bit better with the beastx but I set my v-bar on it again and it is so bad its not flyable again...

[Mixmaster Pilot]

You didn't mention replacing the tail boom after the crash. Are you 100% sure the boom isn't bent? Considering all the other damage in the tail it's a high chance.

[njs77]

I also have some tail wag (bearings checked and links resized), I cannot get the distance between ball link and center of servo to 17.5mm. My options are 16 or 19mm, which one would be better (tail servo is Hyperion DS20X-GCD)?

I also found a surprise when checking tail:

[GimpyGolden]

I would go with the 16mm especially on VBar.
That is quiet the surprise, yikes.
Did the tail blades hit ground or get bumped in transit?
I have run the Hyperions in the past and never experienced anything that.

[njs77]

Originally Posted by GimpyGolden

I would go with the 16mm especially on VBar.
That is quiet the surprise, yikes.
Did the tail blades hit ground or get bumped in transit?
I have run the Hyperions in the past and never experienced anything that.

I have BeastX. I used 16mm but wondered if I could get rid off the wag with 19mm hole. One more thing, I switched plastic tail blades to RotorTech 105mm CF - that helped a little. I have also tried with very low gain, 15.

Tail hasn't hit anything that hard to brake a gear. I suspect casting defect. I ordered metal gear for it.