V-bar blueline taildrift ?

Hello,
I've got an issue with taildrift on my Goblin 700 competition and the blueline vbar with sensor.
Since I started training for F3C hooverfigures I discovered that the tail slowly drifted to the right (counterclockwise). I did a trimflight but now the tail is drifting to the left. It happens in all my 3 headspeeds (1350/1850/2050 rpm), so it's most possibly not related to vibrations (no crashes, all blades are balanced out). The event log doesn’t show any errors. Mechanically everything is setup ok as far as I can see, eg. servo horn 90 degrees, tailblades 2-3 degrees pitch. Furthermore the heli is quite stable during hoovering without any vibrations.
I also did a check to see if my rudder channel was jittering, but it isn't.

So my question is why does the tail drift ? And how can it be solved ?

Attached are my vbar settings from all 3 banks.

thanks in advance
kind regards
Sebastien
The Netherlands

Well - we might be at the edge of teh sensor response and resolution. is ita silverline or blueline sensor?

Anyway - could you program TX in a way which enables trims for each flight condition seperately and one for turning on?

regards (EN) / Gruss (DE)

Rainer Vetter

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Hello rainer,
as the title mentioned, it's the blueline.

So you're suggesting that I should trim the rudder (statically) to keep it in one place ... but with that new position it will slowly drift away as well I would think , because the dynamic behaviour is done by vbar ...

Isn't there any other solution ? The drift over time is significant since before I end up with 1 hoover figure I have to correct the tail already (good for my skills but unwanted of course :-) )

regards
Seb



Edited 1 time(s). Last edit at 04/11/2017 03:05PM by 666yeti666.

Hi Seb,

Rainer's question is valid, we have two blue sensors now, the old blueline (flat, larger footprint) and the new silverline in a blue case (higher, smaller footprint, as the silverline sensors were).

If it was a new blue sensor, we would have to see it differently than if it was an older blueline sensor.

Please tell, and please attach your setup file, this could help identifying a possible sensor issue developing.

Kind regards

Eddi

Born to fly ...
forced to work.

Hi Eddy,
I understand. Well I've checked it and obviously I've got the sensor inside the flat, large footprint blue package.
I've uploaded the zip file again with the setup files of all 3 banks.

I really hope it can be solved

thanks again
regards
Seb

Hi,

nothing in particular in the setup but the fact that the limits for the tail are set pretty high. One hole out on the servo arm and maybe re-setting the horn on the output of the servo to get equal limits (as good as possible), then re-doing the trim flight _might_ help.

But usually the VBar is perfectly capable of holding the tail in a direction, in a hover, even if the mechanical setup or the trim flight is off.

To check again if it's not the radio after all, you could set the RC Deadband to 20 for example and try again, this would open the gap where no input from the sticks (like drift or jittering) is taken in to account.

Do you happen to have the chance to try a different sensor on this machine, to rule to the sensor?

By the database the VBar is from 2010, and if it's still the original sensor it could always be that the sensor has reached the end of it's useful life, at least for high precision.

Kind regards

Eddi

Born to fly ...
forced to work.

Hi Eddi,
I have just changed the servohorn to one hole out and was able to change it such that I have equal limits. Then I have reset the trim. I will do a testflight whenever the weather let me to.

This is the first thing I will try before changing anything else.

By the way, it would be a pity if the sensor is at its end of lifetime after 7 years !

To be continued
Seb

Hi Eddi,
I've done the testflights today with the ball on the servohorn one hole to the outside but there is no change in behavior, the tail still drifts away.

I've also exchanged my sensor, from my other heli. It's the exact same type. Unfortunately a testflight showed the same behavior.

Last test I did was by increasing the RC deadband of the tailrotor to a value of 20, as you've suggested. Now, also, still the tail drifts away.
To be sure I did the transmitter test according to : http://www.vstabi.info/en/transmitter_check
There was only a change of value "1" seen on ALL channels, so no specific difference on the rudder channel. See picture attached.

Conclusion is that the transmitter is 100% o.k.

What's next that I can check ?

thx
Seb



Edited 3 time(s). Last edit at 04/15/2017 08:35PM by 666yeti666.

Quote:

I've also exchanged my sensor, from my other heli. It's the exact same type. Unfortunately a testflight showed the same behavior.

At this point i would be curious if both are ok on the other heli. So we can either narrow it down to a model based or sensor based problem.

regards (EN) / Gruss (DE)

Rainer Vetter

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Posting and answering - please use a PC and a standard keyboard. Answer all questions fully, take the needed time, don't forget probably requested attachments.

Für Posts und Antworten bitte einen PC und eine richtige Taststaur benutzen sowie alle Fragen vollständig abarbeiten. Nehmt Euch Zeit, beantwortet Rückfragen in Ruhe und vollständig.
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Hi Rainer,
frohe ostern !

So, the hoovertest on my Compass 7HV revealed the same drift into the same direction !
This is done with the sensor of the Goblin, and to be honest I think the same will happen with the sensor of the Compass itself, since the same happens on the Goblin with the Compass sensor.

A carefull conclusion is that it must be the sensor of vstabi by type or design. Maybe it's not good enough for high precision F3C flying ... ? Limited sensor resolution as mentioned by you before?

I'd love to stick with vbar since I'm using it for years and years. I've checked the silverline sensor of 159 euro (which is very expensive compared to the neo of 189euro) but who can guarentee that it's solved by then. Even using Neo would be a question for me.

What's your opinion ?

thx
Seb



Edited 2 time(s). Last edit at 04/16/2017 11:11AM by 666yeti666.

Simple:
If you want to get the best possible resolution - use a NEO with its internal sensors.

The external ones have way less resolution reasoned by the compatibility to all external ones (think when VBar started with the black plastic sensors) and by the sensor types itself. A blueline Mini is a bit better because there is no interface in between sensor and processor. Best with serial 152xxxxxxx - we have changed the sensor array from cluster to single sensors there.

But - no one of them can beat a NEO with its internal sensors. The resolution is multiple times higher than anyone of the older devices - and the sensors deliver digital datas which can be used directly w/o any recalculation.


And:
If you would like to use a VBar Control - we have a "Tail Micro Trim" app to eliminate tiny effects - even on a older Vbar, may help too ;-)

regards (EN) / Gruss (DE)

Rainer Vetter

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Posting and answering - please use a PC and a standard keyboard. Answer all questions fully, take the needed time, don't forget probably requested attachments.

Für Posts und Antworten bitte einen PC und eine richtige Taststaur benutzen sowie alle Fragen vollständig abarbeiten. Nehmt Euch Zeit, beantwortet Rückfragen in Ruhe und vollständig.
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Für Einzelkommunikation bitte ausschließlich Email verwenden! - PN, Messenger, Chat usw. werden nicht bearbeitet.
For single user communication please send a email only! PM, Messenger, Chat etc. won't be read.

Hi Seb,

interesting fact: Ennio Graber preferred or still prefers (not current I'm afraid) the blueline sensor over the silverline sensor when we did tests flights with him a back in 2014 at my local club. The tail was never an issue as far as I recall, tweaking the main rotor for hovering maneuvers was more of a challenge.

If two sensors on the same heli show the same effect, and at least one on a different heli does, it's possible that you have two sensors which have reached the end of their useful life, although it's a big coincidence.

The radio can be ruled out I think, and since it's two different main units, they can be ruled out, too, and even then, the main units are almost bulletproof and can hardly cause anything like drift, they just process data. And since it's two different helis, the mechanics can probably also be ruled out.

I would also recommend switching to the NEO (above 2010 technology), but I can also offer that you send in one or both of the sensors and we check them, and see what can be done.

Kind regards

Eddi

Born to fly ...
forced to work.

Hi Eddy,
thanks for your feedback, I will sent you a PM regarding sending back the sensors.

thx
Seb