Tail optimiser / tail offset help

[v58fuy]

Guys,

I've been trying to find the cause of a tail vibe at hover, so before playing with the P and I gains, I thought I would double check the mechanical setup.

The tail is setup pretty good mechanically, if anything there might be a little more offset than the manual asks for, say 5-8 degs instead of 2-3 dregs.

My tail optimiser values are 100 & 10, meaning I have a weak tail on left stick input - would reducing the offset help reduce the optimiser 100?

David

[el guapo]

i used to get optimizer results like that when I used too much tail pitich.

http://www.vstabi.info/en/node/842

[dahld]

Here's how Kyle sets-up his tails on Mikado helis. Optimizer is turned off and never used. Servo arm is placed on a spline that give as close to 90* as possible. Adjust the length of the control rod until the tail's travel limits in the V-Bar are as close to being the same as possible, e.g. if one limit is 100, and the other is 140, lengthen or shorten the rod until the limit values merge. The limits are adjusted out until the slider binds, and then back off a few clicks (no binding). That's it. Leave the optimizer off.

If you've already used the optimizer and have things out-of-wack, do a tail reset, which will default the optimizer...then leave it off. If you then want to experiment with it, OK, as you can always do a reset on the tail and put all your other values back to where you had them prior to messing with the optimizer.

Stop gain 'A' is usually about double the 'B' value ('B' might be 20, and 'A' is 40-50). This helps make stops the same each way, but the effect is subtle.

Tail gain is as high as it can go without the tail chattering when stressed (like in side ways loops), and yaw rate is set to what makes you happy.

Pretty simple, but this is how all his machines are set-up, and well, they fly pretty good.

Hope this helps.

(-: Dave

[v58fuy]

Dave,

Thanks for the advice will do a new setup as you describe, yes my tail has got all out of whack, because I have accidentally left the optimiser on for several flying weeks - now every time I go flying my tail is different (recently learned backward figure 8's, but tail is making me struggle).

Lastly, can you help with my tail wag, it's most apparent in a hover - guess you'd describe it as slow side to side. I have checked the smoothness of the tail and all good, also run the vibe analyser and all good here.

Should say I'm running the mini vbar pro, mounted with the standard white foam pad - should I try different pads,or adjust the P or I gain in some way.

David

[Andy from Sandy]

What do you consider "all good here" for vibration level?

I had issues with the standard tail hub on my Logo 500 but after reading on here about how the bearings may not seat properly I did a very careful rebuild.

I changed the tail output shaft for the hardened one and found a post from Mikado stating the shaft is over size and needs polishing down a bit.

With both of these done and by dynamically balancing the tail the vibration level on my Logo is less than a hundred without main blades spooled up on the bench.

I have the mini v-bar mounted with traditional servo tape that gives a very solid mount.

[v58fuy]

Ok, I have checked the mechanical setup of my tail today - I have about 5 degrees of offset with identical end points of 110/110, if I reduce the 5 degrees to say 2 or 3 then my end poins won't be equal.

With regards to vibration and hover tail wag, the vibration analyser without main blades generally was reading 80-100 after some tweaking - what is standard servo tape you talk of?

David

[dahld]

Don't get overly concerned about how many degrees of tail pitch you have at center stick etc. Frankly, the V-Bar doesn't care. In flight, where ever you leave the tail, the V-Bar uses however much pitch it needs/wants to lock the tail where you want it. In various winds and flight conditions, heli speed, collective input and torque on the heli, the amount of pitch it uses varies to follow what you're doing with the stick. The V-Bar never ever goes back to an "pre-determined" amount of pitch during flight, so it really doesn't matter what you see on the bench in a static condition.

(-; Dave

[Andy from Sandy]

what is standard servo tape you talk of?

I use the Ripmax / Ming Yang tape. It is a foam that contains the adhesive. After applying the adhesive migrates to the surfaces and bonds after a few hours.

There is also the 3M VHB tapes that will work in the same way.

The soft gyro tapes allow the sensor to spring about in hard stops and also allow the wires to pull on the sensor.

[pgleesonuk]

Originally Posted by dahld

Stop gain 'A' is usually about double the 'B' value ('B' might be 20, and 'A' is 40-50). This helps make stops the same each way, but the effect is subtle.

What are typical P and I gain values, and acceleration?

Thanks

[dahld]

'P' and 'I' and Acceleration are all default.

The tail on the Logo 700 is pretty well matched "power-wise" for the heli, and the default settings work great. Kyle has yet to change them on any of his 700's, as the tail's never had any weaknesses that would facilitate changing those settings seeking an improvement.

I know that sounds like an advertisement for the heli, but that's just the way it is

(-: Dave

[v58fuy]

Flew my logo with the tail setup as per dahld, and it flew fine.

With regard to P and I gain, Mr Mel suggests that both of them should be changed to 75 for both, and then lower the precomp - but what does this do etc?

David