general stabilizer question

[dobent4@yahoo.com]

Hi folks, still learning navigation around the site, and hope this locations ok.
Maybe someone can clear this up : I read about setup with many stabilizers advising to "have all control settings at 100% travel/zero expo".
Well, what if your plane flies great with a recommended control throw on a surface of a quarter inch up &down just for example, and getting that requires travel to be at 68 % and whatever expo ?
I know all about control throws changing with servo arm and control horn locations and lengths, but have never read anything advising "change your servo arm/control horn lengths and clevis locations so you can get the desired throws with your transmitter being at 100% " either.
I'm sure I'm missing something very elementary here.
I do that from time to time, tragically :)
Thanks to any and all for clarification !
Doug

[fhhuber]

Mechanically adjust the travel... Move out a hole or two on the control surface's control horn and/or move in at the servo. that lets you set the travel such that the TX programming is 100%.

Having the max travel you actually use be less than 100% is just making it hard on your servos. At 60% computer programming you are only using 50% of potential servo power and you are only getting 60% of travel resolution.

I ALWAYS readjust linkages such that my main TX setting is 100% travel and trim centered.
I've only played with gyro on one plane. Found the gyro to be more annoying than helpful... Part of that was the choice of aircraft (already very stable) and part was an inherent flaw in 3 axis gyros. The gyro can't detect a stall, so it just fights the airplane attempting to self-recover.

[Grossman56]

Personally, I have a three way switch with hi /mid/ and low rates so I can try different travels. I usually start out with 30% expo and then tame it down if I feel its too sloppy, usually ending around 20-25%. I agree with fhhuber in that you should always adjust mechanically first. Center you servos and check to make sure that visually the control surfaces are at neutral. Stand back from the plane and visually check again. I get my pushrods in the closest hole to the center that I can get at and the furthest out on the control surface horn. Also, what he states about a gyro is true, its not an autopilot, but I personally like them (as stated numerous times on this forum) but again, its a personal choice.
Before I forget, try the high/mid/low switch and see what works best for you and under what scenarios. I found takeoffs to go much smoother for me when I'm in mid rates with the warbirds or the Pitts. If my wife wants to fly a Pandora, I'll put it in low rates so things happen a little slower for her as she is a novice, but for me, I leave the Pandoras in high rates as I know them inside out.

Grossman56

[xviper]

Some of my planes, I like to have a stabilizer in them and they help greatly, while most of them don't have them and don't need them. 8 of my planes have some sort of stabilizer and/or flight controller in them of various brands. The ones that are sailplanes all have flight contollers (with Retrun to Home), along with one plane that I intend to use for FPV. Those are primarily for maximizing glide and for bringing them back when they get too far to see or when you're flying through goggles and don't have direct visual on the plane itself.
I have stabilizers on one 3D EDF, one biplane and a large GeeBee. Those are primarily for helping with the hand launch (jet) and for smoothing out the landings (controlling the bounce). They all work as advertised except for the "balance" mode on the HobbyEagle A3. I believe that's due to my lack of ability to calibrate it. Both the Mig29 and the Pitts work quite well in "hover" mode. All of them work beautifully to stabilize in cross winds and wind gusts and that was the main reason (for me) for having them.
The only caveat I've found with installing and setting these things up was to ensure that the trims are all centered as best as possible before adding the stabilizer. This means that the control surfaces need to be manually adjusted for neutral flight beforehand. As far as rates and expos, some products seems to be NOT affected by these while others seem to ignore rates and expo entirely and just do their own thing but again, that may be due to my "missing something".
As already said, these devices will not defy the laws of physics, particularly when stall is happening. They can make things far worse.

[Konrad]

Mechanically adjust the travel... Move out a hole or two on the control surface's control horn and/or move in at the servo. that lets you set the travel such that the TX programming is 100%.

Having the max travel you actually use be less than 100% is just making it hard on your servos. At 60% computer programming you are only using 50% of potential servo power and you are only getting 60% of travel resolution.

I ALWAYS readjust linkages such that my main TX setting is 100% travel and trim centered.
I've only played with gyro on one plane. Found the gyro to be more annoying than helpful... Part of that was the choice of aircraft (already very stable) and part was an inherent flaw in 3 axis gyros. The gyro can't detect a stall, so it just fights the airplane attempting to self-recover.

+1

Agree about gyros, generally! Having come from the old days when we didn't even have servo reversing. We used audio 5K pots on our sticks for expo. I have to admit that the computer expo just doesn't seem to mimic their response.

If looking for more control I'd add, get the fastest servos you can. Servo lag can led to Pilot Induced Oscillation (PIO) and is the primary cause for gyro oscillation, with the resulting needing to turn down the gain.

[fhhuber]

Now the effect of less than 100% servo travel being your high TX rate on the gyro...

Its going to make the gyro seem more sensitive. You'll have to crank the gain down so it doesn't move the controls as much or its going to be over-correcting. You may not be able to dial the gyro gain down enough...

it will simply be easier to adjust the gyro properly if 100% travel (by the servo default) is 100% ATV/EPA (or higher) on your most aggressive "dual rate" setting

EG...
30%, 70%, 100% if its 3 position.
40%, 90%, 120% is OK too if the servos have the range
12%, 25%, 65% is just wrong.

[dobent4@yahoo.com]

Hey, thanks guys ! Very helpful info there. Doug