handyman

My Feedback: (2)

i have a single axel gyro thinking about putting it on a a sail plane that i have (109 in.) 2???????????s first one will it help,next if so (i dont have the info on it) but when installed how do i know if it is installed the right way rudder movement iam guessing that if you tip the wing right down the rudder would go left, any help would be great....................................

BMatthews

Why?

The gyro is not needed in any sort of poly ruder elevator model for basic stability as the poly gives you all you need (assuming a brand name design that is basically sound to start with).

The gyro will tend to counter model displacements caused by thermals making it harder to see the model reacting to the air disturbances that we rely on to "see" the air currents and place the model in a thermal.

And if it's for an aileron bird then the rudder is the wrong place to put it anyway.

And finally the gyro would tend to fight you during thermal turns. Thus requireing more effective rudder throw to achieve what you're trying to do.

Not trying to dump on your idea but I just don't see that it's helping anything that is a problem. Does your model have some flying charactaristic that makes it hard to control?

C_Watkins

My Feedback: (10)

Here's an odd twist I just thought of... (funny what pops in your head at 3am)
What if you put the gyro on the rudder channel, but place it so it was active
in the roll axis instead of the yaw axis? I was thinking you might put it on a
flipswitch, to have it either enabled or disabled, for starters... anyhow, if
you "enabled" the thing, and had it set up right, you could have the glider
turning into thermals on its own. (Left wing rises, gyro gives left rudder, and vice-versa)

Heck, I don't know... just one of those passing thoughts, I guess

bjaffee

If you had it setup that way, the more left roll you got, the more left rudder you'd get, and the more left rudder you get, the more left roll you'd get..etc. You'd quickly have have full left rudder and the glider in a spiral dive.

C_Watkins

My Feedback: (10)

Sorry... but left wing rising is right roll, last time I checked

The actions would be counteractive and into the thermal, though admittedly probably not in the
best possible way. I'd just like to give it a try sometimes, just for giggles and grins.

BMatthews

On a poly model the rudder IS the roll axis. They are "coupled" by aerodynamics..... But it WAS 3 AM so we'll give ya a break...

What you're describing is how I saw it working but more strongly. I figured he wanted it to just hold the model level. What you're suggesting is to turn up the gyro gain to where it would actually be stronger then the upsetting force.

Hmmm..... it might work or perhaps it would be too strong and the model would start oscillating in a high feedback kind of mode. Only testing would tell. But your theory is sound from the standpoint of being an automatic thermal centering force. I'm just not sure that the model would be stable any more with this.

If you've ever studied feedback theory there is a point where the feedback is a self damping effect that enhances system performance. But turn up the amount of feedback and it starts to become a self sustaining effect. Turn it up a little more and the system looses stability and runs away into oscillations. Like the echo effects you used to get with a tape recorder, microphone and speaker. If the speaker volume is low and you speak into the mic you can hear it out the speaker and the microphone picks it up a little and there's a fading echo. Turn up the volume and the echo effect builds and at a critical point becomes self sustaining. Turn it up just a hair higher and it runs away and goes crazy.

A control switch through a spare channel would be a VERY good idea....

drela

On any glider you can use a gyro to drive the rudder opposite to the yaw rate. This is known as a "yaw damper", and it's used on most large airplanes flying today. Almost every poly glider can benefit from more yaw damping, and the gyro is an alternative to building a larger vertical tail. Blaine Rawdon has done this on his Crossbow poly F3J, and he reports the landing qualities are especially greatly improved. The gyro very effctively quashes the wallowing you get from the frantic last-second ruddering during an imperfectly aligned landing.

On an aileron glider you can also use the gyro as a roll damper. Alternatively, you can drive the ailerons with a gyro to obtain spiral stability even for a perfectly flat wing. See Blaine Rawdon's article at www.rc-soar.com . The sensing axis here should not be vertical, but rather tilted back about 15-30 degrees, so it senses mainly yaw rate, and also a bit of roll rate thrown in.

The yaw-damping or spiral-stabilization effects strongly depend on airspeed. Hence, it's important in practice to have a gyro with adjustable gain via an auxilliary channel.

probligo

This raises the "long term project" (otherwise known as "interesting things to think about while otherwise occupied...) that I had going.

For F1A glider -

It would probably never work, but the kibosh was put on it as a dream by CIAM ruling that "self regulatory feedback guidance systems" (which I translate as "intelligent autopilot") are banned from all freeflight competition classes. The reason for the ruling was to stop development before people started spending too much on development.

Judging by reports that came back from the 1998 Worlds, there were several teams at it then.

Otherwiser a very interesting idea...

bjaffee

Sorry, read that a little to quickly. Still, I don't think it would work, for the opposite reason. As soon as the thermal rolled the plane in one direction, the rudder would counteract in the other direction, but just until the plane was level again. It would make for a very stable plane, though. I think the issue then might be that you would tend not to notice thermals as easily.

roadtrip

Can anyone elaborate on which type and brand would be the best gyros to use in a full blown glider, say 108" wing span? Would a dual axis gyro, like the FMA Auto-pilot, (www.fmadirect.com) work effectively?