Incidence

[Crowfly]

I have been lurking here for a while, and I havn't seen Incidence brought up. I have a 2 meter fling to get my foot in the door to flying gliders.
I also bought a video explaning how to use the incedense meter. Sorry I can't find the title.
My firstthought is the airplane doesn't care about the bubble on a level. It needs airflow to actualy get the smoothest glide.

AMA magazine had a kid with an adjustable stab for incidence, which in my mind sounds like a realy inteligent thing to do ;)
The most thermaling bird in my area is a buzzard, and they are very interesting to watch. They have no rudder, and they no doubt have a variablle tail incedense.
Just curious how much attenion the experts here pay to the tail of the plane, or if anyone makes the stab adjustable. Possibly a servo back there?
Fred

[TLyttle]

Sailplanes are really antsy when the wing and the stab are both level with each other. Adding a bit under the leading edge increases the incidence relative to the stabiliser; this shim takes away the nervousness that goes with 0-0 trim. a bit of nose weight allows for this incidence change. Eventually, one can have the wing at a 10deg up angle, and a ton of weight in the nose: it will be stable, but it will no longer "soar"! So there is the balance: nevous to fly, or a slug.

Personally, it takes me many flights to get an airplane so that it flies the way I want it, ie, stable yet manoeverable.

The servo-in-the-tail thing was replaced a long time ago with the all-flying stabiliser, which works very well.

Watch the buzzard carefully: the tail goes up and down alright, but in tight turns, the whole tail turns left and right. Buzzards, hawks, any soaring bird is a real lesson in what we are trying to do with our machines, they can teach you lot!

[BMatthews]

Most models are set up with a couple of degrees of difference between the wing and stab built in. From there you trim the elevator to work with your final CG location for the best glide. There's seldom any need to further trim the fixed surfaces unless for some odd reason the elevator is deflected by more than 5 degrees. And then it's done for a slight performance gain and to ease the worries of the owner that it somehow looks "wrong" with the elevator trimmed off center.

[D_Ryan]

Bruce;

In your post you mention shimming the stabilizer in the event the elevator is deflected a significant amount once you have the sailplane trimmed.

Is there a mathematical equation that one can use to determine the number of degrees the surface must be shimmed to return the elevator trim to centered with the stab? Since the deflected stab/elevator is generating additional lift by virtue of it's increased camber as opposed to a change in Angle Of Attack (my understanding), it would seems that the calculation is more than just measuring the angular differences between datum lines drawn from the leading edge to the trailing edge of the two conditions (elevator centered, and elevator deflected to the proper trim amount)

You mention shimming is not necessary unless the angle exceeds 5 degrees, but since the amount of lift generated by the deflected elevator is airspeed dependent, wouldn't adjusting the incidence of the stab/elevator to restore the elevator to center result in a sailplane that flies more consistently regardless of the airspeed?

r/
Dave

[Crowfly]

What is an all flying stabaliser?

[D_Ryan]

Crowfly;

An "all-flying" or "full-flying" stabilizer is a single surface, a stabilator which pivots about a single point to change it's angle of attack relative to the airflow.

A conventional stabilizer/elevator arangement is composed of a fixed forward portion (the stabilizer) and a aft section which is hinged to it (the elevator) and who's angle is adjusted relative to the stabilizer.

See: http://www.grc.nasa.gov/WWW/K-12/airplane/elv.html

r/
Dave

[BatteryJockey]

Here are some pictures of my skybirds full flying stab. The rear hole in the fin is where the stab pivots. The vertical slot in front of the pivot hole is where the front of the stab is moved up and down by the bellcrank.

Gilbert

[Crowfly]

Thanks for the explanations. That would be very easy to do with my Fling. The rudder and elevator bolt on to the fuse.
The fact is I have yet to fly my fling. I need to get off my BUTT and put it in the air :D
Another fact is if it weren't for the internet I wouldn't have the success I have had in this hobby ;)
But the above statement reflects the fact that I haven't crashed in a while either :rolleyes: Fred

[davidjensen]

Here is a another typical full flying stab.

[Crowfly]

I can see where this might be a huge advantage if set up properly.
Of course advantages must have disadvantages :rolleyes: I would guess this might be where the Stab pivots. I would guess this might be a problem area for flutter,when histarting or even worse winching.
Just thinking outloud :confused:

[schrederman]

All those flutter problems have been solved years ago... well, OK, most of them...

Jack

[John Walter]

Here is a another typical full flying stab.

Only if one considers a Pike Perfect to be a "typical" sailplane! :D

[xfly-er]

CROWFLY There are several threads on the 2 m Fling. Do a search in the "sailplanes" section. I have one & I like it. You can find my post as to what I did to make it a better plane ( not much required).

[Crowfly]

Xflyer. I am not really trying to reinvent my fling. No doubt since I haven't flown it yet. I have a Pinnacle histart and am ready to go,but the wind wont quit blowing. Gusts are 40mph + today :rolleyes: I have read the fling threads. (Thats why I bought one) I am just asking questions.
I am just trying to learn(the next step sailplane)
As stated above (I probably should get off my butt and fly my Fling before I ask more dumb questions),but it is too windy.
AND Incidence is something I feel will make a glider glide, and I am thinking a flying stab might be a (must have) for my next glider. Just thinking out loud.
Fred

[xfly-er]

Crowfly Look here http://www.nesail.com/articles.php?PHPSESSID=206dc55c655dad6b18f96cdb0e1 6538e for a discussion of incidence . Obviously every plane & pilot is different, as well as the conditions that they fly in. I followed Knights suggestions on setting up my planes & found much improvement in every area of flight. Also look at Paul Naton's DVD Performance Tuning For Gliders. I'm not suggesting that you need to "reinvent " your Fling, but there are some inevitable problem areas that can be remedied with a little work & make it a better flying & more durable glider.

[Crowfly]

Thanks for the link xfly-er. There is a lot of good reading,that will keep me busy for a while.
I already have the video Performance tuning for gliders. That is what got me asking questions about incidence.