A high wing trainer plane, a Telemaster40 for instance, has a positive wing incidence of 3.5 degrees. Any opinions on how this type of plane would be affected by cutting the incidence to 1.5 degrees?

How will just changing the wing incidence work?</p>

The wing and horizontal tail are setup relative to each other.  The fuselage is the rigid connection that allows that.  Change either one and you've screwed up the designer's plan for the two.  He set them to work with each other and you've blown that.  </p>

Also, the engine's downthrust is also affected.  What was it doing before?  Who knows, but it won't be doing it now.</p>

Lots of times trainers are designed to give good behavior landing and at takeoff speeds.  The downtrust and two incidences are chosen to be effective at the lower speeds the plane sees during those two times.   Can anyone predict what knocking out just the wing incidence will do to all airplanes?  Not really.  So how about the Telemaster?   If yours really is an average one, and somebody else knocked his Telemaster's wind incidence down and his was an average one, then maybe he could.  </p>

But the rest of us can only BlowSmoke at you.  We don't have a clue what CG you have wound up with, nor what your throws are, and got no clue if you're running the next size up engine or an old ControlLine engine with too much prop or too little and etc etc etc</p>

Aerodynamics really isn't just a checksheet of sound bytes.  Except for people who think it's simple. </p>

One of the great things about our hobby is that lot's of our trainers have rubber banded on wings. And that highwing trainers that don't have that will usually have a couple of hold down bolts at the trailing edge. It's dead simple to wedge up the T.E.s of those planes and see what happens.</p>

Be prepared to have the pitch response change. Which way? Your guess is as good as anyone's, just be prepared. Your elevator stick probably isn't going to move the plane like it did before. Know that up front and you'll be better able to deal with whatever changes you see from what you dealt with before the test.</p>

Good thing is that the test pilot of model airplanes seldom dies. </p>

You won't know until ya try it. It's a trainer and your not going to get much more performance out of it no matter what. Ya want more perfomance build another wing which basically means build another plane. If it was a more symmetrical wing playing with the incidence might improve something.
My hypothesis in your trainer is it'll increase the the take off and landing speed. What is the plane doing that you feel the need for the change? Is it just a geewiz or is it doing something you don't like? Of it's just a geewiz thing I's start out incrementally. Say take out a half degree and see what happens then 1 and so on.

may I suggest that you check the stab incidence also,before changing things.

The Telemaster40 has a stab mounted on the thrust line with 0 degrees incidence, the wing is a positive 3.5 degrees from there. At least that is the way I read the plans.

High performance is not what I'm looking to accomplish. I have other planes that will do that. My present passion is to take a stock Telemaster40 kit then modify the plane extensively. The one I'm wrapping up now has kept the wing and stab relationship intact but the body has had an extensive cosmetic revamp. It should be maidened in two or three weeks so I guess I'll know soon how I have changed her.

The one I'm about to start will have a high wing but separated from the fuselage,, kind of like some of the early aviation planes. To make my life simpler I think I'll design in a rigid base that the wing can bolt to but the base can be easily adjusted for varying incidence (for field adjustments). That type of wing mounting platform will also allow me to route the aileron wiring from the fuselage to the wing without being exposed. In this case the relationship to the stab will change some however I don't "think" it will be affect the performance too much. At least not to the point of being unable to get it back on the strip in one piece (:-).

I was thinking that 1.5 degrees would probably be fairly safe to start but I have plenty of time to rethink and research that.

Regards

I change it by trial and error a little at a time

I had a LT 40 back when they first came out that obviously had too much incidence for the amount of power that I had. I kept shimming the rear of the wing until I was happy.

The LT 40 has a flat stab. The Telemaster has a lifting stab which is supposed to negate the positive incidence on the wing but it doesn't completely do the job.

One good way to judge your trial and error is to watch the apparent attitude of the plane at your normal flight speed. You want the fuselage to appear level. You can adjust wing, stab, and engine thrust to achieve this.

There is nothing wrong with adjusting the wing incidence if you are not pleased with the flight characteristics of the model.  Just shim up the back of the wing with a popcicle stick and see if you like the way it flies better.  Increase the number of popcicle sticks one at a time until it flies the way you want it to.  Its not going to hurt anything to try one popcicle stick at a time.</p>

I just adjusted the wing incidence on a Thunder Tiger Trainer by doing this with a piece of 1/8" lite ply I like the way the plane flies better... it no longer climbs like crazy with throttle increases.</p>

Generally, trainers have positive incidence in the wings. This is so you can climb with increased throttle settings. If you want to gain altitude you add power or vice versa. I personally do not like that but to each their own. Adding 1\8" at a time is a good idea. I know there are variables here but 1\8" will be close to 1 degree. It would be nice to see some pics of this modified Telemaster. Good luck.

I have already followed your suggestion on an LT40 I had on the shelf. I added about a quarter inch to the rear. I also swapped the OS 40 two stroke with an OS52 four stroke. I'm taking it with me on my next trip to the field to see how it worked out.. I should know in about two weeks.

That plane always had a rather odd look about it as it passed over the field. Tail down attitude, more or less. The beast is so beat up I'll probably retire it soon and strip the equipment.

The second time I had it to the field I used a Popsicle stick under the rear.

When I changed the plane to a OS 52 four stroke, tail dragger, and bolt on wing I added 1/4" under the rear of the wing but this sets in a pocket at the rear.

I like it just the way it is now.

3.5 degrees sounds liketoo much to me. Even 1.5 sounds like a bunch. I tend to set things up 0-0.</p>

I have taken some as I built,,, mostly as reference for myself since I didn't take the time to document very much. I posted some last week in Kit Building under "Useful Telemaster Mods".

http://www.rcuniverse.com/forum/m_8752688/tm.htm

Regards

It does sound like a lot but there's no arguing with success (:-).

I built the Senior Telemaster and it came in at nine pounds. With that incidence and super low wing loading (and a Saito 82), it can leap off the field in a few feet. I prefer though to use small power inputs and make it do a more realistic takeoff roll.

Just a little thinking about this over my morning coffee. Has anyone thought about just lowering or raising the ailerons from zero instead of moving the wing incidence?? A turn or two on the control rods in or out will give you an idea about what the difference in incidence will do.
Just an old pattern pilots trick I was taught.
Just thinking!!

I haven't tried it but my quest here is for a permanent mod to the normal characteristics of a Telemaster40 (don't know why I just have a bug I guess). Assuming I get a successful result thru ailerons I'm not sure how I would translate that into a permanent change of the wing.

BTW:While researching this subject I came across an article on the adjustable incidence on a full size Cessna 172. It never occurred to me that you could mod a full size that way. (It certainly never came up back in the 60s when I was an active pilot).

There's a cam adjustment at the rear sub spar on each side. Always was

yes but it is there to adjust only minutes of a degree .NOT hugh amounts like is talked about here.

The idea of lowering the ailerons is just to give you a real world idea of what the plane will do by incidence change. If one of my planes balloons a little bit or dives a touch when I cut power Idon't go running to change the engine thrust angle first thing, Idrop or raise the ailerons a little to see what effect that has.
You can make up an adjustable wing just like an adjustable stab is made and play with the incidence all you like.
Iknow from a past build on a Cub that two degrees is a bunch. It just makes me wonder about the WHY of what you are trying to do. Acorrect incidence and using shims would tell you everything you wanted to know. An adjustable system could be a fun teaching tool for students.
Whatever floats your boat!

The old style Telemasters seem to lend themselves readily to mods. I'm a tinkerer that likes to experiment with "what if" mods,,, it's the reason I'm presently expanding my workshop, too many planes (:-). Actually, I think I'll give your suggestion a try on the present modded Telemaster40 when I maiden her (assuming she is there for a second flight).

On the next plane the stab is most likely going to get an adjustable mounting as well. As you say, it could turn into a great learning tool.

Regards

On training day we put a couple of shims under the trailing edge on a windy day for better wind penetration.

Gord.

If you know what you are doing, just go ahead with it. If you don't know what you are doing, go ahead with it and see what happens.