I've been flying my LT-40 for about a month on my own. I understand that a flat bottom trainer like the LT-40 will have greater lift at greater speeds. If at all possible I would like to prevent this as much as possible. It actually pulls it self out of a dive. I've played with the trim and if I were to add more down trim, the plane would dive very quickly at low speeds.

Is there a happy medium - would I get the effect I'm looking for if I add a some space where the rear of the wing meets the fuselage, therefore, lowering the angle of the LE?

Any suggestions?

It all has to do with the CG (center of gravity) If you place your fingers under the wing, about 2 inches back from the leading edge, you will find the plane will balance on your finger tips. As you add weight to the tail you will find you have to place your fingers further from the leading edge to make the plane balance on your fingertips. A trainer is nose heavy. And for good reason. A plane flies more stable that way. Like an arrow, or a dart. If you look at an arrow or a dart you will see the front is heavy and that’s why it files in a nice stable manor. If you take the weight off the nose the dart becomes unstable and flops around.

An airplane is the same way. With the nose heavy, it is nice and stable. Forgiving if you will. It takes a bit of up trim to keep the nose up. The faster the plane flies the more authority the elevator has. That is why if you trim the plane to fly level at 40% power, you will find yourself climbing if you add full power or go into a dive. The plane goes faster, the elevator becomes more responsive and the nose goes UP.

If you want to stop that from happening, all you need to do is add some weight to the tail. You can do this by moving the battery pack, or by simply adding weight. You can get weight from the hobby shop just for this. Don’t add too much!! Remember the dart with no weight on the nose? Your LT-40 will do the same thing if you add too much weight to the tail, and you will have a bag of sticks. My advice is to have someone with more stick time help you get your plane balanced the way you like it. Don’t try this on your own unless you have a full understanding of the laws of lift and the laws of weight and balance.

If you use stick on weights, they can fall off and complicate your problem. Make sure they are mounted right and won't come off. Don't make it too tail heavy. I wouldn't put the cg much behind the main spar on that plane.

Xavier...even though you do get your LT 40 trimmed out to maintain level flight you will still experience a tendency to climb coming out of turns, either downwind or upwind. Its the flat bottomed airfoil again. That LT 40 wing has lots of lift! Just pay attention and when straightening out of a turn shove the nose down a tad till it gets back at a flat attitude. After a few times you will automaticaly shove the stick forward out of turns. After about 5 years you can get into turning with coordinated rudder. Just joking, but like full size flying, it don't happen right now, it all takes practice, but it will come, just hang in there. Good flying!

actually the LT 40 in our club (the club trainer) when at a normal throttle it will fly level and handle great but when just going forward without a turn if full throttle is given it will start climbing as if up is given but actually I believe it is the angle of attack on the main wing, Designed like that for the extra lift for the newbie learning to land, Wich I believe is the attitude xavier is refuring too. You could try putting a shim under the back of the wing but only put 1/16 of a inch at a time to see how it handles but it will start needing more length for takeoff and need more speed for landing, AND will stall at faster speeds so just do a little at a time until it handles more like your looking for.

xavier is the maiden name of my friends wife, Wonder is there is a relation.
Just my .02
Dauntae

Xavier,

Nothing you do to your LT-40 will give you the desired results. It sounds to me like you are ready to move up to an advanced trainer with a semi-symetrical or symetrical wing.

Congratulations on graduating!

Actually, you can trim a flat-bottom plane to have less pitch trim changes with throttle and airspeed (differnet issues) I've never tried to make it 0 change, but you can reduce it.

You apply a combination of these three things. how much of each is another story, and frankly, MinnFlyer is right, time for a new plane. That said here's what you do:

- Shim up the TE of the wing to reduce wing incindence.
- Put in some down-thrust on the engine.
- Reflex the ailerons, which is basically changes the airfoil shape.

Xavier, I'd suggest you stick with your LT 40 a bit longer, for as a trainer it still has a lot to teach you. Some folks "tinker" a plane to death trying to get something IN it that was designed OUT of it in the first place. You need to learn to fly out of or through these traits so common to most trainers. So what if it climbs on turns, or climbs when adding a bit of throttle. You can control that via the transmitter. After a while you'll be doing it so smooth it'll be second nature. I've gotten back to the basics of flying myself with our LT 40, and am enjoying it a bunch. As for problems with wing lift on landings, simply fly it down. When you're circling to land, set the throttle a little above idle, enough to have a slow forward flight path, then feed in a tad of "down" elevator. This will counter the lift force of the wing. Once the nose drops, pick it up and hold it up at the angle desired with the elevator stick. The throttle is set for a slow rate of descent, the motor is pulling the plane forward, gravity is pulling it down, the wing is holding it up, and you're controling it all by the elevator stick ... that's flying. In my book there's nothing prettier than a well executed no bounce landing. Takes practice, but it'll come.

Another option, that I don't see posted here, would be to mix some elevator into your throttle setting. You'll need a computer radio to do this though...

I did it with my LT-40. I have it setup so my plane is trimmed to level flight at half throttle. As I increase the throttle above half there is some down elevator mixed in. As the throttle goes up, the elevator goes "down".

I just started playing with this so it's not yet perfect. But so far the best feature is that if I get into trouble, with the flip of a switch on my radio, the mix is gone.

Mike