Algodoo

One very important tip. When you build something do it in the center of the scene. The further you are away from the center the more inaccurate will the position detection of objects be. Try zooming in on the construction and you will see what I mean. the whole scene shakes a little. This can lead to parts being moved somewhere else and all kinds of problems. So make sure that you build in the center of the scene. To get there simply click on "default view" in the context menu.
I measured the distance to the center of the scene. You are nearly 14 km away from it. I sometimes had problems with scenes when I was only 500 m away from the center.

To your problem: The glider is unstable because you made the whole body of the plane a controller. The strenght of a controller is determined by its weight and its assigned strenght. Most of the weight is in the back of the plane and that's why it is uncontrollable.
May advice would be to place one controller in the center of gravity of the glider. In order to find that out simply lift it up a few times with the drag tool until you find the point where it doesn't fall over to one side. It should be somewhere behind the cockpit. Make sure that the controller is strong enough to move the glider. I would use a very light but very strong controller, so that it doesn't change the weight of the construction significantly.
In order to steer the nose of the glider would place a second weaker controller in the nose, that uses different buttons.


If you want to make a plane that works without controllers but that behaves more like a real plane take a look at this masterpiece by Kilinich:

http://www.algodoo.com/algobox/details.php?id=36287

With his description it should be no problem to make a decent plane.

thank you soooooooooooooooooo much