Maximizing Flight Time: Tips for Adjusting Flaps on a Balsa Wood Glider

[yuvlevental]

I need to adjust the flaps on a balsa wood glider so it will fly upward in a spiral, reach a maximum, and fly downward in a spiral. I don't think that the model matters.

Basically, I need to get a glider to stay for a long time in the air.

Any suggestions?

--Thanks, Yuval

Edit: The glider will need to go as least as possible from side to side, though height is unlimited

 

[rcgldr]

I need to get a glider to stay for a long time in the air.
The glider will need to go as least as possible from side to side, though height is unlimited

This is a conflict. The glider will remain in the air longer if allowed to glide downwards in a very larger circular path (or a straight one).

This is an unsual combination. "Free flight" models use some power source, such as a rubber band or a very limited run motor. These use a "timing" device to change the control surfaces, typically the elevator. Flaps on such a model would be excess weight.

Hand launched models are radio controlled. The latest technology is a very strong but light composite (fiberglass, carbon fiber, kevlar fiber) model that has a peg at the end of one of the wings to allow the glider to be "discus launched"; a person rotates his body combined with a side arm throw, which is a fairly violent launch. There's a switch on the transmitter to control the elevator setting to transition between initial launch, climb out, and glide. The full length ailerons can be moved together to adjust the wing camber, but they are not extended downward as much as flaps would be. For landing, the ailerons are raised to act as "spoilerons" to reduce lift to drag ratio, allowing the glider to sink faster without gaining as much speed.

 

[rcgldr]

Here's a link to a simple, but relatively efficient balsa glider:

http://www.4p8.com/eric.brasseur/glider2.html

The 7 degree decalage (incorrectly called incidence in the article) might be too much for a hard throw, if the result was a model that curved beyond vertical.

I don't know if a movable elevator would work better with what ever increse in weight would be required to allow it to move than simply using a fixed elevator setting.

One way to make a moveable elevator would be some type of lightly sprung hinge, and trim tabs on the elevator so that the elevator would have less negative pitch at higher speed.

Another method would be to use some type of timing mechanism that would transition from "launch" mode to "minimum sink" mode after a short period of time.