The problem was: How to put a photo or film camera on my glider without buying something very expensive.
This instructable is not finished yet and might never be. There is always something to improve.

 
Camera clamp 1
The structure of the first attempt for the clamp will be made from strips op aluminum. I had to figure out how to get my camera attached to the clamp when I found a cheap tripod at a yard-sale. I salvaged the ball-head from that tripod.
 I started bending and drilling the aluminum. (I have a nice tool for the bending and drilling, but you can also use a vise and a hand drill) Because I don't want the clamp to damage the glider, I rounded all edges and corners. To make it look better, I painted it black.
I also added some foam where the clamp would be on the tubes of the glider.
The first clamp has two aluminum parts and two bolts. The bottom bolt is always in the loose position. The upper bolt with the wingnut will be closed to clamp on the tube.
I have flown with this clamp several times, but I was not totally happy with the grip of the clamp and it was kind of bulky.

Camera clamp 2
I wanted to make a better clamp. Still I used the same materials, but a different design.
 For the second clamp I also bended two strips of aluminum. This time I uses one shackle of a chain to make it hinge. It can open without totally removing the bolt. I used a (metric) M8 bolt and drilled a hole trough the head with a M4 bolt trough it to make sure the bolt can swivel but not turn.
This clamp worked fine, but on many places my camera had to be mounted up side down.

Camera clamp 3
Next I bought a very cheap but nice clamp. It works fine on my bottom-bar, but has no way to aim the camera accurately  on any other tubes and again it films up side down. Great advantage is that it is very small.

Camera clamp 4
The next camera clamp must be better than the rest. I want it to be small, stable and with the picture right side up. I have some ideas already, but I am also open for suggestions.

I will post my attempts.