Canopy Dampers

The plywood canopy of my cockpit is big and weights around 10 kg. Opening required more force than I was willing to muster after a long flight. Closin it was hazzardous: because of it's weight, it tended to slammed shut, endangering my fingers (and thus the nimble handed operation of all those beautiful knobs and dials in the cockpit). To increase safety and comfort, I decided to install two shock absorbers or dampers on the moving part of the canopy.

I found that it is not at all an easy task to determine the exact position for the pivot points of the dampers. Trial and error would result in many holes in my cockpit structure and possibly a canopy that would block halfway through it's travel. So I put Corel Draw to the task. Here is what I came up with:

The drawing shows the area around the upper part of the seat, where the axel of the canopy is located and where the dampers have to be installed. The canopy itself is not drawn, only the piece that connects it to the seat via the axle. In the drawing, I first fixed the left pivot point, where the dampers would be attached to the canopy in its closed position. Than I drew a circle around this point with r = "Min. extension of damper" (compressed state, canopy closed).

Next I rotated the connection piece (with damper attached) to the open position and drew another circle around the same pivot point with r = "Max. extension" (i.e. extended state, canopy open). These two circles intersect in two places. The lower one is the only point where the lower or right end of the damper can be attached to the seat.

Close-up of the canopy's axle and the attachment block where the lower pivot point of the damper is fixed. The attachment points and axel bearings are reinforced with 10mm plywood plates. They must withstand the considerable forces generated by the movement of the canopy. The lower end of the dampers is held in place with a 6mm bolt (the nut is embedded in the attachment block). The dampers have a resistance of 15 KP each. That is enough to make the opening and closing action of the canopy smooth without putting to much stress on the construction.

The 1,5" aluminum tube used for the axle was part of a crossbar from my hang gliding days...