I spent most of the weekend sweating profusely in the sweltering garage, trying to figure out a way to install a lock on the canopy. To keep unwanted visitors out of the airplane, I wanted a to use a small key lock that was simple, easily-obtainable, and reasonably secure. I have no illusions that I'll be able to keep a determined thief from getting into the airplane, but at least the presence of a simple lock on the canopy ought to help keep honest people honest when the plane is parked outside and unattended.
After examining various options available at the local hardware emporium, I picked the same chrome plated cabinet lock that's been used by other builders. For future reference (in case I have to replace it) the manufacturer is Prime Line and the model is U-9941.
Since the canopy skirts are only 0.032", I made this doubler for the lock out of the remains of a spare elevator rib I had laying around.
The doubler will be riveted to the side skirt in two places. The odd shape is to let it clear the C-791 skirt brace. You may notice that although the lock body has anti-rotation flats machined in it, I didn't bother to try making the odd-shaped hole required to make use of them. I found that in practice the nut alone is enough to keep the lock from rotating once it's tightened down. This probably means that you could pop the lock open with a big enough flat-bladed screwdriver, but then again I'm only doing this to keep kids out at airshows.
The flange on the doubler will also be pop-riveted to the underside of the canopy frame.
I trimmed away some of the C-791 skirt brace around the lock and doubler. It's tight but it all fits together.
Careful measuring beforehand ensured that there would be just enough room to get a 7/8" socket onto the nut. I want to be able to remove and replace the entire thing down the road, in case it gets rusty or I twist off the key.
Here's a view from the exterior side. I wish I could have found a more flush-fitting lock, but this one will probably not cost me more than 0.01 knots.
In the unlocked position, this latch arm will be parallel to the canopy track and generally out of the way.
In the locked position, the latch arm will be vertical and will fit into a small slot that I'll cut in the canopy track. I'll wait to cut the slot until after the canopy is completely assembled and fitted, since the spacers underneath the rear anchor blocks are distorting the canopy geometry at the moment.
It's crazy that I spent an entire afternoon working on this. Little custom side projects like consume a lot of build time.