Finishing Kit

March 11, 2012

Detail Painting, Canopy Latch Lock - 6.0 hrs.

Over the last week or so, I've taken bits of time here and there to work on more details. I think I figured out a clever way to install a lock for the canopy that's very simple and lightweight. But meanwhile, I've noticed that there are some additional areas that I overlooked that need paint. So the other day I hooked up my air sprayer and took care of some small painting jobs. First, I know this is going to sound nitpicky (and it is!) but the bottom 1/4" or so of the canopy frame side skirts stick down below the frame, visible when the canopy is tipped up. I noticed it when I was sitting in the plane the other night in my new seats. Plus, the aft inch or so sticks out beyond the frame and it's visible, too. So I decided to just bite it and get it done. Fortunately, this paint is so easy to use and clean up that it wasn't a big deal at all. Mask it up and spray. Here are my side skirts, after the job was done. If you look close, you'll see a couple of tiny parts that I also sprayed. I'll get to those in a minute.

A closeup shot of the detail painting on the side skirts, plus the little parts that I'll explain in a minute:

Another thing that caught my eye was the top flange on the instrument panel. I primed and riveted this on months ago and never thought more about it. But it will clearly show when the canopy is up, so while I was at it I masked it up and painted it as well. Looks nice, huh? Eventually I'm going to paint the sub-panel and the ribs, too, but I didn't feel like dismantling all of this right now. I'll get to it later on.

Now, on to the canopy latch lock. I've been giving this a lot of thought, and I came up with a very simple way to lock the canopy. I put all of this together on the template plate first, to test it and prove it before I go cutting holes in my fuselage skin. I'm using a keyed locking barrel that came with my ACS Ignition/Starter Switch that I'll be using in my Panel. There were 2 of these barrels that came with the switch, intended for things like utility doors or covers, I believe. I really like the idea of having one key for both the ignition/starter and the canopy lock, so this is just perfect for this task.

Basically, it's a short piece of piano hinge wire attached to the lock, using a short lever arm. The piano hinge wire is very tough stuff. I had a hard time bending the end of it! It's actually like a short rod or pin. The length of the lever arm on the lock is equal to the distance you want the pin to move when you activate the lock. In this case, about an inch. In other words, as you turn the lock 90° the pin will move up about an inch. Then I drilled a hole in the lower angle for the pin to pass through. I positioned the hole so that the pin will pass through the cutout opening in the latch handle. With the pin in place through the latch handle, it prevents it from opening when the airplane is locked. The pictures will make sense of it all. Here's the mock-up I made on my template plate. I had to cleco an extension onto the plate to make room for the lock:

Here's a closeup showing the holes I drilled in the angles. The upper one has to be elongated into a slot, because as the pin comes up through the bottom, it's at an angle until it's fully extended.

Here I have the pin installed on the lever arm. As you turn the lock it passes up through the bottom angle. I have the latch in the up position to show how it works, but if the latch handle is down, the pin will obviously pass through it.

When the lock is fully engaged, the pin goes through both angles and is straight as seen below.

Here the latch handle is in the closed position. With this pin passing through the latch handle, it can't be moved and the airplane is locked.

The only challenge to this idea is that when the pin is fully retracted in the unlocked position, it comes fully out of the bottom angle and falls away. I needed some way to hold the pin in place in the unlocked position, so that when you turn the key again to lock it, it's precisely positioned and won't miss the hole. So I ended up fabricating a very small aluminum piece to nest under the lower angle, and hold the pin in place. I carefully drilled and filed the hole with a tiny needle file to elongate it as well, so the action of the pin moving through it works smoothly. The final shape of this hole is cone-shaped. Well, sort of a squashed cone, that is. The exit hole on the other side is simply a round hole, slightly bigger than the pin shaft. Then it's simply glued in place with a dab of proseal! I painted it to match, and I think it looks pretty good.

When the spring is put in place to complete the latch assembly, you can barely even see the piece under the spring. Careful fabrication will make sure the spring clears it and not rub against it.

To sum it all up, I made a short YouTube video showing how it works!

Here's another short video clip, with the latch handles and spring in place, showing the completed assembly, and how the latch and lock work:

This was a lot of detailed, time-consuming work making this thing, but I think I have something here that I'm going to use and enjoy.

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