Sliding Canopy

The Smithsonian National Air and Space Museum credits the Laser 200 for bringing about a new generation of aerobatic aircraft
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Sliding Canopy

Post by davevon » 21 Jan 2017 15:50

I recently had some excitement while practicing snaps with my canopy, it popped open and jammed... I had my cell phone with me and was able to get a hold of neighbor to push the canopy back into the track so I could get out. If you have a tip-over canopy you won't have to worry about this one.

My canopy setup is stock Pitts S-1S/S-1T. The windshield is also Pitts, but it was left about 3" longer front to back which changes the fit between the canopy and windshield. Mine also has longer rails on the fuse so the canopy completely opens beyond the cockpit.

Prior to this I had the canopy unlatch on one side and I had adjusted the slide rails on the fuse so that both latches engage at the same time. I thought that the latches and the canopy to windshield fit was all that contained the front of the canopy. That is not the case!

The way the canopy slider works is that there is a "truck" with ball bearings that rolls between the outer rail attached to the fuse and the inner rail attached to the canopy. In my slide there are 6 ball bearings, 3 on top and three on the bottom. When the canopy is fully open the "truck" with the ball bearings is all the way to the rear of the rail attached to the fuse and all the way forward with regards to the canopy rail. When the canopy closes the "truck" with the ball bearings only moves at 1/2 the speed and distance of the canopy itself. So when the canopy is fully closed the ball bearings supporting the canopy are only half way down the fuse rail and in my case near the rear of the canopy.

So what exactly is supporting the front of the canopy? Turns out it's just a vertical bolt through the inner rail with a rounded head and nut... Per Aviat drawings.

Here's what mine was looking like
canopy front retaining bolt.jpg
canopy front retaining bolt.jpg (63.13 KiB) Viewed 1842 times
My fix was to machine up some cylinders slightly undersize of the ball bearing balls. One was drilled and tapped and the other C-bored. I made a set out of stainless and the other from bearing bronze. The cap screw is Loctited in, but it can't go anywhere anyway.
canopy retaining cylinders.jpg
canopy retaining cylinders.jpg (100.9 KiB) Viewed 1842 times
And this is what they look like installed. The front of the canopy is very securely held in place now.
Canopy front retainer.jpg
Canopy front retainer.jpg (75.75 KiB) Viewed 1842 times
If you have a slider canopy this is definitely something you want to take a look at.


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Re: Sliding Canopy

Post by MonoPlaneForum » 23 Feb 2017 10:32

Very nice, thanks for this. This will certainly help someone out there. Also it will help me as we are discussing canopy options on my build.

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