Finishing Kit

July 22, 2012

The Canopy Latch Lugs - 5.0 hrs.

Only a few small tasks remain to finish this canopy. One of them is to install the pair of latch lugs that go on the aft end of the canopy frame. And once again, a task that sounds relatively simple on the surface turns into much more of a job than I thought it would be. The main problem is trying to figure out how to hold or clamp the lugs in place where they're supposed to go, so you can drill holes for the bolts that hold them on. Sounds simple enough, right? Well, it would be if you could get to them with the canopy closed. Or even see them. I scratched my head for a while trying to figure this out. Fortunately, I still haven't riveted the last top skin on the aft fuselage. The roll bar, or cabin frame, isn't permanently in place either. So I grabbed my cleco pliers and went to work. I pulled that skin off, and then took out the roll bar assembly. It's been a long time since I had these parts off the plane, and it looks funny to see the canopy in place without those pieces, but here you go:

With that skin off and the roll bar removed, it now becomes much easier to work on this. I used a small piece of black tape to temporarily hold the lug in place while I fiddled with the latch mechanism, working it latched and unlatched a bunch of times, trying to get the lug precisely located. The plans say you want the latch fingers to contact the lugs and hold it snugly in place when latched. It's tricky to get it just right. It also says to drill to #30 first, then you can cleco it in place and "cheat" the position a bit when enlarging the holes to the final #12 size. Unfortunately, I already have the #12 holes in the canopy frame drilled. I'm wishing now that I would have left them #30. After quite a bit of time spent on this, I finally have it clamped in place for drilling. I have a centerline marked on the back of the lug so I can see it through the hole in the canopy frame. I'm going to drill just one hole for now so I can see how it will fit.

With one hole drilled, I removed the clamps and lightly bolted it in place. Now, repeat all of this for the other side.

Once I had one bolt in each lug, I clecoed the top skin back on the aft fuse, and installed the roll bar once again. I wanted to make sure the fit and positioning was good once it was all together, in case any slight changes came about. I discovered that I needed to make some slight adjustments. On the left side, it was pulling too hard and it was hard to latch the canopy shut. I needed to loosen that one up a bit. On the right side, the latch finger wasn't even touching the roller on the lug as it closed. That one needed some tightening. This was done by very carefully using a small round file to very slightly enlarge the bolt hole in the lug, so it could be shifted slightly one way or the other, and then the nut tightened up again. It took quite a few iterations of this until I had both of them just right. It took less than 1/64" of adjustment. I was aiming to get them to err on the tight side. I can lightly file on the latch fingers if it becomes necessary to loosen them up just a bit later on. Once I had them both adjusted, I also discovered that the lugs were hitting the forward side of the square hole in the fuselage deck plate, as the canopy was lowered into place. So I carefully filed those holes open a bit larger until the lugs would slip through the holes without touching. Then, finally, when all the adjustments were finished, I drilled the second hole through each lug. Then I cleaned up and deburred everything, and installed the bolts for the final time. With no movement possible in the second bolt hole, I'm confident this isn't going to slip and move out of alignment. Here's the finished product.

I'm very glad to have this done! This was tedious and time consuming, but I'm happy with the final result. This is something you use every time you get in and out of the plane, so I wanted it done right. I now have a canopy that I can latch shut!

<< Previous | Home | Next >>

Contact me: swayze "at" (replace "at" with the @ sign... no spaces... you know the deal)