Monday, October 8, 2007

How to guide a tip-up canopy closed

There were record-high temperatures in the Upper Midwest on Saturday, so I did some work on the tip-up canopy on my RV-7A. I can't seem to dispense with the notion that winter is just around the corner and my building time is running out, given that working with plexiglass in cold weather is a good way to spend a lot of money replacing a cracked canopy.

I also can't get the words of my friend Darwin Barrie out of my head, who told me last spring, "if you had the time, you can probably do the whole canopy in a weekend."

I've been working on the frame since February, and the plexi itself since May. Ugh.

My father-in-law and I installed the safety latch lugs on Saturday and they seemed to fit fine until I drilled them to full size. The instructions have you drill the lugs with a #30 hole. I fit the lugs from the inside of the canopy with it closed, marked (with a drill bit) the location of the soon-to-be-drilled hole on the lug through the rear weldment of the canopy frame, where I'd already opened the holes to a #12.

That was a mistake earlier in the construction. I should have pre-drilled those holes with a #40 (or a #30) because it's impossible to center a #30 hole, using a #12 hole as a guide; there's just too much play.

Sure enough, when I reinstalled the drilled latch lugs on one side, they didn't fit into the latch hole, hitting the fuselage side deck. Once you're in this situation, you really have no choice but to drill them to a #12 immediately, or at least drill to final size through the weldment, hoping your drill bit doesn't fall into the pilot hole of the #30.

So I've ordered two new latch lugs at $13 a piece.

In the meantime, I'm not happy with the way the canopy can twist when opening and closing, even with the reinforcement kit. This creates the possibility of really gouging the side decks (or more accurately, the oval-like (sort of) horizontal piece that attaches the side decks to the F-705 bulkhead.

There are lots of solutions to this as I found when I posted a note on the YahooGroup.

Jeff Bordelon, of Texas, has a terrific Web site and he used Delrin blocks to guide the canopy closed.



I really like this method, although fitting the Delrin block from inside the canopy seems problematic; I would think it would be difficult to get them positioned right. But I'll consider it.

Greg Blakey of Australia sent me this photo. This is more along the lines of what I had in mind -- and actually mirrors a suggestion in 24 Years of RVator.



The latch lug hits the guide and is directed down into the hole. It's an ingenious idea, made with a little bit of angle.



Somewhere I've seen folks who've added a second channel, to create a "V."

Greg sent an additional message this morning.

One thing if your going to use the angle brackets (which are covered on the guide side with UHMW tape) to get a nice snug fit is to initially use double sided tape to get the positioning right. Worked well for me and it fits as 'Snug as a bug in a ........... you get the picture.


Greg also reports he's fabricated a weather strip out of fiberglass that fits "over the top of the canopy where the two pieces of the canopy meet. This helped considerably with rigidity at the rear of the tip/up section."

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I'll think about that.

Any other tips?

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