[Buggsy2]

RV-9A with tip-up canopy. Following Vans instructions, I trimmed first around all the edges of the raw canopy removing obvious excess. Then trimmed further trying to get the forward edges to fit flush to the C-702 canopy skin. And again following instructions,

When you have gotten the fit to be somewhat close (it doesn't need to be perfect: it actually becomes much easier to deal with once the canopy is split)

I got reasonably close and made The Big Cut last Sunday.

My question is, how much trimming and fitting should I continue to do? Right now, the forward edge of the canopy and the C-702 skin fit as follows: at the top (centerline of the canopy and +/- 3-4 inches each side of center) there is a 1/8" or 3/16" gap between canopy and skin. Moving away from center, they fit flush, both sides. Then moving yet further, halfway down each side, there is a gap again, 3-4 inches long, 1/8". This is with the canopy sides flattened against the frame.

The gaps are very easily closed with light pressure. Should I accept them as-is, and close them when the entire windscreen edge is fiberglassed/screwed to the C-702 canopy skin? Or should I continue trimming and fitting? I worry that if I continue trimming I will trim too far soon. I have at least 1" excess on the aft edge.

Gap around centerline, 1/8" to 3/16".

Gap partway between center and side, 1/8".

 

[BSwayze]

I recently went through all of this work, so I may have a few suggestions to help you. Mine had similar gaps just like yours, across the front edge. Basically, you shave or trim away a little at a time from where it's touching the canopy skin now. It will gradually settle down and fit like a glove. I have a lot of pictures and details in my log, if you care to check it out, starting here:

Trimming the Canopy to Fit

 

[bruceh]

Yep, keep trimming a little at a time and eventually it will fit perfectly flat on the frame (give or take a 32th). Once you get it close, make a template of the better looking side and flip it on to the other side. I was able to get a nicely symmetrical cut on the front edge of the canopy bubble. You want to have a nice smooth curve around the front edge. I did a lot of sanding and scraping of the plexiglass edges to keep them smooth after every iteration of trimming. And, of course, do this when the plexiglass is warm. Make the big cut, then iterate again, since the canopy will sit down farther on the frame. You have to then trim up the sides and finish off the aft edge. I chose to keep the "ears" on the front top skin of the canopy frame, and after I trimmed out the notches, I had to make some tiny adjustments to keep the front edge of the canopy bubble sitting down on the skin.

Left side laying flat, prior to the big cut.

Right side also laying perfectly flat to within 1/64".

Here is the end result after bonding the bubble on with Sikaflex.

Lots of photos and dialog on the process I went through on my web site.

 

[jdiehl]

Canopy

My advice is to keep cutting and trimming 'till it lies evenly on the forward skin. I went to great length not to place any stress on the canopy to 'make it fit'. Any stress will ultimately lead to a potential failure point.

My two cents,

Jim Diehl #1976
RV-7a
Lock Haven, Pa.

 

[cnpeters]

I would caution to be careful, though, and not just keep trimming chasing a non-issue. A small gap that closes relatively easy with light pressure is likely OK. The canopy and frame will have far more stresses on it with opening/closing, flight, vibration - plus, the tip up is famous for "being alive", as in alignments slowly changing as one proceeds along the canopy build. One can build several clips to hold down the front edge tight if there is a little gap - many builders' sites I reviewed seemed to have some gap or another and never got it perfect. And no cracked canopies in flight later. Assuming one doesn't Sika the canopy, any small gaps can be filled with flox when the fiberglass layup is done. There will be no movement.
But, of course, check with Van's for a definitive answer.

 

[Buggsy2]

Thanks!

Thanks Guys for the advice. I kept fitting and trimming (actually, grinding + sanding) several more iterations and now it fits with very shallow, short gaps that are hardly noticeable and will easily close with the slightest pressure when it comes time to fiberglass the canopy to the forward skin. I'm glad I took the time to do this.