Canopy repair advice

[DaleB]

I bought a flying RV-12 that had some damage to the rear lower corner of the canopy on the right side. I intended to fix it later, when I had stripped the plane down for paint anyway. Over the past few months it's gotten worse, and I need to do something with it now rather than later. One crack is starting to propagate in a bad direction. Everything you see below is as I found it, other than some very cursory clean-up work.

Previous repairs seem to have been attempted with epoxy and hot melt. There was a triangular piece of .128 or so aluminum screwed in place of a missing corner (removed before these pics were taken, as was a loose piece of acrylic that you see missing). The whole thing was taped over to keep it from flapping in the slipstream. The good news is, the epoxy and hot melt didn't stick to anything and it's fairly easy to remove. The bad news is, stuff was still flapping in the breeze and cracks are getting worse.

From the outside, propped open an inch or two:


From the rear looking forward:


A view from the inside:


The pics look pretty ugly, I know, but it is what it is. Harsh lighting, and I haven't cleaned up all of the old adhesive and crud. One crack was stop drilled with a #40 bit, but a piece still came loose with that stop-drill hole at its apex. I have the piece, it's a clean break so it will go back in easily with the proper glue.

I can see a few possible ways to address this.

1. Replace the entire canopy and re-do all the fiberglass. Quite expensive, a lot of work, time consuming but a sure fix. I think it may be overkill though.
2. Stop drill the new crack (5:00 from the screw in the first pic) with a #50 or so drill. Use a drop or two of Weld-On #4 in to close up all 3 cracks radiating from that screw hole. Glue the loose piece in place. Cut a piece of new acrylic to replace the AL piece that was there. Glue it in place, trim and polish. Flatten out the skirt as much as possible, and replace it when the plane is stripped for re-painting.
3. Use Weld-On to repair the acrylic as well as possible. Either use countersunk screws with C/S stainless washers, or just remove the screws attaching the canopy to the rear of the frame, and re-attach it with Sika. Add a fiberglass or carbon fiber "Targa" strip across the back of the canopy to stabilize and cover everything.

I'm going to pull the canopy off and take it home so I can work on my big bench in a well lighted shop with all my tools handy. I know there are guys here who have had to repair broken and mangled canopy corners before. If it had to be perfect I'd just order a new canopy and skirts, but this will never be a show plane. My goal is to make it sound, decent looking and not obvious. I'm leaning toward #3, but would appreciate input from people who have been here and done this.

[eddieseve]

Try this stuff, works well and is easy to use;

http://www.amazon.com/Urethane-Suppl.../dp/B0007LTXVY

Cheers

[DaleB]

Thanks for the pointer, it looks interesting but I wonder how well it would hang on long term. I can get some acrylic material locally to replace the broken part. Just looking for advice on how well gluing this together with Weld-On (Sci Grip) will work over the long term. I don't want to have to revisit this every couple of years.

[lr172]

I would stop drill the cracks ASAP. Then get two more screws in there (acrylic to frame - one above and one below current screow) to support the canopy in that area. Otherwise stop drilling may not be enough to stop the cracking. At that point the repair is cosmetic to the canopy at large. Only needs to be strong enough to hold the repair together. Use whatever is easiest to piece it together.

[DHeal]

I would be tempted to cut the entire cracked corner out of the canopy -- being sure to encompass all of the propagating crack fissures. Then custom fit a replacement piece.