Canopy stress

Cut and Installed canopy as per plans- cracked when riveted- cut off the aft 4 in crack and built a cap and polyurethaned the canopy back on- installed the side skirts on (riveted) you'd think I'd learn, cracked again-cut another 4" aft off, built a larger cap and resealed inside plex between tubing and thin bead between skirt and plex- oversized holes- counter sunk plex-riveted skirts on first side no cracks, when riveting right side last 4 rivets stress cracked 1/2". Weldon 3 on all the cracks - question1- if I Sitkaflex, is the 1/2" bottom of plex all that is attached to the tubing via e Sitka? how do I attach the side skirts without riveting? I'm a month down on this canopy-no doubt the rivets are causing the cracks-if I drill out the rivets clean off all the rubber urethane, is this canopy worth salvaging? If not I'm ready to order another. I wanted my skirts to be polished aluminum , spent 2 weeks enlishwheeling the skirts, but I'm just about ready to throw in the towel and go fiberglass. I've searched out and read just about every post on cracked canopies and the install methods- sent a few emails. I know Paul Dye did a post on replacing a riveted canopy-couldn't find it- but at is point I don't think rivets and plexiglass belong on the same set of plans.
Mike

Mike, is this what you were looking for??

http://www.vansairforce.com/community/showthread.php?t=87203&highlight=canopy

Cracks

Hi

I did the same and threw away my canopy and replaced it. This time to stop cracking firs of all I sikaflexed the canopy to the rails, then riveted the skirts on. The canopy is much less likely to move.

Sika flex is way to go --just finished my -4 and extremely happy with sika. There is an older post on using sika as well as important instructions on their website....Tom

what I did

I drilled everything up to per plans to a point where it all looked great clecoed together. Then, take apart, oversize Plexi to 5/32" holes and debur. Taped it all up nicely and put it all together with Proseal between Plexi and tube frame,as well as side skins, and clecoed in all holes...set aside for a couple days. Remove clecoes, one at a time and install pop rivet dipped in proseal...wala, bonded,sealed and no stress points, plus proseal will accept paint of any kind. Proseal bonds just like Sika.

thanks

Mike, that is the post I was looking for. Everyone has great ideas. My process was really close to what Paul did except I didn't use the surgical tubing grommets. I figured with 3/16" rubber sealant on both sides of plex would cushion enough. I didn't enlarge the rivet hole to 1/4", could be most of the problem. The 1/4" that close to the edge of the plastic looked like I was inviting a break. If I sika the frame to the plex, how do I attach my skirts without drilling holes through the plex into the frame? This looks like I would defeat the purpose of using the sika.
I am going to try and undo everything and follow Paul's instructions using the old canopy and enlarging the holes to 1/4"- It'll make a good practice piece till the new canopy comes in. In the meantime info on how to attach the aluminum skirting without rivets would be great if I decide to go rivetless.
Thanks for all the response.

sika

Attach the top edge of the skirt with sika to the plexi, and rivet the rest of the skirt with pop and regular rivets. The nice thing about sika is that it won't stick to plexi that hasn't been primed, so you can take your time taping up a perfect bond line on the plexi, flush with the edge of your skirt. Prime, then sika on the skirt. The skirt angles out slightly from the plexi canopy, so you can bring the top edge of the skirt right against the plexi for zero gap and still have enough sika lower on the canopy for a good bond. Sika's great stuff. Use good tape for the bond line - the primer is watery and will creep under the edge of a poor tape job. IIRC I used electrical tape.