Tip up first cuts

[jdeas]

I have started cutting my canopy starting at the front and have a question as to the fwd/aft position during this phase. I have cut the canopy to the base of the curve as it transistions between the edge of the mold to the tilt I would expect to see at the front.
Would it be prudent to trim slowly up to the top of the transistion slope? About how far aft from the tip-ups most forward row or rivets should I place the leading edge of the plex once trimmed? Will the plex laydown on the roll bar before I start trimming the aft side?

 

[hydroguy2]

I don't recall the measurements, but no need to sneak up on the FWD edge. All the lip gets removed

Click on: My kitlog

Started trimming the canopy, August 27, 2008. look at the next few days around that date. for the BigCut.

Then I just recently finished up trimming the aft end. Look at Aug 21, 2009.

Gee, only a year to cut the canopy.

 

[Tbone]

Just did this about 2 wks ago on my 7. The front edge of the canopy will not have any "lip" and it should transition about 1.75 inch from the front of the tip up forward skin. On mine my canopy was about 3/4 inch above the roll bar before I made the cut. It started about 1.75 before my trimming on the front and the rear. Don't worry about the cut line between the front and rear of the canopy. It will not be close to the right width. I have trimmed my front canopy to the line and will trim the rear to match the front.

 

[jdeas]

Sounds right but how are people using Sika

Made the big cut yesterday and it's looking good. My original plan was to Sika the canopy and I purchased the materials to do this but I see no way to get a smooth transition around the edges and maintain the Sika width I feel I need to compensate for the expansion.
Are most builders using Sika also using counter sunk screws to augment the joint? Has anyone changed the metal work to increase the joint thickness?

 

[rocketbob]

I've fitted eight canopies, and have it down now where I can get the job done in about 2 hours. My advice is don't trim anything off the back until you are satisfied with the fit at the front and sides. The rear edge will come forward as you trim the front.

My rocket canopy is sikaflexed, and I've had the misfortune of having to replace the canopy after overheating a spot trying to buff a scratch out some time after the canopy was fit. Turned out to be a blessing in disguise because I am much happier with the shape of the one thats on it now. When I replaced it, I did some experiments to see how easy the canopy will delaminate. Long story short: ain't no friggin way its gonna come off without bending the tubing up and breaking off the welds.

In fact it is bonded on so well that as the canopy expands in the sun, it actually tweaks the frame very slightly.

Sikaflex is some pretty strong stuff.

 

[Noah]

Made the big cut yesterday and it's looking good. My original plan was to Sika the canopy and I purchased the materials to do this but I see no way to get a smooth transition around the edges and maintain the Sika width I feel I need to compensate for the expansion.
Are most builders using Sika also using counter sunk screws to augment the joint? Has anyone changed the metal work to increase the joint thickness?

Yes, several tip-up builders offset the frame sides inboard to increase the thickness of the Sika bond. Check out the Swiss guys' website at www.flyvans.com, they have a nice writeup and great photos of how they did this. You're smart to want to maintain that bond thickness, during temperature excursions that sika will get stretched and if the bond isn't thick enough to allow for differential thermal expansion between the plexi and the aluminum, it can fail. I fabricated spacers with lightening holes similar to what you will find on Alex and Bernie's website. Worked great.