Tip up rear window no longer fits

[revenson]

Attempted final install of tip-up rear window yesterday. It would not fit without resting on the middle support bar that attaches the roll bar to the aft baggage bulkhead.

There is a front to rear 'bow' in the plexi. If fully installed, the middle of the window would get stressed from being forced down onto this center bar.

I think I've seen other canopies with this same shape...a downward slope from front to rear, then a rising curve near the back.

I could lower one or both attach points for the middle support bar, but probably a full 1/4" would be required.

I'm wondering if others have experienced this issue and, if so, what you did about it?

[scard]

Yep, that is how mine is. I put a piece of UHMW tape between the brace and window and just accepted it. My rear window is firm against the top of the fore-aft brace. It still looks fine.

[rv7charlie]

I'm fitting mine now, & will glue it with Sika so I can't 'pull' it into place with screws.

I have the same issue that you see, plus a couple of other places where the edge of the plastic kept the edge of the skin from touching the plastic. The ducktail at the center-back was so much that it wouldn't go between the skin & support bar. From what I read/heard, the lower you set canopy height, the more it will shift the canopy forward (to hit the front-center mark) and the more you'll get into the ducktail area at the back.

I found that I could thin the plexi where needed using a belt sander. (Not an original idea; I think that I got it here on this forum.) I used 60-80 grit (cuts without heating as much) & followed up with finer grit to smooth the surface. That allowed the center back to slide in with minimum effort, though it still touches the brace.

Charlie

[Bdalporto]

Charlie I'm also planning to bond my windows and I'm curios as to how you are bonding the rear window.

Brian Dal Porto
RV-7 Tip-Up

[rv7charlie]

I glued the skin-to-plexi area this afternoon. The pics are still in the camera; I'll try to post some tomorrow.

Charlie

[rv7charlie]

OK, here are a few pics of my Sika rear window install.



I riveted teh 3 top ribs from the back to about 2/3 of the way forward& the back bulkhead between the outer top ribs. I found that I could spread & lift the forward end of the skin, which raised the area above the brace, allowing insertion of the window without forcing it in.

I taped, cleaned & primed the mating surfaces of the top skin, roll bar & window.

http://img109.imageshack.us/i/backgl...llsetupme.jpg/

I spread Sika on the window, just on the area that mates to the skin. I spread it as thin as possible with a popsicle stick. I applied Sika to just the vertical area of the roll bar (see below).

I set the window in place, with ~1/8" thick shims across the top of the roll bar, with the space tapering to zero at the bottom of the roll bar (matches the way the main canopy was shimmed). If I were starting over, I'd leave off the shims & just spread the Sika thin on the canopy frame/roll bar, then fillet the corners.

I clecoed the skin in place & used cheap ratchet clamps in 'push mode' to push the canopy out in the 2 areas that weren't quite a perfect fit to the skin

http://img109.imageshack.us/i/backgl...ststepout.jpg/
http://img97.imageshack.us/i/backgla...ststepinm.jpg/
http://img682.imageshack.us/i/backgl...ststepinr.jpg/
http://img42.imageshack.us/i/reargla...rtoutmedi.jpg/
http://img196.imageshack.us/i/reargl...leftoutme.jpg/

I shut the canopy a few times to be sure the back glass was in the right place, then clamped the sides to lock everything down while the 1st round cured.

Next day, I double checked the canopy/back glass fit, squirted a dollup of Sika next to each shim & clamped lightly.

Today, I finished filling & filleting the roll bar and the edge-to-skin joint.

I haven't pulled the tape yet, but the exterior skin-canopy joint looks like it will turn out fine, with no big 'step' from plexi to skin.

Charlie