Paging Jack Olsen or Tyson:

[speeder]

Or TRE Motorsports or anyone else who really knows this stuff...

My buddy ordered this lexan rear window for his street/track toy, (turbo RX-7). It sits on a CF hatch which is painted. It's a pretty good fit but it "potatoe chips" a little on the sides, i.e. it is not a perfect seal against the channel on the sides. It either needs to be glued down with some really strong stuff or screwed down? You can pretty easily hold it tight to the sealing surface but if you let go, it will of course revert to its normal shape which is maybe 1/2" shy of sealing.

The top and bottom fit perfectly. It's actually a pretty impressive piece of plexiglass or lexan with the complex curves.

What should he do? Screw it down? Glue it? Seems like screwing into CF is less than ideal. If the car was a Porsche, obviously I would post this on the tech board or the racing/track board. This guy is a devout member of the church of light weight, you'd like him.

TIA.

[porsche4life]

Urethane? Clamp it like it needs to be while the urethane cures?

[speeder]

[speeder]

Originally Posted by porsche4life

Urethane? Clamp it like it needs to be while the urethane cures?

There is no way to clamp it. Two people would have to hold it down until the glue cured.

[porsche4life]

Sandbags?

[speeder]

Not a bad idea. Thanks!

[trekkor]

Large headed aluminum rivets.


KT

[EarlyPorsche]

Glue and weights. I don't know what glue to use but I bet the manufacturer of the window does. If it were my car it would probably get black silicone and weight to hold it in place - but I have no idea if the pressure in the car going down the road would be able to pop the silicone out.

[porsche4life]

That's why you use urethane.... Not silicone....

[Tyson Schmidt]

Windshield installer said household clear silicone sticks best to lexan. But he used the factory urethane, which worked just fine too.

Either way he needs to install mechanical retainers of some kind. Two vertical aluminum straps is the usual method.

[speeder]

Thanks buddy! We're goin to make a pilgrimage down to the OC to see you at work soon.

[John Rogers]

All the lexan or plastic I have seen have had screws holding the window in with about 4 to 6 inches between each one. They used a strip of thin aluminum to act as a washer and the holes in the lexan were slightly oversize so the body could move, expand and contract and not crack the lexan as it is pretty stable. My buddy Ted did not drill the holes oversize and the stuff cracked from stress.

If I remember correctly I have not seen any that actually sealed either as the material can not be installed to do that?

[Jack Olsen]

Mine has little nuts and bolts as fasteners. Adhesive is fine -- and might even help with weatherproofing -- but I think you want a mechanical fastener as well.

[john walker's workshop]

silaflex 292 in black.

[island911]

John and Sid are giving the best advice - use a urethane(Sikaflex). (glue & screw?...may as well use duct-tape & bailing wire)

Anyway, a better adhesive would be an acrylic urethane. ..clean the PC w/ isopropyl alcohol ...clean the epoxy side by sanding, MEK or both. ..fixture w/ sandbags, if that works.

Oh, and get some money out of your buddy for the advice, as you'll need it to cover those Nov. bets.

...because sometimes celebrity =/= competence.

[kaisen]

Can't you apply a little heat to the Lexan in the affected areas and re-shape to seal better?

[island911]

oh, and Silicone is a bad idea (+1 to Sid on that too)

Cracking at holes in PC... often that problem is set-up when the hold is drilled. ...not from tight fasteners, as many conclude.

[island911]

Originally Posted by kaisen

Can't you apply a little heat to the Lexan in the affected areas and re-shape to seal better?

Clear PC is a pain to heat uniformly, and has a high T_g. ...it also cold bends for large radii just fine. (read: I wouldn't use heat)

[tevake]

These windows were glued in almost 20 years ago, and have stuck in place perfectly.

these windows are plexiglass. And were glued in place using silicone. There are different kinds of silicone adhesive. The key to success I was told at the time, is to use little pieces of spacer material to maintain a minimum thickness of the glue line.
In this case the installer used little pieces of plastic that were about 3/16' thick placed between the surfaces to be glued. The thick glue line allowed for the difference in expansion between the plexi and the structure.

Using sandbags should maintain the clamp pressure while the glue goes off. The installer that did the windows on the boat used blocks glued with glue from a hot glue gun applied to the surrounding freshly painted surfaces. these blocks were shaped to extend over the area where the plexi was going, then wedges were used to apply pressure. Once the glue went off the clamping blocks were tapped on the side to release from the painted surface, with out damage to the painted areas.

There are many types of silicone, and there is one formulated just for this application.

The problem with fasteners is the likelihood of cracks while tightening the fasteners in place . Or later when the structure if flexing while in action. Causing cracks radiating from the fastener wholes.

Hope this is helpful to you.

Cheers Rich

[speeder]

Originally Posted by island911

John and Sid are giving the best advice - use a urethane(Sikaflex). (glue & screw?...may as well use duct-tape & bailing wire)

Anyway, a better adhesive would be an acrylic urethane. ..clean the PC w/ isopropyl alcohol ...clean the epoxy side by sanding, MEK or both. ..fixture w/ sandbags, if that works.

Oh, and get some money out of your buddy for the advice, as you'll need it to cover those Nov. bets.

...because sometimes celebrity =/= competence.

I appreciate the advice on the window. I really do. But I do not appreciate or even understand the second half of this post. Can you leave the personal/political remarks off a technical thread? Thanks.