Dave E

Does anyone have any insight on how to best do this, short of paying someone else? I'm installing mine now on a spare frame and specifically want to know how to glue it in, I have some 3m windshield stuff, but don't really know how well it will work with Lexan, and I want to be able to take the Lexan out someday when it gets too scratched up. Also, I need to support the Lexan so it doesn't move, I was hoping to come up with a way to do this without using aluminum strips on the inside and outside, screwed together ala NASCAR. I will be using the car on the street occasoinally and I'm trying not to attract too much of the wrong kind of attention, and the strips surely will...

Adam Richman

I've helped do this on a Mustang Cobra (American Iron racecar). I do not believe you will be able to avoid the stripping as there is a lot of flex on lexan at that size. We ended up with two vertical strips. I cannot visualize the rear hatch of a 944 right now but on this car, we drilled the mounting surface in preparation. Once the lexan was cut to size (leaving the backing material on the lexan - pretty important item), we laid it in place. One of us (me ) got inside and with a marker, marked through the drilled holes on the lexan (covering). We then took an exacto knife and cut a perimeter around the entire piece (used a straight edge and clamps) 3" off edge. We drilled the marked holes, pulled the perimeter backing material, painted it with a glossy black (on the inside, not the outside) and when it dried, pop riveted it in place (with washers on each side and used a foam type gasket that had the peel off backing - don't think it was an automotive specific product). Then we pulled the backing off the center piece (we removed the backing off the outside before pop riveting it in place) and it came out pretty spiffy (the black ends up a nice shiny border that won't scratch (since its on the inside). We pre-bent/curved the aluminum strips and applied them vertically after it was in place (just pop-riveted them every couple inches). That's to the best of my memory, this was a couple years and 25+ races ago. Its still in use - not sure if it leaks or not. We also did the quarter mirrors for NACA ducts. The whole thing came out very nicely.

Dave E

Thanks Adam, I've drilled and tapped for machine screws the perimeter holes to serve as a clamping arrangement for gluing, as the fit of the pre-formed piece was not perfect and there would be no good way I could think of to clamp the lexan to the frame while the hatch is shut, which I think is important for alignment while the glue dries. I was thinking that using fasteners alone to hold the lexan in would be ideal to facilitate the inevitable replacement when the time comes, but figured that stress risers would be created at the screw locations, eventually cracking the lexan. There is not as much curvature in the lexan as there is in the glass so I will need to have the supports impart some of this as well, and I figured this would also exacerbate the potential for fatigue cracking at the screw holes. That's why I was considering gluing the lexan in.

Peckster

Anyone use silicone seal for gluing the stripping on one side? It must be strong enough, they build aquariums with it. If you put them on the inside they won't be as obvious.

924RACR

I wouldn't trust the silicone aquarium stuff. I put my hatch (931, but same as a 944) together with 3M Windo-Weld glue, the same stuff as for the glass hatch. I noticed too that it was a real PITA to get the lexan held to the frame all the way around. In fact, I need to go back over one spot - will have to clean the glue off and re-bond it. No huge deal, at least the glue's not 20 years old! I still have to do the aluminum strips. I did talk at length with the retailer (Dave's Auto?), who recommended the use of the aluminum strips on the outside due to the flexure of the lexan at speed (especially considering that'll be a low-pressure area).

I ended up using a lot of those cheap A-clamps from the hardware store at regular intervals around the frame to hold the lexan to the frame (except where I ran out of clamps, which is where it came back apart). Though I do have to admit I like the idea of pop-rivets even better!!

Now I just have to remove all the corroded screws from my spoilers to reinstall... unless I can't, and have to get a fiberglass spoiler...

Dave E

I have the window weld too, but haven't tried using it yet. What is it like to work with? am I going to stink up the whole house and should I wait til I can open up the garage on a warm day?

924RACR

It isn't that stinky, IMO, but you may wish to wait for warmer weather for shorter curing times. I did mine in the cold out of necessity, and it took forever! Working with it, just like caulk, no big deal. Takes a while to set, hence the need for many many clamps.

Dave E

Does it adhere to the lexan well? My garage is heated so the cure time isn't a problem in that sense, but I bought the tube over a year a go and the 3m website says the shelf life is 12 months. I guess the worst that happens is I'm out the tube and have to buy a new one. Do you have any trouble getting the hatch to seal out water and exhaust?

924RACR

Haven't driven it, couldn't really say yet - but I'm fairly confident of a good seal.