Rear window lexan

[Gary]

Hmm. I countersunk all my windows 8/32 in the rear clam, doors and windshield. I've not seen a single crack in any of them in 14k miles. I think the trick is Fran recommended using black nylon screws. A huge amount of give. My last track event we ran counterclockwise on Eagles Canyon. The front was getting airbourne on bad pavement in turn 8 for four sessions x 8-10 laps. Still no cracks... no yellowing either since 2009.

The Nylon will creep and relieve some of the hoop stress . A stainless fastener will not. The difference between an acceptable level of stress and too much stress could be a little as a quarter turn of the bolt. It is very difficult to control torque on small diameter bolts. Polycarbonate is much stronger in compression. The following is from page 20 in the "Lexan Sheet Processing Guide" attached.

• Do not use countersunk head screws as the ‘wedging’
action of the countersunk head causes excessive
hoop stress on the sheet. This can lead to part failure.
• Be sure that all oil, grease and other coatings are
removed from the screws before assembly. Certain
oils and greases can cause environmental stress
cracking.

 

[Jack]

Good info Gary!

 

[Alex]

Has anyone ever tried using standard windshield butyl glue to set the Windows? It's flexible, water tight, and if you ever remove the "lexan" it should come off with a standard windshield removal tool.

Thoughts?

:huh:

Just bolt it down - 4 #6 screws are good enough.......I'd hate to glue it in and then have to remove it ... I can just see the amount of damage you'd do to it getting it out.

 

[Randy V]

Just bolt it down - 4 #6 screws are good enough.......I'd hate to glue it in and then have to remove it ... I can just see the amount of damage you'd do to it getting it out.

Let's see yours! :thumbsup:

 

[Cam]

I guess its personal preference but i think it looks pretty tidy with countersunk black on black border paint. I tapping straight into the F/G I can get my windows out in about 1 min flat. I bet they have been in/out 50x and still not a single problem with the lexan or with the F/G stripping out.

 

[Alex]

Let's see yours! :thumbsup:

find the home depot machine screws, lol

 

[Randy V]

The thread's talking about the rear window...

 

[Alex]

windshield .... rear window .... same supplier, same material.

 

[Randy V]

True - but air pressure works to hold the windshield in place while the dramatically reduced pressure in the rear works to suck the window out.. How is your rear window retained? Have you had the car to speed without any issues?

 

[Alex]

my rear window is bolted down with 6 #6 machine screws (seeing a pattern here )