SailNet Community - Reply to Topic
Thread: polycarbonate window thickness? Reply to Thread
Send Trackbacks to (Separate multiple URLs with spaces) :
Post Icons
You may choose an icon for your message from the following list:

Register Now

In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

  Additional Options
Miscellaneous Options

Click here to view the posting rules you are bound to when clicking the
'Submit Reply' button below

  Topic Review (Newest First)
06-30-2014 10:01 PM
Re: polycarbonate window thickness?

Andy, go look it up directly with the source. GE is one of the prime manufacturers who have architectural installation sheets online. There is no question or issue or debate about screws. If you simply drill a hole and snug the glazing up with a screw, you will destroy it as it expands and contracts and, pinned down by the screw, crazes and cracks.

"Simple" use of screws guarantees plastic glazing will self-destruct.

OTOH, correct use of screws (bolts, etc.) is perfectly acceptable. You must (MUST) drill the hole in the glazing large enough so that it will allow full expansion and contraction without the glazing hitting the screw. The hole has to be big enough so the glazing can literally be lifted off. Then you add fender washers or similar trim under the screw head, and torque them down gently so that the glazing is left to slide back and forth, under the washers, without being forced up against the screws.

Every glazing manufacturer specifies the same requirements.
06-30-2014 09:11 PM
Re: polycarbonate window thickness?

Dow 795 is a Silicone based compound so it will work for polycarb (lexan) to fiberglass or metal.

4200 is a polyurethane and will work for the metal to fiberglass. Or should it be Butyl tape instead?

Seems like I need both these. The first to fill the spaces between the glass and the brackets and the second to place around the frame. I will be using screws to screw them back on even though several posts online suggest not using them.
06-29-2014 08:07 PM
Re: polycarbonate window thickness?

Never use a urethane base adhesive/sealant with poly or acrylic. It can/will case plasticizer migration and cause the glazing to craze. This could be anything from a cloudy appearance to spider cracks. As far as expansion goes, figure on 1/8 " per 3 feet per 100 degrees for clear. Gray or bronze is twice that.
06-27-2014 09:54 PM
Re: polycarbonate window thickness?

DO NOT use 5200. Read this.

Which Sealants To Use
06-27-2014 07:39 PM
Re: polycarbonate window thickness?

Originally Posted by andyselzn View Post
Also, is 5200 ok to use as an adhesive?


There are very few uses for 5200 on a boat. Do yourself a favor and don't use it for anything. 5200 is very permanent, and should require a special license to use! I don't understand why people want to use this stuff for everything.
06-27-2014 04:57 PM
Re: polycarbonate window thickness?

andy, 3M makes special adhesive for polycarbonate, 3M 4200 as I recall. West Marine actually STOCKS it, along with their own version, and oddly enough the 3M product is also way cheaper than the WM version.

If you do not use an adhesive that specifically is designed for polycarbonate, it WILL let go within the year.

All the plastics do suffer from thermal expansion, so if it is "short" now and the temps are 60F, I wouldn't worry, I'd let the sealant fill it. But if temps are 90F and it is is only going to get shorter, so remind them "Measure once cut twice." [sic]

Kinda depends on how long the plastic is, and how big the gap is. You can look up the expansion specs online for whatever brand and grade of poly it is, it can easily be 1/16" per foot for the range of freezing to heatstroke.
06-27-2014 01:13 PM
Re: polycarbonate window thickness?

Originally Posted by andyselzn View Post

...Also, is 5200 ok to use as an adhesive?

Dow Corning 795 is a good sealant to use for this kind of thing. I wouldn't use 5200 for this.
06-27-2014 12:39 PM
Re: polycarbonate window thickness?

Got the polycarbonate from the local store. Had to go back a couple of times as they were making cutting errors. Question: the height and width of the windows are fine but the length is not flush to the edges. Seems a bit short but fits in the frame. Am trying to figure out if I need to go back and make a fuss and get them "exactly" to spec.

Also, is 5200 ok to use as an adhesive?

06-24-2014 08:53 PM
Re: polycarbonate window thickness?

Acrylic is harder therefore less capable of taking an impact than polycarbonate. Poly is softer, so it flexes under load and impact. Since they are both petroleum based, they are stupid expensive. 3/8 or 1/2 would probably be cost prohibitive. Working with it can be done with anything that will cut. But use a table saw with a fresh fine toothed carbide blade for best results. A router works fine but tends to heat up and fuse the scraps. If you drill, clamp a scrap of wood to the back and use a drill press if possible. The drill will probably pull and want to blow out the back. Sand the holes smooth. The scratches in the hole are what we engineering geeks call stress risers. Cracks will propagate out from them, given the chance. Some folks hit the holes with a torch to melt and fuse the scratches. I did that on the edges of mine. What size peice are you looking for?
06-24-2014 03:14 PM
Re: polycarbonate window thickness?

Originally Posted by SHNOOL View Post
......................... 3/8" lexan is some pretty stout stuff. Did you find it hard to drill through?
I cut or drill polycarbonate with the protective adhesive paper coverings still on them and without difficulty. I's my understanding that Acrylic is known by several manufacturer's names like Lucite or Plexiglass and polycarbonate is known by manufacterur's names such as Lexan.
This thread has more than 10 replies. Click here to review the whole thread.

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

For the best viewing experience please update your browser to Google Chrome