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1971 F26 Front Window

Posted: Mon Jun 04, 2018 10:25 pm
by The Dog House
I need to replace the front cabin window on my 1971 F26. Does anybody know how thick the plexiglass is? I think it is 1/4 inch thick, but would like to buy the replacement before I take it out of the boat. Also, I'm planning on replacing the plexiglass with Lexan. Any comments regarding the change of materials?

Re: 1971 F26 Front Window

Posted: Tue Jun 05, 2018 7:16 am
by Paul
I replaced my 2 front windows many years ago with 1/8" tinted Plexiglass, this thickness takes the curve of the window frames easily. I did not have the retainers to hold the windows into the frames so I bedded them with GE UltraGlaze SSG (I don't remember the number off hand but I can find if for you if required), I think that it has to be about 14-15 years since I did this job and still no leaks. It is important that you cut the plastic a little smaller than the opening that it sits in to allow for thermal expansion, if it's too tight in the frame on hot days it will want to push its way out of the frame otherwise.

Hope this helps

Re: 1971 F26 Front Window

Posted: Wed Jun 06, 2018 7:15 am
by The Dog House
Hi Paul,

Thanks for the information. Using 1/8 inch material will be less expensive and also make getting the material into the frame much easier. Did you use GE SCS2000 SilPruf sealant? Looking at the various options on the GE UltraGlaze SSG website the SCS2000 appears to be the most appropriate. Dow Corning 795 construction adhesive has also been recommended to me. Both the SCS2000 and 795 have + 50% joint movement capability. I'm curious if anyone has experience with the Dow Corning 795.

Thanks again for the help.

Re: 1971 F26 Front Window

Posted: Wed Jun 06, 2018 4:40 pm
by WayWeGo
1/8" sounds kind of thin to me. I would use at least 1/4" if it were my boat, though Paul has obviously had good luck with thinner material.

As for the materials, Lexan (polycarbonate) is stronger than Plexiglass (acrylic), but less UV and scratch resistant. A good comparison of the two materials is at: https://www.acplasticsinc.com/informati ... vs-acrylic.

Re: 1971 F26 Front Window

Posted: Wed Jun 06, 2018 7:20 pm
by The Dog House
Lexan EXELL D is UV protected and backed by a 10 year warranty. Regular Lexan wouldn't work for this application, but the Lexan EXELL D is designed to be used in skylight applications so it should be fine for this. Race cars use 1/8 inch Lexan for their windshields, so it should be ok. My boat is only capable of travelling 20 mph. :mrgreen:

Re: 1971 F26 Front Window

Posted: Wed Jun 06, 2018 7:29 pm
by mikeandanne
One quick tip for you, on the cut edges, sand them nice and smooth as any ragged edges, or sharp bits can start cracks.

Re: 1971 F26 Front Window

Posted: Wed Jun 06, 2018 10:26 pm
by WayWeGo
I used to be a plastics fabricator and worked with many kinds of plastic. Polycarbonate is significantly more impact resistant than acrylic, so I would be more comfortable with it in a thinner sheet. Also, if the window is small enough, thickness is not as much of an issue.

Race cars are a very different application. They have supports behind the windows and don't have large impacts like drunken boaters falling on them... :roll: They also change out the windshields frequently due to visual damage from airborne particles, not something you probably have to worry about.

Glad you found a UV protected version of Lexan, that should help avoid it turning yellow. Just be careful when you clean it because it scratches easily and the UV coating is on the surface.

Re: 1971 F26 Front Window

Posted: Thu Jun 07, 2018 9:27 am
by Paul
The silicone that I used was GE UltraGlaze SSG4000 Structural Glazing Sealant.

Re: 1971 F26 Front Window

Posted: Thu Jun 07, 2018 4:04 pm
by P-Dogg
WayWeGo wrote:
Wed Jun 06, 2018 10:26 pm
Just be careful when you clean it because it scratches easily and the UV coating is on the surface.
Do not use paper towels. Microfiber or equivalent is what you want. Avoid wiping it when dry. Will scratch more easily, as electrostatic buildup attracts dirt.

Re: 1971 F26 Front Window

Posted: Sun Jun 10, 2018 8:46 am
by Paul - SW Ontario
Then after the new glass install, have one of these made and never replace the windows again.
IMG_1783.JPG
IMG_1783.JPG (88.29 KiB) Viewed 3468 times

Re: 1971 F26 Front Window

Posted: Sat Jun 16, 2018 10:03 am
by Boppy
I'm back on the Forum after a few years hiatus, but I replaced the front windows of my 1977 F26 HT about 12 years ago with 1/8" gray glazed polycarbonate (Lexan) and used black silicone sealant to bed the plastic into the frames. I used butyl tape to bed the frames back into the boat's frame. No leaks since and I used the cover over the front windows to keep the plastic from "glazing" or hazing in the hot sun. I worked for several years for GE in their silicone division and you can used either the GE or the Dow Corning stuff. The best 795 is excellent as is the GE Silpruf. Some of the silicone use an acetic acid cure (smells like vinegar when it's dispensed). This can corrode some metals but usually it's not an issue. The Silpruf uses an alcohol cure and smells "sweet" when curing. This is a more mild sealant to metals. They both expand well when cured and will bond tenaciously to most plastics like polycarbonate. I took the time to sand-blast the metal frames and then prime and repaint them. They still look brand new. Good luck with your project!

Re: 1971 F26 Front Window

Posted: Sun Jun 17, 2018 7:45 am
by The Dog House
I got a quote for $400 to fabricate a Sunbrella window cover for my F26, so I'm going to have that done. I need to install snaps in the fiberglass. I'm going to overdrill and then fill the holes with epoxy to prevent any water intrusion. It shouldn't be too hard.

Re: 1971 F26 Front Window

Posted: Sun Oct 21, 2018 6:34 pm
by The Dog House
The canvas cover I installed kept things dry but the cracks in the 47 year old plexiglass keep getting bigger. They just don't make things to last! :mrgreen: Now that the boat is under shrink wrap I'm going to have to start the window replacement project. The first step is to remove all of the old sealant. Then I'll need to remove the rubber retainers. I'm going to put packaging tape on the window as reinforcement and then tap it out of the frame with a rubber mallet. If everything goes well I'll be able to use the old plexiglass as a template.

After I get the Lexan cut I'll need to install it in the frame. How exactly do I use the sealant to bed the Lexan? Do I just put the sealant in the frame and then put in the Lexan, or do I put the sealant on the Lexan? For some reason I'm not grasping the concept, so please enlighten me. I only want to do this once! Thanks.

Re: 1971 F26 Front Window

Posted: Sat Dec 01, 2018 2:17 pm
by The Dog House
The plexiglass window is out. It is 1/4 inch thick (6.35 mm). I'm going to replace it with 6 mm thick solar grey Lexan EXELL D. I probably won't be able to put the replacement window in until the Spring due to the temperature. I'll try to post pictures once they're available.

Re: 1971 F26 Front Window

Posted: Sun Dec 02, 2018 11:09 am
by The Dog House
To remove the plexiglass window, I first removed all of the sealant on the outside between the window and the frame.

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I then removed the rubber strips that were installed. These strips were very brittle and broke apart as I removed them.

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At this point, the plexiglass window was sitting on top of sealant. It did not go into the frame at all. The only thing holding it in was the sealant. I removed as much of the sealant from the underside of the plexiglass window as I could and gently pushed up on the bottom part. I was able to cut the sealant with a razor knife and insert popsicle sticks between the window and the frame to keep it from sticking.

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I slowly worked my way around the frame by cutting sealant, inserting a popsicle stick, cutting some more sealant, etc.

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After I made it all the way around the frame I was able to lift out the plexiglass window from the frame. I reinforced the plexiglass with packaging tape before lifting it out, but it still cracked some more. It still is in one piece though, so I should be able to use it as a template to cut the new piece of Lexan. I'll post updates as they become available.