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Old 12-03-2014, 16:41   #1
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Window, from scratch

My cat windows are in the following condition. The material is crazed and so UV damaged visibility is almost not there. The mounting screws were torqued down so tightly there are either cracks or spider webbing on the majority of the screw areas. The windows are not inset but just screwed to the same surface of the exterior fiberglass. None open. I temporarily smeared and sealed with cheap silicone which helped immensely but not even close to a decent cure. I have it under quality tarps so no more water intrusion while she is "in bed" until I am confident my interior will not sustain any more damage which is minor at this point but obvious and I wanted an easy removal and eventual replacement so I used economy silicone.
Many advice from both sober and bar talkers so I wanted to ask the pros. I don't know enough to make any kind of a decent decision. First, the windows are only 6 years old from a 3rd world country. I did not install. There is a slight curve to the panes. I have had many water intrusion problems from keeled sailboats and was always able to make them dry.
Without shortcuts and breaking the bank, how would you start from the beginning, what materials would last, and what applications/tricks would you use if you had the time? I figure I will do the leakers and eventually replace all.
I own a Dean Oceancomber 10 meter if you want to see what I am dealing with.
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Old 12-03-2014, 18:22   #2
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Re: Window, from scratch

The crazing you describe, plus the cracks at the screw holes makes me think the ports were made of acrylic. One of the most common causes of cracks at the screw holes is due to the acrylic expanding (25% IIRC) and there not being a big enough gap to allow for that heat expansion.

When you replace the ports, instead of using the drill bit that is the "right" size, go up some, but not so much that you bury the screw in the hole. I have also heard of people using polyurethane sealant (3M 4200 is one), and holding the ports in place while the sealant cures.

You will need to be extremely thorough in removing all the silicone seal, it sometimes makes it so nothing sticks. Myself, I'd wash the area scrubbing hard, with a cloth soaked in acetone. You'll want a good surface forr the glue in any event, especially if you don't use screws.

The large panels you see in skyscrapers are held in only with sealant, and replacement acrylic panels are not too heavy, so solve the problem of holding them in place (duct tape, perhaps) and you'll be good to go.

Someone more knowledgeable than me may be able to help more.

Good luck with it.

Ann
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Old 12-03-2014, 19:12   #3
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Re: Window, from scratch

Boat windows

1) Use 3/8 Thick tinted Lexan

2) Use Dow795 silicon sealant

3) Use Dow Automotive Betaprime 5404 Pinchweld and encapsulation Primer. Used only on the plastic window sheet. Lightly scotbright 2 around bounding edge and apply this primer onto the sanded 2 area around the outer edge

Note: Dow795 silicon sealant will not stick to Lexan unless you use a primer on the edges of the Lexan. Primer has to be used on just the window so the adhesive will bond.
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Old 12-03-2014, 19:59   #4
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Re: Window, from scratch

This might be able to help you. You could also do a search. If I remember correctly, there have been some other threads about replacing windows in catamarans. The bottom line that I remember is, prep prep prep. And also use the right adhesive. Like they say, high-rise buildings have windows that are simply glued into place. If you prep properly and glue with the correct glue, You're done for a long long time. Most of the time, no screws are necessary. They just make people feel better.

https://www.google.com/url?sa=t&rct=...62922401,d.eW0
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Old 13-03-2014, 10:51   #5
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Re: Window, from scratch

Quote:
Originally Posted by Ann T. Cate View Post
The crazing you describe, plus the cracks at the screw holes makes me think the ports were made of acrylic. One of the most common causes of cracks at the screw holes is due to the acrylic expanding (25% IIRC) and there not being a big enough gap to allow for that heat expansion.

When you replace the ports, instead of using the drill bit that is the "right" size, go up some, but not so much that you bury the screw in the hole. I have also heard of people using polyurethane sealant (3M 4200 is one), and holding the ports in place while the sealant cures.

You will need to be extremely thorough in removing all the silicone seal, it sometimes makes it so nothing sticks. Myself, I'd wash the area scrubbing hard, with a cloth soaked in acetone. You'll want a good surface forr the glue in any event, especially if you don't use screws.

The large panels you see in skyscrapers are held in only with sealant, and replacement acrylic panels are not too heavy, so solve the problem of holding them in place (duct tape, perhaps) and you'll be good to go.

Someone more knowledgeable than me may be able to help more.

Good luck with it.

Ann
Thanks, definitely no screws this time. Your advice is consistent with almost everyone I asked about this.
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Old 13-03-2014, 12:52   #6
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Re: Window, from scratch

I am interested in keeping weight to a minimum. Is there any reason 3/8" is more desirable than 1/2"? None of my windows are over 40" X 26". I have shipping concerns also but so far Lexan seems to be the most recommended by those I trust. Any advice on mirror or tinted applications you may additionally have? What is your experience cutting this stuff? I was told a super fine tooth plywood blade installed backwards and a power sander work best.
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Old 13-03-2014, 13:10   #7
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Re: Window, from scratch

Quote:
Originally Posted by Cotemar View Post
Boat windows

1) Use 3/8 Thick tinted Lexan

2) Use Dow795 silicon sealant

3) Use Dow Automotive Betaprime 5404 Pinchweld and encapsulation Primer. Used only on the plastic window sheet. Lightly scotbright 2 around bounding edge and apply this primer onto the sanded 2 area around the outer edge

Note: Dow795 silicon sealant will not stick to Lexan unless you use a primer on the edges of the Lexan. Primer has to be used on just the window so the adhesive will bond.
Lexan will last less and cost more than cast acrylic. I redid all my ports with cast acrylic and did a test with Dow 795 and I could not pull it off with my hand - I had to use a scraper - so it stuck very well - not sure why it does not stick to lexan. The only thing I used was diluted alcohol (50% with water) to clean the sheet before I lay a bead of Dow.
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Old 13-03-2014, 13:23   #8
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Re: Window, from scratch

Quote:
Originally Posted by captainwireman View Post
...but so far Lexan seems to be the most recommended by those I trust.
Most if not all ports and hatches made today use cast acrylic. Lexan may be stronger but does not last. Check this post:

Lexan Bonding

Quote:
Originally Posted by captainwireman View Post
...Any advice on mirror or tinted applications you may additionally have? What is your experience cutting this stuff? I was told a super fine tooth plywood blade installed backwards and a power sander work best.
Tinted cuts the rays and keep the temperature down, mirror may get too dark down below. You may also have a reflection problem with mirror ports.
Its a personal preference.

Its easy to cut, you just have to be careful not to scratch it by pressing too hard and ripping the protective paper/plastic. Use a fine-toothed wood blade (not super fine) on a jigsaw on low to medium speed so not to melt the plastic.
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Old 13-03-2014, 13:31   #9
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Re: Window, from scratch

wireman, you'll find most of the plastic manufacturers have technical and architectural drawings online, which show exactly how to install their plastic glazings. There's nothing wrong with screws or through-bolts, but you *must* use oversize holes and washers, to allow the plastic to expand and move "past" the screw or bolt. Which also means you need to seal under it, and use a compatible expanding sealant if you do it that way.

All that stuff is online.

You can also use 3M's VHB tape. This is similar to the double-sided tape you can buy in the hardware store for mounting things, but this is used to mount windows on skyscrapers, with no other fasteners. Again, there's a right way to do it and wrong ways to do it, and 3M is happy to talk tech. This has also been used on boats, it should be compatible with your hull and the glazing but as always you'd need to check.

Many ways to skin a cat, all documented and discussed online.

The crazing can also be just a simple matter of abuse. Any petrochemicals or ammonia, as found in most common cleaners, can cause crazing. And if you just use "plastic" that's designed for napkin holders, not outdoor glazing. You want a more expensive UV- and scratch-resistant grade of glazing to use outdoors. Again, documented on the makers' web sites.

Don't just buy a sheet of whatever the local plastic shop has in stock, make sure you get the stuff you want.
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Old 13-03-2014, 13:38   #10
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Re: Window, from scratch

Nothing wrong with screws so long as they are not of the countersunk variety. Ideally, rather than being over-sized, the holes are instead slots which are aligned with the long axis of the window.

Interesting boat BTW, not a lot of bridgedeck clearance on that bad boy!
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Old 13-03-2014, 15:53   #11
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Re: Window, from scratch

Read up on cast acrylic. I am almost sold.

Delancy, I REALLY like the wrap-around one piece look. Very modern and with just a little added black paint between panes, easy. This may solve custom shaping on several panes too. This slower and very solid cat tends to not knock the fillings out of your teeth compared to many models this size despite the low bridgedeck. I certainly like the ease of single-handling her.

SVTatia, sounds like a few extra layers of masking tape may solve the tearing paper/coating problem?

HelloSailor, Are you telling me people who have palm frond roofs, dug out tree trunks for canoes, and a waste paper basket for um...used paper storage may not know some cleaning products and a 1/2 inch breaker bar for tightening screws can damage some types of plastics? HahaHa! I think you nailed the crazing and installation problems. The materials may have been just fine. I am thinking poly, black tint, only recommended cleaning products, and doing all the work myself.
Any other ideas welcome!
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Old 13-03-2014, 16:23   #12
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Re: Window, from scratch

I do mine in plexi/acrylic. See Trimaran - Especially Searunner - Owners for details.
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Old 13-03-2014, 19:53   #13
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Re: Window, from scratch

Quote:
Originally Posted by captainwireman View Post
...SVTatia, sounds like a few extra layers of masking tape may solve the tearing paper/coating problem?
Yes, and that is what I did - put a run of the wide masking paper, mark the cut on it, and make sure the jigsaw shoe is clean.
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