Window/portlight replacement

Aug 10, 2020
511
Catalina C25 3559 Rocky Mount
I am replacing my leaky, deteriorated windows on my 1984 Laguna 26. The original windows seem to be obsolete, so I am looking at .25" cast acrylic and cutting them .75" oversize all the way around and bonding them in. As an autobody man, my first thought was windshield urethane, but it is not exactly UV stable.

So.... what are your suggestions? 5200? silicone? Duct tape and bubble gum? screws with trim washers and butyl tape?
 
Apr 8, 2010
1,942
Ericson Yachts Olson 34 28400 Portland OR
Stock fixed ports on our boat are polycarbonate, and installed externally with about an inch overlap all around. And... also secured with screws about every 8 inches or so all around as well. These lens' are roughly 8 inches by 28 inches. Last time I re-bedded them, I used black "LifeSeal" , made by the BoatLife company.

Set properly in an eighth inch thick bed of sealant, they remained totally leak free for 25 years. The lens surfaces did get hazed by UV, and all are now being replaced with new ones.
As for strength, our boat was designed and built for extended time at sea including offshore racing.
There are other good adhesives for this, but this is the one I have personally experience with.... i.e. the question can have several 'right' answers! :)
 
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Aug 10, 2020
511
Catalina C25 3559 Rocky Mount
Stock fixed ports on our boat are polycarbonate, and installed externally with about an inch overlap all around. And... also secured with screws about every 8 inches or so all around as well. These lens' are roughly 8 inches by 28 inches. Last time I re-bedded them, I used black "LifeSeal" , made by the BoatLife company.

Set properly in an eighth inch thick bed of sealant, they remained totally leak free for 25 years. The lens surfaces did get hazed by UV, and all are now being replaced with new ones.
As for strength, our boat was designed and built for extended time at sea including offshore racing.
There are other good adhesives for this, but this is the one I have personally experience with.... i.e. the question can have several 'right' answers! :)
thank you for your input! I will look up LifeSeal and see if it still available. I lake sail in fair weather and doubt my boat will ever see the conditions your boat faces on the sea.
 
Jan 11, 2014
11,323
Sabre 362 113 Fair Haven, NY
A photo of the ports you are trying to replace would be helpful.

There is some debate on the relative merits of acrylic vs. polycarbonate (plexiglass vs lexan). See for example this article:


Use Dow 795 or Sikaflex 295 UV to bed and seal them. Screwing and bolting is not recommended. A few screws along the edge (not through the acrylic) can be used to support the acrylic until the caulk cures. The lens rests on the screw and the edge of the lens is captured under the screw head, use a round head or pan head screw.

While cars and boats have some similarities, there are important differences. Solutions for cars are often poor choices for boats. One area this is true is in the DC electric system. SAE wire is smaller than AWG wire and has fewer but larger strands. AWG has more strands that are finer which makes it more flexible and less susceptible to work hardening. You are wise to recognize that auto glazing has different requirements from marine glazing. Boats experience more vibration and the hull and deck twist and move more than the parts of a car. Sealants must be able to adhere, flex, and stretch on a boat.

5200 is an adhesive, not a sealant or caulk. It is often referred to as the "Devil's Glue" because it adheres so well, but it is fairly rigid when it cures and extremely difficult to remove. There are only a very few applications on a boat that requires an adhesive as tenacious as 5200.
 
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Nov 6, 2006
9,885
Hunter 34 Mandeville Louisiana
 
Feb 8, 2014
1,300
Columbia 36 Muskegon
A photo of the ports you are trying to replace would be helpful.

There is some debate on the relative merits of acrylic vs. polycarbonate (plexiglass vs lexan). See for example this article:


Use Dow 795 or Sikaflex 295 UV to bed and seal them. Screwing and bolting is not recommended. A few screws along the edge (not through the acrylic) can be used to support the acrylic until the caulk cures. The lens rests on the screw and the edge of the lens is captured under the screw head, use a round head or pan head screw.

While cars and boats have some similarities, there are important differences. Solutions for cars are often poor choices for boats. One area this is true is in the DC electric system. SAE wire is smaller than AWG wire and has fewer but larger strands. AWG has more strands that are finer which makes it more flexible and less susceptible to work hardening. You are wise to recognize that auto glazing has different requirements from marine glazing. Boats experience more vibration and the hull and deck twist and move more than the parts of a car. Sealants must be able to adhere, flex, and stretch on a boat.

5200 is an adhesive, not a sealant or caulk. It is often referred to as the "Devil's Glue" because it adheres so well, but it is fairly rigid when it cures and extremely difficult to remove. There are only a very few applications on a boat that requires an adhesive as tenacious as 5200.
And the only thing 5200 won't stick to is acrylic windows.
 
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DArcy

.
Feb 11, 2017
1,691
Islander Freeport 36 Ottawa
I used acrylic bonded in with Sikaflex 295 UV when I replaced fixed ports. After 10 years they were still holding strong and perfectly clear when I sold the boat.
 
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Feb 27, 2004
172
Hunter 335 North East, MD
I replaced a fixed portlight on my Hunter this summer (got the port light at this website) and used 3M VHB tape and Dow 795 sealant. Very pleased with results. There are a couple of good You Tube videos on this
 
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Apr 8, 2010
1,942
Ericson Yachts Olson 34 28400 Portland OR
thank you for your input! I will look up LifeSeal and see if it still available. I lake sail in fair weather and doubt my boat will ever see the conditions your boat faces on the sea.
A boat wright friend of mine has total faith in the 795 product. Equally important, or more so, is that the window lens is "floated" proud, on at least an eighth inch of sealant. That allows the sealant bond to lens and cabin side to stay intact as the lens expand and contracts with temperature changes. (the coefficient of expansion of polycarbonate is higher than the FRP laminate of our boats...)
 
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DArcy

.
Feb 11, 2017
1,691
Islander Freeport 36 Ottawa
A boat wright friend of mine has total faith in the 795 product. Equally important, or more so, is that the window lens is "floated" proud, on at least an eighth inch of sealant. That allows the sealant bond to lens and cabin side to stay intact as the lens expand and contracts with temperature changes. (the coefficient of expansion of polycarbonate is higher than the FRP laminate of our boats...)
Yes, spacing is important. I used foam mounting tape to ensure a consistent gap.
 
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Apr 8, 2010
1,942
Ericson Yachts Olson 34 28400 Portland OR
If you use screws to hold down the window, make sure the screw-holes are oversized, to allow for expansion...
Right-O. And to make spacing the lens easy.... (secret method being revealed) AFTER you do the last dry fit, with all tape in place, a toothpick in each screw hole, and you are ready to gun on the sealant.... put a small 1/8" black O ring around each toothpick.
Gun on the sealant, and don't skimp. Press the new lens on, and insert each screw as you withdraw the toothpicks one by one. Be damned sure that every bit of plastic surface is taped right up to where the sealant starts. And..... sand the mating surfaces of edge of lens and corresponding cabin side with some 80 grit.
Have a lined wasted basket at hand to deposit your scads of paper towels into as you clean up. The sealant will still find its way onto where you absently scratched your ear!
:(
 
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Aug 10, 2020
511
Catalina C25 3559 Rocky Mount
Right-O. And to make spacing the lens easy.... (secret method being revealed) AFTER you do the last dry fit, with all tape in place, a toothpick in each screw hole, and you are ready to gun on the sealant.... put a small 1/8" black O ring around each toothpick.
this a sounds like solid advice.

I think I am going wil Dow795 by what I have read about it vs sika 795uv.

I like the idea of the mounting tape and sealant. I haven't decided if I will use screws or not.