Acrylic or Polycarbonate for windows - Page 2 - SailNet Community
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post #11 of 27 Old 11-11-2009
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one more point on drilling holes in acrylic or polycarbonate... you should probably chamfer/countersink the holes on both sides to help prevent them from becoming a starting point for stress cracks.

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post #12 of 27 Old 11-11-2009
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Fast,
We're just about to redo the Womboat's ports so thanks for all that. I've done this before on previous boats but hadn't used the "leave the backing paper intact" idea, wish I had.
SD recommends 3/8" perspex. Is that what you used ? I'm wondering whether 1/2" would be overkill. By the looks of things our ports are about the same length but not as big top to bottom as yours.

Now here's an interesting question....our existing ports are two piece covering a single opening that has a vertical support in the centre. My thinking was to do the new ones in single piece cos ironically enough the only leaks we have are where the two pieces of perspex butt up to each other.

There is no great curvature involved. Can anyone see any good reason not to go one piece ? They'd end up being about a metre (three feet) long.

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post #13 of 27 Old 11-11-2009
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td.. we had a considerable (compound) curvature and ended up using 1/4" - for the sailing we do I think it's adequate and they are not that large an opening really.

Don't see any problem going to a single lens in your case - our forward lense is pretty close to a meter long and narrower than the aft one. That mid-port seam just has to be asking for trouble.. Since your boat is built from plate, I'd expect no problem whatsoever getting plexi to follow the same shape.

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post #14 of 27 Old 12-06-2009
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Just an FYI

Lewmar, the port & hatch manufacturer associated with Sailnet, uses acrylic in their products.
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post #15 of 27 Old 12-06-2009
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Virtually every major port and hatch manufacturer and boatbuilder uses acrylic (plexiglass) as the lexan is destroyed by uv in a few years.

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Living aboard in Victoria Harbour
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post #16 of 27 Old 12-06-2009
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What about Lexan MR-10, it has great UV protection, great scatch resistance and exceeds tempered in the impact resistance

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post #17 of 27 Old 12-06-2009
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Acrylic us also less subject to scratching.

Brian
Living aboard in Victoria Harbour
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post #18 of 27 Old 12-06-2009
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I am making a new set of bolt in place windows as we speak. The old ones were leaking, I removed them last week. I can see why, they were sealed with butyl tape. The plexiglas was bowed in at the bolts while the fiberglass bowed out at the bolts, leaving gaps beteen bolts. The Pan head bolts though had rubber washers under the heads, which seemed like a good idea.

I am most concerned about the seal around the windows though. In a previous career I researched sealing thing that have to have lots of room for expansion (aluminum against concrete) Everything I could find on the subject from the manuafacturers was moslty concerned with having the sealant THICKER than the motion needed. For silicone the sealant can take a motion equal to its thickness in any direction without it breaking loose. So my plan is to pad the windows out away from the hull using 1/8" rubber washers. Then I'll run a nice bead all the way around the plexiglass to form the seal. This should alow the window to move yet never break the seal. A fillet bead around the edge of a plexiglas sheet doesn't work because when the plexiglass moves it shears the sealant off.

I'll let you all know in about 5 years if it works!

Gary H. Lucas
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post #19 of 27 Old 12-06-2009
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Gary
Remember to overdrill the holes. A neighbor in my Marina has redone most everything on his Beneteau including the windows. He is using a soft washer under the bolts that is "T" shaped when looking fron its side. The hole in the plexi is just large enough for the washer and the bolt a good fit inside the washer. I asked where he got them and he said they were original from Beneteau, but it looks like a good idea, must be able to source them somewhere.

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post #20 of 27 Old 12-06-2009
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I'm using the old windows as a template, just route around around the outside with a flushcut bit and drill through the existing holes. All the existing holes were properly oversized. McMaster Carr sells ruber washers in any size or elastomer you could want, neoprene, EPDM, even Viton. EPDM has the best weather resistance I believe.

Gary H. Lucas
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