Glass windows?

[Robert Jansen]

How about marine grade abrasion resistant lexan (MR-10)?

[JPA Cate]

@Epicurean:

It is very likely someone used a ammonia based cleaner, even only once, like I did on a couple of our ports. There is some kind of chemical reaction between the ammonia in the cleaning product and the acrylic. I can't begin to say how distraught I felt to ruin my own ports!

If you will have to pay for a mold in either case, that is where the main part of the labor is, for forming acrylic. Making certain it is smooth as a baby's bum is really important. And, you may even be able to make arrangements to retain the mold in storage against the next time. We had done that, and it worked very much to our benefit when we had had a knockdown, and broke the molded acrylic dodger window. We had paid for 6 mm thick, but the shards were 4mm. It may thin as it droops over the mold. Our new one was still clear when we sold the boat 7 yrs. later.

Good luck with your project.

Ann

[cndcruiser]

The terms acrylic, perspex and plexiglass are often used interchangeably. Genuine German made Plexiglas (one 's') is made via a casting process rather than the cheaper extrusion process used by the many Asian manufacturers. Plexiglas has a 30 year guarantee against yellowing. I had to replace curved laminated glass windows in a hard dodger. The laminated glass had been end-sealed with acrylic sealant and moisture had wicked into the plastic interlayer creating an unsightly appearance. Also, laminated glass is extremely vulnerable to cracking if the edges are exposed - edges must be buried inside a molding and not exposed to sealants. I had the laminated glass windows replaced with 10mm genuine Plexiglas. The shipwright was able to form the gentle curves in a large oven. It's not easy to achieve optical perfection without a proper manufacturing process, but the results are good enough. My preference would have been to get curved toughened glass, but the manufacturing cost for a one-off project like this in Australia would have been prohibitive. Whilst curved glazing might create better aesthetics, this benefit is far outweighed by the cost and complexity of repair and boat windows are quite vulnerable to damage. The hard dodger on my boat could easily have been designed for flat panels giving the option for either toughened glass or Plexiglas.

[CarlF]

My previous boat had glass. It was a joy. When I sold it after 10 years the glass was as clear and perfect as new.

So after you look at the costs and weight -- if glass is even in the ballpark, I'd go that route. You'll be happy you did it years down the road. And for some reason, custom glass for boats isn't as expensive as I'd expect. Not like custom stainless work prices on boats. Don't know why.

If you go the glass route be sure to get it from a company that does boats. They'll understand how to toughen it and you'll most likely want it tinted. You may also want to have it laminated. Here's a Florida company a friend used and was happy. https://www.curvedglasscreations.com/contact

Also, with any type of glazing you have to deal with the different coeficients of expansion between the fiberglass frame and the glass or acrylic after it's installed. In most cases you need to have the caulk at least 1/4" thick so that it can stretch in the daily temperature cycling from the sun. Otherwise with large windows the bond fails after a few months.

I installed a large acrylic skylight a few years ago. I used 1/4"x1/4" black foam weatherstipping tape as sort of a "dam" at one edge and put the caulk behind it. The tape kept the glass from compressing the caulk while it hardened - and provided a very neat interior finish. Another route is to put little 1/4" high plastic standoffs in the caulk.

The acrylic company had me use Dow 795 caulk which is used to hold glazing on skyscapers curtain walls with no mechanical fasteners. It worked great. No primer needed. Much better than any "marine" caulk I've used for windows.

[cndcruiser]

Just reinforcing the previous comment re sealants. The only two sealants I would use for either glass or acrylic are Dow Corning 795 or GE Silpruf SCS2003, both in black. These are high quality, architectural glazing/construction sealants used for windows in sky scrapers. Polyurethane sealants will fail.

[ggray]

My catamaran has very large plastic windows which do need replacement at 23 years.

I keep them covered with covers of two layers of sunbella, white over black, at least six months of the year to keep the heat out and protect the plastic. Doesn’t imprint like mesh.

In most of the covers I have strategically located cutouts (portholes) with removable Velcro attached covers.

Just another thought.