What the heck happened to my Lexan windows? And can it be fixed?

[Chotu]

Originally Posted by a64pilot

Glass is heavy, but will last decades, my windows are 33 years old and look new, plus glass is impervious to just about anything, get paint on it, scrape if off with a razor blade.
however if you go glass, do NOT go with tempered, tempered is designed to break into tiny pieces like gravel so you don’t have a large guillotine piece of glass, think shower door.
Go with laminated glass, a cars windshield is laminated so that when struck with an object that breaks the glass, the plastic layer laminated between two pieces of glass will keep the windshield in place.
All of the other windows in a car which are not required to keep the window in place are made from tempered glass.

Point being that in heavy weather it’s entirely possible to have the entire window knocked out if tempered, where if it’s laminated it will shatter, but it will most likely stay in place.
Drop a winch handle on tempered and the whole window explodes.

Or go with the best solution of all if weight is an issue;

Stronger (therefore lighter for the same strength) tempered glass with a film on it to keep it together if broken. A film such as 3m ballistic is perfect

[deblen]

https://www.leveretteautoglass.com/

[noelex 77]

Originally Posted by a64pilot

Point being that in heavy weather it’s entirely possible to have the entire window knocked out if tempered, where if it’s laminated it will shatter, but it will most likely stay in place.
Drop a winch handle on tempered and the whole window explodes.

True, but laminated glass does frequently suffer from moisture creep along the internal plastic film. This creates an unsightly hazy area that begins around the edge of the window progressing towards the centre.

Toughened glass is the same strength as laminated glass (this depends on missile size) and does not suffer these problems. If toughened glass breaks, while it does not form sharp dangerous splinters, it generally leaves a large hole whereas laminated glass frequently maintains a reasonable degree of water exclusion.

However, glass is much heavier than the plastic alternatives. Marine glass is typically specified around 3x thicker than domestic or automotive glazing so even though boat windows are not large the weight is significant. I don’t think this is a practical material for most catamaran windows.

BTW, both acrylic, polycarbonate and the frequently applied anti scratch coatings can be attacked by some common household products. Even some oils such as WD 40 can cause damage over the long term. My guess is something has been used on the cabin top that has subsequently washed down onto the plastic and damaged the surface.

[Chotu]

New technologies are coming out too.

https://www.windowtint.com/collectio...w-tinting-film

There are now films available for polycarbonate. A game changer if they work!

I’m going to keep my polycarbonate windows and try buffing them out. The outer layer of the windows was attacked by Florida mold while I was gone. This left tiny pitting everywhere.

When I buff out the pitting, it will eliminate the UV protective layer. So I need to add a new one to keep the windows going.

I will add a polycarbonate exterior tint film and let you all know how it goes over the years.

[LifePart2]

Originally Posted by noelex 77

Marine glass is typically specified around 3x thicker than domestic or automotive glazing so even though boat windows are not large the weight is significant. I don’t think this is a practical material for most catamaran windows.

So if we have 10mm Lexan on our windows and want to switch to laminated glass, what thickness would we go with and how much would that weigh?

Can we get them tinted, and where would we get it from? Or would we get a uv excluding film for the tinting, such as a available for buildings?

[noelex 77]

Originally Posted by LifePart2

So if we have 10mm Lexan on our windows and want to switch to laminated glass, what thickness would we go with and how much would that weigh?

It is hard to equate the strength exactly. Laminated/ toughened glass is generally a very similar strength to same thickness in Acrylic. It does depend on the missile size. If hit with small missile, acrylic is a little stronger and vice versa for a large missile. Glass has much greater scratch resistance and does not suffer from the strength degradation that happens with plastics. Old UV exposed boat windows/hatches can be very weak whereas glass will have (almost) its original strength.

Polycarbonate is much stronger, but it flexes so much that in practice it pulls away from the framing structures, leaving a big hole. Therefore it sometimes needs to be thicker than acrylic just to have enough rigidity to prevent it becoming pushed in with a wave strike.

So the simple answer is that on a practical level, when new, roughly acrylic, polycarbonate and laminated/toughened glass of a similar thickness is a very similar strength for boat window/hatch glazing.

However, catamaran windows are frequently as thin as they can possibly be (to reduce weight and cost) so there is often little margin to play with. 10mm is thin for such large windows. Also the glazing can be a part of structural strength of cabin tops. Glass will be less flexible than the fibreglass cabin top creating problems with stress risers etc unless this has been taken into account at the design phase. I would not normally recommend simply swapping plastic for glass.

The weight can be calculated from the density and area. UV protection of glass (especially) toughened is slightly poorer than acrylic and significantly worse than polycarbonate.

[LifePart2]

Why is nothing ever simple?

The windows are bedded in a lot of sikaflex, so have a very flexible bedding. Consequently I can't see them providing any stability to the overall structure.

From all this discussion I think I would like to go with laminated glass, but how do I know if that is feasible and sensible? And how and where would I get that done? At least Acrylic is easy to put in. At this point I can't remember if we went with 10mm or 12mm.

I am so tired of getting work done by so-called professionals who then botch it up or give the wrong advice.

[LifePart2]

Ok, we have a conclusion.

It looks like this CAN be polished out, though it is quite a bit of work. That tells us that the damage is on the outer surface, not inside it caused by UV tunnelling.

After checking our log book and memory, we recalled that the sequence of events was:

1) March 2019 Got Awlgrip done in Trinidad by Perfect Finishes in Power Boats.
2) May 2019 Had windows replaced in St Martin by Custom Fit Marine
3) June 2019 had to go back to Trinidad to get their shoddy job redone.
4) March 2020 left the boat on a mooring in Grenada
5) Came back to find the damage.

So our conclusion is that Perfect Finishes used some kind of product on the coach roof which destroyed our windows. Their re-done job is also still far from a 'Perfect Finish'. Nedless to say we are very unhappy with their work and seriously regret having the Awlgrip done, which was hugely expensive.

I think we will try to polish out the damage as well as we can. Then maybe cover it with a UV-protecting file.

Maybe that will last a while. Eventually I guess we will replace it with Acrylic or maybe glass.

Thank you all for helping us figure this out.

[sdowney1]

When I put in a 1/2 inch thick sheet of lexan on a hatch cover as a window, one side was labeled as should be towards the sun. Something about it had a UV protective layer on one side. So that's what I did, and so far nothing like what I see in those pics. And it does get stepped on sometimes. I have found it difficult to keep sealed.

Its been on there over 10 years, and if you look at a big angle up close, you can see some tiny crazing developing. I actually think glass would hold up better.

[Nicholson58]

Be very careful with an electric buffer, polishing compounds. Frictional heat at high enough speed will wreck it for good. Try first on a test piece to get the nack and learn the procedure. Are you sure your installer used a proper material? Maybe a cheap substitute?

[er9]

Originally Posted by Chotu

New technologies are coming out too.

https://www.windowtint.com/collectio...w-tinting-film

There are now films available for polycarbonate. A game changer if they work!

I’m going to keep my polycarbonate windows and try buffing them out. The outer layer of the windows was attacked by Florida mold while I was gone. This left tiny pitting everywhere.

When I buff out the pitting, it will eliminate the UV protective layer. So I need to add a new one to keep the windows going.

I will add a polycarbonate exterior tint film and let you all know how it goes over the years.

not necessarily. acrylic and polycarbonate have a natural amount of UV protection built in. i forget what polycarb is but acrylic is somewhere arounf 90% uv blocking. polycarb is often coated with a thin film to give enhanced protection. if you buff polycarb with a thin coating you will see it worn away, its pretty obvious but wont negate your uv protection 100%. i think the uv coatings on polycarb are more about prolonging the life of the polycarb than protecting whats behind it.

[Bbolino]

try a product called 210
it's the best product i have ever found for cleaning plastic windows
it will remove scratches etc

[Bruce hartley]

Originally Posted by LifePart2

In March we left our boat on a mooring in Grenada. We just got back to her last week.

When we left, our side windows were pristine - they had been newly installed just a year ago. Now look at them.

We did not use any chemicals on our roof. We did not do anything, in fact, as we were gone for six months.

The areas that look like drips are not sitting on the surface of the lexan. They look like very superficial very fine crazing. It looks like something has dripped down the windows and caused the lexan to craze. It does not wash or rub off.

So,
a) what happened to cause this?
b) can it be fixed? Can it, for example, be polished out, and if so, how do we actually do that (never having tried to polish out scratches before).

All suggestions appreciated!

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Check with manufacturer. I use micro mesh for my plastic dome ports on my underwater camera. Check out on the net how to repair plastic windows.

[zeppelin]

H, there s a product called Novus, it is a 3 stage polish for Lexan, acrylic and plastic, comes n 3 bottles. We have used it with all of these materals with good success.

[jlubinsky]

Reefmagnet's suggestion of headlight restoring kit worth trying. Did some headlight work myself. It's tedious and if you go too deep it begins to leave a haze. Auto body shops can perform this task professionally.