sealing flat perspex windows, temp repair

ShipsWoofy

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I need new windows on the saloon, two of them have cracks. The aft windows should be fine but need to come off and be re-bedded.

The front windows all have leaks now, bad goo used when fitting originally. I doubt I can take them off and seal them without losing a few screws and causing some of the cracks to become fractures. As I intend to replace them as soon as finance allows (big windows) I would rather bodge a repair to survive at least our cruise this year.

I have tried silicon seal around the edge, keeping it is neat as possible, but this has had mixed results from nearly to "is that drip worse than before?"

Any repair should be easy to remove, I don't want to double the work when it comes to fitting the new ones. Should I be concentrating on the screw holes, i.e. put a blob of mastic over each screw, will this come off afterwards?

Question?

Someone here will have bodged a repair on a perspex window, (no frames), how did you do it? Looks are not too important.
 

Aja

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I did it successfully on my Jeanneau and it lasted till I sold the boat.....

....used 'Super Glue'. Nice and runny and wnt along the whole of the top edge of the window and down the sides a couple of times.

Warning dont do as I did and apply just before it rained..... super glue doesn't like rain.

Donald
 

vyv_cox

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I find that silicone varies enormously, some just falls off, others stick well and do the job. Try buying the stuff used to make fish tanks. As well as having no additives that will kill the fish (be green as well!) it seems to stick better than some of the others.

In your situation I would try backing off the screws a little and squirt some silicone beneath them before re-tightening. If you are sure the windows are perspex you might get away with a solvent based sealant, polyurethane has worked well for me. If there is any chance that they are polycarbonate don't let any solvent near them as it will lead to much worse cracking. Sika make a sealant specifically for polycarbonate to prevent this. I have never used it.
 

Twister_Ken

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Creeping Crack Cure?

2366.jpg
 

ShipsWoofy

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woah there,

polycarbonate / perspex ??

How can I tell? Maybe it is polycarbonate and why they have cracked, though I think my dad who fitted them should have gone for a thicker glass than he did, I intend to go to maybe 6mm on the fronts, hence me saving up rather than getting the cheapest..

I like the idea of the stuff Ken has posted, does anyone know how difficult it would be to remove when I change the windows? I would never have thought to use super-glue, this would be quite expensive as the windows are big, but I imagine very easy to remove later as it should just chip away.

The problem with the screws, unfortunately they are not stainless, so I fully expect to snap a few or have to grind off some heads during the removal. If they were stainless I would have re-bedded the windows a couple of years ago. The aft cabin windows have ss and are much better glass, he did those later on and they are much smaller, I fully expect to be able to whip these off easily (hah hah).
 

vyv_cox

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I've had mixed results with it. Seems to cure very fine cracks but not the larger ones. Its viscosity is very low, which I suppose is why it creeps along them, but it cannot bridge anything bigger than a hair's width.
 

ShipsWoofy

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Does anyone see any mileage in wide insulation type tape. Like I said this is only a temporary measure, I would have to be careful to use a tape that does not leave residue, any thoughts?

the actual cracks in the perspex do not seem to be leaking, only one of them is over a window, the other is between windows, but the entry point of water to the boat may not be where the leak is, I do understand that.
 

davierobb

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If replacing use polycarbonate, much easier to work with, it is easily cut with saw and can be finished with a small plane. You can double it back on itself and it wont break. I managed to get some gash stuff from work and it was only about 3mm thick and its indestructible.

If removing Perspex with cracks then you can stop the crack getting bigger by drilling small hole at end. Afraid you’ll have another hole to fill but it stops the crack creeping. Araldite seals the hole and looks ok.
 

aitchw

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[ QUOTE ]
polycarbonate / perspex ??

[/ QUOTE ]

If they are cracked they not likely to be polycarbonate. You can damn near fold it in half without it cracking and it doesn't generally develop stress fractures under normal circs. Much more likely to be perspex.
 

rhumlady

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If I am right in thinking that the perspex or whatever is in a long strip which covers the windows and the grp between the you should make sure that no leaks get into the parts where it covers the GRP. You could end up with a rash of the dreaded Osmosis!! It gets everywhere not just on the underwater hull.
 

Niander

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Whats wrong with silicon sealer?
I've just changed a perspex window...the previous owner[numpty] had used steel screws like yours ,they were falling apart/out
so i wacked brass ones in no probs using silicon to seal..and the rusty ones came out easier than i thought...
 

vyv_cox

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<< If they are cracked they not likely to be polycarbonate. >

Absolutely not true. There is loads of literature available on stress corrosion cracking of polycarbonate due to solvents. Several people have died as a result of this problem, after putting adhesive stickers on their helmets, both motorcycle and industrial. If you use normal adhesive/sealants to fit polycarbonate windows to your boat they will grow a network of cracks around every screw hole within a week. I've done it!
 

aitchw

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Thanks for that!

I had forgotten to raise the issue of the effect of solvents and their presence in many sealants. It is one of the reasons I have tended to use neoprene gaskets or rubber seals rather than a sealant.

A timely and welcome correction.
 

Bajansailor

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FWIW, I re-glazed a Lewmar hatch with a piece of Lexan, and bedded it down on 5200 (American equivalent of the most tenacious of the Sikaflex gunges) ten years ago, and it is still doing fine - apart from the lexan going cloudy, because it was not the special U-V resistant type.
I didnt use any screws though.
 
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