What plastic for windows?

[JumbleDuck]

There’s a slight curve to them so that rules out toughened glass

It doesn't! My Jouster had toughened glass windows which were straight when removed but took a surprising bend when fitted. When I had my Hunter 490 windows rebuild, toughened glass cost only a pound or two more per side than plastic. Glass is so much nicer that I'd strongly recommend investigating the possibilities.

 

[john_morris_uk]

Acrylic is not necessarily better or worse than polycarbonate with respect to UV resistance. It all depends on the specific grade of each. Car headlights are polycarbonate with the vast majority of the manufacturers using uv resistant grades. Just because an acrylic supplier says their product is uv resistant, will they guarantee it? When I replaced mine i used Perspex brand acrylic as Perspex say "30 year guarantee against outdoor weathering". I purchased from Cut to Size Acrylic (Perspex) Sheet, Tube & Rod - Simply Plastic

www.solocoastalsailing.co.uk

I’ve used a company in Petersfield that specialises in boat window replacement so I rather hope they’re supplying suitable acrylic! I wish I’d known to ask... The company is Boat Windows & Hatches, Washboards, Marine Mirrors | Port Synthetics and they seem kosher. Not the cheapest but offer a ten year guarantee.

 

[john_morris_uk]

It doesn't! My Jouster had toughened glass windows which were straight when removed but took a surprising bend when fitted. When I had my Hunter 490 windows rebuild, toughened glass cost only a pound or two more per side than plastic. Glass is so much nicer that I'd strongly recommend investigating the possibilities.

Well I learn something every day! I understand completely about toughened glass as we’re gradually replacing most of the windows in our Sealord with it and we’re really pleased with the results so far. I’d have been holding my breath bending toughened to fit the curve of Eowyn the Pandora though. You don’t get a second chance with toughened either!

 

[PaulRainbow]

Well I learn something every day! I understand completely about toughened glass as we’re gradually replacing most of the windows in our Sealord with it and we’re really pleased with the results so far. I’d have been holding my breath bending toughened to fit the curve of Eowyn the Pandora though. You don’t get a second chance with toughened either!

My Discus has 2 perspex and 2 glass "windows" in the saloon, i guess they should all be glass and two have somehow got broken. Where are you getting the toughened glass for the Sealord John ?

 

[john_morris_uk]

My Discus has 2 perspex and 2 glass "windows" in the saloon, i guess they should all be glass and two have somehow got broken. Where are you getting the toughened glass for the Sealord John ?

I’ve got a man who takes away the frames and brings them back restored with toughened glass. I haven’t got his name at my fingertips but he’s Gosport/Portsmouth based and I can find out contact details if it helps.

 

[PaulRainbow]

I’ve got a man who takes away the frames and brings them back restored with toughened glass. I haven’t got his name at my fingertips but he’s Gosport/Portsmouth based and I can find out contact details if it helps.

Thanks John, an idea of cost would be good, PM me if you prefer.

 

[Owl]

Key point with any kind of plastic windows is the thermal expansion and contraction. When I did my Jaguar 21 windows - about 1m long I think - I calculated that the expansion would be around 10mm over the likely temperature range in the UK. Holes round the fixings and penny washers are the easy bit. The harder bit is how you seal the window when it is going to move that much.
As mentioned butyl tape never sets and thus will cope. Anything that sets will break unless the depth of sealant is enough for the sealant to flex. This generally means that the depth of sealant must be at least the same as the expected movement or more. For my boat I just bought some neoprene sheet as a gasket and fitted the windows without any further sealant. This worked extremely well and meant that I could take the windows out very easily if there was a problem.

 

[JumbleDuck]

Well I learn something every day! I understand completely about toughened glass as we’re gradually replacing most of the windows in our Sealord with it and we’re really pleased with the results so far. I’d have been holding my breath bending toughened to fit the curve of Eowyn the Pandora though. You don’t get a second chance with toughened either!

Refitting the windows to my Jouster terrified me. They were only about 3' long and with the centre of the frame touching each end was - from memory - about 3/4" proud, but it all worked out fine. Of course that had metal frames with a rubber seal to spread the load; if the Pandora has the windows through bolted to the GRP with sealant in between then it's probably not safe to try, as the loads would be much more concentrated.

It might be worth asking about curved glass, though. I have an occasional plan to fit a third window across the front of the Hunter 490 and when I made enquiries a curved, toughened window wasn't significantly more expensive than a plastic one. I suspect that when they have the glass hot and soft enough for toughening, a bit of a bend isn't much of an extra.

 

[JumbleDuck]

Thanks John, an idea of cost would be good, PM me if you prefer.

If you have a good local glazier it's could be worth asking them. For example, Viewforth Glazing in Edinburgh will cut and toughen glass to order, though I don't know if they toughen on site or send stuff away. It's not a desperately complicated process.

 

[rogerthebodger]

I suspect that when they have the glass hot and soft enough for toughening, a bit of a bend isn't much of an extra.

The issue with curved glass is the jig/form to hold the curve while the glass stiffens. Its the same issue with curving perspex but perspex is able to take up small curves without heating.

 

[UK-WOOZY]

the windows on my boat were remade with acrylic by Hadlow marine using the original crazed and damaged originals as templates and fitted by myself and a friend in winter the first year i had the boat in 2018. the large front window is 12mm thick and we bent it into shape without heating it first in the cold and it flexed fine using the bolts to get the curve. the sides are 6mm acrylic. Used window backing foam tape and bolts and then put a bead around them with Geocel marine sealant. seems fine still even after i noticed i put impact marks on most of them when i got my halyard caught around the radar reflector and was chucking the heavy metal clip at the end over the spreaders to try and free it and that had impacted the windows causing the damage, but they seem ok despite the damage i caused.

 

[Plum]

Key point with any kind of plastic windows is the thermal expansion and contraction. When I did my Jaguar 21 windows - about 1m long I think - I calculated that the expansion would be around 10mm over the likely temperature range in the UK. Holes round the fixings and penny washers are the easy bit. The harder bit is how you seal the window when it is going to move that much.
As mentioned butyl tape never sets and thus will cope. Anything that sets will break unless the depth of sealant is enough for the sealant to flex. This generally means that the depth of sealant must be at least the same as the expected movement or more. For my boat I just bought some neoprene sheet as a gasket and fitted the windows without any further sealant. This worked extremely well and meant that I could take the windows out very easily if there was a problem.

I think you will find that the thermal expansion of GRP is not that much different to Acrylic.

www.solocoastalsailing.co.uk

 

[JumbleDuck]

Key point with any kind of plastic windows is the thermal expansion and contraction. When I did my Jaguar 21 windows - about 1m long I think - I calculated that the expansion would be around 10mm over the likely temperature range in the UK.

That's a 1% change in length. Since the coefficient of thermal expansion of perspex is around 0.000075 per degree C, it would take a temperature range of 133C to achieve 1%. You must live in a more interesting bit of the UK than I do, climate-wise.

 

[C08]

It is worth considering laminated glass which is not expensive from any glass merchant. When I replaced a broken fore cabin window that had a bash from a neighbours boat the inner layer was broken but the outer layer was still intact. When I came to remove the broken window from the frame it was really difficult evn with alump hammer to breach the watertight integrity of the window. With the inner crazed all over and the outer similarly damaged the central layer remained intact and withstood a lot of blows to break it through.

 

[john_morris_uk]

It is worth considering laminated glass which is not expensive from any glass merchant. When I replaced a broken fore cabin window that had a bash from a neighbours boat the inner layer was broken but the outer layer was still intact. When I came to remove the broken window from the frame it was really difficult evn with alump hammer to breach the watertight integrity of the window. With the inner crazed all over and the outer similarly damaged the central layer remained intact and withstood a lot of blows to break it through.

I went through the same logic on our Westerly Sealord but was assured that toughened was the way to go and extremely unlikely to shatter. We’re off to Oceans Blue one of these days so we’ll see!

 

[DownWest]

Key point with any kind of plastic windows is the thermal expansion and contraction. When I did my Jaguar 21 windows - about 1m long I think - I calculated that the expansion would be around 10mm over the likely temperature range in the UK. Holes round the fixings and penny washers are the easy bit. The harder bit is how you seal the window when it is going to move that much.

Think you missed a decimal point or so. Ally has a coefficient 3X that of glass. So the frames would expand by 3cm?? I don't think so..

 

[john_morris_uk]

Regarding the frame question. There’s a rebate in the GRP moulding that’s deep enough to allow a trim to be clipped over (to tidy up appearance from the inside) and for the acrylic to nestle in (bedded on a suitable sealant/mastic. Then there’s a Black GRP moulded trim with about fifty screws in (thank you Makita drill acting as a powered screwdriver). This is also bedded onto more mastic/sealant.

I’m debating whether to use butyl (cheap and comes recommended) or Sikaflex window sealant that’s designed for exactly this job.

I’ve managed to find a picture that doesn’t include daughter grinning out of the hole where her boat window used to be. Hopefully you can see the rebate I was referring to.

 

[Hallberg-Rassy]

It is worth considering laminated glass which is not expensive from any glass merchant ... the inner crazed all over and the outer similarly damaged the central layer remained intact.

I think that's toughened (aka tempered) and safety (laminated) glass. A two stage operation which has to be the best, although not necessary essential.

In essence, they cut two pieces of glass, tough it (so it breaks like a car windown), and then laminate them together.

You do also get non-toughened safety glass (that breaks like normal window glass, but is still held together by the plastic.

Single layer, unlaminated toughened glass is funny stuff. It can actually shatter really easily if hit with a sharp edge. Think car theives with a centre punch, or a flint. The problem being it's a total loss at that point. If its stressed, eg bent, it can pop. The process of making it has to account for the higher proportion of pieces breaking while processing, if they have the smallest fault on their edges. Many a year ago, I used to work for a glass furniture maker. Laminated on its own, I would not be a fan off because it leaves lots of really nasty shards barefeet will find laters.

There is a compay who specialises in making windows and frames for narrow boats but glazing companies would worked from a template if you know what to ask for, without a marine surcharge. Can't remember their former's name right now.

 

[Hallberg-Rassy]

Oh, for some reason my posts are being moderated by matron again, and I can't correct the typos. My apologies.

Toughened laminated glass also has some insulation benefits and can be done in colours etc.

 

[DownWest]

Think the toughened/laminated combo is for doors. Less nasty if you walk into it.