Graham_Wright
Well-Known Member
I am told by the manufacturers (now demised) that their glass windows will bend. (If I remember from physics lessons, glass is a fluid).
Anybody any idea by how much?
Anybody any idea by how much?
Bending windows.
- Thread starter Graham_Wright
- Start date
NigeCh
Well-Known Member
All glass will bend. It's what's called 'post-forming' and is done under controlled heating, bending (2D only) around a heated former followed by controlled cooling. It's not a DIY thing and is V E R Y expensive.
Graham_Wright
Well-Known Member
Sorry;- once again I haven't explained properly.
The manufacturers meant during installation and cold, i.e. free (but risky?).
Anyone tried it cold?
The manufacturers meant during installation and cold, i.e. free (but risky?).
Anyone tried it cold?
DavidGrieves
Well-Known Member
Hi
Speaking as a joiner and fitted many windows, glass will not tollerate being bent whilst cold. I remember once trying to fit a piece of glass to a bow-fronted window which had been made out of true, the glass would not bend.
You are not quite correct in saying glass is a fluid, it is a "coloid" it's like a solid/fluid mix. When using a glass cutter on a piece of glass, it scratches the surface allowing you to break it in the required place, if you don't break it straight away the coloid properties will start to repair the scratch, but it takes a long time.
Speaking as a joiner and fitted many windows, glass will not tollerate being bent whilst cold. I remember once trying to fit a piece of glass to a bow-fronted window which had been made out of true, the glass would not bend.
You are not quite correct in saying glass is a fluid, it is a "coloid" it's like a solid/fluid mix. When using a glass cutter on a piece of glass, it scratches the surface allowing you to break it in the required place, if you don't break it straight away the coloid properties will start to repair the scratch, but it takes a long time.
rjp
Well-Known Member
Recently fitted new windows to my wooden boat where the glass is held in a rebate in the cabin side and retained by a brass frame. Overtightened some of the many fixing screws around the frame - crack!! 6mm laminated glass had tried to conform to the slight curve in the cabin side (and I mean slight) but couldn't bend enough. Still it's only the outer layer so still watertight but sporting a nice crack across one corner until I get around to visiting friendly glass merchant again.
billcowan
Well-Known Member
ACTUALLY -
Toughened glass will bend quite a bit, if thin enough, which it can be because it doesnt break as easy. Shop display cabinets are always toughened and often only 4mm. A panel 1.5M long easily flexes by 30mm in the middle.
Toughening of glass isnt that expensive, but cant be cut after, so you have to order your exact size and shape from friendly glazing co.
BUT I dont think Graham's supplier meant actual glass windows. He was probably offerering Polycarbonate under a brand name that included the word "glass" as in the way supermarkets sell things as"chocolate" or "*finest"
But Polycarbonate is good for boat windows, you can do it all yourself, no seals no frame. best 6mm thick and 20mm bigger allround than the orifice, stuck with mastic and fixed with countersunk ss self tappers.
After about 15 years when the mastic goes and they have crazed, you just chuck them away and start again.
Toughened glass will bend quite a bit, if thin enough, which it can be because it doesnt break as easy. Shop display cabinets are always toughened and often only 4mm. A panel 1.5M long easily flexes by 30mm in the middle.
Toughening of glass isnt that expensive, but cant be cut after, so you have to order your exact size and shape from friendly glazing co.
BUT I dont think Graham's supplier meant actual glass windows. He was probably offerering Polycarbonate under a brand name that included the word "glass" as in the way supermarkets sell things as"chocolate" or "*finest"
But Polycarbonate is good for boat windows, you can do it all yourself, no seals no frame. best 6mm thick and 20mm bigger allround than the orifice, stuck with mastic and fixed with countersunk ss self tappers.
After about 15 years when the mastic goes and they have crazed, you just chuck them away and start again.
Graham_Wright
Well-Known Member
Yes, he did mean "glass". What sort of glass it is, I don't know but it certainly isn't polycarbonate
(which I work with).
My boat is a Colvic Countess 33 centre cockpit, stern cabin. I have seen photos of the same mark with long windows fitted to the stern cabin. This surface is a plane curve midway between the cockpit and stern hatch and a lesser but complex curve a bit further aft.
I would be grateful to hear from any 33 owners who have aft windows so fitted (and whether they are glass or plastic).
(which I work with).
My boat is a Colvic Countess 33 centre cockpit, stern cabin. I have seen photos of the same mark with long windows fitted to the stern cabin. This surface is a plane curve midway between the cockpit and stern hatch and a lesser but complex curve a bit further aft.
I would be grateful to hear from any 33 owners who have aft windows so fitted (and whether they are glass or plastic).
jerryat
Well-Known Member
Well I bent 4 or 5mm glass to the coachroof shape when I replaced the windows on my Hustler 30 a good few years ago. I checked and re-checked with the suppliers and glass manufacturers and they all said go ahead.
The method was to do it slowly. We put the first inter-screws in at the centre (top and bottom, then the next two (fore and aft) and so on, gradually tightening each as the window deformed to the shape required.
Long slow nreve racking job, but perfect fit and totally watertight when I sold her five years later. The total 'pull' or deformation was about 8-10mm over a 600mm length.
If your dimensions are similar, I'd have a go.
Cheers Jerry
The method was to do it slowly. We put the first inter-screws in at the centre (top and bottom, then the next two (fore and aft) and so on, gradually tightening each as the window deformed to the shape required.
Long slow nreve racking job, but perfect fit and totally watertight when I sold her five years later. The total 'pull' or deformation was about 8-10mm over a 600mm length.
If your dimensions are similar, I'd have a go.
Cheers Jerry
Calluna
Well-Known Member
I think that we were told by the manufacturers that glass windows could be bent by up to 2" per metre. Ours are 6mm thick and had to bend by just over half of that. We used the method described above by Jerry and they were surprisingly flexible, even though we fitted them in freezing temperatures in January.
Heather
Heather
Avocet
Well-Known Member
Rather than a polycarbonate (if you go down the plastics route) try an "impact modified" acrylic. We use stuff called "Resist 65" at work. It's an acrylic so it doesn't scratch as easily as polycarbonate and it doesn't go milky but because of its impactmodified properties, it doesn't shatter like a sheet of "Perspex".
Captain Coochie
Well-Known Member
trying to fit a piece of glass to a bow-fronted window which had been made out of true, the glass would not bend.
erm i dont think out of true was the problem /forums/images/graemlins/blush.gif)
Speaking as another joiner ..... Glass does have some tollerance as all my joinery is out of true , i would call it flex rather than bend but i will check with my glass man in the morning
erm i dont think out of true was the problem /forums/images/graemlins/blush.gif)
Speaking as another joiner ..... Glass does have some tollerance as all my joinery is out of true , i would call it flex rather than bend but i will check with my glass man in the morning
MedMan
Well-Known Member
I have fitted new windows throughout, two of which are on a slight compound curve. The glass is 8mm toughened which is definitely not flexible. The secret was to have sufficient depth of mastic both inside and outside the glass. As the inter-screws were slowly tightened the aluminium frame took up the curve but the glass remained flat, the difference being taken up by the compression and extension of the mastic.
mrplastic
Well-Known Member
you can't bend glass cold..it will break. You need loads of heat...read LOADS of heat...you can bend it then but only if it's not toughened to start with and if it's laminated the plastic intermediate layer will melt.....specialist stuff I'm afraid
Graham_Wright
Well-Known Member
Well! - what a diversity of replies!
Some say impossible and some say have done it!
I will have a go. My fore cabin windows are mounted on a cabin side which is curved about 15mm over 600 and they have been there a few years without problems. It is certainly possible that the mastic bewteen the frame and the glass has taken up some bend although it doesn't look like it.
I'll report back;- perhaps the searing heat of this summer will help (or did I miss it?).
Some say impossible and some say have done it!
I will have a go. My fore cabin windows are mounted on a cabin side which is curved about 15mm over 600 and they have been there a few years without problems. It is certainly possible that the mastic bewteen the frame and the glass has taken up some bend although it doesn't look like it.
I'll report back;- perhaps the searing heat of this summer will help (or did I miss it?).
jerryat
Well-Known Member
Hi Graham,
Just take it really slow and easy - this is not one to hurry! By the way, may I suggest you use the purpose made closed-cell hatch/window sealing tape available from (almost) any chandler instead of mastic. Excellent stuff. /forums/images/graemlins/smile.gif
Using the tape not only saves having to clean up an incredibly filthy mess, but also allows you to take whatever time you need to VERY gently pull the window into position.
I suspect you may be getting near the limit pulling 15mm over 600mm, but it seems to depend on the thickness of the glass - the thinner stuff having more flexibility, and if the existing windows did it, why shouldn't the new ones?!! This argument was the one that persuaded me to do mine. /forums/images/graemlins/smile.gif
Anyway, the very best of luck and please DO let us know how its goes. /forums/images/graemlins/cool.gif /forums/images/graemlins/cool.gif
Cheers Jerry
Just take it really slow and easy - this is not one to hurry! By the way, may I suggest you use the purpose made closed-cell hatch/window sealing tape available from (almost) any chandler instead of mastic. Excellent stuff. /forums/images/graemlins/smile.gif
Using the tape not only saves having to clean up an incredibly filthy mess, but also allows you to take whatever time you need to VERY gently pull the window into position.
I suspect you may be getting near the limit pulling 15mm over 600mm, but it seems to depend on the thickness of the glass - the thinner stuff having more flexibility, and if the existing windows did it, why shouldn't the new ones?!! This argument was the one that persuaded me to do mine. /forums/images/graemlins/smile.gif
Anyway, the very best of luck and please DO let us know how its goes. /forums/images/graemlins/cool.gif /forums/images/graemlins/cool.gif
Cheers Jerry
bigmart
Well-Known Member
As a supplier of fittings to the Glass Trade I find some of the replies, you have received, laughable.
One of the biggest problems that I have is to educate my customer about is the amount of flex that glass has. Try explaining to an enthusiastic Architect, that the 8 foot high, piece of 6mm Toughened will flex around 100mm in the centre & he will be most surprised.
Laminated Glass is a whole different animal & has its own problems.
Of course you can bend Glass to very tight curves with heat, but as many have said, that is a very specialist job, well out of the scope of many professionals, let alone amateurs. If you want this done then I know a man who can.
Nowadays you can make Springs out of Glass. I sell a Glass Radiator for your Bathroom & can offer Glass with LED Lights built in. Some others can also offer Loud Speakers built into Glass. I am told that Glass Concrete is the new Building Material to amaze.
Glass Technology is moving foreward at a pace.
Be very wary of the experts who tell you that it cant be done cos I'll bet it can.
Martin /forums/images/graemlins/cool.gif
One of the biggest problems that I have is to educate my customer about is the amount of flex that glass has. Try explaining to an enthusiastic Architect, that the 8 foot high, piece of 6mm Toughened will flex around 100mm in the centre & he will be most surprised.
Laminated Glass is a whole different animal & has its own problems.
Of course you can bend Glass to very tight curves with heat, but as many have said, that is a very specialist job, well out of the scope of many professionals, let alone amateurs. If you want this done then I know a man who can.
Nowadays you can make Springs out of Glass. I sell a Glass Radiator for your Bathroom & can offer Glass with LED Lights built in. Some others can also offer Loud Speakers built into Glass. I am told that Glass Concrete is the new Building Material to amaze.
Glass Technology is moving foreward at a pace.
Be very wary of the experts who tell you that it cant be done cos I'll bet it can.
Martin /forums/images/graemlins/cool.gif
Plum
Well-Known Member
I fitted out a GRP motorcruiser many years ago and the cabin windows were toughened glass (not laminated) in aluminium frames and the cabin sides had a distinct bend/twist. The larger window (about 1.2m long) was of 6mm glass and the smaller one (about .7m long) was of 4mm glass. The bend seemed frighteningly large to me but by gradual tightening of the frame screws the glass did in fact bend without breaking and they were still OK when I sold the boat after 15 years. I have no idea now where the boat is so cannot measure the curvature for you but from memory I would say it was not less than 50mm in a metre.
Plum
Well-Known Member
Hello. I fitted out a GRP motorcruiser many years ago and the cabin windows were toughened glass (not laminated) in aluminium frames and the cabin sides had a distinct bend/twist. The larger window (about 1.2m long) was of 6mm glass and the smaller one (about .7m long) was of 4mm glass. The bend seemed frighteningly large to me but by gradual tightening of the frame screws the glass did in fact bend without breaking and they were still OK when I sold the boat after 15 years. I have no idea now where the boat is so cannot measure the curvature for you but from memory I would say it was not less than 50mm in a metre.
2Tizwoz
Well-Known Member
Plexiglass is a brand of acrylic and like polycarbonate can be bent considerably before it breaks. I recently changed my 10mm acrylic windows which are bent several inches out of flat by design. The previous ones were substantially weakened by age crazing.
Laminated glass continues to fill a hole when damaged as do the plastics. Toughened glass breaks into myriad crystals leaving a hole where previously you had a window.
Will your boat be seaworthy in the absence of your window ?
Laminated glass continues to fill a hole when damaged as do the plastics. Toughened glass breaks into myriad crystals leaving a hole where previously you had a window.
Will your boat be seaworthy in the absence of your window ?
MedMan
Well-Known Member
Two further recollections from fitting my windows. With 8mm toughened glass in an aluminium frame I have little doubt that the fibre glass bent to fit the window rather more than the window bent to fit the fibre glass. Furthermore, quite a bit of the curve was taken out by the flange bending away from the frame rather than the frame bending. This is not ideal, but you have no control over it. Add these two factors to the first one I mentioned - differential compression/extension of the mastic used to bed the glass into the aluminium frame - and you can see that quite a substantial curve can be accommodated without any flexing of the glass itself.
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