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Crazed windows


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You could but I suspect the crazed ones are acrylic. There are two common forms of clear glazing, Acrylic and polycarbonate. Acrylic is a bit cheaper but softer so it scratches easier. I would suggest that you use polycarbonate. Perspex is just a trade name, I think it is polycarbonate but not sure so best to use the material  name and don't worry about the trade name. Personally I would not trust the likes of B&Q not to call any clear plastic perspex because perspex is a bit like hoover in that many call any vacuum cleaner the hoover.

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51 minutes ago, Norman Lives said:

One of the front cabin windows on my 1980 Norman 23 and the hatch window have badly crazed, seems to be perplex, can you use any perplex like from B&Q or is there somewhere that still supply Norman parts? TIA :) 

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Don't think you will get windows off the shelf, you will need to make your own.

Use 4mm acrylic which you may have to order off the internet unless you can find a local supplier.

It looks like your windows are in an ally frame and having replaced the windows in my Norman, I am sorry to tell you it is a pig of a job.

The frames are easy enough to get out, but dismantling the frames is not. they are held together at the corners with steel strips and tapped for tiny screws which will be rusted solid, and will most likely have to be drilled out.They will most likely be scrap when you have done this and will have to make new corner pieces out of ally and use small self tappers to re assemble.(cut or file the points off, or on tightening up you can crack the new perspex)

You will also need new rubber seals (Seals Direct) and suitable mastic to seal the frames to the cabin.

A tip!  when you have got the frames out, cover the opening with plastic sheet and gaffer tape, cos it is guaranteed to piss down as soon as you get the frames out!

Best of luck

As Tony says, polycarbonate will probably be better for the job. 

Use the old window as a pattern, and use a cutting disc. DO NOT use a saw or any reciprocating device, it will crack it as sure as eggs is eggs.

Just thought, there was an excellent post with drawings some years ago on the Norman Owner's Forum on replacing Norman windows.

If you Google it, and click on "problem page" it is in there somewhere.

I will try and post it across although I am pretty numb at doing this sort of stuff.

 

Edited by Mad Harold
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When cutting this stuff to size stick masking tape on first and then draw your cutting lines on that or it will probably splinter or crack. Lay it on a solid surface to cut it. A workmate  is ideal with the jaws open a little to take the cutting blade, moving the perspex about as needed keeping the blade in the jaw slot whilst following the drawn cutting lines.

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18 minutes ago, bizzard said:

When cutting this stuff to size stick masking tape on first and then draw your cutting lines on that or it will probably splinter or crack. Lay it on a solid surface to cut it. A workmate  is ideal with the jaws open a little to take the cutting blade, moving the perspex about as needed keeping the blade in the jaw slot whilst following the drawn cutting lines.

Would a jigsaw do the trick? With a fine tooth cutting blade, again with the masking tape to stop splintering. 

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26 minutes ago, Goliath said:

Would a jigsaw do the trick? With a fine tooth cutting blade, again with the masking tape to stop splintering. 

Some time ago on "Wheeler Dealers", they were refurbishing a Messerschmitt three wheeler and it had a perspex canopy.

The mechanic (Ed) used a jigsaw to cut the canopy to shape, and about three quarters of the way through the job, CRACK! and bless the tv company they left that in and didn't edit it out.

Shows that even professionals can drop clangers.

Sorry, Ed wasn' t using a jigsaw, it was a reciprocating hand saw.

Edited by Mad Harold
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My experience with cutting acrylic sheet goes back to the days of homebrew record deck plinth covers.

 

I found it was the very devil to get a clean edge and a coarse metal file took hardly any material away, while also stressing the material. In the end a Surform proved to be best for tidying up rough edges, planed in the direction of the cut.

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37 minutes ago, Mad Harold said:

Some time ago on "Wheeler Dealers", they were refurbishing a Messerschmitt three wheeler and it had a perspex canopy.

The mechanic (Ed) used a jigsaw to cut the canopy to shape, and about three quarters of the way through the job, CRACK! and bless the tv company they left that in and didn't edit it out.

Shows that even professionals can drop clangers.

Sorry, Ed wasn' t using a jigsaw, it was a reciprocating hand saw.

Yes but that wasn't a flat piece on a solid surface, it was the rim of the curved canopy all flopping about while he cut it. I thought he was an idiot for trying to do it like that . I've seen him do the odd very dodgy things fixing cars. He wouldn't go near mine for all the beer in Bishops Stortford. 

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2 hours ago, Tony Brooks said:

You could but I suspect the crazed ones are acrylic. There are two common forms of clear glazing, Acrylic and polycarbonate. Acrylic is a bit cheaper but softer so it scratches easier. I would suggest that you use polycarbonate. Perspex is just a trade name, I think it is polycarbonate but not sure so best to use the material  name and don't worry about the trade name. Personally I would not trust the likes of B&Q not to call any clear plastic perspex because perspex is a bit like hoover in that many call any vacuum cleaner the hoover.

Perspex is actually an acrylic.  Poly methyl methacrylate to be exact.  It is harder and clearer than polycarbonate (Lexan and the like) which is very tough ( so good for riot shields) but scratchable and a bit prone to going yellow.

 

  For windows an acrylic is OK.  With a bit of practice acrylic sheet can be cut like glass- score and break, but a pendulum action  jigsaw, fine blade, used gently, at slow speed on well supported material has always worked for me.  Use masking tape to mark out on and cut through.   Don't go mad, if the acrylic gets hot it melts and sticks to the blade. Disastrousess ensues. Leave the protective film on both sides for as long as possible.  Ideally you want it there until the window and its frams are fitted to the boat.

 

Cut a bit large and shape to size with a sharp smoothing plane or surform, working along the edge.  That will take out the saw marks and any tiny cracks which can otherwise grow into your new window pane.

 

Alternatively find one of the on line firms that cuts to shape and send them a template.  Let them have the hassle.

 

N

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4 minutes ago, BEngo said:

Perspex is actually an acrylic.  Poly methyl methacrylate to be exact.  It is harder and clearer than polycarbonate (Lexan and the like) which is very tough ( so good for riot shields) but scratchable and a bit prone to going yellow.

 

  For windows an acrylic is OK.  With a bit of practice acrylic sheet can be cut like glass- score and break, but a pendulum action  jigsaw, fine blade, used gently, at slow speed on well supported material has always worked for me.  Use masking tape to mark out on and cut through.   Don't go mad, if the acrylic gets hot it melts and sticks to the blade. Disastrousess ensues. Leave the protective film on both sides for as long as possible.  Ideally you want it there until the window and its frams are fitted to the boat.

 

Cut a bit large and shape to size with a sharp smoothing plane or surform, working along the edge.  That will take out the saw marks and any tiny cracks which can otherwise grow into your new window pane.

 

Alternatively find one of the on line firms that cuts to shape and send them a template.  Let them have the hassle.

 

N

Ta, I knew there were two different clear ;plastics, got their properties the wrong way round.

6 minutes ago, BEngo said:

Don't go mad, if the acrylic gets hot it melts and sticks to the blade. Disastrousess ensues.

 

Absolutely, the slowest speed, take care not to force the jigsaw and I found having an assistant blowing cold air from an airline onto the cutting face not only helped prevent melting but also kept the job swarf free. I wonder if spraying a fine water spray would also keep the cutting face cool.

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27 minutes ago, Tony Brooks said:

I wonder if spraying a fine water spray would also keep the cutting face cool.

Yes, but I am not sure the jigsaw is going to like it, either on the sliding bits, or in the cooling air ports.

 

I have seen jigsaws with a built in blower, but that was more to keep the swarf away from the cut so you could see where the blade was going.

N

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3 hours ago, BEngo said:

Perspex is actually an acrylic.  Poly methyl methacrylate to be exact.  It is harder and clearer than polycarbonate (Lexan and the like) which is very tough ( so good for riot shields) but scratchable and a bit prone to going yellow.

 

  For windows an acrylic is OK.  With a bit of practice acrylic sheet can be cut like glass- score and break, but a pendulum action  jigsaw, fine blade, used gently, at slow speed on well supported material has always worked for me.  Use masking tape to mark out on and cut through.   Don't go mad, if the acrylic gets hot it melts and sticks to the blade. Disastrousess ensues. Leave the protective film on both sides for as long as possible. 

I spoke to the Mrs who has 20 plus years experience working in the design and tech department of a very large school - she was the technician responsible for setting up all the students work and cutting acrylic and polycarb were part of her daily job.

 

She agrees fully with this. Said that the kids would use a coping saw to work on the small projects and that even that, if worked too fast, would melt the edges.

 

She had the luxury of all the machine shop tools - CNC, routers etc so when we came to make our internal clip in double glazed acrylic porthole windows we just sent the sheets in to the school and they were done on the laser cutter which gives an absolutely perfect edge. Her advice for something like boat windows would be to get a machine shop to cut it, because doing it by hand will be very slow and you can guarantee that you'll be just about at the end of the cut when it overheats and trashes the entire thing.

 

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46 minutes ago, George and Dragon said:

Absolutely.

 

If the OP is near a major town there will almost certainly be a business that can do this for them. 

 

They're very unlikely to do polycarbonate though as it catches fire when cut and is very difficult to achieve decent definition with. Acrylic cuts beautifully, but then there's the problem of durability 

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