Model Boat Mayhem
The Shipyard ( Dry Dock ): Builds & Questions => Lifeboats => Topic started by: lesfac on April 14, 2017, 08:20:23 am
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Heres a bit of information that I have learned the hard way.
If you apply a solvent to perspex which has a polished edge it causes the edge to propagate small cracks that sparkle in the light. If you are going to paint it then no problem but if not it might be a visual issue.
I have been building the windows for my 1/12 Severn and let me say immediately that I didnt follow the advice to use silicone glue because I overlooked it. I thought plastic weld would do the job of gluing in the clear perspex. However on using it and looking at the window I could see sparklies around the edge of the windows which looked unsightly.
Fortunately I was able to disassemble what I had done. I found that on putting solvent on a laser cut edge the sparlkies grow from where the solvent is applied. I thought this must be something to do with the laser cutting setting up stresses but on reading up on it since I found that this will happen on any polished edge on acrylic and laser cutting leaves a nice polished edge.
I read that if you are bonding perspex it helps to rough up the polished edge although the advice I read said to take 1/32 or 1/16 off which might not be possible.
I got some 3mm perspex and remade the window panes milling them and sanding what I couldnt mill (rads) I found that the milled edge did not make the sparklies like the polished laser cut edges.
Of course if I had followed the instructions remaking the window panes would not have been necessary.
Hopefully sharing this will save some one else having the same issues
Les
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5 min. or normal Araldite works as well. If you use superglue it will turn clear perspex white especially if in enclosed locations.
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5 min. or normal Araldite works as well. If you use superglue it will turn clear perspex white especially if in enclosed locations.
most super glues will do that . There are super glues made to glue perspex and will not cloud them up .
John
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Many plastic welds are used all the time on perspex without cracking , it depends on the perspex and the plastic weld formula all are different.
Some perspex is extruded some cast , but usually with a polished or smooth laser cut edge there are no problems with a good plastic weld usually its due to scratched rough cut or poor quality cheap acrylic,
I have never had cracking with our Poly-Weld on extruded or cast acrylics it is made for use on perspex as well as many other plastics but it could always happen with poor grade acrylics.. but... i have never seen it in tests or model building, we always have bits of perspex and other acrylics welded with it on display at shows.
Any plastic weld with acetone or mek in it should be avoided on perspex some sell them as plastic weld or mix in to reduce cost or posting weight as mek and acetone are lighter and cheaper than things used in industrial grade perspex welds.
Using a water free canopy type glue would give a clearer and better bond than silicone as silicone tends to be slightly cloudy and tend to yellow with age. Odourless cyano would also be suitable as it would not fog.
Standard superglues can also...if too much is put on...cause micro cracks to form on a lot of clear plastics but it is very rare and only with a non polished edge.
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most super glues will do that . There are super glues made to glue perspex and will not cloud them up .
John
Hi, Do you have any product names that can be used please?
Dave
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We used to get this affect "Crazing" years ago in the days of Methyl Methacrylate which is not a cross linking material. Problem stopped when it became cross linked,ie ethyl methyl methacrylate. Nemesis
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Hi, Do you have any product names that can be used please?
Dave
Hello Dave
It is made by Deluxe Materials and is there odourless rocket glue . I use it to glue in the windows on my bridge . No problems at all.
John
https://www.deluxematerials.co.uk/gb/24-cyanoacrylates-epoxies
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I make the cases for my miniatures from clear Perspex and use contact adhesive to put them together. It works very well.
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Canopy glue is the stuff to use....dont panic when you apply it,it will look milky at first, but dries perfectly clear and it is the stuff the flying lads use to stick the canopies on their planes..
Dave
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Hello Dave
It is made by Deluxe Materials and is there odourless rocket glue . I use it to glue in the windows on my bridge . No problems at all.
John
https://www.deluxematerials.co.uk/gb/24-cyanoacrylates-epoxies (https://www.deluxematerials.co.uk/gb/24-cyanoacrylates-epoxies)
Thank you John.
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When i used to a lot of perspex boxes we used sonic welding. Not much use but it worked a treat