Polycarbonate or perspex

I beg to differ.   

Polycarbonate is very soft and almost indestructible by impact, it just deflects and recovers.  I recall it was/is used for the bodies of RC model racing cars and it will never split or crack from an impact, but because it is not hard it scratches very easily.  I would suggest that it is quite unsuitable for windows for this reason. 

Perspex (acrylic) is hard, brittle and must be worked with care - for example holes should be drilled with a blunt drill bit that wears away the material and doesn't snag on it.  I have used it for the windows of my last three boats, including heavily curved windows on an Edwardian style launch, all with great success.  It is not as hard as glass, and will scratch, but not to the extent of polycarbonate.

So, perspex acrylic every time.  Of course if you really want it to be bullet proof then thick polycarbonate is essential, but it would need to be about an inch thick, and you would need to replace it every few weeks because it will get scratched quickly.  I have suffered several reasonable impacts on my perspex windows when navigating through tree-strewn backwaters against a strong current, but no damage that couldn't be polished out  in no time.

I used a mini circular saw (the blade is about 40mm diameter) to cut straight and slightly curving cuts, if done with care it will not shatter.  A very fine jigsaw blade might work, but it will probably clog very quickly.  I fired up the cuts with a belt sander medium grit, done very gently.

bodger that's another question how do you polish out scratches? Do you use a proprietary perspex polish or something else?

Perspex can be scored and snapped like glass, a cutter can be be made out of an old hacksaw blade. I may well have one in a drawer in the shed, I can send you a pic. For straight cuts it's the easiest and cleanest way. The problem with a jigsaw and probably a slitting disc, the heat generated melts the sawdust and it sets in blobs behind the blade.

5mm is what I will use. Interesting option if I can snap it like that. I was wondering about clamping it between two pieces of wood in the vice then scoring the line somehow but not sure how to get it deep enough.


Clamped upright like that then slitting disc along the top of the wood board as a guide is quite interesting then tidy up the edges with a sander.

That would be a pretty quick way to process the stuff. I also have some psycho circular saw blades for the angel grinder but that's a bit mental.

if you're lucky it will follow the score, but it is not as brittle as glass so it doesn't always break as you would like - you may waste a large and expensive sheet of perspex doing that.

please don't ask me how I know.  

Thanks for that it's an interesting option for the straight 'edges.