by angib » Sat Jun 23, 2007 6:57 am
My experience is that heat guns aren't a good way to try to mould plastics - it's just too difficult to get the temperature right over the whole object and too easy to put too much heat into one place (causing little bubbles inside the plastic). An oven would be nice, but even better is a radiant heater - like an old, old electric fire with those glowing-red bars (did you have those in Merka?).
But do you need any of this? Thin plastic will be just as strong as your plywood and will bend about as easily - in fact it will bend a lot further than the ply before snapping. Polycarbonate (eg, Lexan) would be good, as it is so strong. The only thing to watch out for is the window trying to pull the wall flat - for that reason, I'd choose glazing no thicker than the plywood, and even then you'll have to watch out for flattening, as the plastic is stiffer than most ply.
A backing ring of ply on the inside and a very thin trim ring cut from aluminium sheet on the outside would give you a strong joint and a waterproof seal - again, you would need to watch when fitting the ply backing ring that you didn't flatten the sidewall locally.
Andrew