We’re about to replace the left (port) rear window on our DR1050. It was cracked during wing replacement. The last item before flying.
We’ve got an acrylic sheet, bought when we replaced it about 10 years ago.
Someone saw a YT video comparing a acrylic with polycarbonate, and the majority seem in favour of waiting and getting polycarbonate.
Have any of you experience or views on this? It’s the side with the rear tank filler.
Acrylic cracks easily when being drilled but once installed is good because you can polish out scratches. Polycarbonate is stronger, less notch sensitive and therefore much less fragile but the material is soft and gummy so scratches cannot be removed over time by polishing. I’d try with the acrylic on hand and use the correct flat angles drill bits to drill any holes.
I have both on my Onex. The wind shield is polycarbonate (Lexan), the canopy is soft acrylic. Polycarbonate i “unbreakable” (almost literally), but acrylic has better chemical properties and better optical properties. With acrylic you can saw and drill easily, but you have to take a bit care, too aggressive and you can chip out larger pieces than you planned to. With acrylic you don’t really drill or saw, you rather sort of melt the drill through, or cracks will develop on an instant. There are special drill bits for acrylic, they work just as well on polycarbonate.
The ordinary European (DIN) drill bits are way too aggressive. US aluminium drill bits are much better, but still a too aggressive. OK for polycarbonate in my experience, but not for acrylic. Acrylic drill bits have a much more pointed angle as well as barely cutting. You really need a drill dressing tool to make it yourself.
Polycarbonate will get duller over the years due to chemicals (fuel) and the sun probably, and there is no way to fix that other than replacing it. But it is really easy to work with, so making new ones is a piece of cake. Acrylic lasts for ages, it can be polished and fixed, but cracks very easily.
I would also say go with the acrylic at hand, and replace when/if needed either with polycarbonate or acrylic.
LeSving wrote:
With acrylic you don’t really drill or saw, you rather sort of melt the drill through, or cracks will develop on an instant.
It looks like you don’t want to melt it, either. There is a video on Youtube showing alcohols (ethyl, methyl, isopropyl) causing the propagation of cracks in acrylic; as it turns out, intact acrylic surface is immune to alcohol, and so is a sawn-off edge. However, if the edge has been flame-polished (i.e. the roughness has been melted off), dipping it in alcohol causes cracks to appear within seconds. Apparently, melting the surface creates some kind of stress in the material (mechanical or chemical), and then alcohol triggers the cracking – a pure chemical interaction with alcohol cannot be so fast. Bottom line: I would suggest water jet cutting.
Thanks guys. We’re fitting the acrylic sheet (which we already had) next week.
Ultranomad wrote:
Bottom line: I would suggest water jet cutting.
Forgot to mention. Acrylic absorbs water, up to 10% if left soaked. I don’t think polycarbonate does that, but I’m not sure. I agree, water jet cutting is probably the best method though, but who got a waterjet cutting machine readily available ? 
