Are you using polycarbonate or just an acrylic? My poly-carb started to crack around mounting and flood holes I drilled in my ballast tank area of my WTC. But only after a rupture in my gas line. The poly-carb didn't like the extreme cold I guess. Haven't seen cracks like your's though. Ted SC# 611
The vast majority of acrylic and polycarbonate tubing is extruded and tends to have stresses in it. For the most part this doesn't pose a problem for our models. However there are different grades of the material, and some acrylics can be very fragile. I can't speak for polycarbonate, as I've only used polycarbonate in sheet form,and that was GE's lexan, which is probably the best out there.
That tubing looks like it received a whack at some point. Has it ?
The only time I have had lexan crack like that I was gluing something to the wall and hit it with kicker. It must have had a stress line right there because the heat made it shatter. Ive tried to reproduce the effect with no success though. My conclusion...Bad luck.
I am not aware of any hits to the tube. The tube had no visible signs of cracks just prior to the ones you see here. It has been sitting in my shed for some time as I worked on it on and off. I has been hot down here and in the shed the temps may be too hot. Perhaps the heat?
I am not sure of the composition but can find out.
I think that SubCulture is on the right track.
In any production process, a certain percentage of the production shows some flaws. It seems to me that your tube is from a less-than-perfect production batch and the high temperatures in your shed have brought its flaws rather clearly and dramatically to light.
This reminds me of an instance when I sprayed the inside of a cylinder with electrical contact cleaner, just after I had sunk a model and soaked all my electrics. (I'm good at sinking 'em)
The water was removed but the next morning the cylinder had crazed and looked more like a shattered windshield. I was horrified. I poked the crazing and it opened up. If I had pushed it more it would have fallen apart into hundreds of pieces, just like a broken windshield.
However, I repaired the cylinder (still good today) by painting a wet coat of methyl methacrylate (windshield repair material) or the raw material for Plexiglas or Lexan. The liquid melted the cylinder pieces and they welded back together. Methyl Methacrylate has that 'solvent weld' capability.
I like the clear PVC idea. How is it for "standard" end caps? You say it works but I did not understand the routing of the edge completely.
What sort of cost is there to the PVC? How does this compare to the usual stuff? BTW, The tubing I have been using comes from a local supply company. I am wondering about the mixture of the material. It may be too brittle and time, temp and stress do it in. the tube in question is over two years old.
I think there's been a misunderstanding. The point I was making about PVC here in the UK is that it's only easily available in opaque form, i.e. grey, black etc. and that the PVC is filled for the pipe to be this colour. PVC in it's natural state is transparent, but it's difficult to find a supplier of transparent PVC, and when you do the price is very high.
Lexan tubing is also difficult to procure here in the UK, which is why most model submariners use Acrylic tubing or opaque PVC, both of which are inexpensive and readily available.