Modified polycarbonate

What's to say these "different properties" make it more suitable ? Could be less for all we know. As for the "poor attitude to life", have indeed tried risky experimental things, but you have to weigh up the odds of success, it is one thing to revel in the idea you are a pathfinder going where none have succeeded before, against a sober assessment of just why that success may have eluded others. That we are way smarter than the average person that has tried, is apt to be an inaccurate assumption.

 

Thats where you are incorrect, its not about being smarter, its about chancing upon something different. Like you said might not work out but its poor attitude not to try just based on negative assumption and speculation and fear of falling of the disc

 

Unless there is some peculiarity of this modified material that somehow opens the possibility of it being suitable to make boats, it won't be working out, or we would have seen polycarbonate boats galore out there. In sporting parlance it is a low percentage play, like the miracle pass that comes off once in a blue moon, the rest of the time you look like, and are, a mug.

 

Lol if trying something different and failing is the hallmark of a mug then so be us, better then being a cow following the herd. Enough words wasted on your negativity. Now back to having fun making boats!!

 

Take your polycarbonate sheet and pour some petrol on it. That should frighten you enough. You will not avoid your boat coming into contact with petrol and it's derivatives for ever, whether on the sea or inland. FWIW polycarbonate will craze (very fast) and become structurally useless. There are some very special coated polycarbonate applications which have a special film on the surface and some heat treatment to help retard this crazing. Motor sport and motorcycle visors being one such application. The UK test is a 6mm steel ball at 130 mph (200Kph) without breakage.

Absolutely no way I would make a hull out of it except as a vacuum formed limited life knockabout for inland use only. A Drascombe lugger type out on the open sea would evntually, maybe days, maybe a couple of years just fall apart.

 

Ok - an update at last, as I've been waiting for the epoxy to fully cure before subjecting the test pieces to any destructive testing.

The 3-ply laminate (circa 4.5mm) stiffened-up very nicely as the epoxy cured, and it's stiffness would certainly have been sufficient for boat-building - about the same as 6mm plywood, more or less.

Ok - testing - firstly I hammered nails into a single thickness sheet fairly near the edge, expecting it to split - which it didn't. I then did the same with the 3-ply laminate sheet. Same story.

Thinking I might be onto a winner - I then subjected the 3-ply test piece to the 'big hammer test' - this being a good clout with a 2lb lump hammer with the test piece held in a vice, using about the same force that would drive a 2" nail approx. 3/4" into hardwood. Nothing more than a hull would experience if pushed hard against pilings by another boat's wash.

Much to my surprise and disappointment the test piece shattered. I was hoping that the laminate would at least bend, showing some evidence of ductile distortion at the bend point. But such an abrupt and catastrophic mode of failure quite clearly makes this material completely unsuitable for boat-building.

 

This is pretty much what we and others have been saying for the last couple of weeks. Most monolithic plastics aren't strong enough to make much of a boat. There's a reason that fiber reinforced composites have been used for the last 60 or so years for boat building very successfully.

 

Try it again, but this time "caramelize" the surface with a torch, after applying an aggressive tooth (80 grit or less) with paper. You'll dramatically improve the bond, though I suspect the physical properties will still exist, it would be interesting to see if the improvement is "good enough".

 

I am a little dubious about the tests applied to the laminated material, and just how well they replicate "field" conditions. Rather than restrain it in a vice, I'd be more inclined to support both ends of the panel on pieces of timber, then walk on it, jump on it etc, and compare the performance with plywood. but you still have this issue of stress cracks that travel, to contend with, that won't apply to ply. Are you using epoxy to laminate it ? Sounds expensive, you might try interleaving it with fine glass cloth to restrict the cracking, but in the end you finish up with something that seems to have no advantage, including that of cost.

 

Agreed, I think crack propagation and interlaminate sheer will ultimately prove this combination, less than desirable. It's flexural qualities as a laminate, will constantly test the glue lines under load.