Modified polycarbonate

Like the man said, all the stuff about the regular polycarbonate is irrelevant, his material is different. Someone has to be the first one to use a potential new material. He has some on hand and is ready and willing. I am keen to see how it goes. May work and may not, but if it does then great. If it doesnt then lots still learnt. I am constantly amazed with the attitude on this forum. Lol if there were some more of that attitude going back through history then the world would still be flat

 

Well, if you are at sea and the hull splits wide open you are risking your life as well as the lives of all the others aboard. I've used polycarbonate, cut it and broken it, and building a boat out of it probably isn't a good idea based on my limited experience. The reason for that is that if you start a crack in the material it simply splits because of the notch sensitivity.

Fiber reinforced composite materials don't spit or crack like monolithic materials and if they get hit the can withstand the damage with only some local delamination.

It's kind of like making a section of a bottom of a boat out of polycarbonate so that you can have a glass bottom. If properly framed and reasonably thick it can be made safe in glass or polycarbonate. But making the entire hull out of such a material could easily be a disaster if the hull splits wide open.

While the material was free, that doesn't mean you should risk your life trying to use it for something that it was never intended for. If someone gave you 3,000 pounds of lead, that doesn't mean you should make a boat out of that either...

Take the polycarboante, sell it, and buy some material that well suited for the construction of a boat and the OP will be a lot better off.

 

Unless you can tell us the difference between "compax" and regular polycarbonate that makes it more suitable as a hull material, we are none the wiser, for all we know it may be less suited. If the thing goes down into Davey Jones locker because of hull failure, it is potentially a life-altering choice. Even a life-ending one. ( cue dramatic music)

 

Lol and he could fall of the end of the world

How did the first maker of a ply boat know it will be safe? Glass? PE? Wonder what the 'experts' had to say when they raised the concept? I dont have to know if its more suitable or what the difference are, but it will be a good experiment to watch. Someone has to be the one to first try out a different material

Looks like this fella is willing and from how he has raised the concept I cant see him being as the type to duct tape it together and whacking huge donk on and going for 40 knots

 

Yes, a good experiment to watch, maybe less so to be the "guinea pig". Polycarbonate is not some new-fangled wonder material that arrived recently, it has been around a long time, the fact it has not been adopted as a hull material tells me something.

 

Do you mean that particular polycarbonate has been around for a long time and has not been used for hull material?

Thought that was some new stuff with different properties to regular stuff?

 

You seem to be confident this "new" polycarbonate changes the game, what are you basing that on ? As I said earlier, it may be less suitable for all we know, do you have some insight into that ? I think it a very low percentage probability that the OP has happened on something that is well adapted to the purpose he proposes.

 

Huh, where did you get that beauty from! I wouldn't know anything about it but as I stated previously am very interested in seeing how it turns out, in pretty simple English I might add

Well did you mean that particular polycarbonate has been around for a long time and has not been used for hull material?

Thought that was some new stuff with different properties to regular stuff?

Are we about to fall of the end of the world!!!

 

I very much appreciate the 'heads-up' on this aspect - indeed, it's the one feature which continues to trouble me. On my excursions around scrap yards hunting for stainless steel I've often seen machine guards made from >10mm clear polycarb which have failed as you describe - around the bolt holes, even when these have been an inch in from the sides.

Although my reasons for laminating are principally to gain stiffness, perhaps such laminations will act to spread the stress concentrations which are the origins of such crack formations ? - who knows - only destructive testing of samples will reveal that.

The epoxy on my first test samples has now set, but I'll let 'em cure for a few days before testing. First impressions are a little disappointing, as I'd hoped for more stiffness than appears to have been generated. It may be that this stuff is best used as a skin material - so I'll make up another test piece this evening in the form of a plywood-filled sandwich.

To clarify (a little, but not much ...) this stuff has been chemically modified to make it more physically 'stable' when subjected to the heat from continuous sunlight - as one might encounter in countries such as Israel (where it is known to be used) - so that it won't buckle or warp, as dark-coloured uPVC most certainly would - so that it can be used to manufacture moulded exterior doors etc. by vacuum thermo-forming and such-like. So thermal moulding and subsequent bonding with 2-part adhesives is how this stuff is normally treated - but not secured with screws or bolts. Bummer.

I asked the tech dept in what way it had been modified, and they just laughed (albeit sympathetically) ... so that's clearly a commercial secret, with only one company in the world making this particular sheeting. So - the only option is to 'suck it and see'. Either that, or junk the stuff.

But don't fret about the hull opening-up at sea - this stuff will be subjected to exhaustive testing (including the 'big hammer test') long before it's used to build a boat with. At my age, I'm not afraid of dying, but have no wish to accelerate the mortality process.

 

Hey mate, have you came across this thread yet?
http://www.boatdesign.net/forums/boat-design/3-5m-hdpe-jetboat-44992.html

A very different type of plastic from what you have but its built using sheets. Is there a way you can use your stuff like this? Does it heat weld? Or can you use in conjunction with fibreglass fabric and create box section stringers and frames and get a good stiffness?

I was checking out corrugated plastic that is used in sign making, I think its polypropylene but not sure. Individual veneers of that stuff makes for pretty floppy but creating a structure between the veneers makes it board like. I wish I could get my hands on things like what you have, would love to tinker!
Would be great if a way can be found to make good use of it as a replacement for ply. I love plastic boats btw

 

Great experiment - somebody's got to do it....
Thermal expansion/contraction in sheet plastics has bitten me a few times - I wonder if the cold water side of the lamination would play well with the hot sun side with epoxy as the referee? Just a thought. Moe

 

Thanks for that link - good to see that there are other lunatics out there building boats.

It's proving difficult to see exactly how to use this stuff - the basic problem is that the sheets are all 7ft x 3ft (i.e. front door size ), but only 1.5mm thick.

It probably does weld, but the problem again is the bl##dy thickness. In order to make it stiff enough, it looks as if it'll need to be laminated. But - once laminated, could I still weld it ? My gut says that the epoxy would be badly damaged in the process. But - it's certainly an idea worth keeping on the back burner... Your suggestion to use in conjunction with glass etc, is where my thinking is focussed right now.

Just for you - I've attached a few photos of my source.
The first two just show the operation as seen by joe public.
The second two show what's around the back, where all the grot and garbage winds up. Lovely, lovely sheets of plastic - which nobody wants. Maybe there's something similar near to where you live ?

'best

 

Yeah - a good thought, too ...

I've just looked up some Coefficient of Linear Expansions
(expressed as 'mm per metre per °C') - here are some:

Compax = 0.065
epoxy resin (unfilled) = 0.055

So that looks good - except I usually use talc as a thickener - which will reduce the CofLE even further - as does glass.

Polycarbonate = 0.070
Glass Reinforced Polycarbonate = 0.021

Here's a surprise:

Acrylic, sheet, cast = 0.081
Acrylic, extruded = 0.234

Who'd have thought that exactly the same material, albeit produced in a different manner, would have such different characteristics ?

 

Anything that "fell off the back of a truck" usually brings problems ! Seeing that the actual cost of material to sheet a hull is not that great a percentage of the total cost of creating a viable vessel, what you gain if it actually works isn't that much, but everything you put in, including your time, is wasted if it doesn't work. Easy for others to say "go for it", no skin off their nose if it all goes awry.

 

That's a very poor attitude towards life Mr Efficiency. Even when things dont work out there is much to be learnt. The important this is that the person who wants to experiment recognizes the possibility of failure and addressed the possibility or wastage along various fronts. Have you ever achieved any thing unique and risky that sets you apart from the masses? How about answering the question I have put to you twice?

SAE140
Mate wading through the negativity and all that, when I see your pics the thought I get is about my old boat. Mac 360 Attack from NZ made of PE. They used the pontoon concept to make a rigid hull. How rollable is that stuff you have?

I have this image forming in my mind of sheet on tube type boat made of your sheets. I like boats under 4.5m. Here is what I would explore a 4m concept

Pair of tubes
Splice the sheets so it will form a pair of 4m tubes with a max diameter of 50cm once rolled with an oval cross section. Rip 3" strips and attach those to the sheet like stringers. Maybe using 'L' brackets fabricated from fibreglass. When that is rolled it could possibly make a very rigid tube. Cut the ends of the tube at a slant that will give a nice bow shape when the tubes are placed 2m apart and skinned

Support structure
Make some more thin diameter tubes to use as a keel and stringers. Make a transom in the manner of a inflatable boat with something substantial like laminated ply and make some lateral frames that would slot over the keel tube and stringers on the bottom and make for a flat floor support over the top

Skin
Form the sheets over the framework of tubes and laterals. Laminate the whole lot with glass. Fill the lager chambers with foam

Inside the hull make a honeycomb structure to support the sole. Laminate some strips and make hard chines and strakes and such

Well that's the type of boat that I see being built from that and something I can execute using the basic set of tools I have. As to whether if any of the engineering is valid in that I wouldn't really know other then intuition says it could work. Would prolly strap on a lifejacket and what an 8hp and see what happens, if all good then try increasingly larger engines until something starts groaning. Just watch the horizon so I don't fall off the end