Cardboard instead of plywood?

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matt167
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Location: Prattsville Ny

Cardboard instead of plywood?

Post by matt167 »

My work ( ski slope ) is having a cardboard downhill racer derby on Saturday and I thought about getting out my drift pram plans and building one out of cardboard, duct tape and string ( 3 allowed components ). But, it's in 3 days so it's too late.. However, that gave me an idea. UPS shipping centers, and other places sell 4x8 sheets of cardboard in various thicknesses. In the past I have fiberglassed boxes with poly for cars so that they were sturdy and could be carpeted and used as cleaning supply organizers for trunks. What I'm thinking is using the cardboard for a form that would remain inside, wetting it out, then laying it up with a few thicknesses of CSM, finished with some cloth. Seat boxes would still need to be plywood, and it would need stringers front to back and a deck along with a plywood backed transom, but in the case of the 8' drift pram, it would cut the hard materials list down to 2 sheets of cardboard and 1 sheet of 3/8" Marine ply, but it would be a fiberglass boat and could be built with polyester resin.. Anyone think this could actually work?

Trackhappy
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Location: Sunshine Coast, Queensland, Australia. Building Gentry.

Re: Cardboard instead of plywood?

Post by Trackhappy »

Sounds feasible. Should come with a "Dangerous Goods" label though for future buyers ...
Any small crack would let the water in , which would soak the cardboard and become a very soggy mess inside. Apart from becoming very heavy, not sure what other bad effects it may have.
By the time I have built a boat, I'll be ready to build a boat....

jcallends
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Location: Coldwater Michigan

Re: Cardboard instead of plywood?

Post by jcallends »

Do you really meam corrugated board? If so then the previous post says it all except many types of corrugated board are made of plastic and is used for all kinds of things. Political signs and RC airplanes come to mind immediately. Plastic board would solve the water problem but would create others noteably adhesion. Sounds like a good idea to me but needs some developement.

matt167
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Location: Prattsville Ny

Re: Cardboard instead of plywood?

Post by matt167 »

Coreplast used in sign making would work too, which is just common plastic corrugated board used in sign making. I'v never fiberglassed it, but if sanded it should stick, but it's pretty expensive so there would be little cost savings other than being able to cut with a cheap razor blade. The intentions with the cardboard would be to saturate it so that it has resin through 100% of the structure. There might be a slight amount of dry paper on the inside but from my experience, cardboard soaks up poly resin very well. If I did the inside and let it stiffen, then I could then saturate the outside without any distortion and keep it wet and lay up the fiberglass. Fit the wood components on the inside, sand the resin coated fiberglass and then lay up the inside. Total fiberglass thickness should be in the 3/8" range with only 1/8" or so being cardboard

If I were even to consider selling something like that, I wouldn't sell the first attempt and I would see what kind of damage it could take and still float in a 6' deep pond.

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jprice
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Re: Cardboard instead of plywood?

Post by jprice »

If the idea is to just to try something different, then I think it's a cool idea, and could probably work.
If the idea is to save weight, then I think it's a bad idea. All that resin soaked CSM would probably end up weighing more than the plywood.

matt167
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Location: Prattsville Ny

Re: Cardboard instead of plywood?

Post by matt167 »

More than likely weigh more than a wood boat but not more than a run of the mill 'glass boat of the same size..

I still have the wood version of this boat I have to finish, and then my big boat ( 1961 Custom Craft ) needs resto so this will likely not get done for a while, but I'm thinking on ordering extra resin/ CSM and 1708 with my big boat order so I have the materials to start on the cardboard construction boat. Just to see if it works or not. I think they could be built faster and make a work/ fishing boat easier

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Mr Hot Rod
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Re: Cardboard instead of plywood?

Post by Mr Hot Rod »

If using carboard, seal the mold with cheap enanel or acrylic enamel automotive paint. When cured, apply PVA release agent or wax and polish the mold before laying up the hull. Using cardboard as a core material is a bad idea. It has no structural strength and will wick up a significant amount of resin which will produce a resin-rich brittle lamination and add unwanted weight to your hull.

FRP is an engineered product, so to determine your hull's fiberglass skin thickness, I'd suggest ordering Ken Hankinson's book Fiberglass Boatbuilding for Amateurs. You'll find most everything you need to know about molding techniques and materials. Conversion factors for converting between plywood, fiberglass, aluminum and steel are also covered.

Here's a recent post which may be of interest in the plywood alternative thread :

____________________
Paul Kane
Kane Custom Boats Ltd.
Chelsea, Quebec

Building the Glen-L Hot Rod : http://www.kanecustomboats.com

Glen-L Boat Video Directory : http://www.kanecustomboats.com/pages/vi ... ctory.html

matt167
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Location: Prattsville Ny

Re: Cardboard instead of plywood?

Post by matt167 »

That makes sense. I thought about using the cardboard as a mold. That would work great. I have PVA release agent somewhere but it may not be good anymore.

polarisman14
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Re: Cardboard instead of plywood?

Post by polarisman14 »

Plus, keep in mind if you are using decent quality resin then the expense of soaking the entire thickness of cardboard with it would get expensive pretty quickly. If you're looking to craft something on the cheap just use B-C grade ply or luaun instead of marine grade ply and go a little thicker on the fiberglass.

matt167
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Joined: Wed Sep 05, 2012 8:03 am
Location: Prattsville Ny

Re: Cardboard instead of plywood?

Post by matt167 »

I'm thinking more into this, except bigger, as in Console/ Cabin Skiff big. someone on a hotrod forum scratch built a 1933 Ford body out of cardboard and then wrapped it up in duct tape and laid 'glass on it, then ripped the cardboard out from the inside when it was done as duct tape does not stick to 'glass... My thinking is that the hull could be made of cardboard wrapped in duct tape, the form/ bulkheads used for shaping could be made out of any old plywood, then after I have a fiberglass hull, I could build the bulkheads, stringers and transom out of ABX plywood bedded in polyester resin filler as is common with fiberglass boat restorations. I would need to make a fiberglass cap like a regular fiberglass boat, but more cardboard could be used as a mold along with some ABX plywood to make the cabin which could be fiberglassed or just sanded and painted.

Still working on my old Custom Craft and the 8' drift pram is sitting, but I'm thinking I'm going to order extra materials and try this when I get time to.

I want a cheap boat to cruise the NY canal system and rivers. Looked into the Lewis boat works Chugger and had an idea to build it to 18' with a wider beam, but I'm not sure of the construction and by the time I fiberglassed below the water line, used the right woods, nails and sealants to build it as correctly as I could I would have a lot of $$$ invested into a realisticly non sea worthy boat, great for my intended purpose but with no capability of even remotely rough water.

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