Flexing Paint for a Folding Boat?

Discussion in 'Materials' started by netbuz10101, Oct 6, 2012.

  1. netbuz10101
    Joined: Oct 2012
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    netbuz10101 New Member

    I am currently working (slowly) on a Flapdoodle Dinghy.

    Here is a link to the inventor's site to get an idea of what it is.
    http://flapdoodle-dinghy.tripod.com/

    It is basically four panels with a keel strip. They are stitched together at the seams and keep water out with pvc cloth. the boards flexes quite a bit and regularly, going from a flat surfboard shape, to a curved boat shape. This is a boat that spends only a few hours in the water at a time.

    The plans recommended varnishing first, then painting.

    I used some Elmer's wood filler (the grey tub that is somewhat gritty) when a jigsaw blade caught in the wood and went wonky, and when large splinters caught my sandpaper in a few spots. It recommends an water based paint over top of it.

    I got some advice that exterior paint would be okay, but my understanding is that it is brittle and perhaps not best suited for this boat.

    I am a poor student right now, so cost is the biggest factor, but I don't want to throw away this project just because i did a poor job of protecting the wood. I have time, no money, and limited experience.

    I would like to protect my marine ply as best i can, and wouldn't mind touching up the paint whenever it gets scuffed.

    Any advice would be helpful.

    Thanks a bunch
    -David
     
  2. CDK
    Joined: Aug 2007
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    CDK retired engineer

    Chlorinated rubber paint is what you need. It is used for text and decorations on truck covers, tarpaulins and anything else that must be flexible and weatherproof.
     
  3. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    I've used the Krylon Frusion paint on sails and poly tarp and it's held up well, considering how it must flex, though the rubberized paint CDK's suggesting will likely out preform it.
     
  4. netbuz10101
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    netbuz10101 New Member

    Hmm. Do you mean for painting the pvc cloth, or the bare marine ply? Painting the cloth is not a bad idea. The cans look pricey based on a quick google search. I was mostly concerned about the wood. The pool paint instructions I found are also not very helpful. I'm not sure how to apply that type of thing to plywood. Acid Etching!? That'd be dificult to do at my appartment complex! Am I looking at the wrong thing?

    This may not be a bad idea for the pvc cloth, and all i'd need is a can. I'm not sure how well it'd work on wood even though it says it is compatible. It's also a lot more surface area than the cloth (a little over 130 square feet of coverage for the inside and out) .

    I was looking for something I could paint multiple coats of onto the marine plywood for a little more abrasion resistance without going up to specialty products. Something I could just slather on a bit more when the paint get's banged up.

    Perhaps I was exagerating the amount of bending going on (Easy to do when all i have a flat panels on the floor). Take a look at the video of another Flapdoodle to get an idea of how much flexing is required.

    http://www.youtube.com/watch?v=Z4u_06UjVQU
     
  5. rwatson
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    rwatson Senior Member

    For what its worth, a freind and had a 16ft Folbot (folding kayak) that had very severe folding on ********. he used to carry a can of rubberized compound on each trip, as it would invariably end up cracking overnight and letting in water.

    I was building very light canvas kayaks at the time, using a product called 'Brushable Hydroseal', a not too thick, black , bituminous compound that was able to be painted onto wet surfaces, and immediately immersed. It was designed to seal water tanks for example. It seemed to retain its flexibility under all circumstances. It solved out Folboat waterproofing problems.

    With a bit of luck, you may be able to find a similar product in your area. It worked very well, and wasn't too unattractive in matt black. It could also be painted over.
     
  6. netbuz10101
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    netbuz10101 New Member

    Is this something for the PVC fabric? That is a great idea for reinforcing that.

    What about the marine plywood? This is what I was most concerned about. I stopped by a sherwin williams for some advice, and the sales guy wasn't sure that marine paint would work on my 1/4 inch plywood when it flexes. I sure liked the idea of it's longevity though..
     

  7. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Asking the counter guy at a paint store, about the physical properties of the products he sells, isn't the best way to get information. He's not paid to know what he sells, just to sell it, preferably the products with the highest "margin".

    You shouldn't be worried about paint sticking to marine plywood, as it's quite stable and takes all paints well. Your fabric is going to have the most problems. There are some polyurethane coatings designed to have considerable elongation. Those intended for roof's (elastomeric), used as vapor seals on masonry, pool paints, truck bed liners, etc. If the plywood is stabilized with epoxy, then any paint can be used. If it's not epoxy encapsulated, then avoid the LPU's as these will probably be too stiff, but the single part polyurethanes will certainly work.
     
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