foam/carving

Discussion in 'Boatbuilding' started by tailchaser, Jul 12, 2010.

  1. tailchaser
    Joined: Jul 2010
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    tailchaser New Member

    Hi all. New to the forum, had a question (or several) regarding foam etc. I want to use a pourable foam to create a 3'x16'x1' blank from which I'll carve a kayak (sot, fishing oriented), spackle and glass over. Second step is to make reverse molds and glass into, pull the halves and glass them together. I'm new to this and am looking for advice. What would be the appropriate foam? Closed cell I assume, I'm just trying to keep the cost down. Does this sound workable? Thanks.
     
  2. jonr
    Joined: Sep 2008
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    jonr Senior Member

    Have you considered carving extruded foam, glassing over it and then dissolving out the foam with a solvent?
     
  3. tailchaser
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    tailchaser New Member

    I actually haven't even heard of extruded foam. Can you direct me to a good site? I googled it but didn't get anything that looked applicable.
     
  4. lewisboats
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    lewisboats Obsessed Member

    Extruded foam= the pink or blue or purple stuff available at the box store like Lowes or Home Depot. Expanded foam is like styrofoam...not so good. Pourable foam is expensive to make a mold from. Just glue a bunch of sheets of 2" extruded stuff together then carve away. Personally I have been considering making a sit on-ish kayak out of the foam itself. You can use epoxy or a polyurethane glue to stick the sheets together.
     
  5. tinhorn
    Joined: Jan 2008
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    tinhorn Senior Member

    That would be my approach, too. Have you ever tried to shape or sand pourable foam? The stuff I've used was very difficult to shape--it likes to operate in "chunks".

    You're proposing to build 1) a "plug", 2) a set of molds, and then 3) your actual kayak. Take a tip from Ed "Big Daddy" Roth who built some wild custom car bodies 40 years ago by stretching chicken wire over wood, then applying too much fiberglass which he smoothed out with a grinder (creating too much dust) after knocking out the wood and chicken wire. Somewhere between your multi-stage plan and "Big Daddy's" chaos lies a practical process for a one-off part.

    But maybe you want to produce more than one kayak. I've made small molds and plugs by gelcoating directly over urethane foam--no fiberglass required. The gelcoat was applied thick enough to sand to a smooth finish, and I used a light touch with the pad sander so as not to crack the gelcoat. I don't know how well this would work for a larger part such as a kayak. I like urethane foam for plugs because it's rigid enough to hold a shape, it's easy to sand, and it's very easy to separate from resin. (If you need to join pieces together, use contact cement and not resin. Foam is soft, resin is hard. Shaping over a resin seam will make you crazy.)
     
  6. tailchaser
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    tailchaser New Member

    lewisboats, so where do I get 2" sheets of that stuff? My local hd etc. only carry up to 3/4".
    tinhorn, I've thought of something like that. My original building experience was with skin on frame kayaks. They're great but that method of construction doesn't work well with concave parts, i.e. the hull would come out great, the deck wouldn't work. Also, my plug needs to be a paddle-able kayak first (r & d) and a plug second (once the r and the d are complete).

    Thank you for the input guys, keep it coming!
     
  7. lewisboats
    Joined: Oct 2002
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    lewisboats Obsessed Member

    Time to think outside the box then...try a siding company or perhaps a local lumberyard/contractor supply. Online is always an option. Living in SoCal...2" stuff might be hard to find...outside of the mountains. Then again...you can get ANYTHING in California if you look hard enough.
     
  8. jonr
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    jonr Senior Member

  9. Petros
    Joined: Oct 2007
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    Petros Senior Member

    The 3/4" foam would work fine; cut them into 1" wide strips and use it to build in wood strip fashion. Make some plywood cross sectional molds mounted on a strong-back, and tack on the 3/4" thick strips, final sand into shape, and cover with fiberglass. Once it is cured you pull it off the forms and than fiberglass the inside to make a foam sandwich construction. You make the top and bottom to meet at the gunwale line, bond them together and you have your proto-type and a plug. IF you want to make changes you have the wood molds to build another one from with the changes you want.

    Simple and inexpensive home made tooling to make your prototype. Easy to change the design if you want. Yet still produces a decent enough boat to sell off if you want to recoup some of your costs if you want to start over.
     
  10. apex1

    apex1 Guest

    Whith extruded foam yes?
    And you have tried that yes?

    May we have some pictures of your success? Must not be too difficult to share your pride.

    R.R
     

  11. junkman
    Joined: Nov 2009
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    junkman Junior Member

    RC plain,car rebuilding and paint, Bronze sculpting or metal casting forums there is a plethora of information on this medium that could be useful to incorporate in boats negative positive molds. With a crafty mind and nimble fingers ?
     
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