a boat from foam-fiberglass laminate panels

Discussion in 'Boat Design' started by TacoFace, May 29, 2021.

  1. ExileMoon
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    ExileMoon Junior Member

    Through reasonable segmentation, you can combine your flat plate with the largest size into a better hull close to the curved surface, and its performance should be almost the same as that of a fully curved hull.
    For example like this:

    flat board boat.png
    But the main question is, what is the use of doing this? If you consider economy, ordinary plywood can make a good curved hull, and its price (if purchased from the factory) is not higher than your foam flat plate.
     
  2. sharpii2
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    sharpii2 Senior Member

    The problem with cutting them into strips is that, if you try to bend the strips, the foam will probably shear, or the sheathing will delaminate.
     
  3. Mr Efficiency
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    Mr Efficiency Senior Member

    As I mentioned earlier, the standard PU foam density of 2lbs/cu ft is not to considered as a structural foam, and if that is what this is, (probably) not something to even contemplate as the foundation of a boat. The next density up, 4lbs/cu ft, you might have a basis to work from.
     
  4. DogCavalry
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    DogCavalry I aim to misbehave.

    Not much reading going on here. Page 4 isbasically the same as page 1.

    Tacoface, make a slow barge form. Those panels are too rigid. You could make an awesome houseboat, but keep it very simple- hull material costs are such a small part of overall costs the savings aren't worth anything elaborate.
     
  5. Kayakmarathon
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    Kayakmarathon Junior Member

    The thin fiberglass faces separated by 2" is very stiff and will not bend into panels very well. The panels are best used for cross sections, decking, built in cooler, and cabin walls.

    If you can get a truck load of the foam without the fiberglass faces; then you can cut them into 2"x2" strips, which will make a great core. After placing the core on cross sections (just like wood strip method), laminate the entire hull inside and outside with several layers of fiberglass and resin. The hull will be stiff, light, and buoyant.
     
  6. zstine
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    zstine Junior Member

    I believe the OP is getting the foam board for free (or nearly) as production waste, and ply has gotten quite a bit more expensive than that!
     
  7. OneWayTraffic
    Joined: Jun 2018
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    OneWayTraffic Junior Member

    Been a while since I posted here. You could certainly make a boat shaped object out of those panels, but good luck finding an actual design.
    Best ideas I can come up with would be to build a hull and use that for flotation, or build a raft type shape for a dock or lake.

    In NZ we have a company that makes rotomoulded plastic pontoons. You could do something similar using the pontoons for the hull and the panels on some beams for deck and superstructure.

    Home (pontoonzboats.com)

    BTW I am building a glass plywood epoxy boat from Bateau. There's a lot of design details that goes into a good plan. You really need to decide whether you want:

    1. To build a boat in which case you are going about it wrong: start with the design you like, then price it up. The materials for the hull is the least of your costs. I'm building from marine ply and WEST epoxy, and the hull is the cheap part. The motor costs a lot more.
    2. Or just want to use those panels in which case I'd be building a sleepout, a caravan camper or iceboxes.
     
  8. TacoFace
    Joined: May 2021
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    TacoFace Junior Member

    Yes, you did mention that before. Then I replied that this material was close to 11 pounds / cut ft. I believe that would suggest, by your logic that it was a different material.

    If I ever run across some 2 lbs/ cu ft foam, I will be sure to pass on your feelings about it.
     
  9. TacoFace
    Joined: May 2021
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    TacoFace Junior Member


    You win the reading comprehension test! Yes! Flat. Dead-rigid panels. Non-bendy building material.

    Stealth design did cross my mind. This one you posted looks fun.

    The geometry of cutting 3-dimentional panels (2-inch thick) into an approximation of a curved exterior surface.

    Also, if anyone I just want to mention again that the weight of this stuff is just under 12 pounds per cubic foot. Not 2 or 4 pounds per cubic foot. 12 pounds. It weighs around 2 pounds per 1/6th cubic-foot or 4 pounds per 1/3 cubic foot.
     
  10. Saqa
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    Saqa Senior Member

    What's the bet that the next few responses will keep talking about 2lb stuff!!

    I could use those panels. I would make a small row boat for fun

    I'd butt join some to make a few 4m long panels
    Mark out a SUP shape on some of those panels and cut it out
    Stack and draw a centre line
    Drill through the stack at the bow, stern and middle
    Drop booker rods through the holes
    Use ply plate washers and wingnuts to secure the stack
    Mark out the foot wells and storage compartments on the face plate
    Cut them out with a jig saw
    Cut more panels to the same length but make each one a bit narrower than the previous
    Secure them in the stack
    Glue all together using foaming PU glue
    Use aerosol expanding foam to fill the steps under the stack
    Use a long sanding board to tidy all up
    Seal with glass/epoxy and paint

    You can create really nice lines by careful sizing of the plates in the stack
    The more foam that you cut out, the lighter she will be
    You can make a pair of narrow hulls like that for a rowing or sailing cat
    You can make a tri like that two. The floats can be done in vertical plane instead of horizontal, if you know what I mean
     
  11. Mr Efficiency
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    Mr Efficiency Senior Member

    Hold the phone here, 11 lbs per c ft without the glass ?
     
  12. fallguy
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    fallguy Senior Member

    11 # foam would be too heavy for most applications
     
  13. Mr Efficiency
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    Mr Efficiency Senior Member

    Most unlikely, it might be more than 2lbs but not much
     
  14. sharpii2
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    sharpii2 Senior Member

    I did a little math.

    I estimate that the foam weighs about 8.6 lbs/sf. I did this by first subtracting the weight of the GRP laminate, which I assume is close to the same weight as the same volume of water. Then I converted remaining weight into board ft by dividing it by 1.875. Then I multiplied this by 12 to get cubic ft.

    I played around with an idea for a kayak. One of the goals to this preliminary design was to end up with as few cuts as necessary.

    Since kayaks are long and sleek, I found that a reasonable hull could be made by using only nine hull facets. Each of these are 64 inches long. All the cutting would be to get the right widths, shapes, and bevels.

    The kayak ended up being 15.75 ft long and 28 inches wide. It would displace 432 lbs.

    I estimated the weight of this kayak, with the deck made of the same material, at around 120 lbs. Without the deck, it came in at close to 85 lbs.

    Perhaps the hull could be built of this material, but the deck of lighter stuff, say 1/8 inch plywood, or even fabric. Then it may be possible to bring it in at around 100 lbs.

    I hope to have a scanned image available soon.
     

  15. fallguy
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    fallguy Senior Member

    Your fiberglass would sink. The method of ascertaining the density of the foam needs to be redone.

    Weigh a piece of it with the glass cut off with sides neatly table saw cut.
     
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