Nutin but foam

Discussion in 'Boat Design' started by tarrysailor, Dec 2, 2004.

  1. tarrysailor
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    tarrysailor Junior Member

    A startling conclusion that I have come to is this: boats are holes in the water waiting to be filled with the water. And given the nature of water, it sooner or later will. I've decided not to build a roofed-over hole in the water, but instead to build a raft. Wineglass-shaped and properly ballasted, yes. Monohull, certainly. But a raft.

    So here are my thoughts. First, create a shell of the rock-hard type of foam. Back it with a foot or so of the medium-density stuff, for bracing. Put the 5-pound density stuff in the middle. Build a deck and cabin on top and attach the ballast to the deck by triangular struts. Glass over the whole thing.

    I think that the hull has to be rigid to carry the imposed loads. Loads due to the perfect storm south of the Horn leading to the pitchpole. Thus the reason for the hard shell and the bracing. Otherwise the thing could all be made of the 5-pound stuff.

    Will this work? I will appreciate any comments.
     
  2. Not A Guest
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    Not A Guest Junior Member

    no. no.
     
  3. nero
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    nero Senior Member

    Getting this idea to reality will take some more thought. Your foam needs some reinforcement in it. Maybe some PVC pipes or maybe some glass rods. Some one on this forum said think of foam like concrete.

    Perhaps your inter layers or blocks of foam could be 4 lb or even extruded polysterene (cheap stuff) The loads in the center will be slight.

    How big is this boat? Did you do a sketch or drawing to post?

    Anything can be made to work. For how long it will work is another issue. smile
     
  4. gonzo
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    gonzo Senior Member

    They make cheap sailbords of white styrofoam. As kids we used a block of styrofoam to make something along the lines of what you are talking about. It was about 9' long. I assume it is a daysailor where you are always on deck.
     
  5. tarrysailor
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    tarrysailor Junior Member

    Well, no, I don't have a CAD program yet to make sketches with. But it should be larger than the Tahiti and not nearly so large as the Marco Polo. Lines like Tahiti or maybe Spray. Incidently, I've never heard of glass rod, but I had thought about nylon straps. It's also quite possible to make ribs of rock foam, poured between cardboard hexagon spacers that are taken out after the foam sets up. The hex ribs do not have to be shallow, given that the interior is not inhabited. What I do worry about is thermal expansion. And contraction in cold waters.
     
  6. PAR
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    PAR Yacht Designer/Builder

    Some folks will do anything rather then call a pro. We read about them all the time, sunning themselves on the same island the multi hull designers have sailed to in the south seas . . .
     
  7. gonzo
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    gonzo Senior Member

    If you worry about cold waters, the contraction of the foam should be the least of them. Have you ever sailed in the cold? Camping on deck is a very bad idea.
     
  8. tarrysailor
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    tarrysailor Junior Member

    I'm glad to hear that the foam won't contract too much to delaminate or something drastic. As for the weather, yes, a cabin on deck is necessary. The good thing about foam is that it's an excellent insulator, so making the cabin out of it would keep it warm. But a cabin on deck forces the sail up higher, so as to clear its top. I don't see any other alternative, except to use a crabclaw type sail. A definite disadvantage of this big pontoon is that the living area has to be on top, so it has to be bigger to just give the same living area. But if it's inexpensive, it can be made longer. That's good.
     
  9. B. Hamm
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    B. Hamm Junior Member

    Foam while it seems rigid and stable when it's sitting in your shop does some nasty things when it's exposed to the elements. UV light from the sun eats foam alive, stick a piece outside for a couple months as a test. Animals love to eat the stuff too, geese around here for some reason love the stuff, anything unprotected from them has a fairly short life. Foam also will absorb a surprising amount of water, to the point that after a year in the water some foam will actually sink.

    All in all, bad idea.

    Bill H.
     
  10. tarrysailor
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    tarrysailor Junior Member

    Well, I specifically said that the foam needs to be protected from the elements. So does wood, so does practically anything except bronze or monel. (And I wouldn't be suprised to find out that there isn't something in salt water that eats those, too!) More critically, foam has to be protected from fire. It burns and the fumes are toxic. But in all these ways, foam is no different from other building materials. They all have their limitations and disadvantages that have to be worked with. In my mind, foam's greatest asset is not that it floats but that it is rigid and easily worked. The buoyancy is secondary.
     
  11. JR-Shine
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    JR-Shine SHINE

    You have just described a boston whaler - more or less. A big surfboard, or better yet a cooler shaped like a boat.
     
  12. Skippy
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    Skippy Senior Member

    Won't the VCG be too high for a monohull?
    Not to mention extra windage?
    Other than just making a catamaran, which would be very easy, how about putting lots of foam fore & aft, around the edges, and in any leftover nooks & crannies, then have a smaller cabin amidships? Still a small hole, but maybe an unsinkable hole???
    (caveat: this is still purely speculative, I agree it really does sound impractical.)
     
  13. CT 249
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    CT 249 Senior Member

    If you want an unsinkable mono, just do what manufacturers Sadlers (UK), Etap (Belgium) and yachting writer Andrew ("Aussie") Bray do; just line the hull of a normal boat with foam.

    You don't really notice the volume the foam takes up in Sadlers and Etaps, or in Andrew's own Max Risely (IIRC) design which is around 42'.

    The problem with building a crab-claw sail and a deckhouse to live on its the very high C of E of the sail and the fact that if you have the pitch-pole you're worried about, the deckhouse is normally the first thing to crack or go (see Suhaili and IIRC Tzu Hang etc). So then you're left off Cape Horn with no shelter, no equipment.....

    The racing sailors that many cruisers despise so much have built boats out of solid foam. They worked, but not well enough for others to follow (although I wouldn't mind having a go myself).


    As for building a Spray.....the first one ever built was lost without trace. So was the third (I think), Pandora from Australia.
     
  14. Nels Tomlinson
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    Nels Tomlinson Junior Member

    Build a proper boat

    Build a proper boat, and fill it with foam, from the lowest point to a level a bit above the fully loaded waterline. Now, it has full positive flotation, and if you somehow fill it with water, it should possible to make it self-bail, like a Boston Whaler.

    That would probably work best with something like a sharpie, or some other light-displacement boat, where the majority of the acocomodations are above water. A traditional displacement hull, with half or more of the cabin below the water line, wouldn't be very useful after such treatment.

    The good side of this method is that building usable boats is pretty much a solved problem: you can take something like one of Bolger's Advanced Sharpies, and know exactly what you'll have when you've built it and filled it with foam. There's no need for experimentation, and no need for expensive mistakes.

    The bad side of this method is that it will surely cost more. Obviously, it will cost more than a standard boat, even for the same size hull. It's worse than that, however. Any boat which is used for more than day sailing is a cargo boat: it has to carry spares, repair materials, personal effects, and lots and lots of food and water. Literally tons of stuff, if you're going to be away for a couple of years. Folks usually stow all that in the bilges, which you just filled with foam. That means that to have enough cubic for all the stuff for even a spartan existance you'll need a larger, more expensive boat if it's to be unsinkable.

    Another bad point is that you've probably gone from full standing headroom to sitting headroom in the accomodations. The places with sitting headroom went to ``wriggling-on-your-belly room''.

    Finally, flotation isn't enough: if your boat breaks up, having some bits of foam in the bilge isn't going to be worth much. You need to begin with a design which can take the pounding the ocean will dish out. One consistant thread that I noticed in ``Heavy Weather Sailing'' was the most of the boats were ok until they began to break up, usually because of a weak trunk cabin or cockpit. Monolithic metal structures (i.e., metal hull, deck, et cetera, all welded into one piece) seem good, in that light.

    I've considered this, and I think it's not impossible to make a livable boat with foam-filled bilges, but it may or may not be practical. For a day sailor, there's really no reason not to go this route, except that if it doesn't ``sleep six'', you'll never be able to sell them at the boat shows.
     

  15. CT 249
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    CT 249 Senior Member

    Nels, have you been in an Etap or Sadler or Risely 42 with full foam flotation?

    I have, and it seems to make astonishingly little difference to the interior space.
     
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