Lightest and Strongest Hull... What Materials and How??

Discussion in 'Fiberglass and Composite Boat Building' started by kyboatbuilder, Jan 12, 2008.

  1. kyboatbuilder
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    kyboatbuilder Junior Member

    Say you wanted to build the lightest, yet extremely strong hull; what materials would you use and how would you do it? Basically looking for the lamination schedule you would use. Assume money and time are of no issue! (Just looking to get some interesting ideas!)
     
  2. Capt Mike
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    Capt Mike Junior Member

  3. JorgenBeyer
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    JorgenBeyer JorgenBeyer

    Obviously UHM carbon fibre and NOMEX core would give the greatest stiffnes/weight ratio, however, a hull like this do not respond very well to puncture and pointloads. and, due to the shape of the NOMEX core, the bonding area between the fibre and the core is very small, and could easely cause de-lamination. a good idea would be to use some distance-material such as divenycell, between core and fibre...
     
  4. Capt Mike
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    Capt Mike Junior Member

    we have west epoxy but I was talking to a guy one dat that was building his own airplane at his house he told me that the aircraft epoxies were a lot stronger then any marine epoxies


    http:www.bigwoodenboat.com
     
  5. deepsix
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    deepsix Senior Member

    If money is no issue what about boron fibers? Its stronger and stiffer than carbon, but thats about all I know about it.
     
  6. PAR
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    PAR Yacht Designer/Builder

    Kyboatbuilder, you're not going to get a laminate schedule without engineering a laminate.

    Strongest and lightest laminates come at an incredible cost. Most have little choice but to accept some weight penalties, but have a project they can afford to build. Most of us don't have America's Cup budgets to work with.

    Clever engineering can keep weight down so can equipment and gear selection.

    Other then this, you question is so broad that more definition is imposable. What are you interested in doing?
     
  7. TeddyDiver
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    TeddyDiver Gollywobbler

    Diagonal strip planking core (fir) with +-33(upright) boron biaxial on the surfaces. As a core material, wood is the only choice wich gives all diagonal strength needed.
     
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  8. PAR
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    PAR Yacht Designer/Builder

    From a technical stand point, Lord method (a strip method) will be among the lightest, though I suspect you can get lighter with some of the truly exotic fabrics and materials.
     
  9. alan white
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    alan white Senior Member

    Stiffness isn't strength, because resiliance is also an attribute of strength. Yet resiliance may not be called upon in a race. A very light hull could be designed and built that you could punch a hole through with a sharp pencil.
    The core would be thick enough to get the immense stiffness needed and the skins would be very thin. This would be true no matter what materials were used----- kevlar, carbon fiber, various foams, etc..
    So long as only water is in contact with the hull, all is well. Just be careful not to throw pencils in the water.
    Imagine a round Christmas ornament but even thinner, and with two layers, and with a core of some light material that keeps the two layers apart.
    Already, a glass ornament is amazingly stiff for its weight. One could float for ages around the worlds oceans without breaking. The two-skin cored ornament could have skins one quarter as thick as the single layer model.
    It would be even stiffer than the single layer model, and it could also float around for years. Until it contacted, say, a beach pebble with a sharp edge.
    On a bigger scale, boats are like this. But factor in the requirement that the hull survive normal conditions, and a metal skinned boat (like titanium) offers
    perhaps the ultimate in overall strength, at least in the larger boat sizes.

    Alan
     
  10. timgoz
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    timgoz Senior Member

    PAR's quesition as to what ou intend to do is important.

    In larger boats, say 50 feet upwards, I would look to steel or aluminum for geneal use. You must assume you 'will' contact something hard.

    A fellow pushing the superiority of carbon fiber was at a boatshow. He had a thin panel of the material, which he was hittng hard with a carpenter's hammer to display how "strong" it was. Another fellow walked up, took the claw side of the hammer, and easily puncured the panel. So much for that kind of strength.

    Take Care,

    Tm
     
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  11. Capt Mike
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    Capt Mike Junior Member

    Now thats funny I would love to have seen that
     
  12. marshmat
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    marshmat Senior Member

    I've done that test too on several prototype laminates. Puncture and impact resistance is an easy thing to ignore until it's too late.

    ky, we really do need to know what you're planning in order to offer meaningful suggestions. A strong, light hull for a dinghy and a strong, light hull for a trans-oceanic racer are not going to share the same structural design.
     
  13. MikeJohns
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    MikeJohns Senior Member

    It is probably most sensible to stick to proven materials. As others have said the lightest boats are being built of carbon fibres in an epoxy matrix.
    Unfortunately weight and strength are different faces of the same coin, the considerable material expense for super lightweight boats comes accompanied with low durability / lifespan.
    Fatigue is the enemy of all structural materials and ultimately it is the fatigue resistance of the material/composite that dictates use. Carbon fibre-epoxy composite has a good fatigue response providing stresses are kept below certain thresholds.
    If you are not racing in sheltered waters then the advantages of high-tech materials quickly diminishes. Often they are used to reinforce high stress areas in more traditional construction as a compromise cost weight trade-off.
    As far as I am aware aircraft grade epoxies are not stronger. Just better manufacturing quality control and application guidelines.
     
  14. kyboatbuilder
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    kyboatbuilder Junior Member

    More details...

    Okay I guess I need to put more details or limitations on what I am looking for.
    A 21' Bass Boat built to withstand the rigors of hardcore fishing, rough water, all types of weather, lots of use, and of course a nice 250+hp motor bolted on the back. Let say I want to boat fully loaded to go 80+mph yet not fall apart when it hits the water (hence the strong yet light requirement).
    As far as money goes, say you have $30,000 (US) to spend on building materials alone.
    Run wild with the ideas!
     

  15. Jimbo1490
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    Jimbo1490 Senior Member

    Clearly you will want a hull built with sandwich architecture, preferably using a structural foam core, 'S' glass reinforcement or possibly even carbon fiber skins. It makes no sense to use materials like these if you are not going to vacuum bag, so count on acquiring that capability, too. You should be able to find a set of used molds for a good design. Do invest some research to make sure you've found a hull design that you're going to be happy with long-term before you build it. Then hire a naval architect/engineer to design a laminate and layup schedule . Will you be laying up and assembling/finishing the boat yourself? If not, you'll have to find a builder or yard that's capable and interested in doing a small one-off project.
     
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