What is the best material for a hull?

Discussion in 'Boat Design' started by El_Guero, Oct 26, 2013.

  1. El_Guero

    El_Guero Previous Member

    We have had many questions around this topic.

    http://www.boatdesign.net/forums/multihulls/carbon-ply-polystyrene-47053.html was one thread.

    But, what are the best materials for building hulls? The best combinations of materials?

    It is ok to give your preferences, but do so in a manner we can all learn from.

    For example, plywood core is a stronger core than foam .... BUT, because of the greater weight, most people choose foam over plywood for a composite core.

    It seems that we move from wood (plywood) to composites to metals as boats get longer. Bigger.

    When (and why) does plywood clearly lose to composites?

    When do composites lose their advantage to aluminum (aluminium), titanium, and steel?

    If carbon fiber (CF) comes down in price would CF composites dominate all boats and ships?
     
  2. alan white
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    alan white Senior Member

    Balance the variables of initial cost, safety, longevity, maintainance costs, weight, aesthetics, resalability, availabilty of materials, personal preferences, and performance.
    Every sailor weighs the above considerations differently and that is why there are so many ways to build a boat.
    If safety is a paramount concern, steel and aluminum are more likely to survive a collision intact than other materials. If low maintanance tops the list, then aluminum and fiberglass. If performance, kevlar and carbon fiber allow you to put weight where it does more good. Personal preference? If you don't love your boat, why sail in the first place? Some folks absolutely must have a wood boat.
    There is, in other words, no best material, only different comprimises to achieve different ends.
     
  3. srimes
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    srimes Senior Member

    Birch bark. But sealskin is better around ice.
     
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  4. PAR
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    PAR Yacht Designer/Builder

    These question a assumptions are too broad to get real definitions.

    If Monel came down in price . . . if aluminum came down in price . . . if hookers charged less . . . if taxes where lower . . .

    When has this ever been a consideration? "Darn, I wanted a composite hull, but with the advantages of titanium, I just had to go there?" Really?

    Material choices are based in the SOR. If you arbitrarily toss out elements of the SOR, such as the high cost of a specific material, of course other materials look better, but this isn't a fair assessment. Plywood is the most common building material in terms of numbers of vessels built, simply because it's weight/cost/strength/stiffness ratio is very high (comparatively), in the craft that will likely employ it. The same is true of steel in larger vessels. 'Glass is preferred in production work because it can be molded, saving considerably in time and build complexity. High end SOR's with demanding performance requirements will understandably insist on lighter, stiffer materials, so high tech choices have to be made. There's no MDO or ACX used on an AC 72 for this very reason, the goals of the SOR just can't permit these material choices.

    Simply put a design's goals (the SOR) will dictate the material choices.
     
  5. El_Guero

    El_Guero Previous Member

    That is funny, I want to see how long sealskin would last around Portland ....

    :D
     
  6. CBD Boat Design
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    CBD Boat Design Junior Member

    But, what are the best materials for building hulls? The best combinations of materials?
    Depends of the boat application, what is your priority?, reduce the manufacturing cost, reducing the displacement, reduce maintenance, prioritize the mechanical strength, what is the environment that the vessel works, ...

    For example, plywood core is a stronger core than foam .... BUT, because of the greater weight, most people choose foam over plywood for a composite core.

    Exists a large number of cores with different density foams, there are some with better mechanical resitencia the BalsaLite, the decision depends on the availability of the material, the type of lamination, the final displacement to be achieved, ...


    When (and why) does plywood clearly lose to composites?
    The poywood is heavier and more difficult to work than foams, but has excellent mechanical properties and is non-porous, so if the water enter the nucleus (due to a collision), the water not penetrates the entire core of the hull.

    When do composites lose their advantage to aluminum (aluminium), titanium, and steel?
    In the large boats the composites structure is more expensive that steel and aluminium

    If carbon fiber (CF) comes down in price would CF composites dominate all boats and ships?
    Probably not, because the other problem of the carbon fiber is the complexity of work with this material, you need a estrict specific envoirment conditionts and this conditions are very dificult in big boats.

    ---------
    We can design the boat do you need.
    www.customboatsdesign.tk
     
  7. Wayne Grabow
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    Wayne Grabow Senior Member

    If Monel came down in price . . . if aluminum came down in price . . . if hookers charged less . . . if taxes where lower . . .

    I love it. Humor is always appreciated.
     
  8. hoytedow
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    hoytedow Wood Butcher

    Never make a hull from peanut butter. It will stick to the roof of Moby Dick's mouth and make him whistle funny.
     
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  9. Stumble
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    Stumble Senior Member

    Just fill your tanks with milk and it's fine.
     
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  10. rustybarge
    Joined: Oct 2013
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    rustybarge Cheetah 25' Powercat.

    No competition, the Curraghs(pronounced: Curricks) from the west of Ireland.
    Covered in canvas and tar.
    They brave the Atlantic swells in all conditions, after a few bottles of Jameson Whiskey!


    [​IMG]

    [​IMG]
     
  11. erik818
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    erik818 Senior Member

    I've concluded that for me, wood strips protected with glass and epoxy is the best material/method. I build small one-off boats for myself. Wood is easy to work with and the result can be very beautiful. No mold is needed which saves work.
    In contrast to plywood, wood strips allow compound curves and allow the strength to be directed where its needed the most. The result is a light, stiff and strong hull. My understanding is that, for small boats, composites would be needed to beat the strength to weight ratio of wood.
    Maintenance on a wood/epoxy/glass hull isn't worse than on pure plastic boats. Re-sell price isn't an issue because I don't plan to sell my boats.
    For a small boat (less than 10 meters), aluminium would be the only other material I would consider when building a boat for myself. I enjoy working with wood and that's enough to settle the issue.

    Epoxy is the magic that solves the issues with wood in boats.

    Erik
     
  12. erik818
    Joined: Feb 2007
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    erik818 Senior Member

    A photo of my new 2-man kayak, built with spruce strips covered with glass and epoxy. The photo is from one of the trips close to Stockholm.

    Erik
     

    Attached Files:

  13. rustybarge
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    rustybarge Cheetah 25' Powercat.

    A skipper on another forum who drives a commercial 24mtr aluminium catamaran, said they have to constantly re-weld the hull after a bumpy trip out to the offshore wind-farms; the welds keep on getting hairline cracks.

    They end up welding the same area over and over again. :eek:
    Makes you think.
     
  14. Stumble
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    Stumble Senior Member

    Ya, it makes you think they are doing a poor job welding the repairs, or the boat was poorly designed from the get go.
     

  15. rustybarge
    Joined: Oct 2013
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    rustybarge Cheetah 25' Powercat.

    i've always heard that aluminium welds have to be clinically super-clean, so maybe that's the problem.
     
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