Is this a sound boatbuilding method?

Discussion in 'Boat Design' started by rapscallion, Mar 15, 2007.

  1. rapscallion
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    rapscallion Senior Member

  2. tri - star
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    tri - star Junior Member

    Had trouble acessing the site.....

    Although, the word "foam" causes me to take a deep breath - and pause.
     
    Last edited: Mar 16, 2007
  3. lewisboats
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    lewisboats Obsessed Member

    Accessing :p :D :D :D :D

    Ateve....I mean Steve

    PS: Me too on the site link...error message 404
     
  4. Raggi_Thor
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    Raggi_Thor Nav.arch/Designer/Builder

    I think that boat is sound as long as it's on a sheltered lake!
     
  5. Raggi_Thor
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    Raggi_Thor Nav.arch/Designer/Builder

  6. ted655
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    ted655 Senior Member

    :mad: The ##%%^$$@**@ link captured my browser! Making me reload the forum. BUT... my answer is... If it floats and performs after it's built, then it was successful.
    That being said, you couldn't give me a foam core boat! Water eventually finds its way into the core. Even though it doesn't sink, it becomes a water ladden sponge with no real fix. Give me a boat with a material that keeps the water on one side & displacement on the other. THEN, it can be fixed from both sides.
    Take a sponge, put it in a baggy and support a load on it. Now make a teeny-tiny hole in that baggy and watch the load. NOW, remove the sponge/baggy & try to dry that sponge again while still in the baggy.
    Just my opinion of "cored" boats
     
  7. Raggi_Thor
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    Raggi_Thor Nav.arch/Designer/Builder

    I agree :)
     
  8. tri - star
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    tri - star Junior Member

    Agreed !

    I agree with the last 4 posts !

    - Several posts re: low density cores, have been made by us.
    - Will not repeat myself here.
    Except that the hull is maybe 20% of a vessel. In cost - and otherwise.
    So why, scimp here - and jepordize the whole venture ?!

    Cheers !
     
  9. CapKos
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    CapKos Junior Member

    Well sandwich construction is not something new. Currently Cup of America boats are building using this method:
    http://alinghi.epfl.ch/page10240-en.html

    In my opinion it depend what kind of boat we are talking about. For cruising boat the argument of Raggi_Thor about the thin skin, which hit something, is valuable. However it is not expected that a Cup of America boat hit something and if so will be immediately repair by competent experts. It is not cheap however :D .
    All the best,
    CapKos
     
  10. erik818
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    erik818 Senior Member

    I would say that I find much merit in a sandwich design. It is possible to build very strong and light hulls that way. America's cup participants have a slightly larger budget tha most of us amateurs and can afford to use epoxy, kevlar, carbon fiber on aluminium honeycomb structures as core. (See e.g. http://www.victorychallenge.com)

    A sandwich bottom also insulates from the cold water, an important aspect if you want to use the boat out of season in northern waters.

    As for the building method with fibre glass, polyester and uretan foam as core, I mostly object to the polyester resin. Polyester will let moisture through. I wouldn't trust injected uretan foam as core without test data showing that it can withstand the forces the design brings.

    If polyester is exchanged for epoxy and each volume being filled with uretan foam isn't too large, I don't see why the method wouldn't work well. As far as I know, uretan foam won't absorb water in case the epoxy/glasfiber surface is breached.

    For a leasure boat, as a contrast to a racing boat, I think it makes sense to design the bottom surface for more abuse. If the intended payload of the boat is e.g. 1 ton, it doesn't really make sense to design a superlight hull (200 kg?) even though it is possible with the sandwich techniques available with large budgets. I would add a few hundred kg in the bottom, also improving stability.

    A boat isn't only the bottom, and for the rest of it I don't see why the proposed sandwich technique with polyester/glasfiber/uretan foam wouldn't work, though I still prefer epoxy

    Opinions from an amateur open to new ideas,
    Erik
     

  11. tri - star
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    tri - star Junior Member

    Easy to agree with you; CapKos:

    However, using Gold Cuppers, as examples of anything useful:
    can get you onto sticky ground. As, even if they cost a jillion Eros/Dollars....
    They are throw - away - boats.
    Their value diminishing rapidly after their last race.........

    The question asked was:

    " Is this a sound boat building building method ?"

    - If it's a special purpose vessel - with a limited life expectancy, speaking
    for myself - I might be persuaded, to design such a creature.
    - However; if the owner wants a craft, that they wish to cruise on - with minimum time spent in boat yards......I will not design them a yacht with a
    low density, cored hull.
    Irrespective, of how deep their pockets are.

    After a few years, cruisers, will often exceed the designer's worst
    expectations re: actual weight in the water.

    Well exceeding, any theoretical savings in displ. gained by light weight
    sandwhich construction. Within the hull structure, proper.

    Within the vessel it's self - I have less reservations.
    But even there, honeycomb - and a mutitude of other mat. Will be well
    ahead of foam - in my personal vessel.
    i.e.
    Having been also, in the business of designing/building houses, I have
    noticed some areas - of concern - that no one seems to want to talk about:
    Re: Foam(s).
    Like time, temp. and catalysts.

    In the lab - a few days old - you will always get impressive numbers, for
    various foams.
    Re: Insulation R values. Or impressive gains, acheived in strength in
    cored situations.

    Now everything fades with time. This is expected.
    However, when I looked at real world situations.
    Time and Heat can be of more concern, with foams.
    - Than with many; better understood, traditional materials.
    Consider:
    Most foams are created by a catalytic process.
    The catalyst never stops working. So the properties of the foam
    are not static. So 3 yr. old foam will not show the orig. specs.
    Heat adds to this concern. A cored vessel in the tropics will see faster
    changes than one moored in Rhode Island.

    Why don't we do a survey ?
    I will predict - right now - foam will not be the first choice of
    experienced custom boat builders.
    Production boat yards are another story.

    Cheers !
     
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