Buying a hull to start a project boat- another option found....

Discussion in 'Boat Design' started by parkland, May 21, 2013.

  1. parkland
    Joined: Jul 2012
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    parkland Senior Member


    Upon much searching and looking, it seems similar sized houseboat use at least 3/16" aluminum.
    Indeed the hulls I posted seem to be weak compared to almost any design I can find.
     
  2. JSL
    Joined: Nov 2012
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    JSL Senior Member

    I think you have enough opinions & info here to determine that these hulls might not be a good deal... for the buyer anyway.
     
  3. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    Eric,
    I will not argue with you because I think it is going to lead to anything interesting.
    I only said two things that, as much as you say, are correct:
    - The frames, in a ship of longitudinal structure, are not as important. Need web frames and transverse bulkheads to prevent racking.
    - For the type and size of boat we are talking about, I'm sure that the structure adopted is lighter and easier to build. I do not say that I´d adopted such a structure.
    Regarding the rest of your opinions, though most of them do not share, I prefer not to discuss.
    The structure of a ship is an exciting topic that depends on many variables. No fixed rules can be given at all. Within a certain type of vessel may be equivalent parameters. But these parameters are quite different in other ships. Surely you already know it before I speak.
    If you want another day, in another discussion, we could talk about how to handle the scantling of ships.
    Regards
    Ignacio
     
  4. parkland
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    parkland Senior Member


    Yes sir, once again, my exciting new plan is shot down in flames... lol.
    But, thanks everyone.
    One day, I'll hopefully find what I'm looking for.
    These discussions are always good anyways, lots learned.
     
  5. Eric Sponberg
    Joined: Dec 2001
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    Eric Sponberg Senior Member

    Well, my wife doesn't think ship structures are very exciting--her eyes kind of glass over when I mention engineering. But then, my eyes glass over when she speaks Spanish or French, so I guess we're even. I get your point, though, yes, an interesting topic with many, many facets. Until another time. I guess we were able to help Parkland make a well-informed decision, according to his last post. That's the point of our input.

    Eric
     
  6. parkland
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    parkland Senior Member


    Keeping in mind, that my knowledge is limited; I always thought of the longitudinal structure as being a support for a thin hull skin.
    Once the skin, or plating is thick enough, I can't find an advantage to having any longitudinal beams, other than to possibly support the ribs from flexing. (or allowing lighter, smaller ribs to be used.)

    I think of a boat hull as a giant chunk of channel, which in a way is essentially what it is.
    The walls of the hull create a giant beam. The entire surface creates strength.
    I think that the support beams, more than providing strength to the overall boat, utilize the strength of the boats hull plating.

    Of course that seems to change with the size of the boat, and the design.
     
  7. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    At the risk of oversimplifying things I would say that the transverse structure holds very well hydrostatic pressure. If what you need is to support the hull girder bending moment, longitudinal structure is better.
    But this is to simplify the problem and therefore can not be taken as absolute truth.
    It all depends on how the structure of the ship has to work.
    This is my opinión.
     
  8. parkland
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    parkland Senior Member


    I don't think I better immerse myself too far in these types of discussions, lol. far above my head.

    Even the "depends" have "depends" lol :(
     
  9. messabout
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    messabout Senior Member

    Some hulls, made of aluminum, are adequate and some of them are not. That is because more than a few fabrication shops, in moments of unbridled inspiration, decide to build boats without benefit of engineering or marine design education. They know how to form, weld, or rivet metal so it is easy for them to delude themselves into believing that they can design and build a perfectly good boat.
     

  10. Skyak
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    Skyak Senior Member

    What you need to know is there are rules called scantlings, and if you don't value light weight for performance reasons (which you do not on a houseboat) hull plate thickness rules. You can add bracing to a good hull. Nobody puts new plate on a good frame.

    It was wise of you to measure, take pictures and post here. You just dodged a bullet buddy!
     
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