50' LDL design project.

Discussion in 'Boat Design' started by Robjl, Jun 29, 2014.

  1. Mr Efficiency
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    Mr Efficiency Senior Member

    Not exactly sure what you meant there, TANSL, but I think if I was the OP, I'd employ someone to talk me out of it !
     
  2. TANSL
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    TANSL Senior Member

    I just wanted to express, with some irony, that the OP, as he says, has experience sailing with a single ship, which, in my opinion, is not enough to design a boat and, of course, to predict the behavior in the sea of a new design.
    Moreover, the forms he has shown us, have details that are impossible to construct in practice, or at least very costly and useless. Although he says that yes, the forms he has shown us, have totally NO developable areas.
    But all this is only an opinion and that, and only that, is the value we have to give it.
     
  3. Mr Efficiency
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    Mr Efficiency Senior Member

    He says he intends to construct it from sheets of solid GRP, which does not sound practicable to me. Even if it was developable.
     
  4. nzboy
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    nzboy Senior Member

    I think basically the design shape is reasonably robust .My preference is single chine which is more suited to wood or round chine which would suit foam strips over station moulds .I loved the build process of the Japanese guys thread in nz building a cat(origami style) obviously quite experienced in glass not so in joinery Im happy as larry epoxy laminating, epoxying dynel .but with glass you need a team on board .So as a hull design it has merit and is not diverging from the norm But build process and scantlings need a look into and might be treading new ground
     
  5. WecBoat
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    WecBoat Navy Blue

    The market for a use boat is very low.

    Good time to buy. I bought 3 years ago a 50 feet trawler style, 300 hours on the motors, alluminium hull for less then 40 K. Teak inside and all the electricity redone...

    I have built boats before. C-flex, wood, steal, allu. But I have to agree with Mr Efficiency.

    It is not the best way to go out now, unless you have deep pocket and you want something special.

    Life is short. I can circle the globe the time you build a boat.
     
  6. nzboy
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    nzboy Senior Member

    This website is called boatdesign.net I guess a website to discuss the merits of a design and that's why I keep my comments to that end Some professional boat designers I know don't own a boat and don't really have any dreams of doing so.I being more comfortable with paper and pencil to draw boats freeship has been a great timesaver to calculate hydrostatics and a 3D view . Of course I can then scale to increase beam ,depth of hull or length to get the hydrostatics I prefer because I manually input a offset table to get my view So my only reservations with peoples designs using software are, is it easy to build ? Is it a developable shape especially when it comes to multichine. A good eye can pick 1cm in 10 metre if something isn't fair so you have to pretty smart to build boats in panels wether it be GRP ,alloy or steel .I often thought if I wanted a 50ft liveaboard I buy a cheap boat and gut it and modernise here are a few examples of boats under 100k in Aus Most of them have a raft of useful gear like a new prop 3.5k or a new paintjob
    0_3.jpg

    0_4.jpg

    5_3.jpg
     
  7. Mr Efficiency
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    Mr Efficiency Senior Member

    I think there is an element of "vanity" designing in this proposal, but it is a hell of a lot of money, hard yakka, and potential tears to be able to say, "I designed and built this beauty off my own bat". And that is far from guaranteed to be how it pans out.
     
  8. Robjl
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    Robjl Senior Member

    Nzboy, i have to agree with most of what you say, and I have really looked hard at the s/h market. My conclusion,and i have looked at and seriously considered several boats 45 to 50 foot, is that i am better off starting from scratch. The bare hull is less than 50% of building a boat. I know this from experience. I also know that it is easier to build a hull from scratch than to gut a boat and build a new interior and fit a new motor. The unexpected problems are always significant and usually costly... and once you are commited there is no going back. A new hull build is more expensive in terms of materials though. And a new deckhouse no matter how neat is still sitting atop a forty year old hull. In terms of hull strength there is no comparison between the modern grp hull and 40+ year old carvel, I know some will disagree.
    Also thanks for the comment about the forum. I started my question in the Design section to get feedbach on the hull shape which i have appreciated.
     
  9. fcfc
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    fcfc Senior Member

    I know this is an old post.

    But powering and fuel efficiency is only a part of boat design.

    A fuel efficient boat, but uncomfortable, or unsafe basically worth nothing.

    On this design, what about roll period, or vertical acceleration in head seas (comfort)?
    And angle of vanishing stability, or quartering sea handling (safety) ?
     
  10. TANSL
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    TANSL Senior Member

    In my opinion, if the body lines plan has major flaws, not worth going further with the calculations.
     

  11. FAST FRED
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    FAST FRED Senior Member

    2 thoughts on your concept.

    A 50 ft boat with a 49ft LWL will be cheaper to operate at 7K than 8K , unless its very light and skinny which yours is not.

    The power requirement would best be met with an industrial 24/7 rated engine , not a car or lorry transplant or a marinized farm implement.
     
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