Strong Back Material

Discussion in 'Materials' started by BTScow, Nov 17, 2020.

  1. BTScow
    Joined: Dec 2006
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    BTScow Junior Member

    I have drawn up a strong back for my 23ft power boat design. It consists mostly of nominal lumber and can't help to think it would be more expeditious to have those parts machined from sheet stock (OSB or MDF or the like). Any suggestions or anecdotes anyone would like to share regarding this would be appreciated. Thank you in advance.
     
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    And what is the strong back's role in this build ? Or I should ask, what kind of build is it, in terms of the hull material ? Obviously, if out of doors, or if it could get wet at some stage, you don't want particle boards.
     
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  3. BTScow
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    BTScow Junior Member

    The role of the strong back is to keep the hull shape during construction. I envision building her inside and upside down. She will be cold molded.
     
  4. Mr Efficiency
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    Mr Efficiency Senior Member

    So timber frames, and veneer ? Or are you aiming for some kind of monocoque construction and the bulk of the framing is temporary ? If all the framing will stay in the boat, you just need a couple of longitudinal bearers that won't sag, plus a cross member at each framing station that contacts the two longitudinals. What would the particle board be doing ?
     
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  5. hoytedow
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    hoytedow Wood Butcher

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  6. bajansailor
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    bajansailor Marine Surveyor

    If you can design your strongback such that all the components can be easily bolted together, using standard lengths of 'proper' timber and trying to minimise wastage, then you should be able to recycle most of it for use in other building projects when this boat is finished.

    Re your 23' powerboat design, can you tell us a bit more about it please?
    How much deadrise, what sort of speed are you looking to achieve, etc?
    If you can post a sketch or two showing what she will look like, then that would be well appreciated by everybody on here.
     
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  7. BTScow
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    BTScow Junior Member

    I think Mr. Efficiency nailed it. All of her frames will be staying in her. She will have a cold molded bottom (2) x 1/4" layer of marine ply and (1) x 3/8" glued lapstrake topsides. I'm sure improvements will be made, but overall the plan is sound with several longitudinals (that won't sag) and a cross member(s) at each of the frames. As for the design, I have uploaded a GA and Lines Plan for your consideration. Any and all comments welcome. Speed target is 20knots with a 45hp inboard.
     

    Attached Files:

  8. Mr Efficiency
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    Mr Efficiency Senior Member

    Is this a design of your own ? the 20 knots might be a touch optimistic unless you are ruthless in restricting weight. The transom I would rather see with some rake and curve, but it isn't my eye it has to please. Big job you have ahead of you, good luck with it.
     
  9. BTScow
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    BTScow Junior Member

    This is my own design (sometimes I wonder if I have some sort of sickness that I would undertake the design in my spare time). The boat is drawn and parts have been made. I was wrapping up loose ends for potential builders - hence the question about the strong back. Often times it seems I can't see the forest through the trees and wanted to check my thinking - so thank you for that. As for the powering, 20knts is optimistic and targeted in the light load condition - 18kts will be more like it.
     

  10. gonzo
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    gonzo Senior Member

    It is a pretty antiquated design. Are you looking for diy's that would buy the design from you? In that case, it will need to have a step by step instruction manual.
     
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