Enlarging plans by percentage

Discussion in 'Boat Design' started by flipper 15, Jan 18, 2013.

  1. flipper 15
    Joined: Jan 2013
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    flipper 15 New Member

    I want to enlarge a boat by percentage. By what value does weight capacity increase? Let's say I want to double the weight capacity of a boat. By what percentage do I increase the boat size?
     
  2. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    It depends on many things, mainly what the dimension or dimensions that you can change. In general, the cheapest thing is to change the length, but you can not take as absolute truth. Of course one can not speak of a percentage of the size depending on the percentage you want to increase payload. Because I imagine that is what you want to increase the payload or, what is the weight you want to raise?. The first thing you have to do is express yourself properly to obtain valid responses.
     
  3. gonzo
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    gonzo Senior Member

    It doesn't scale directly. If you change more than 10% or so, the whole structure, stability, etc. needs to be recalculated.
     
  4. philSweet
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    philSweet Senior Member

    Welcome Flipper.

    There are a score of threads here on the subject. Hit the search button and do a google search for "scaling"
     
  5. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    If you want to double the weight capacity of a boat, you need a new or different design, not a scaled version of what you have. Scaling is not proportional and can have a huge impact on the design, as hinted to by others. Maybe it would be simpler to tell us what you have and what you want.
     
  6. CDK
    Joined: Aug 2007
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    CDK retired engineer

    In theory you'd have to increase everything with approx. 26% to reach your goal. Then you must do strength calculations for all the load carrying parts because 126% of the original width/height of beams etc. may not be enough for a 200% load. Much depends on the design and hull material.
     
  7. flipper 15
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    flipper 15 New Member

    Thanks so much for the replies. CDK thank you, that was basically all I was looking for. It was more of a theoretical question, but I was looking at my 10' 6" single person cedar stripper the other day going, HMMM...
     
  8. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    Probably I have not understood the question but I do not agree that to increase weight twice, each dimension has to be multiplied by 1.26. (I know 1.26 cubed equals 2).
    For example, the weight of some structure may have nothing to do with the length of the boat. The thicknesses of the plates, the reinforcement modules, etc. are a function of the design loads, which may depend, or not, of the boat length.
    If we talk about the payload that can carry the boat, much more depends on the depth, that of the length.
    This is my opinion
     
  9. HJS
    Joined: Nov 2008
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    HJS Member

    Scaling

    Try this excel file

    good luck

    js
     

    Attached Files:


  10. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Again, small scaling attempts can work, though they have to be small. I've seen many different attempt to scale at larger amounts, but none work well, compared to a design specifically intended for the new size range.
     
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