Total mass of the things in your boat.

Discussion in 'Boat Design' started by zimbodave, Jan 11, 2016.

  1. zimbodave
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    zimbodave Junior Member

    Greetings All,

    Been buggering around for years toying with the idea of building my own boat to go cruising. Starting to work out what we want on board and how much it all weighs so that when I go to the architect, I don't look completely dumb. I've searched but can't find much. Is there a way of estimating what the contents of the boat weigh? Or do I have to do a spreadsheet listing everything then run around with a scale / look up on net then add all together?
    It's a bloody long list :eek:

    Regards to all
  2. gonzo
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    gonzo Senior Member

    It is a bloody long list. There is no shortcut to it, except that a spreadsheet can make some of the calculations easier. For example, you can input what a square meter of plywood weights, and then enter the surface area of each part. The architect will do that further down the design process. What you can do to help the designer is to start an SOR (statement of requirements); basically a laundry list of everything you want to have in the boat, area of operation, amount of passengers, preferred materials, approximate size, and anything else you can think about. The next step is to study the list and decide what is missing and which things are in conflict.
  3. daiquiri
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    daiquiri Engineering and Design

    Just make a list of the things you want in the boat and the architect will transform it into weights and weight distribution.
    Don't be one of those patients who go to the doctor with the self-made diagnosis.
  4. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Welcome to the forum.

    Agreed, don't over think this, just contact your designer and tell him what you need and want. The very fisrt part of the process is establishing these sort of requirements. We have weights and CG locations for most common items that might be installed. If not, we know where to get them.
  5. TANSL
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    TANSL Senior Member

    For a small boat, estimating the weight and center of gravity does not have to be as "dramatic". The calculations are laborious but should not be exaggerated.
    Attached file shows the estimation of the lightweight and full load of a boat 25 feet in overall length. Hope that helps.

    Attached Files:

  6. zimbodave
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    zimbodave Junior Member

    Thanks for all the replies.
    I think I'll do a list of contents anyway, it can't hurt and will give the architect an exact idea of what we want on the boat.
    As for weighing everything, sheesh, think I'll weigh / look up the main ones and dump the rest together as other or sundry :)
    There's hundreds of things.
  7. JSL
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    JSL Senior Member

    For the 'contents' one good source is a mail order catalogue such as West MARINE etc. they describe the item & list the shipping weight etc
    The weight estimate is done by the NA and will cover all aspects right down to the paint and is an important part of the design process....regardless of boat size
  8. fredrosse
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    fredrosse USACE Steam


    Many boats end up with this condition after all the stuff gets added to the boat. I made a fairly complete (to my simple thinking) estimate of the weight for a 20 ft boat I was building, at 1500 pounds.

    After a couple of years running, with some added "this and that" stuff, I put two load cells on the lifting winches that remove the boat from its trailer and lower it onto wintertime storage blocks. 2200 pounds, with no passengers aboard, what an overweight boat! Not unlike so many Americans that find themselves about 50% over the designed weight a few years after getting underway.
  9. The Q
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    The Q Senior Member

    In the Lysander class (plywood 17ft 6 inches)I remember reading of someone who weighed his boat as he normally sailed it and then went home and emptied the boat and remeasured....

    It was half a ton lighter!!!

    When it's empty ready to sail weight is only 800Lbs, you realise how much junk you can accumulate on board!

  10. PAR
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    PAR Yacht Designer/Builder

    I try to convince folks of the importance of periodically emptying their boats. Most just assume "I have to carry what I got", not realizing what we already know.
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