salt water vs fresh water bouyancy in boat plans

Discussion in 'Boat Design' started by blackdaisies, Apr 29, 2009.

  1. blackdaisies
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    blackdaisies Senior Member

    I was just peeking in to ask about the water line and balance change from fresh water to salt. Will it have a major effect on a boat usually sailed in fresh water?

    Salt water is denser, weighs more, and displaces less, so a boat built for fresh water sailing will act differently on salt water?

    Thank you for your time.
     
  2. Ad Hoc
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    Ad Hoc Naval Architect

    If you're talking about a 300m supertanker...yes
    If you're talking about a small dinghy...no.
     
  3. blackdaisies
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    blackdaisies Senior Member

    It's a small boat, but I was wondering what a difference it would make. Even small ones with ballast or keels would be effected by a relevant change. I was wondering if that would be needed in choosing a design.
     
  4. Ad Hoc
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    Ad Hoc Naval Architect

    The difference, if a small boat, is so minor it is not worth even worrying about. In reality you wont notice any difference at all, even though there is technically a "difference".
     
  5. lewisboats
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    lewisboats Obsessed Member

    The difference is 1.6 lbs/cu ft of displacement. say 16-32 lbs in a smallish boat. total difference in draft is in the order of an inch or less. You'll float a bit higher in salt than in fresh...so bring another case of soda or whatever.

    Steve
     
  6. ned L
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    ned L Junior Member

    I can tell you that I remember a 'well previsioned' 46' 1950 Chris Craft floating maybe an inch lower on her lines in fresh water than in salt water, so as said, not a big differance.
     
  7. blackdaisies
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    blackdaisies Senior Member

    Is it better to be higher than lower in a design? I would think I would want to build for fresh water and be higher in the water than for it to be lower.
     
  8. Brent Swain
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    Brent Swain Member

    Many BC fishboats with greedy skippers have been loaded to deck level in salt water. They do OK until they hit the freshwater of the Frazer River , then they sink like a stone. Not a problem ,unless your decks are awash in salt water.
    Brent
     

  9. blackdaisies
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    blackdaisies Senior Member

    I'll remember that. You never know when that may come in handy. Don't be a greedy sailor in fresh water.
     
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