any sailboats using "aggressively" transferable water ballasting?

Discussion in 'Boat Design' started by Squidly-Diddly, Mar 24, 2011.

  1. Squidly-Diddly
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    Squidly-Diddly Senior Member

    As in port/starboard transfer of water to keep the boat more upright in high wind?

    By "aggressively" I mean all the water from one side to the other in less than 60 seconds as a normal performance enhancing part of sailing. Maybe equalize the tank levels in preparation to tack or jibe(so you don't get caught with water on the wrong side...hedge your bets), then tack or jibe, then transfer the remaining half to the new high-side.

    http://www.sponbergyachtdesign.com/Globetrotter66.htm
    This design says the water ballast would normally be equal, but could be transferred to balance the boat if extra other weight is brought aboard, but it sounds like such a transfer would be a "once a voyage" event. I'd want to be able to shift weight on any reach lasting more than a few minutes.

    I'm talking about 6" or larger pipes able to transfer a lot of water fast, probably using a low pressure(under 30psi?) compressed air.

    To me this seems like a "no brainer" and while it does introduce some complexity it isn't voodoo or rocket science.

    The Sponberg design only speaks of dedicated fresh water tanks.

    I'd consider using transferable water ballast using seawater or a combo with bladders for fresh water.

    Maybe the low pressure compressed air system would require the tanks to be cylindrical, and thus not nearly as good volume-wise, but I think it would be plenty do-able in form-fitting shape.

    I'd want transferable water ballast even if it required a fairly slow transfer with electric pump.
     
  2. michael pierzga
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    michael pierzga Senior Member

    Sea Water Ballast tanks and associated plumbing are heavy and take up so much interior volume that they are unusable on a cruising boat.

    Passive fresh water ballast.....keeping the windward fresh water tank topped up...is common and can be accomplished....slowly.. with a simple manifold and transfer pump.

    Its far better to build in a many fresh water tanks as possible, then use these fresh water tanks to your advantage as drinking water or trim control.

    If you are starting from scratch, a swing keel fitted to a hull with the correct hull shape, is most effective
     
  3. Timothy
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    Timothy Senior Member

    Roger Martin Design Grey Wolf
     
  4. frank smith
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    frank smith Senior Member

    There is a method of using water bags of about 200LB
     
  5. michael pierzga
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    michael pierzga Senior Member

    Unless you re sailing a dingy, 200lbs of water ballast, a man sitting on the rail, is not going to develop significant righting moment and would hardly be worth compromising interior volume and living space .

    Much better to keep parasitic weight ....Anchor chains, batteries, machinery, tankage....out of the ends of the boat, eliminate weight aloft, then sail with a deep bulbed keel hung on a form stablity generating hull shape. The resulting vessel will be simple, light and stiff enough to cause fatigue to its sailors.



    Be aware that modifying the righting moment of an existing vessel with added water ballast or any ballasting, has significant implications concerning standing rigging , hardware and structural scantlings.
     
  6. frank smith
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    frank smith Senior Member

    Thats it , Im leaving her her in port .
     
  7. Doug Lord
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    Doug Lord Flight Ready

    water ballast

    Generally, waterballast requires a wide hull-at least at deck level to get far enough outboard. But they also require a keel.
    Most ocean racing boats(even wide ones) now use canting keels exclusively-like Open 60's, Volvo 70's etc. They move relatively quickly side to side and keep all the ballast fairly low.
    A few years ago as the discussion raged about what was better-water ballast or canting keel two virtually identical boats were built-one with waterballast-Alfa Romeo-and fairly wide to get the water outboard and the other-Pyewacket-fairly narrow with a canting keel. Both boats were designed by Reichel-Pugh. Until she went up against Pyewacket Alpha had never been beaten. The canting keel boat won in every encounter....



    There have been some concept boats designed to use water(or lead) moving side to side on deck-this is one from Julian Bethwaite. On this project Bethwaites clients were Paul Cayard and Russel Coutts. Coutts wanted lead to slide athwartship and Bethwaite/Cayard wanted water piped across:
     

    Attached Files:


  8. Eric Sponberg
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    Eric Sponberg Senior Member

    Squidly--You could have whatever water ballast system you want--all sea water or all fresh water, and you are right that the faster the transfer, the bigger the pipes you need between the tanks. It is just a matter of working out the engineering for the boat at hand and being able to fit it inside. The simplest system would allow gravity feed from the high side to the low side prior to tacking, with a pump available to fill the tanks initially, and to pump out the tanks fully, or for an intermediate transfer.

    As for time to transfer and tack, on round-the-world races, you don't necessarily need to transfer water in a matter of seconds, a minute or even more will do. Fast tacking is required really only on shorter day races or short offshore races, if the race rules allow it. Traditionally, the amount of water ballast allowed has been restricted to that which causes no more than 10 degrees of heel, which has proven to be safe and conservative.

    Eric
     
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