Water Ballast in a Multihull

Discussion in 'Multihulls' started by BeauVrolyk, Jun 19, 2009.

  1. BeauVrolyk
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    BeauVrolyk Sailor

    Does anyone design water tanks into multihulls to hold the windward hull down?
     
  2. TeddyDiver
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    TeddyDiver Gollywobbler

  3. BeauVrolyk
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    BeauVrolyk Sailor

  4. catsketcher
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    catsketcher Senior Member

    Has been done

    Tristan Jones had a tri designed by an Aussie that had things called Cool tubes (I think) they trapped water in them when required.

    Racing boats have tried water ballast - it was done in the eighties in boats like Verbatim(40ft Crowther tri) . They didn't use the tanks.

    Russ Brown has tanks in his pacific proas but his boats are crazy.

    So the answer is it has been done but it is probably not worth the effort. Cruising boats have become heavier anyway with all the gear on them so they don't need extra ballast.

    On a racing boat the placement of ballast may become problematic. On a reach you want to ballast in the windward float. Then if you bear away the ballast needs to shift to the stern of the main hull. If you have more sail area up because the boat is stiffer sideways then you will probably pitchpole. So it is probably better to try to reduce drag in the rig and deck to reduce pitchpole and capsize worries.

    cheers

    Phil
     
  5. Doug Lord
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    Doug Lord Flight Ready

    The Aussie foiler "Spitfire" carried 1000lb of ballast-I think it was water. And "Hydroptere" carries water ballast (800kg-1760lb)pumped from an intake on the rudder to the windward ama. Additionally, "Hydroptere" uses water ballast in the main hull to assist with pitch control.
    http://marine.bdg.com.au/spitfire_features.html
     
  6. Steve W
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    Steve W Senior Member

    The Gougeon brothers(west system epoxy) built a production catamaran that used water ballast to make up for the stability lost by making the G32 only 8ft 6in fixed beam, they only built a dozen or so because they couldnt keep the price down.The boat was blazing fast though.
    Steve.
     
  7. rayaldridge
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    rayaldridge Senior Member

    The G32 was also very prone to capsize, which may have had more of an effect on production than expense. It was a courageous idea, but I think a little misguided. It's almost a perfect example of compromising everything in order to have trailerability. It just doesn't seem practical to have a cat that long (and with some accomodations) that's trailerable. Tris are better suited to that niche, because they can tuck their floats up under the deck. I once went aboard a MacGregor 36, and the hulls were truly claustrophobic inside. It would be a fun daysailer, but I wouldn't want to spend many nights snuggled down in those coffin berths.

    In general, I think ballast is a poor idea for cruising multis, though obviously it's been used to good effect in one-way speed burners. David Lewis' Rehu Moana was a ballasted cat, and it sailed around the world, but it was slow and wet.

    To me, more beam is the better solution. Multis are only fast when light; it seems counter-productive to make them heavier.
     
  8. Doug Lord
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    Doug Lord Flight Ready

    =========================
    Good comments, Ray. But this is not true if you were referring to Spitfire and especially Hydroptere which was designed to sail either way and specifically designed as an ocean racer. Tom Speer once had a really good quote of one of the Spitfire designers about ballast-but I can't think of it-I'll try to find it. We know that on beach cats movable ballast is indispensable-why shouldn't that be true on larger racing multies? I know,I know -but the fact remains a boat like Hydroptere makes good use of it and may be the fastest sailboat in the world.
    -----------
     
  9. Chris Ostlind

    Chris Ostlind Previous Member


    This is, perhaps, a bit breathy when it comes to L'Hydroptere's exploits. The boat is yet to make any attempt at all on any kind of open ocean speed record. One of the few times it ventured into the big blue, it saw one of the foils completely smashed-off and it had to limp home.

    Interesting boat, to be sure, but not at all ready to go out into the stuff where Joyon and Coville play on a daily basis.

    Perhaps letting them make some kind of successful attempt at grabbing the 500 meter run record should be the obtainable target, and then... and only then, could they possibly consider anything that is so massively committed as making an attempt on the Discovery Route?
     
  10. Doug Lord
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    Doug Lord Flight Ready

    WSSR Newsletter No 134. Hydroptère records
    The WSSR Council announces the ratification of 2 new World Records, both by Hydroptère, an 18m ocean going hydrofoil sailing yacht.
    RECORD: World Record Nautical Mile
    Yacht: Hydroptère
    Sailed by: Alain Thebault FRA and a crew of 6.
    Dates: 4th April 2007
    Elapsed Time: 86.7 seconds over 1853.93 metres.
    Average speed corrected for current: 41.69 kts
    Venue: Quiberon Bay, France.
    Previous record: Bjorn Dunkerbeck, Windsurfer. 41.14 kts, Walvis Bay October 2006

    RECORD: World Record "D Class"
    Yacht: Hydroptère
    Sailed by: Alain Thebault FRA and a crew of 6.
    Dates: 4th April 2007
    Elapsed Time: 21.80 seconds over 500.96 metres
    Average speed corrected for current: 44.81 kts
    Venue: Quiberon Bay, France.
    Previous record: Navarin/Columbo, Techniques Avancees. 42.12 kts, Toulon 1997

    John Reed
    Secretary to the WSSR Council
    =================================
    And they also beat a Bleriot's(airplane) record across the English Channel...
     
  11. Chris Ostlind

    Chris Ostlind Previous Member


    None of which, it should be noted, are open ocean environments. The Bay of Quiberon is a part of the ocean, to be sure, but it is very nicely protected from the really big conditions of the Atlantic save for very large storms.

    If this Hydrop stuff qualifies as ocean-going to you, Doug, then the records by all the kiteboarders are also ocean-going marks, as the course in Namibia is very directly connected to the Atlantic... as is Walvis Bay.
     
  12. yipster
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    yipster designer

    ai, you remind me to do the math, WSA / LB or so?
    rightning moment too, but hey its summer outside
     
  13. BeauVrolyk
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    BeauVrolyk Sailor

    It is summer, so what the hell am I doing on a keyboard?

    Doug, thanks for the pointed to the article on the French foiling tri. Very interesting use of water ballast indeed.

    B
     
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  14. Alan M.
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    Alan M. Senior Member

    The advantage water ballast has is that you only carry the extra weight when you need it. Building a boat with more beam will make it heavier all the time.
     

  15. rwatson
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    rwatson Senior Member

    Did you mean a Macgregor 26 ?

    Were the 'coffin berths' the berths under the cockpit ?

    If so, then the amount of room in the berths is not a product of water ballast.

    The Mac Tanks are under the mast step very close to the bow. You can see it on their web site with the hull sections.

    Every other 26footer I have been in had a flippin great centreboard case taking up all the room.
     
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