Self-Righting Catamarans

Discussion in 'Stability' started by kvsgkvng, Mar 11, 2012.

  1. HakimKlunker
    Joined: Aug 2009
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    Location: Thailand

    HakimKlunker Andreas der Juengere

    Not insulting this patent. BUT....
    Look at this - emm - construction.
    Of course beauty is a relative thing, and even this keelboat-catamaran-almostsailing-boat will find a lover.
    Although it appears that the creation shown on the document is not really a success in sales numbers.
    No wonder, I would say. The solution here spoils many expectations we have on a catamaran.
     
  2. whitepointer23

    whitepointer23 Previous Member

    all new boats in australia have to be unsinkable by law. in the trailer boat market anyway. i don't know what the rules are for larger craft.
     
  3. upchurchmr
    Joined: Feb 2011
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    upchurchmr Senior Member

    I believe in this case it means to right the boat without outside assistance - The sailor would right it by himself.

     
  4. Richard Woods
    Joined: Jun 2006
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    Richard Woods Woods Designs

    How do Australians define a trailer boat??

    Presumably one that is under the normal legal towing width. But what about length or weight? Suppose you have a 38ft lift keel monohull that is 12ft wide and you tow it on its side. Is it still a "trailable boat", after all it would be under 8ft wide (but 12ft high) on the trailer, and so could be towed any where in the UK or US without a permit or escort.

    Just curious

    Richard Woods of Woods Designs

    www.sailingcatamarans.com
     
  5. upchurchmr
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    upchurchmr Senior Member

    Richard,

    I'm shocked. You usually leave the cute questions to others.

    What a new design requirement. You have probably started something.

    The next question would be does towing width include the mast - I.E., could you mount it besides the deck or would you have to have it on "top" of the boat, 12+ feet in the air?
     
  6. kvsgkvng
    Joined: Jan 2012
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    kvsgkvng Senior Member

    I must clarify myself. When I mentioned "sef-righting" I indeed meant a catamaran which would be able to right itself without any help from outside. A skipper would be able to do it alone. Of course, it is not a monohull which goes up by itself. But it should work.
     
  7. Richard Woods
    Joined: Jun 2006
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    Richard Woods Woods Designs

    upchurchmr

    I assume you take the mast down before turning the boat on its side (BG)

    Richard Woods of Woods Designs

    www.sailingcatamarans.com
     
  8. KJL38
    Joined: Jun 2008
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    KJL38 Junior Member

    The buoyancy requirements apply to boats up to 6m in length. http://www.nmsc.gov.au/recreational_boating/index.php?MID=24&CID=24
     
  9. ImaginaryNumber
    Joined: May 2009
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    ImaginaryNumber Imaginary Member

    This is Tony Bigras' idea of how to right his 50' catamaran.

    http://www.ideaintegrator.com/boats/o7/flipper.htm

    ^^^^^^^^^^^^^^^^^^^^

    "I have no plans to test the righting method before there is an actual need. However it seems prudent to pay attention to the design details during construction given that they can provide a theoretical option for self rescue at negligable extra cost. The centers of gravity and bouyancy and the physics say it should be doable.

    That said here is how it is supposed to work.

    First off we plan for a bit of habitability when upside down. Just relying on the foam insulation/floatation it should sit about with the deck about 12" underwater and slightly bow down. There is an access hatch at the bottom of the wet locker to get out onto the bridge deck. Tie points are in place to rig hammocks to get out of the water down below. A few waterproof flashlights are kept below. The fuel and batteries are all out in cockpit lockers and any leakage should stay out there.

    When the weather is ok for righting we give it a try.

    The actual righting method involves stern over bow righting. The bows are flooded and submersed which puts the stern into the air, then the stern is pulled down to the surface. At that point the bows are bailed out. Everything get soaking wet but we are right side up.

    If the mast is still up (down) when capsized it helps the righting effort with its sealed bouyancy, but it is not critical.

    The forward sections are not foamed so they are easy to flood and when flooded the mast should bring itself to the surface. Getting the rest of the way requires a lever and some weight. The lever is the catwalk/boarding_ladder/righting_lever. The weight is just a bunch of 4 gallon emergency_bouyancy/water containers I normally carry in the bows.

    About 50 of these tied together provied the weight. The catwalk is unpinned from its pivots up forward and connected to the pivots on the underside of the bridgedeck. The anchor windlass is on the catwalk and is a spooling ratchet type ( sorta like a huge trailer winch ) and provides the purchase via a 2/1 block at end of the cockpit. Swell action should help with the takeup being done as the swell lifts the floating containers.

    Extra stuf for the contigency includes:

    Pivot points welded on for the catwalk.
    A couple of permantently rigged blocks.
    Making the wetlocker drain also removable.
    Hardpoints welded in for the hammocks.
    Multi use 4 gal containers ( used cooking oil jugs about 50 cents each )
    Using fastpins rather than bolts for the catwalk pivots.
    Non skid and harness tie points on the underside of bridgedeck.

    I worked on a 40' production cat in El Salvador in 1978 with this designed in ( never got into production ) and also included it on my 23' cat. It is just a simple bit of low cost planning for a bit of peace of mind for the most part I think. One nice aspect with the use of aluminium is that it is easy to adjust the flooded center of bouyancy with the placement of foam. "
     

    Attached Files:

  10. CatBuilder

    CatBuilder Previous Member

    Dumb question about the inverted hull time period.

    This plan calls for hammocks. Others talk about living in the inverted hull awaiting rescue or waiting to wash up somewhere.

    My questions are as follows - and I know they are dumb:

    1) With all the holes in the deck and hulls, why doesn't the main section of each hull fill up with water, with just the two extra watertight bows and sterns to keep it afloat?

    2) If air pressure (once you have sunk a capsized cat past the hatches, ports and other holes) is what is keeping the hull up, wouldn't you die in short order living in there by CO2 asphyxiation?
     
  11. Petros
    Joined: Oct 2007
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    Petros Senior Member

    if the cat capsized in heavy weather, would any of these methods work to right it in those kind of conditions? If not it looks like the crew would have to wait it out in the inverted hull until the conditions calm down.

    I wonder if cleaver placement of bow thrusters would allow it to self right. The thrusters would be useful for docking anyway, and have a secondary emergency function.
     
  12. Luc Vernet
    Joined: May 2004
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    Luc Vernet Senior N.A.

    Hi,

    I am sorry that I cannot remember any reference, but a very valid architecture - and not "system"! - was patented years ago. I had experimented it on a scale model, and it worked beautifully. No real life test though!
    Basically, this patent is (or was?) about the use of two buoyant masts, one on each hull, forbidding the boat to go past 90 deg. The patent was specifying un-stayed masts, which was a good thing since no flexibility when they "slam" into green water may destroy a conventional one if big enough to provide the needed buoyancy. Once capsized at 90 deg, the windage of the immersed part of the boat did make it rotate to leeward, and any wave - or strong wind - straighten it up again. However, the patent had loopholes that we were intending to exploit on a cruising catamaran design, but I finally did a conventional design....and no construction followed. This was some....25 years ago! Still don't know....one day? I have happily been more successful with power cats!

    I had, at that time, patented another system for a folding catamaran for children, which made righting this capsized little boat very easy. Besides a prototype that we did, that never saw the light of the day either (simply too expensive to build), so the patent was dropped before patenting in many countries.

    However: both of these were working!

    I shall say a word about patents, while on it: they are extremely expensive, and very hard to defend against copies. They need extensive research to make sure the invention you are so proud of has not been already invented - and eventually patented. A single country that has been omitted can become a major player. Look at the case of the Windsurfers, whose actually only the articulation of the mast was patented, but the patent did not include France....who became with Dufour (at that time) one of the biggest makers of windsurfer clones.
    What you want when patenting is to keep the right to use your invention for your sole benefit, but what is often much wiser is to publish your invention, forbidding by this action anyone to ever patent this invention....since it will not be an invention anymore. At least, you do not have somebody "inventing" something at the same time as you and you discovering one day that you are not allowed to use your "invention". Quite an unpleasant eventuality! also consider that news ideas are often "in the air" amongst people confronted with the same problem at the same time, and you do not know what is happening next door, specially since not only they are not obliged to disclose their invention but months are needed for an invention to be published. In the meantime.....you may loose a lot of money!!!
     
  13. HASYB
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    HASYB Senior Member

  14. ImaginaryNumber
    Joined: May 2009
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    ImaginaryNumber Imaginary Member

    Of course, water will enter the cabin and hulls. Tony mentions foam/floatation supporting his inverted cat, estimating that only 12" of the (upper part) of the hulls will be submerged. Perhaps Kurt could give you an estimate of where your cat will float when inverted.

    Multihulls which are intended for off-shore use should have escape hatches built into the hulls. This allow both ingress and egress, without resorting to an axe. :(

    Below are some photos of a Wharram with an escape hatch. They use it for non-emergency purposes too. :)
     

    Attached Files:


  15. rapscallion
    Joined: Oct 2006
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    Location: Wisconsin

    rapscallion Senior Member

    The G32 self rights. Look at the promo video on you tube. There is also a patent issued in 1993
     
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