Movable Ballast for Small Multihulls / Self-Righting?

Discussion in 'Multihulls' started by Doug Lord, Nov 27, 2010.

  1. Doug Lord
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    Doug Lord Flight Ready

    High Performance Small Multi Design for Disabled Sailors-and others

    I have been interested in movable ballast for high speed monohulls for some time. In the course of that research I found out some interesting things:
    1) Hydroptere, the fastest sailboat on earth uses movable water ballast,
    2) The Spitfire 40 in Australia-also a surface piercing foiler uses up to 1000lb of ballast,
    3) and we all know that beach cats, A Class Cats, C Class cats use movable ballast.
    It occured to me that on monohulls of all sizes but particularly those under 20'- a design could be done to allow disabled sailors to sail a boat that was nearly as high powered as a skiff from a more or less central seat.
    Disabled versions of such a boat would probably have to be self-righting. I did a lot of research on the subject and am completely convinced that relatively high performance boats using such a system could be designed and built-in fact my current project is a prototype to test the concept. The thread is here: http://www.boatdesign.net/forums/sailboats/design-challenge-trapwing-deck-ballast-12-22-a-29610.html
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    I have been wondering if it would be feasible on a small tri(or cat?) to use movable ballast instead of and/or in conjunction with foils to create the RM. The price of using foils to create RM can be a lot of drag and there can be serious structural considerations as the wind pressure increases. The price of ballast can be high in terms of how to move it, how to get rid of it ect. A boat with a design capable of carrying the weight is not a problem-in fact a two person design could probably be converted to a singlehander with a movable ballast system.
    ----
    But ,it seems to me , that for disabled uses or use by less than physically fit people a system would have to be devised to allow some form of self-righting and/or crew initiated righting. It seems like if movable balast was integrated into a small multihull design like this than maybe it could be used in a way that would allow the skipper to right the boat. I read a story about a disabled guy that sailed a small tri around Britain-he capsized three times if I remember correctly. I think he's lucky to be alive.
    ----
    So can a high performance small multihull be designed to use foils for foil assist or full flying coupled with movable ballast and at the same time be rightable by a disabled or out of shape person?
     
  2. cavalier mk2
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    cavalier mk2 Senior Member

    How about a catamaran with a ballasted centerpod on gimbals that is always right side up? if you put an OB on it and could jettison the rig it would get you home. The occupants safety wouldn't be dependent on lever arms or inflating bags etc...the gadgets that often don't save the wadget. Such things have their place but initial survival should be virtually automatic.
    This is a problem that is easier to approach from a monohull.
     
  3. Doug Lord
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    Doug Lord Flight Ready

    High Performance Small Multi Design for Disabled Sailors-and others

    ========================
    You're so right but it's not so easy there either-especially for a high performance boat. This is very tough. Thanks for taking a shot at it......
     
    Last edited: Nov 28, 2010
  4. cardsinplay
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    cardsinplay da Vinci Group

    For any of you folks who might be new to this site, here is a quote lifted from a page posted by Doug previously on 2-27-09 at this link: http://www.boatdesign.net/forums/sailboats/16-18-sit-planing-monohull-trapwing-26289.html

    Seems to me that this is simply deja-vu all over again and not some new and fresh idea as Doug would have you believe. Later, this design morphed through at least four different variations in length overall, all with the seriousness of a partial design proposal that one might expect for a boat that, as Doug promised, would be the priority project of his boating life.

    It's all been haggled before and a simple search for anything having to do with Trapwing will show you all you need to know. I'm getting more than a passing feeling that you are simply looking to post more information that you already posted some time ago.. something like the latest episode over on the Speed Dream thread where you posted, once again, a subject that had been put up back in June. see just below:


    Come on, Doug. Rather than recycle the same old discussion, perhaps you could share with all of us your progress on the Trapwing boat in your garage. I'm sure that the guys here would get a lot more interested and be able to learn a lot more if you took us through the build process, the assembly techniques and the unique structural solutions you have included in the completion of that boat.


    16-18' "Sit-in" Planing Monohull ("Trapwing")

    --------------------------------------------------------------------------------

    "I have always wanted to sail a boat like a 2.4 Meter but with much higher performance. I suggested a concept years ago and wonder if anyone else has any thoughts on how to make something like this work or improve the concept.
    The idea I had was to use a molded "wing" that would have ballast slide inside it to give large RM-similar to a two handed dinghy where one of the crew is on a trapeze. The ballast could be moved by hand, foot power or electrically. The boat might have a small fixed keel. The ends of the "wing" would be slightly larger in section to provide extra buoyancy. Each side of the wing would be supported by a "trapeze" wire making moving the whole wing(and the ballast inside it) fairly easy since it all moves horizontally.
    The idea is to sit in the boat like a 2.4 meter but plane early and fast.
    I'm interested in any ideas that would accomplish this in a relatively small POSSIBLY self righting monohull....

    Personally, a boat that would sail like a Windmill- with me sitting in the center- would be cool. That boat planes in 10 knots or slightly less and is a great ride offwind in a breeze. But a boat could be built that would be a bit more powerful and meet Bethwaites criteria for upwind planing:
    LOA 16'(or so)... meaning 16', 17.5', 17', then 22' and now back to whatever length that Aeroskif hull came out to be berfore Doug shuffled it off to the folks at the windsurf school
    SA-around 160 sq.ft. upwind
    12' sliding "trapwing" with 160 lb ballast
    All Up boat weight minus wing,wing ballast and keel ballast including rig:160lb
    75lb keel bulb
    130lb-180lb crew
    SCP/Total Weight=30% @ 180lb crew

    As I envision it the wing+ballast is supported by trapeze wires-side to side movement would not require a whole lot of effort....

    Just as a rough illustration here is a picture of a Melges 24 model fitted with a "trapeze power ballast system". The battery was part of the sliding ballast and that could be done on a full size version. The "wing" on the model is just two carbon tubes that form a track for the ballast to slide on. To me, a molded wing on the full-size version would have a number of advantages including lower aerodynamic drag, buoyancy and it could be built with a slight curve.

    A well designed, tested and proven version of this boat(that was self-righting) COULD offer disabled sailors(and/or grumpy old men like me) a high performance single-handed alternative to the 2.4 meter. BUT,and this is important: to be viable this boat does not have to be suitable for disabled sailors! Don't view this concept ONLY thru the lens of what might be suitable for disabled sailors."
     
  5. cardsinplay
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    cardsinplay da Vinci Group

    Right off the top... I think that any of us are lucky to be alive, so that argument is moot. Here's a more fundamental question. Did the disabled sailor complete his goal of sailing around Britain? If he did, do you still interpret his effort as unsuccessful?

    How about the quadriplegic young lady, Hilary Lister, who sailed her boat across the English Channel? http://www.timesonline.co.uk/tol/news/uk/article558264.ece http://www.hilarylister.com/A96C9/Home.aspx Is she, too, lucky to be alive by your standards? What kind of boat did she use? http://www.hilarylister.com/2BDBA/Round_Britain_Dream/Hilary_s_Boat.aspx
    Did it have moveable ballast on the deck, or was it a conventional style sailing monohull with weighted bulb keel for stability? By the way, Hilary also sailed her boat solo around Britain successfully.

    I notice that you do not state in the title of the thread that this discussion is about how to prevent a capsize. That means that this design conversation is just as dangerous to disabled sailors as the tri you mention above. Both will capsize. What is needed, even more than self-righting is a fool-proof method to prevent capsize in the first place.

    The disabled sailing community already has a collection of boats that can do that and they are used successfully all over the world.
     

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  6. cavalier mk2
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    cavalier mk2 Senior Member

    I liked the cat roto pod .....seemed like there was a market for racers who don't know when to ease the sheets...
     
  7. Doug Lord
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    Doug Lord Flight Ready

    Here is a bit on the Challenger trimaran-designed by a disabled woman and sailed around Britain:

    http://smalltrimarans.com/blog/?p=2501


    And the specs:

    Challenger Trimaran( not rightable w/o outside assistance)

    LOA: 4.57m / 15'

    Beam: 3.50m / 11.5'

    Weight: 145.62 kg / 320lb

    Construction: GRP

    Draft, center board up 12cm /4.7", down 45 cm 1.5'

    Portsmouth Yardstick rating: 1200

    Mast height: 6.5m / 21.3'

    Sail Measurements

    Sail area: 7.5 sq. mtrs / 80.7 sq.ft.

    Classs Approved sail confirguration UNA-RIG

    Cost: £5995

    Builder: White Fomula

    Sailmaker: Mouse Sails roger@pointnorth.co.uk

    Spars: Needlespar gowarhunt@hotmail.com Updates

    As fron summer 2006 the mast manufacturer has changed to Hawk Marine Products and the contact is Adrian Brunton. His email address is adrian@hawkmarin

    on the right side image, click and then again on the resulting image-Geof Holt in the Challenger tri he sailed around Britain:
     

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  8. cavalier mk2
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    cavalier mk2 Senior Member

    We have a old Macgregor 23 (much faster sailing than the new 26) that worked well though it is tender upwind. Offwind it can plane being a uldb with a dinghy type hull. I often thought of putting low aspect foils on a beam for more power to windward and close reaching. The challenge there is to make sure the foil and beam don't interfere with self righting. A boat like this could be safe (it has internal flotation) and offer more performance to the cockpit bound. For others it is a good trapeze candidate.
     
  9. Doug Lord
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    Doug Lord Flight Ready

    High Performance Small Multi Design for Disabled Sailors-and others

    ---------------
    Intriguing, but how would you right the rest of the boat?
     
  10. cavalier mk2
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    cavalier mk2 Senior Member

    The roto pod was for safety (five minute idea) with righting secondary. It would be possible either by flooding a hull and using a small amount of ballast or doing a for and aft turn and flood if the pod was set up on compass style gimbals. For multihull righting I really like a flooding and waterbag approach as shown by Jim Brown's "The case for the Cruising Multihull" but with the modern addition of a kite sail for pull. How did the guy who capsized going around Britain right?
     
  11. cardsinplay
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    cardsinplay da Vinci Group


    You mean like a Weta is not rightable without outside assistance? These two boats have similar length, beam and the Challenger has considerably less sail area. Yet, there are video clips on the Weta site showing that it is easily righted from a capsize by a solo crew. I would expect that a paraplegic person in decent shape could do that very same procedure with a Challenger, or a Weta. I think that you are underestimating the potential of a disabled sailor in your assumptions.

    Other than that, you are completely avoiding the information presented in the previous post. Kinda makes a person go, hmmmm.

    I think that maybe this thread is about a solution looking for a problem to which it can be attached.
     
  12. Doug Lord
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    Doug Lord Flight Ready

    High Performance Small Multi Design for Disabled Sailors-and others

    =============
    He had outside help. This is a tough problem-I appreciate "5 minute" ideas to help think it out. There are a lot of disabled people(and lazy,out of shape old guys and gals) who might benefit from a viable solution. Thanks.
     
  13. cavalier mk2
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    cavalier mk2 Senior Member

    The keel boat uldb with foils 5 minute concept offers more performance without capsizing in the first place. The idea is to let the foil beam stream back for docking etc...or to keep from tripping in heavy seas. Knockdowns are something to brace for. A small trailer sailor could be set up for a wheelchair cockpit and ramp into the cabin for a disabled person weekender.
     
  14. Doug Lord
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    Doug Lord Flight Ready

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    Something like this but more of a multi and no ballast?
     

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  15. cavalier mk2
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    cavalier mk2 Senior Member

    I would want the arms to be individually deployable for different situations, then they also don't interfere with the deck/cockpit. Perhaps the degree of performance and ballast/mono roto cat etc...multi choice could be sorted by who minds crashing and recovery and who doesn't. Prevention is always easier.....a good sheet release system would take care of most situations.
    When we have taken old,hurt or new people sailing it is amazing the difference a multihull makes for a safe platform. For the excitement crowd I do agree with our cardplayer that many of these people have a high degree of mobility for more active recovery options.
    It would be best on a mono to have some ballast for stability when docking, trailering etc...or the day something breaks.
     
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