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

    ===================
    My interest is to see if a high performance multihull could be designed that would be safe for most disabled people. The Challenger looks like a great little boat but it is not a high performance multihull. It's tough to come up with an answer to something like this but it may be worth the effort.
    A multiple role boat may be an answer.....
     
  2. Doug Lord
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    Doug Lord Flight Ready

    Rave foiler

    The Rave and Hobie Tri foiler have a neat arrangement for the crew sitting in the center of the boat. That's because the foils develop almost all the RM and the crew doesn't have to move to keep the thing going fast. But for the application in this thread there is a big problem: it would be impossible for a significantly disabled person to right the Rave(and probably the trifoiler).
    In order for a multihull to be high performance AND suitable for most disabled or physically restricted sailors, it seems to me that there must be a solution to the righting problem.
    Boats like the Challenger could easily be outperformed by the Trapwing in a high power self-righting configuration.
    -----
    I think a solution for small high performance multihulls may be able to be developed but it is not going to be easy-but that is the point of this thread. There are many disabled,potentially disabled and people with physical restrictions that have a need for speed and I don't think designers should ignore this real need. I think high performance multihull sailing can be opened for a lot more people than it is now.
    -----
    But the competition will be tough: monohull technology is improving with breakneck speed and the thought of a self-righting MONOHULL foiler is not just fantasy anymore: it is a real possibility. I think with a lot of concerted effort it may be possible to develop a high performance multihull that could be faster than any monohull and -somehow- be self-rescuing. Very tough problem, though.

    I'm hoping Dave Trude will post a comment in this thread..........


    Pix: Trapwing model 1& 2, Rave, Weta, Challenger
     

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  3. cardsinplay
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    cardsinplay da Vinci Group

    Except for one really big issue...

    Not all boats need to be high performance in order to be extremely successful designs. In fact, most boats are not high performance and they outnumber those that are by an enormous margin.

    This thread could have been so much more relevant to the majority of sailors, as well as members visiting the site if it had been constructed to recognize that powerful point.
     
  4. Doug Lord
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    Doug Lord Flight Ready

    High Performance Self-Righting Multi Design for Disabled Sailors-and others

    Well, an idea:
    1) a boat that for another use would be a two person tri,
    why: to allow room in the "numbers" for ballast,

    2) a tri that would be very wide-about 1.4 times length-a bit more than Hydroptere,
    why: to have very high righting moment for high performance in a folding design and to facilitate 3) b. below,

    3) to have two hydrofoils on the main hull(rudder on extendable gantry) utilizing a wand based altitude control system,
    why:
    a. the foils allow the main hull to fly in a 5 knot wind(very important design target)- it wouldn't fly until much later wind wise without the foils,
    b. since the crew will not move and the requirement for righting moment will increase with wind speed the foil system will automatically add righting moment as required with no intervention required by the crew.
    c. As the wind increases the foils will unload and then load again with downforce up to a max wind pressure of 1.8lb per sq,ft,(same max pressure before reefing/depowering as an F18 catamaran),
    d. the foils, together, act to control pitch very effectively and allow more sail area than could otherwise be carried,

    4) small amas designed to keep the boat upright in an as yet undetermined gust when dead stopped,
    why:
    a. to reduce ama weight yet provide essential buoyant RM but not enough buoyancy to support the total boat weight. "Foil assist"( perhaps DSS), a planing surface or full flying foil would support the total weight at speed.
    b. amas would be well clear of the water(dihedral in cross arm design) at static in order to allow ama buoyancy to work toward minimising the effect of a capsize or pitchpole ,

    5) the clincher: the boat would use ballast on the hydrofoil strut-just enough to recover from a capsize or pitchpole. This simple solution eluded me for the longest time but I believe it will work because, as per #1 above, the boat would be designed to carry the weight. This would allow a very high performance foil assisted(or full flying) trimaran that could be sailed safely by almost anyone.

    pix "bulb" on the 26' foiler Mirabaud-this would have a larger version/click on image:
     

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    Last edited: Dec 6, 2010
  5. cavalier mk2
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    cavalier mk2 Senior Member

    You would need to crash test that one to sell it Doug. Another pressing need is adaptive controls because some people have the use of hands,some feet, some a hand and foot etc...And a self righting system has to take into account varying degrees of assistance. In order to reach more people without government funding a less exotic approach needs to be contemplated. A self righting el-toro might reach more people. The challenge with rocket ships is to keep the aquanauts from getting lost in space....space....space.....or the wet blue yonder!
     
  6. Doug Lord
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    Doug Lord Flight Ready

    ================
    There is room for improvement in adaptive design across the board ,Cav. But this thread is about trying come up with a viable high performance multihull solution for disabled sailors. I think this may be it. I had never considered combining the MPX system with a fixed keel-so simple and so workable. I couldn't sleep last night going over this thing-it is very is exciting to have put these two ideas together. Neither one by itself would work for a high performance multi that is self-righting but the two together appear to be a breakthru in design thinking. It's really got my attention......
     
  7. cavalier mk2
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    cavalier mk2 Senior Member

    I think I'd start with a outrigger/proa. The ama ,lightly ballasted has a flooding -pumpout system that can be run electrically. A mast with buoyancy is the other tool. After a capsize the aquanaut swims to the panel and presses the start button. The ama floods and with the mast helping the boat turns to 90 degrees and the sail is lowered. Our sailor starts the next sequence and the ama starts to pump out, the mast won't let it right the wrong way. The aquanaut swims over the ama and deck/tramp as it rises and is lifted out of the water as the ama is pumped out eliminating reentry gymnastics. He/she then raises the sail (or unrolls it, also could be electric) and blasts away. I think I'd make it a Pacific configuration with a sliding seat so the aquanaut could really power up.
    This is a lower tech reasonably high performance boat that would also suit older sailors and the less athletic. Foils could be a accessory for those with deeper pockets but it would get more people more speed with safer recovery than they have now. It is simple enough to be built at home or in a school setting opening another avenue of empowerment and therapy.
     
  8. Clarkey
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    Clarkey Senior Member

    The Challenger tri was designed by Rod Macalpine-Downie. The design was commissioned by Diana Campbell
     
  9. Doug Lord
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    Doug Lord Flight Ready

    High Performance Small Multi Design for Disabled Sailors-and others

    ============
    Good thinking . Not sure if you could achieve a boat that would be "high performance" when compared to already existing high performance designs but it sounds like it could work assuming the crew can swim, hoist sail and move on a sliding seat.
     
  10. cavalier mk2
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    cavalier mk2 Senior Member

    The crew if life jacketed (as they should be ) just needs to be able to float and slither as the sail can be set up to furl electrically as stated.
     
  11. cavalier mk2
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    cavalier mk2 Senior Member

    The seat could be electrically powered too if needed. Set up with a Newick/Brown style pod/wing on the main hull it should be hard to capsize in the first place making it easier to chase the beachcats. Retrofitting a cat is possible but it is harder to get the sail carrying power assuming that trapezes couldn't be used.
     
  12. Doug Lord
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    Doug Lord Flight Ready

    Roughly, how much SA, all up weight and beam would you envision?
     
  13. cavalier mk2
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    cavalier mk2 Senior Member

    Play with the concept, this is another 5 minute idea for the roll your own people. The limits are when the concept stops making sense. Beach boat to cruiser the idea is applicable, the size range should be determined by use. 18-25 feet seems a good place to start for a solo performance boat that could also carry an instructor/friend when wanted.
     
  14. Doug Lord
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    Doug Lord Flight Ready

    High Performance Self-Righting Multi Design for Disabled Sailors-and others

    It seems to me when discussing "high performance" small multihulls that perhaps a benchmark might be appropriate. So I've picked an F18 cat, that while somewhat heavy for its length is considered by many to be high performance. The boat has twin trapezes and an asymetrical spinnaker downwind. Also, I just happen to have the data for it in a convenient location:

    F18
    Specifications:
    Length: 17' 11" / 5.46 m
    Beam: 8' 6" / 2.59
    Draft w/Rudder Up: 7.1" / 0.18
    Mast Length: 29' 6" / 8.99
    Sail Area:
    227 sq.ft. upwind SA
    454 ft2 / 42 m2 downwind SA
    SA/WS:
    --two hulls in water- 4.77/1
    -- single hull in water- 6.03/1

    Bruce Number: 1.66
    SA/D: 44.16
    W/SA: 3.29
    Weight (with spinnaker): 397 lbs / 180 kg
    ================
    I'm not sure but I don't think a Pacific proa singlehanded by a disabled person could approach these ratios or this performance.
    Heres a comparison to an 18' tri design-originally conceived of to sail with one or two people sitting in the center of the boat. Both the F18 cat and the 18 tri were compared with 2 175lb people aboard. So, for the purposes of this thread the tri would be sailed singlehanded with 175lb of ballast at the foil strut juncture-and be self-righting. The tri would use two foils on the main hull as per post 19 of this thread.

    18 Tri
    Specifications:
    Length: 18' / 5.49m
    Beam: 16' / 4.88m
    Draft w/Rudder Up: 6.4"
    Mast Length: 31.5' / 9.6m
    Sail Area:
    277 sq.ft. upwind SA
    575 ft2 / 53.4 m2 downwind SA
    SA/WS:
    -- not flying-5.73/1
    -- flying main hull-10.26/1
    Bruce Number: 1.83
    SA/D: 53.89
    W/SA: 2.71
    Weight (with spinnaker): 400 lbs / 181.9 kg
     

  15. cavalier mk2
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    cavalier mk2 Senior Member

    Perhaps it would be wiser to think of appropriate performance. A Pacific proa could have very long akas to make up for the trapezes and such things can be carried to extremes. "High performance" for me will be defined as a boat capable of exceeding 12-15 knots. In fact higher speeds can be managed but the goal should include safety and safe recovery as the higher performance priorities. Knots per dollar will also be a useful benchmark in comparisons.
     
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