Canting Keel Mechanisms

Discussion in 'Sailboats' started by SuperPiper, Dec 1, 2005.

  1. SailDesign
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    SailDesign Old Phart! Stay upwind..

    Doug,
    Yes, I have designed a canter (2 were built), but they were both hand-pumped hydraulic for offshore use. The trick is to let the keel gravity-drop to the "new" side before tacking, then tack and pump it the rest of the way if needed. THis saves an amazing amount of weight even over the electric versions, which was important for a 40' Open boat.
    I have drawn water-ballasted 60s that used power to pump and dump, but they have always had a manual backup in case the rules changed. :)
    Steve
     
  2. Doug Lord

    Doug Lord Guest

    canting

    Thanks, Steve! Very interesting.I respect your opinion on this and your consistency; I guess I just have a bit of a different view....
     
  3. SailDesign
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    SailDesign Old Phart! Stay upwind..

    We'd never have guessed, Doug... :)

    Steve
     
  4. Sly
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    Sly Junior Member

    Since were on the topic of Canting Keels...how do they seal the part of the keel that goe through the hull and in to the water so that a minimum amount of water comes in?
     
  5. SailDesign
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    SailDesign Old Phart! Stay upwind..

    Sly,
    On my canters, the "sump" gets sucked dry by the venturi effect at speed, but I can't (pun intended) speak for others' designs. I do remember Aqua Quorum having a similar setup.
    Steve
     
  6. Hoff27
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    Hoff27 student

    Very interesting discussion so far.
    I think that at time, or when volvo checks out, the moving keels will be banned from this race. Number of competitors have dropped and only a last minute bending of the entry rules brought the minimum of 7 competitors set by volvo.

    It will be banned just like computer controlled F1 cars and the likes.

    Sure bringing in diesel power is argueable in a sailing race, but men.. have you seen the canters sail? It amazing.
    I'l say ban all power moving keels from races an set up a two yearly race for power driven canting keel, masts and winches
     
  7. feetup
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    feetup seeker

    canting keels

    This thread has gotten to the heart of two diametrically opposite opinions and it's been fun to follow. I'm dragging it back out here a bit both for my penny's worth and to ask a question.
    I can see a parrallel with competative cycling where two camps exist, one which says 'regulate the cycle and let the winner have the best thighs and heart.' the other says 'lets see how far we can go using the latest and best in technology and let the winning team have the biggest wallet'. Even in the world of motor sports you have classes that are one design, relatively inexpensive where the driver and how he/she uses the luck of the day will dictate the result, and then you have F1 where the largest bankroll and what and who it can buy will inevetably be the champion.
    I believe there is a place for both worlds, even in sailing. Without classes like the VOR and the huge sums of money it consumes we wouldn't have the motivation to develop things like a power actuated canting keel. Sure, it's not a race of man vs. man, using only skill and the forces of nature, but it IS a race of designers, engineers, builders, technologists, and sailors. As long as there are vast quantities of money there will be classes like the VOR.
    I think that the new ruling allowing more power to cant is in the interest of safety and as long as none of the power is propulsive I can't see how it matters. It would be interesting where it would lead if all things except propulsion were allowed to be power assisted.
    As long as there is a place for the purist who competes on the basis of preparation, skill, and seamanship, I see no problem letting technology have a go.

    Now my question. With the keel canted to windward, the lift it creates vectors progresively more downward, effectively negating some of the vertical lift the hull will generate at speed, and reducing the lift to windward needed to counteract leeway. How do the designers deal with this paradox?

    Feetup

    Give generously, Epoxy CAN be cured.
     
  8. DGreenwood
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    DGreenwood Senior Member

    Now my question. With the keel canted to windward, the lift it creates vectors progresively more downward, effectively negating some of the vertical lift the hull will generate at speed, and reducing the lift to windward needed to counteract leeway. How do the designers deal with this paradox?

    That is what the dagger boards are for.
     
  9. feetup
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    feetup seeker

    DGreenwood;
    Do all canters have daggerboards?
    Feetup
     
  10. DGreenwood
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    DGreenwood Senior Member

    They do these days for the very reasons you describe. The foils used for the keel are designed for minimum resistance and still be able to carry the loads of the ballast. The idea is that the daggerboards will do all the "heavy lifting".
     
  11. CT 249
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    CT 249 Senior Member

    IThe Cookson 50, Radical 40 and Dovell designs have no centreboard. The lateral resistance comes from wings on the keel or (in the Cookson's case) a trim tab and limited cant on the keel.
     
  12. Doug Lord

    Doug Lord Guest

    Canters/lateral resistance

    Feet, developing extra lateral resistance as a keel or strut cants is one of the challenges of designing a canting keel boat. Some canters only swing the keel a few degrees; some like the CBTF(canting ballast twin foil) boats swing the keel around 55° to each side. The more the keel cants the more need there is for some other form of lateral resistance in addition to the area of the keel itself. Some of the main systems are:
    1)CBTF uses an aft foil and forward foil to steer and to develop lateral resistance. Because this system allows for "collective" steering upwind(turning both foils the same direction) the size of the ballast strut can be reduced and have a fatter section than a canting keel that also develops lateral resistance. Examples of this type of boat are Wild Oats, Alfa Romeo II,Maximus, Genuine Risk, the Schock 40 and two of the three Max Z86's-and there are others.
    2) Wings-Some systems -notably on the older Procyon, on the Backman 29 and on Andy Dovells Atomic- and now the Radial 40 use wings on the canting bulb so that as the keel comes up the foils generate the lateral resistance required. One main advantage with this system is simpicity-it doesn't take up any room inside the
    boat. Can have a cant angle comparable to a CBTF boat.
    3) twin asymetrcal daggerboards-used on some Open 60's and all(current) VOR 70's. One board is pulled up while the other is down. Each is generaly "toed in" a little to help reduce leeway . Generally used with 40-45° cant angle systems but could go more.
    4) The Cookson System-uses a trim tab on the back end of the canting strut but since this has limited effect the canting angle is not as high as CBTF boats or most others.
    --------------------------
    The same guys that patented the CBTF canting system have also patented a system that uses a trim tab on the back of the keel strut (like Cooksons but turned the other way when used) to develop downforce on the canting strut.Requires a high cant angle to be effective as well as using twin foils. Could conceivably reduce, even further, the amount of ballast required in a canting keel boat.
     
  13. DGreenwood
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    DGreenwood Senior Member

    OK---I should have said most of them
     

  14. RHough
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    RHough Retro Dude

    Nice synopsis Doug.

    Just to clarify the statement in the quote.

    Changing the angle of the foils has very little effect on leeway. The amount of lift required and the drag from producing that lift determins the leeway angle. What changing the angle of the foils does is change the angle of the hull in relation to the boat's course. A small reduction in leeway can be the result of reducing drag from the hull by changing its angle to match the course.

    CBTF boats have the ability to alter the angle "on the fly", the dagger board boats have the angle designed in.

    Randy
     
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