Remove my Daggerboards???

Discussion in 'Multihulls' started by Imi Loa, Mar 8, 2010.

  1. Imi Loa
    Joined: Mar 2010
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    Location: Catalina Island

    Imi Loa New Member

    Most of you are probably familiar with the Choy designed cats, I own 43' Imi Loa. The original owner added daggerboards as he was a racer, transpac etc.
    We have rebuilt this boat as a family cruiser, I am hauling out again next week for multiple projects, I am considering removing the daggerboards and trunks as they are a huge space taker in my two main cabins.
    I am more than qualified to do the work just looking for opinions on weather I should actually take them out, or leave them . Thanks Doc
     
  2. Corley
    Joined: Oct 2009
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    Location: Melbourne, Australia

    Corley epoxy coated

    Well, you will lose some pointing ability with the daggers removed but there are a lot of highly succesful cruising catamarans that use low aspect style mini keels for sideways resistance they also offer a good platform for drying out the boat.

    The specifics of what would be best in terms of a keel would be best calculated by a naval architect but the general gist would be to retain the relative area of the daggerboard in the design of the mini keels the negative is of course you gain some additional drag and wetted surface area which is no longer adjustable and will effect performance but for a cruising boat that may not concern you.

    From what I understand the Choy designs were quite fine fore and aft with a considerable amount of rocker do you have access to original plans for the boat as Choy may simply of intended the rocker to act as resistance to leeway but I think you would find mini keels offer better performance.
     
  3. Imi Loa
    Joined: Mar 2010
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    Location: Catalina Island

    Imi Loa New Member

    Thanks for the reply, I do have the original plans and yes it is fairly fine aft and fore. We have sailed it with them up and down learning the feel of the boat. It definetly tacks easier with them down and does point higher with them down. but it sails fine with them up. the boat was originally designed without them. I just want to make sure I'm not doing something stupid by removing them.
     
  4. Chris Ostlind

    Chris Ostlind Previous Member

    Doc,

    Get in touch with Wayne Iwamoto at Gil's Cats in Newport Beach, CA at: 949-646-5750

    Wayne's Dad, Gil, had an ongoing, boatyard relationship with all of the Choy/Polycon genre boats over many years.
     
  5. Imi Loa
    Joined: Mar 2010
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    Location: Catalina Island

    Imi Loa New Member

    Chris thanks for the heads up, I know Vic Stern the original owner had a relationship with Wayne and was a friend of Rudy Choys. I talked with Barry Choy ( Rudys Son) today at Choy Design, he recomended since they are allready in and in good shape just leave them in as they will assist in tacking and going to weather.
    I will call Wayne in the near future you are the third person to pass along his info to me and recomend talking with him, not to mention he is in my neighborhood of So Cal. Thanks for the help
     
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  6. kelldog
    Joined: Jun 2009
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    Location: Bakersfield, CA

    kelldog Junior Member

    Ima Loa;
    Do you keep your CSK in Catalina? I have a friend who just sailed his 33ft CSK to the Marquesas.
     
  7. Alan M.
    Joined: Jan 2006
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    Location: Queensland

    Alan M. Senior Member

    Have you tried sailing with just one board down? You might be able to just remove one, leave the other in place, if space is more critical in one hull than the other.
     
  8. oldsailor7
    Joined: May 2008
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    Location: Sydney Australia

    oldsailor7 Senior Member

    Take out the daggers and their boxes and fit Norm Cross type low aspect ratio fin keels. It will transform the boat and you wont notice any extra drag. A big advantage of LAR keels is the ability to dry out on the beach with no damage to the hulls.:D
     
  9. cavalier mk2
    Joined: Mar 2010
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    Location: Pacific NW North America

    cavalier mk2 Senior Member

    I agree with Barry. You may find yourself racing around the buoys one day and the CSK cats eventually evolved to carry daggerboards to compete upwind. Try sailing against a monohull with and without the boards to see how you perform. The one board option is worth a try. One of the best reasons for having retractable boards besides performance and the convenience of shoal draft is safety. with those boards pulled up in a storm you can sideslip with the waves instead of trip. CSK did offer metal delta shaped mini keels on some models but they need to be able to take the ground in a cruising boat. My Nicol vagabond/ cavalier has a cross style keel and I can't wait to cut it down to the stock size and install a offset daggerboard. The hazard of adding too much section width, and depth is reducing your prismatic coefficient and increasing your pitching moment on those large rocker hulls.
     
  10. oldsailor7
    Joined: May 2008
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    oldsailor7 Senior Member

    ??? Please explain. :confused:
     

  11. cavalier mk2
    Joined: Mar 2010
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    cavalier mk2 Senior Member

    Norm Cross explained it well with the area rule he brought in from aerospace. A boat keel essentially adds area to the hull. On his fast boats like the cross 32 the hull is narrowed in depth and girth in where the keel attaches so the overall section area of the hull-keel combination approaches that of a hull without a keel. This results in reducing/eliminating speed transition humps. Obviously a wide keel , say you wanted some big water tanks in there, adds more area than a narrow one. If you blend/average the area in with the hull you will notice it is like making a hull with more rocker. As you add rocker to a hull you start reducing top speed and increasing pitching moment. Think about raising the fulcrum on a see saw. This seems to apply more to rounder hulls than slender ones but look at the profile of fast boats, not much rocker. In the case of my Nicol . the float fins were removed and the area was added to the keel and a wide fairing for a airfoil section was installed. This had the result of turning a hull with the area curve of a torpedo boat into something resembling a cruising Piver. It creates a speed transition hump the boat has to fight through. On his last designs like Stilleto, Piver went the other direction ans started winning more races. A dagger board or centerboard because it is thin doesn't add much volume to the hull and hardly affects the area curve at all. A thin keel has much the same result except that you can't retract it for safety, shallow water etc... James Wharram's keels on the tiki series are probably a good choice for a CSK, less added depth, faster tacking, good grounding skids....I wish the folks at Choy Designs would publish those old plans. They are great boats that a new generation could learn from studying. Modern cruising cats are invariably surprised when my vintage tri sails past them, I know a good CSK could do the same.
     
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