Upwind daggerboard installation on a production displacement sailboat

Discussion in 'Sailboats' started by peterchech, Jan 2, 2012.

  1. peterchech
    Joined: Aug 2010
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    Location: new jersey

    peterchech Senior Member

    I have a hunter 25 with shoal draft keel, drawing 2'11". The boat goes upwind, but due to the keel and the fact that I rarely have much crew aboard to straighten up the boat, it's upwind performance leaves much to be desired especially as wind speed kicks up.

    Many racing boats have canted daggerboards (think mini 650) just ahead of the unheeled clr that are lowered when beating upwind. Mostly this is on boats with a canting keel.

    The j-108 is a shallow draft j boat that has the same draft as me, but has a centerboard for upwind work. According to a review linked on the manufacturers website This really helps the boat climb to windward.

    I bought my boat for $1400 and don't care much about cabin space or resale value. I have some experience with fiberglass and have built a few small boats. My question is, has anyone put lifting canted daggerboards on a displacement production sailboat to get some better upwind performance? Assuming I have the time and skill to do it, is there any reason this couldn't work? I am thinking a 15 degree can't to the boards would be perfect, with maybe a 2 degree toe in. They would be located about a foot ahead of the upright clr. The exit point would be above the upright waterline, and the cases glassed to a bulkhead. Thoughts? Ideas?
     
  2. michael pierzga
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    michael pierzga Senior Member

    Find the Righting moment numbers for a Hunter with a deep keel and compare them to your righting moment with the stubby keel. Find out what the designed waterline is...displacement....deep keel vs stubby. Is your keel lead ?


    Better foils will certainly help windward performance but you still need righting moment....power ...and float on the designed lines. Perhaps an off the shelf performance keel from a wrecked boat could be substituted.

    To make a boat perform upwind all the different variables must work to your advantage.

    The rudder ???

    Duckbill prop ?

    Sail trim is also important for upwind work. Check your genoa sheet tracks to see if they are placed for tight sheeting angles.

    On the race course I can tear up sister ships upwind with a polished bottom...perfect underwater surfaces.
     
  3. sorenfdk
    Joined: Feb 2002
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    sorenfdk Yacht Designer

    You said it - the problem is lack of stability! And this is not solved by adding daggerboards.
    My suggestion is to build a deeper keel with the same displacement, maybe with a bulb. This is probably not something you can do yourself, but it is a much more efficient solution to your problem!
     
  4. sharpii2
    Joined: May 2004
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    Location: Michigan, USA

    sharpii2 Senior Member


    Two things to consider first:
    1.) Reefing
    2.) Adding ballast. The ballast can be installed inside the boat temporarily, to see if it helps.

    If I were to add appendages, I would consider lee boards. They end up far enough from the fixed keel to, hopefully, not interfere with it, and they are relatively cheap and easy to install or remove.

    If they are much higher aspect ratio than the keel, the keel will be doing little of the upwind work. Its weight will still help hold the boat upright, but, other than that, it will be there mostly for the ride.

    Same goes for your proposed canted dagger boards. So, figure their area accordingly.
     
  5. peterchech
    Joined: Aug 2010
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    peterchech Senior Member

    Well changing the 2000 lb keel is a bit more than I want to bite at right now (I don't even know how I'd go about it) and i really like the shallow draft of this boat so a deeper fixed keel isn't really an option for me right now. A lifting bulb keel would be cool, don't get me wrong, but that is much more of an investment in time and money on a displacement boat than its worth for me at least.

    Hmmm if keeping the boat upright is crucial, maybe instead of foils water ballast might help? A port and starboard tank, maybe under the settees, that could be filled alternately during each tack? (another race boat trick)... I wonder how much would be used, I imagine the weight of two crew would be a safe number, so about 6 cubic feet of tankage per side. That would not be difficult to do at all, much easier than making daggerboards and fitting cases...

    Would the foils just not do as much as simply keeping the boat straighter, even with my stubby shoal draft keel?
     
  6. sharpii2
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    sharpii2 Senior Member

    Added foils would not help keep the boat level. They would only improve the boat's pointing performance.

    The water ballast is a good idea. Like my suggestions, it is relatively easy to instal and get rid of.

    It's a pity water ballast isn't used more often. Much of the reason for that are the development rules of the off shore single handed boats of the '80's and '90's. The moveable ballast was allowed as long as it didn't heel the boat more than 10 degrees when on one side in calm conditions. I don't remember if the canting keel had the same restriction.

    The canting keel is probably at least twice as effective, but probably eight times as expensive.

    The water can be shifted from one tank to the other with a hose and a simple gate valve. It could be allowed to run down hill to the low side, just before changing tacks.
     
  7. michael pierzga
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    michael pierzga Senior Member

    Water ballast generates righting moment but it also makes a boat heavier. Its also difficult to get enough water ballast up under the sheer clamp to justify all the work.

    First do an inclination test to determine the righting moment of your boat.

    Additional lateral risistance from added foils causes a boat to trip. Lateral restance must be offset by righting moment.

    As an experiment fabricate a small plywood foil, daggerboard, and epoxy fillet it to the boat on one side only.




    If the angles are correct you dont need much daggerboard...a little stubby one will prove your concept.
     
  8. Gary Baigent
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    Gary Baigent Senior Member

    Here's a radical suggestion to either dismiss or think about: get rid of the stubby keel, clean up and fair the bottom, melt the lead and pour into moulds shaped so they fit between the (glass reinforced) floors and place them like bars of chocolate around the ex-keel base area (just like a NZ Mullet boat or Laurie Davidson's champions Fun and WaveRider). Build two asymmetrical, deep daggerboards and cases and mount them in line where the old keel was but at an angle through the turn of the bilges (so when the boat is heeled, the leeward one is vertical) - plus make two ballast tanks against the interior hull sides, or ... have a sliding athwartships double rail system carrying some of your lead pigs up to windward, (will clutter the interior but you're not concerned about that) either or, both will work - and will take much the same time to build. Now you've got a clean hull with highly efficient leeward foil down, windward one up - the boat will really crank to windward - plus you've got the same ballast but with some of it carried up to weather (where you really want it). Now the boat will really perform.
     

  9. Petros
    Joined: Oct 2007
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    Petros Senior Member

    Replacing the keel with dagger boards also sounds like a lot of work.

    THis is what I would try: add winglets to the existing keel. No moving parts, no through hull alterations. Keeps shoal draft. If they are made of something heavy like cast iron or lead they not only improve the effective keel aspect ratio but also adds ballast. You get the benefits of more righting moment AND more effective keel.
     
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