Pivoted Daggerboard

Discussion in 'Sailboats' started by ancient kayaker, Apr 3, 2012.

  1. kvsgkvng
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    kvsgkvng Senior Member

    Here is a picture of the same concept for you to understand.
    I hope you understand it. Nice reference to "unobtanium" it has got under my skin, ;) Regards, kvsgkvng.
     

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  2. kvsgkvng
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    kvsgkvng Senior Member

    You don't. And I have no desire to sink myself in this discussion.
    If you want to gnaw on it -- the s.s. plate should be abit bigger and wider.
    That is all.
     
  3. ancient kayaker
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    ancient kayaker aka Terry Haines

    That concept would be no use to me as I launch and retrieve in extremely shallow water, or on concrete ramps which would wreck it, but thanks for the idea, and also for the comments, good and bad from others.

    I personally appreciate the people with experience and knowledge who take the trouble to comment, and perhaps we should leave it there for now. Of course, those who wish to pursue what is a side issue for me are always welcome to start another thread.
     
  4. PAR
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    PAR Yacht Designer/Builder

    I too live and play in very shoal waters, so attending to effective shoal designs are something I have a bit of experience with. With small craft, in the need of extreme shallowness, the leeboard or dagger are the logical choices, as they have the smallest footprint and internal volume/division within the hull. I have to admit I prefer centerboards, because of adjustability and the ability to use it as a depth sounder. Leeboards van be used this way too, but I hate the way they mess up the flowing lines of a sheer or other profile elements.

    I have managed to use a stub keel and short case with good success. It's a compromise (surprise) as you pick up a few inches of draft, but the decrease in case height inside the boat is a big consideration. In many designs I can get the case completely under the sole, but small craft don't have this accommodation, because of size. Another feature I've used recently is an offset centerboard, which hide completely under a cabinet and part of the V berth. The usually divided cabin (centerboard case) is wide open and the case is only 10" off the centerline, making for reasonable preformance.

    There are lots of shoal options, but the simple ones usually work best, unless absolute sailing preformance is desired.
     
  5. ancient kayaker
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    ancient kayaker aka Terry Haines

    I don't object to leeboards but on the current plan appearance is more important to me than usual. The stub keel provides a place to attach ballast as well, but that won't do on a beach launcher. Moving the trunk off center works well in a cruiser cabin, but I'm planning an open cockpit and the further the trunk moves off center the higher it will have to be! I think the simplest solution is to have two daggerboards: a short one for shoal waters and in bridge-infested areas and a long one for the occasional foray into open water.

    "I think I'd better think it out again!"
    (Fagin in the movie "Oliver" . . . )
     
  6. PAR
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    PAR Yacht Designer/Builder

    You can't live with a 6" stub (my other half does) and a 6" tall case inside the boat? This offers about an 11" wide board, which for most small craft is plenty. 6" is only ankle deep, so assuming your boat also draws 6", you'll be getting out in mid calf deep water, right? Let it flop over on it's bilge turn and you drag it the rest of the way up the beach.
     
  7. ancient kayaker
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    ancient kayaker aka Terry Haines

    The beach isn't the problem, I have a wheelie that fits in the trunk and turns it into a wheelbarrow. However, I then have to wade out a surprisingly long way as the lake bottom has a very gradual slope; with a flat bottom the boat will float in a couple of inches and I can just push it the rest of the way and hop in, but a stub would require me to carry it much further. I suppose I could just leave the wheelie in the trunk but the bearing is not waterproof - I'm not sure how long it would last once immersed.

    I could launch on the concrete ramp, the slope's steeper there, but for that, or for dragging up the beach, I would need to glass the bottom - I avoid glass if I can.
     
  8. tspeer
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    tspeer Senior Member

    If you want something that combines the pivot of a centerboard with a narrower opening in the hull similar to a daggerboard, I suggest you put the pivot point well forward of the opening in the skin, resulting in an inverted L shape to the board and head. This will allow the board to rise up as it kicks aft. The farther forward the pivot, the more vertical motion to the board. The downside is a large board case, however it may be shorter (but taller) than a centerboard case.
     
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  9. ancient kayaker
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    ancient kayaker aka Terry Haines

    I would like it to fit under the foredeck which would limit the height, although up to that height the trunk would be no problem - a deck would be higher than a thwart for example. Another option would be to have a lower aspect daggerboard, as I'm not looking for a performance boat. Perhaps a combination of the two will do the job . . . a nice aspect of a pivoted instead of a sliding daggerboard is, it may be possible to have the forward part of the "L" drop into the extended slot forward of the board, in the deployed condition. Par was concerned about this in his earlier post.
     
  10. gggGuest
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    gggGuest ...

    Just remembered: here are some photos of a sliding daggerboard boat, although the board isn't in place. As I recall the curved bits under the foredeck ensured the board cleared the end of the slot: there were rollers on the board that acted as limit stops as well as guides as the bord slid up.
    http://www.sailingsource.com/cherub/tomg1494.htm
     
  11. PAR
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    PAR Yacht Designer/Builder

    Yep, that's the curved case trick, which produces a long curved board and a long case, though it's forward and can be fairly low. Likely will interfere with mast steps, heavier than necessary and still will not "kick up" on a bottom strike, though if on a bungee and rollers, maybe move enough to prevent major damage.

    How about the "fan" style, which were common on sailing canoes 100 years ago. No real case to worry about and it'll be quite low.
     
  12. ancient kayaker
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    ancient kayaker aka Terry Haines

    Must be a ballasted daggerboard - I cannot see any pulldown arrangement. Took me a while to figure the mast is stepped on deck with associated standing rigging - slave of symmetry or large sail area? So much simpler to step it a couple of inches to one side . . .

    I have seen the fan type centerboards: arn't they bronze? 100 years ago is closer to my time but not quite my style Paul!
     
  13. gggGuest
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    gggGuest ...

    Its a perfectly normal shaped board in fact.

    No, not a ballasted board, but I think just being used as a straight daggerboard in the pics so the strings aren't rigged. The boat, BTW, is probably under 120lbs stripped of spars and loose gear, and was a serious racing boat in her day, so off centre spars weren't really very desirable.
     

  14. ancient kayaker
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    ancient kayaker aka Terry Haines

    - actually for my purposes an off-center trunk would make more sense, preserves keel integrity and leaves the far more visible mast dead-center.

    I must admit that - ever since I studied a gondola - asymmetry in a boat ceased to bother me. The farthest off-center I have placed a mast (so far) was on the starboard gunnel - The purists will probably stop talking to me now . . .
     
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