Center board and rudder

Discussion in 'Boat Design' started by SeaPig, Dec 18, 2020.

  1. SeaPig
    Joined: Dec 2020
    Posts: 26
    Likes: 0, Points: 1
    Location: Fl

    SeaPig Junior Member

    hi All,
    I’ve read so many posts here I figured it was time to join. I picked up a small sailboat this summer that needs a bit of cosmetic repair. (So I thought.)

    upload_2020-12-18_10-23-12.jpeg

    Some things I think I need to sort out with some help from this group.
    16 ft long with a 32 inch bowsprit
    100 sq ft of sail
    problems:?
    Only 2 sq ft of dagger board
    About 1.5 sq ft of rudder and both are just flat boards with no foil
    Also, the “new” dagger board trunk’s center is 24 inches in front of the hulls CLR (found with a float check). I think it was replaced in 2016.

    This little craft needs 20 degrees of rudder to drive the nose windward underway. So that is slowing me down. And as found during the maiden voyage, pointing into irons to drop sail and releasing the tiller results in a surprising Lee turn and a swim!
    My plan is to build a new center board that is 4 sq ft of wet surface with a NACA foil. It would be 2 inches thick, so a new trunk would need to be constructed and I figure moving it to the CLR would improve overall performance.
    I also plan to build a new rudder. Also with a foil and possibly a larger area. (The discussions on this topic are not simple solutions.)
    SEAPIG
     
  2. bajansailor
    Joined: Oct 2007
    Posts: 1,798
    Likes: 574, Points: 113, Legacy Rep: 37
    Location: Barbados

    bajansailor Marine Surveyor

    Welcome to the Forum Sea Pig.

    Your new boat looks very fine -was the above photo taken after you completed all the cosmetic repairs that were required?
    Do you know who designed or built her?

    It sounds like you have a massive amount of lee helm - or is it weather helm? With the board so far forward I am thinking it will be weather helm?

    You mention the CLR - do you mean the centre of buoyancy (re how you did a 'float check'?)
    You generally want to have a bit of 'lead' - ie the centre of the combined sail area is a bit further forward than the CLR.
    Edit - sorry, that should be the other way around, as noted by Messabout below.

    Have you got any photos of her out of the water with the daggerboard and rudder down?
     
    Last edited: Dec 18, 2020
  3. SeaPig
    Joined: Dec 2020
    Posts: 26
    Likes: 0, Points: 1
    Location: Fl

    SeaPig Junior Member

    Bajansailor,
    I do have a photo, but I saved it as a pdf and when I figure out how to post it I will.
    As for the work, not yet! That’s what the cold season is for.
    I don’t know who built it in 1965. It is fiberglass over cypress by design. Some of the nice veneer hull is rotten and needs to be done. Not Structural. The fiberglass is stout! I want to get it sailing well (less Lee helm) and then bring it back to looking good.
    It has a LOT of weight sitting above the waterline. The deck was redone in 2016 with 3/4 ply. The mast is solid.
    I’ll post a picture of the dagger board.
     
  4. SeaPig
    Joined: Dec 2020
    Posts: 26
    Likes: 0, Points: 1
    Location: Fl

    SeaPig Junior Member

    Sorry,
    With the boat floating in the slip, I pushed it sideways until I found the hulls center of resistance. I did this with and without the dagger board in. I believe one discussion referred to this as the centerline of resistance CLR. Most depicted sail plans have the center above or just in front of the CLR.

    SP
     
  5. SeaPig
    Joined: Dec 2020
    Posts: 26
    Likes: 0, Points: 1
    Location: Fl

    SeaPig Junior Member

    upload_2020-12-18_12-45-43.jpeg
    right at the wear Mark prior to the bend it’s 9 inches wide as it leaves the hull.
     
  6. JSL
    Joined: Nov 2012
    Posts: 807
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    Location: Delta BC

    JSL Senior Member

    That's a long sprit? Is it 32" from the stem head or 32" length overall.??
     
  7. messabout
    Joined: Jan 2006
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    Location: Lakeland Fl USA

    messabout Senior Member

    Seapig, just to clear the understanding, let me describe lee helm/weather helm so that we are all talking about the same thing. Lee helm is when the boat wants to go in the direction of the wind if the rudder is near neutral. The opposite is true for Weather helm. The boat will want to climb toward the direction of the wind. Weather helm will have you pulling the tiller in a direction that points downwind. Lets say that you are sitting on the weather side, ...then you will be pulling the tiller toward you.

    No way you have enough board to accommodate 100 square feet of sail. Rule of thumb is in the region of 5% or more of the sail area. If you do not have enough leeway resistance by virtue of the board, then the boat will be a pig (no pun intended) to sail.

    A modern boat of that size does not often have a bow sprit. Modern outlandish hot rod boats have retractable sprits If you have a jib or foresail rigged to the forward end of your sprit, then the sails center of effort is going to be pretty far forward. That means that board will need to be pretty far forward as well. The balance of the rig versus the lateral resistance of the boat is usually determined by a wild guess and then experimentation. In general the center of lateral resistance of the boat, including the board and rudder needs to be somewhere in the neighborhood of 5% or more forward of the sail's center of effort. With that long bowsprit, I suspect that you may very well have the lee helm that you describe.

    Weather helm, you can live with if it is not excessive. Lee helm is dangerous because the boat can not do what you tell it to do.

    Are you in Florida? If so where? Your picture looks like it might be in a salt marsh somewhere. we have plenty many of those locations here in the sunshine state. Fresh water maybe? I did not see any Mangroves........
     
    bajansailor likes this.
  8. SeaPig
    Joined: Dec 2020
    Posts: 26
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    Location: Fl

    SeaPig Junior Member

    Messabout,

    we are on the same page. Having a background with flying scots (initial training) hobie cats and some 40fter time I was startled (and then wet) when my new boat ran with the wind as I tried to drop sail when the wind came up.
    I don’t mind jibes, but I hate surprise jibes!
    So, the dagger board is forward, but so much that I feel that tacking requires a hefty amount of energy to overcome the boards location. Rather than the usual pivot around the location of the keel or boards center.
    No work has been done, other than re running the main sheet to make it sailor friendly.
     
  9. SeaPig
    Joined: Dec 2020
    Posts: 26
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    Location: Fl

    SeaPig Junior Member

    Location,
    Emerald Coast of north west Florida. Chocktawatchee bay. Just enough salt to make it easy to keep a boat.

    I’ll share pictures of the remains of whatever was there by the dagger board before the refurb in 2016. Maybe this had a center board and not a dagger board? Perhaps I’ll get really lucky and someone will recognize their work and help me bring it back to its original glory.
    Either way, it’s to pretty to let it rot away in the woods and I’m not in a hot dog rush to get anywhere or it would be another Hobie.
    Pig
     
  10. SeaPig
    Joined: Dec 2020
    Posts: 26
    Likes: 0, Points: 1
    Location: Fl

    SeaPig Junior Member

    Final thought,
    Sorry but I’ve been researching like crazy.

    if I move the dagger board back and increase its area, that will give me up to 2 feet to move the mast step backward (experiment if you will) until the Lee helm neutralizes and/or I get some weather helm.
     
  11. SeaPig
    Joined: Dec 2020
    Posts: 26
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    Location: Fl

    SeaPig Junior Member

    Here is the pdf picture rigged on the trailer.
     

    Attached Files:

  12. Blueknarr
    Joined: Aug 2017
    Posts: 1,075
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    Location: Colorado

    Blueknarr Senior Member

    I think the bowsprit is an add on. Try sailing with just the main.
     
  13. SeaPig
    Joined: Dec 2020
    Posts: 26
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    Location: Fl

    SeaPig Junior Member

    32 inches that protrudes forward of the bow.
     
  14. SeaPig
    Joined: Dec 2020
    Posts: 26
    Likes: 0, Points: 1
    Location: Fl

    SeaPig Junior Member

    It does all right with the main. I sailed a day like that after I changed the way the main sheet runs. As I recall, the rudder inputs were more neutral but the boat doesn’t like to tack. I believe it’s because the dagger board is so far in front of where the boat wants to pivot it has to be pushed laterally through the tack.
    I will sail it again with just the main and take better notes.
    I think I’ll also do a handling test while the mast is off. With and without the dagger board to see how the boat maneuvers.
    Don’t get me wrong; it’s not all bad. This boat loves to sail downwind!
     

  15. Blueknarr
    Joined: Aug 2017
    Posts: 1,075
    Likes: 228, Points: 63
    Location: Colorado

    Blueknarr Senior Member

    It seems like a job was added to help pull her thru a tack.
    Unfortunately it is too big of a jib.

    A smaller jib might be easier than moving the dagger board.

    I agree that a bigger board is in order.
     
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