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  1. #1
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    Default replacing a TS16 centreboard with bilgeboards

    I've got this TS16 which I am wanting to turn into (my) ideal cruising boat.
    One of the things I'm toying with is replacing the large and intrusive steel
    centreboard with a couple of swinging bilge boards, set up something like
    B&B's Bellhaven 19' or Selway Fisher's Lynx 16.

    The new cases would sit along the second stringer, not too far from
    centreline so as to be hopelessly out of parallel water flow, but wide enough
    to take the ground flat. This would give unobstructed foot / portapotti /
    standing-up room midships.

    They would butt to frame 3 at the forward end, and past frame 4 at rear,
    tying to cabin wall, bunk tops & cockpit floor. Coupled with suitable logs &
    reinstating the hole at the back of the cabin where the centrecase exits,
    I think they would be well enough supported.

    They would protrude maybe 4" below the bottom, level with the keel.
    The pivot bolt would move into this protrusion - external to the cabin -
    eliminating a common leak/weep point.

    The total wet area of the two boards would be about 10% greater than the
    existing centreboard, and move CLR in fully down position about 8" forward.
    This would be offset by the ability to independently vary the board angles,
    plus the likely moving the sail COE forward by changing the rig to cat ketch.

    I would expect some slight loss of performance, but I'm not racing so not
    worried.

    Question - what (if anything) am I missing?
    Why would this not be a good idea?

    cheers
    Alan J
    Last edited by b.o.a.t.; 15th June 2012 at 01:44 PM. Reason: add pics

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  3. #2
    Join Date
    Mar 2007
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    Adelaide
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    Default

    Well AJ my first thought was you have been watching too much KTL and Mr. Winter has brain washed you.

    Then I thought hmm......seems like a lot of work for a potti but one must not underestimate the importance of these items.

    So without any concern to performance from a practical point of view seems like a worthwhile project.

    As for the impact on how she'll sail think I'll leave that to one of our regular knowlegable types.

    Cheers
    Mike
    "Working to a rigidly defined method of doubt and uncertainty"

  4. #3
    Join Date
    Dec 2004
    Location
    Rushworth, Victoria
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    Default

    If you seal the board pivot well it doesnt leak, I had a pivot bolt with head/nut cut off and two sealed and screwed covers over the ends. And the centrecase makes for a very good place to brace ones foot when the wind gets up.
    "World's oldest kid"

  5. #4
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    Sep 2011
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    kallangur qld
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    Default

    I have just built a pivoting center board, into a sailing canoe, this was not sealed at the pivot bolt.

    Fro what you are doing , I would counter sink the bolt hole with a speed bore( both sides), by 3mm, seal the timber with epxoy resin, then cut washers from gasket rubber, with a slightly undersize hole for the bolt.

    Fit a s/steel washer under the bolt head, and under the nut , then just nip the nut , does not need to be over tight .

    Just a suggestion,

    Jeff
    vk4

  6. #5
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    Rushworth, Victoria
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    Default

    I just thought of something else too Alan, having looked at your drawings again.
    Your bilge boards dont project very far up into their cases so the sideways leverage would soon wrench them out I'm afraid. The standard centerboard projects the full height of the case and that is in turn braced by the bulkhead.
    "World's oldest kid"

  7. #6
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    Default

    Noted Andrew
    These are 30 second concept sketches, not final plans.
    The pivot would be somewhat further aft to give a goodly amount of board
    still in the case to resist twist & lateral loads. Most important seems to flow
    as an extension of a comment PAR made a few weeks ago, about transferring
    loads to the keel. The bottom isn't strong enough to handle the sort of loads
    that drying out & bumping into things would impose. Also, given a bit of
    shape, the downward case extensions should contribute to lift.

    Still thinking through control line arrangements to keep their exit above water
    line when heeled.

    Jeff, there are a number of ways of creating a reliable seal on the pivot bolt.
    I like John Welsford's pivot tube with sealing rings each end the best. The
    attraction of moving it outside is that I don't have to worry about any of them !

    Also still thinking through sail plan, mast location & tabernacle design.
    Solo, including installing the outboard, it used to take me about an hour from
    arrival at the ramp to sailing away. Same in retrieval. I want to halve that,
    or better. At this stage, a cat ketch keeps all the bits relatively small & low-
    stress - therefore light & cheap - without sacrificing sail area from Hartley's
    original. (Unfortunately, Richard Hartley is long deceased, so I can't waste
    his time with this stuff.)

    regards from a daft & incorrigible fiddler
    AJ

  8. #7
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    Default

    ps...
    I guess I'm trying to turn a TS16 into a de facto Murray Isles Chestnut Teal.
    I've seen nothing else that comes close to what I'm trying to achieve in cabin
    head-room, stability, sail plan & user-friendliness.

    Why not just build a Chestnut Teal ?... Simple.
    I got the TS on a trailer for under $1K .. less than the price of a trailer,
    let alone building the Teal.

    By the same token, I'm not quite willing to turn a perfectly good TS16, albeit
    one which hasn't been in the water for almost a quarter century, into unsailable
    & unsaleable firewood. If I am not reasonably confident that what I'm thinking
    will 'work', I'll either do the boat up as standard & flog it (or just flog it as-is),
    and build/buy something else.

  9. #8
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    Quote Originally Posted by m2c1Iw View Post
    Well AJ my first thought was you have been watching too much KTL and Mr. Winter has brain washed you.
    If this were true, I'd just buy plastic snot & go sailing.
    That is probably the most rational course of action, but stuffit.. what's the big
    attraction of being rational anyway ??? "Rational" is totally overrated IMHO

  10. #9
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    Feb 2008
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    Eustis, FL, USA
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    Default

    You'd be better off placing the case inside the furniture, so you can gain free triangulation with the rest of the boats structure. The most important portion of the case is the top, directly above the pivot point. This is where the case will be tested.

    The lanyard can be enclosed, not dangling in the water and the case top can also be sealed tight, so no water spurts out of a slot. I've been using a board and lanyard design that I stole from a S&S design years ago. It eliminates the usual lever arm on the back of the board and keeps the lanyard out of the water. It also permits a tackle (weighted boards) to be employed easily.

    Shown is the setup I usually use, though in this case it's a modification to a popular home build, which had an open slot and lever arm (shown in pale blue). The board on this boat had a 15 pound weight, which caused it to sink with authority, so a whip tackle (2:1) was used to make the hoist easy. The tackle lands on a cam cleat under a midship thwart.

    The difference with my versions and this one, are I'd have a lower pivot point, to gain a slight leverage advantage and make the pivot easily replace, being "let" into the bottom planks. When at all possible, I try to keep the pivot out of the boat, placing it in the planking.

    The other image is one of my designs with better detail about the pivot arrangement. It still has an internal pivot, mostly because the bottom planking is too thin to bury one outside. Note the cross bracing at the top of the case at the pivot pin location. This is where the case will try to twist itself out of the boat.

    I should add that I never make an internal pivot pin, accessible with removable covers. I glue them on and they become part of the case sides. Removable covers eventually leak. If you need to access the pin, then a chisel and a few swats with a hammer will get you in, grind it smooth again and glue on new pin plates. It's simpler and leak free.

  11. #10
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    Thanks Paul
    Snap! on most items, including building the cases into the furniture.
    They would become the bunk faces. Tying the inner face at the pivot to the
    structure will probably have to be accomplished via the top cap & bunk framing.

    Will probably have to lead the lifting lanyard aft & up through a tube, as I think
    the case top would be at or below water line at 20degree or greater heel.
    Intending to significantly weight the boards to offset loss of the steel plate, so
    I'll also need to support the boards to de-load the lanyard whilst trailering.
    regards
    AJ

  12. #11
    Join Date
    Jun 2011
    Location
    Melbourne
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    Default

    In other news, What do our fellow TS16 owners think about modifying the current standard centreplate in a similar fashion as PAR's examples- eg. Fully enclosed case, lanyard over rounded top, instead of the lever arm it has now? I'm not worried about the class certificate so would there be any major issue doing it?

  13. #12
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    Aug 2008
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    Melbourne
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    Default

    Quote Originally Posted by PAR View Post
    ...... I never make an internal pivot pin, accessible with removable covers. I glue them on and they become part of the case sides. Removable covers eventually leak. If you need to access the pin, then a chisel and a few swats with a hammer will get you in, grind it smooth again and glue on new pin plates. It's simpler and leak free.
    Thanks Par, I'll have to do that. I have one of the larger Hartleys, and in thirty or so years the only times we've removed the covers is to reseal them when they leak. The pin has never been removed.

  14. #13
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    Default

    Quote Originally Posted by Asrainox View Post
    In other news, What do our fellow TS16 owners think about modifying the current standard centreplate in a similar fashion as PAR's examples- eg. Fully enclosed case, lanyard over rounded top, instead of the lever arm it has now? I'm not worried about the class certificate so would there be any major issue doing it?
    You might have to up the purchase ratio on the lifting tackle, or increase the
    thickness of the rope to hand. The extended lever arm that I hate so much
    about doubles the purchase around the pivot compared with PAR's rounded
    CB top.

  15. #14
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    I should note that this setup is reserved for small, light weight, non-ballasted craft. Larger boats, with ballasted boards use a different setup, though more purchases can be employed. I have a 23' ketch that lifts a 600 pound (272 kilo) board, using a similar system, except a winch is used, instead of tackle. The winch has a small powerboat destroyer style wheel (my idea to prevent fouled lines), instead of a crank. It's 10 turns from full up to full down and a clutch permits it to stop anywhere along the way.

    There are many ways to skin a cat folks. With the above arrangement I was hoping to solve some common issues such as; an open top case, that likes to spit water, a lever arm sticking up through the case, further intruding into living spaces, eliminating the lanyard dragging in the water causing turbulence, complicated hoisting arrangements and a lower profile case. I've seen some clever case arrangements over the years, but none addressing small craft for the home builder have been particularly impressive or innovative, simple yes, but often contrived.

    One case designed by Phil Rhodes, uses a very clever hydraulic ram arrangement. Very simple, few moving parts, quite robust, no leak points, nothing dragging in the water or sticking out of the case. I've blatantly stolen this design for use on large craft.



    This is a S&S tackle arrangement, similar to mine, though done vertically. The board is narrow and mostly under the sole on this boat, except for this triangular shaped tower inside, with the lanyard tube, that goes up to a winch. The pivot pin isn't visable, but is located just out of frame on the left, in this view. The lanyard, just drops the puppy down on a whip tackle. The triangular portion of the board provide leverage.

    Get out your sketch pads and dream one up. There's all sorts of ways to approach them, so don't let convention hold you back.

  16. #15
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    I mentioned I like using an external pivot pin arrangement, so I dug up a drawing for an 18'er of mine. The board is lightly ballasted (30 lbs./13.6 kilo), uses the same rounded top/lanyard arrangement and places the pin in the planking, outside the hull.

    What isn't shown is the epoxy block this pin and related support is buried in. The armature inside the board and the angle steel pin holders are buried in thickened epoxy, within the planking. This seals up the exposed end grain and protects the steel too. Naturally, all the hull penetrations (bolts) are set in epoxy bonded holes too, so no moisture can get at the wood.

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