Single Dagger Board vs Double Boards

Discussion in 'Multihulls' started by CatBuilder, Apr 26, 2011.

  1. hoytedow
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    hoytedow Carbon Based Life Form

    Excellent point.
     
  2. Alan.M
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    Alan.M Junior Member

    Tie it to a shroud?
     
  3. sabahcat
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    sabahcat Senior Member

    Mid point of tarp was tied to a shroud
    The front of tarp, that was in line with mast attached to the top of board
     
  4. rattus
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    rattus SeƱor Member

    After revisiting some of our old pics from 2 different Maine Cat 30 charters (once in the FL panhandle, another in the Abacos), I see that you are absolutely correct! Where did the port board go? Really would like to do the 41 sometime.

    We have chartered many cats over the years (1-2 weeks annually), many of which were more performance-oriented than those from the big condomaran charter houses and had boards. As my age advances, it appears some synapses have begun to cross. ;-) How embarrassing. Yet inevitable.

    Fun boat, especially with a screacher, and the ONE board down on a tight reach.

    Mike
     
  5. redreuben
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    redreuben redreuben

    From John Shuttleworth:

    Reuben

    You can post this from me.

    In a nutshell, we tank tested one board vs:2. It showed that one board, was better, and the size was similar to what we had developed for the trimarans.

    Then we tested the leeway if the board was to windward or downwind, and there was a very small difference showing that the upwind board is less effective. The amount would never be noticeable on a cruising or fast cruising cat.

    So I now always design my fast cruisers with one board, usually on the opposite hull to the galley hull. they are canted so that the impact on the interior is minimised.

    I was so used to sailing racing trimarans that it never seemed a problem to only have one board. But if someone was really concerned to have a spare, just carry a spare, no need to build a whole other case etc.

    However as has been pointed out on the list, if you build in a sacrificial part at the bottom of the board and make the case very strong with a crash box behind you should be fine, - we have never had any problems with completely losing the board. But I do design them strong. We also developed a kick up system for the daggerboard. where it is held back under a pin through the case at the aft end, and if the board hits, it pivots around the bottom of the case and kicks forward about 2 inches at the top, releasing it from the pin, and it shoots up under the tension of a nylon rope up haul. This work well.

    Racing boats need two boards, because by definition you are trying to get every ounce of performance from the boat.

    Regards

    John

    Cheers,
    RR
     
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  6. cavalier mk2
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    cavalier mk2 Senior Member

    Thank you.
     
  7. keysdisease
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    keysdisease Senior Member

    Looks like Catbuilder is going to have a bigger galley.

    Steve
     
  8. CatBuilder

    CatBuilder Previous Member

    Now the big questions are:

    Will I take a resale value hit?

    ... and

    Will I be able to find the right sizing for the board, given that my designer didn't answer me when I asked him about more paid work to design a single board vs. the doubles?
     
  9. cavalier mk2
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    cavalier mk2 Senior Member

    I'm not a off the rack guy and design and build for my own needs versus someone elses so I'm somewhat disqualified for the first question. If you are worried about somebody driving the price down because of a change your absent (?) designer didn't sign off on why don't you get somebody like John Shuttleworth to consult? Most professional designers would be happy to do such work and then you would have a name brand "improvement" to market. The formulas are pretty basic for area (think trimaran) if you decide not to give away the fun.
     
  10. keysdisease
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    keysdisease Senior Member

    How big a resale hit do you think there might be? I doubt if done right it would be significant enough to be a factor. Considering how long you plan to own the boat against the good/bad galley arrangements vs a few thousand dollars hit you "might take" and I think its a no brainer.

    The second question is more difficult. Cavalier had a good suggestion. You might also blow it off and go with the one board as designed. Or you might hedge the question with time and as you build consider you may have to enlarge the trunk and act accordingly until you can get an answer from Kurt.

    I still think you're going to end up with a bigger galley

    Steve





     
  11. rayaldridge
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    rayaldridge Senior Member

    Hey Red-- thanks. Nice to get it directly from the horse's mouth.

    I believe Bernd Kohler uses a similar system to retract daggerboards more or less automatically in case of grounding.

    You know, I've thought about it, and considering that you'd probably be reselling the boat to someone who wanted performance, you could sell the single board as a performance feature, with the right documentation-- most of which is available on the net. "Yeah, she's probably a little better to windward, because of that single big efficient board."

    By the way, Kurt Hughes, on another forum, recently mentioned he gets a lot of email -- 150 or so a week, so he is a little behind, he says.
     
  12. CatBuilder

    CatBuilder Previous Member

    I know. It's frustrating. He should charge $500 more for his plans and hire an assistant. He is unable to provide proper support to his builders, IMO.

    I would have gladly paid an extra $500 for better support.
     
  13. rberrey
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    rberrey Senior Member

    Richard Woods site says he will consult by the hour for a fee. rick
     
  14. downunder
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    downunder Junior Member

    Richard Woods might be better value for your money on a budget than John Shuttlewood.
     

  15. redreuben
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    redreuben redreuben

    On 10 May 2011 01:33, Reuben Filsell <filsell@myplace.net.au> wrote:
    Hi John,

    Couple more questions if I may,
    Is there a performance difference placing a single board on the inboard or outboard side of a hull ?
    And what is the rule of thumb for sizing a single board, ie: percentage of sail area ?
    And a question on your cats, what is the difference in internal beam between the 28' and the 31'

    Cheers,

    Reuben. M. Filsell

    The loss from canting it a few degrees either side is not significant. The lateral projected area is only 1.5% less at 10 degrees cant. So really not much of a difference. Racing I would put it inboard.

    Canted inboard is easier to pull out with a halyard.

    On the Shuttle 31 Daggerboard area to sail area ratio is 2%

    Shuttle 28 1.76m max
    Shuttle 31 2.025 m max

    regards

    John
     
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