Wishbone Ketch - Details

Discussion in 'Sailboats' started by pchenrrt, Mar 24, 2009.

  1. pchenrrt
    Joined: Mar 2009
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    Location: ottawa,canada

    pchenrrt Junior Member

    I am looking for more information regarding the wishbone ketch's advantages/disadvantages. (I have read the other threads pertaining to this subject but there are still many unanswered questions I have). This is for a hypothetical/theoretical purposes as I am "designing" a cruising sailboat for myself but don't expect myself to ever be in a position to built/have a custom boat (nor do I think I'd design a safer/better boat than a professional), but would like to work through the exercise to help me understand sailing/cruising challenges and compromises better. I am leaning toward a cutter rig and am basically comparing the wishbone ketch to a cutter as far as tradeoffs in performance, ease of handling (or lack of it) etc. Specifically:

    1) As the wind rises, the cutter has easy, progressive reefing/dousing of sails to reduce sail area and keeps it central. What would be the best order for reducing sail on a wishbone ketch (WBK)?

    2) On the WBK the mainsail has its greater area high up but the staysail/jib/genoa etc. has the greater area in the conventional lower position. How does this affect the intereaction between the two sails?

    3) Assuming that it would affect the interaction between the two negatively, would essentially flipping the fortriangle's sail so that you had a shorter leech and longer foot improve the slot effect? (This would also probably mean moving the mast's forward so that you would have a narrower foretriangle, I think).

    4) If you did the above, where would you lead the jibsheet as it would appear to me that it would need to be led much further aft to be able to maintain adequate tension on the foot for when you want the sails flat, likely beyond the dimensions of the boat; also, in this position is there a good way to ensure that it doesn't foul the wishbone's boom

    5) The reasoning commonly given for a ketch's poorer performance to windward is that the mainsail backwinds the mizzen. If the sails were arranged as described in 3 (above) would the windward performance improve since the mainsail, being higher than the majority of the mizzen, should impact the mizzen less.

    6) Does the current WBK perform better to windward than a traditional bermudan/marconi ketch given identical hullforms (on average - I know that individual rigs may be better or worse and there does seem to be quite a variance in this particular rig)

    Okay, maybe I should limit my questions to these at present or no one will respond. I'll look at ways to overcome the complicated rigging required later.

    Any comments welcome!
     
  2. catsketcher
    Joined: Mar 2006
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    Location: Australia

    catsketcher Senior Member

    Wishbone where?

    Where are you thinking about putting the wishbone -is it up top to make a gollywobbler, on the staysail or on the mainsail?

    cheers

    Phil Thompson
     
  3. pchenrrt
    Joined: Mar 2009
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    Location: ottawa,canada

    pchenrrt Junior Member

    re: wishbone where?

    The wishbone would be on the mailsail.

    The mainsail would be an scalene triangle with the longest edge along the mainmast and the second longest edge would be cut to follow the mizzen's forestay (but not have any attachment to it) that way the mainsail would fill in the space between the masts except for what is already covered by the mizzen's staysail.

    The wishbone mast would be approximately perpendicular to the mainmast (~horizontal) and would therefore be positioned at the height of the mizzen masthead (to which it has been traditionally sheeted, but I'm also trying to figure out ways to avoid that) to maximize sail area. I'd imagine that the horizontal position would be most effective and at the least weight aloft but if there is a good reason to peak the wishbone please let me know.

    Here are two links (if they work) that show what I'd intend for the mainsail and both mizzen sails, but the main foresail arrangement would be different:

    http://www.spanishpropertyworld.com..._classic_yacht_for_sale_in_southern_spain.htm
    and
    http://www.boatdesign.net/gallery/showphoto.php?photo=9070
    (though this one has more of a peaked wishbone and less aspect ratio)
     
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