Biplane Rig running rigging

Discussion in 'Boat Design' started by endeavor, Oct 27, 2014.

  1. endeavor
    Joined: Dec 2013
    Posts: 16
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    Location: New York City (NY)

    endeavor Junior Member

    Hi all,
    I am very curious as to how the sheets, vangs, outhauls, etc. are set up on a biplane rigged catamaran.
    It is relatively easy to run the rigging to one point on a cruising cat such as a lagoon, gunboat, etc. because it all goes to one place. However, if the rigging has to be set up to be sailed from two places like on the sig 45, or extreme 40's etc. it becomes a whole lot more difficult. Now, what if there are two rigs - a biplane rig setup - that have to be able to be trimmed from each hull. Ideally you should be able to have control over everything without having to leave the cockpit - regardless of which hull you are situated in, but I have no idea as to how this would be set up.
    I have been looking around, but could not find the answer to my question.
    Any help would be appreciated.
  2. rob denney
    Joined: Feb 2005
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    Location: Australia

    rob denney Senior Member

    We built the rigs for a 40' cat and have a couple more under way. Leading the halyards etc aft can be done with either a stub mast which does not rotate, or a sleeve outside the mast between the bearings. The latter has the lines running through sheaves in the bottom bearing.

    All our rigs have the booms rigidly fixed to the mast so vangs and high sheet tensions are not required. The mainsheets are usually 2:1, sheeted to the bimini with the lines lead back to the helm position.

    Incidentally, the rigs on the first cat the same sail area as the standard rig. They were so powerful, the owner chopped 14' off each one. The boat still performs extremely well.

    Interestingly, the 2nd and 3rd boats have hinges just above the booms so the mast can be lowered to get under bridges.

  3. endeavor
    Joined: Dec 2013
    Posts: 16
    Likes: 0, Points: 1, Legacy Rep: 10
    Location: New York City (NY)

    endeavor Junior Member

    Thank you Rob Denny for responding. That is a great idea of running the halyards through a sleeve and then to the cockpit. I was never particularly fond of the halyard winches on the mast - especially while single handing in heavy seas and trying to reef. Its just easier and much more convenient to be able to do everything from one place.
    However, I do not understand how the twist of the sail would be controlled (especially with a square top) without a vang. Is the sail raised and lowered via halyard and downhaul until an optimal position is reached?
    Were you part of the design team for the rig of the spitfire? if so, very impressive.

    My next question is how the sheets should be led so that they can independently be controlled from both cockpits of a biplane catamaran (something like the Mediatis). ideally a loop could be led through a network of pulleys, but I don't like the idea of knots, the connection at the end of the loop, snagging, and maintenance... What do you guys think? Im sure it's been done before - I just cant seem to find it.
    Last edited: Oct 28, 2014
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