Bi-Plane rig on a 20m cat

Discussion in 'Multihulls' started by Becaris, Jun 28, 2010.

  1. Corley
    Joined: Oct 2009
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    Corley epoxy coated

    Michael has both his masts fitted to his Schionning Waterline and sails fitted, looks good.
     

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  2. tomas
    Joined: Nov 2012
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    tomas Senior Member

    Congratulations to Whimsical/Mike.
    Nice progress.


    What about the OP's cat?
     
  3. Gary Baigent
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    Gary Baigent Senior Member

    DreadO of course is no cat, nor is the rig bi plane - but it is a double rig, a sketch, (schooner/ketch) and the equal sized double rig performs far better than any of us would have thought possible.
    Especially to windward.
    That was a real surprise because the boat points very high (has no instruments so can't give you any figures) but it climbs away and sails faster than many much larger boats, even multihulls.
    This is possible because of the two equal sized rotating wing masts.
    To anyone who thinks such masts are too daunting/dangerous/tricky to contemplate - think again - because they are very easy and simple to control.
    The latest Everglades Challenge was won by two ketches with close to similar sized double rigs. Very interesting. Beat the multihulls too.
    DreadO would be perfect in the EC.
    Except we live halfway round the world.
     

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  4. brian eiland
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    brian eiland Senior Member

    Interesting, that pointing ability. with the double rig (fore-aft)

    I guess I'd be stirring up old debates if I suggested that it had anything to do with the interaction of the two sails :rolleyes: ....as I have championed before with the interaction of the large headsail with complimentary inner jib or the mainsail (while others have insisted that the best windward rig is a uni-rig)
    http://www.boatdesign.net/forums/hydrodynamics-aerodynamics/sail-aerodynamics-457.html#post5685

    Wonder how Chris White is coming along with his twin foil rig...the MastFoil?
    http://www.chriswhitedesigns.com/atlantic_cats/mastfoil/index.shtml

    Gary, I'd sure like to hear more about DreadO, if you could point me in the right direction?
     
  5. Gary Baigent
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    Gary Baigent Senior Member

    Brian, if you search boat design.net for Cox's Bay Skimmer you'll
    find all the information on DreadO.
     
  6. brian eiland
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    brian eiland Senior Member

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  7. James Higham
    Joined: Mar 2013
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    James Higham New Member

    Biplane issues

    I've posted on my site a few times on the biplane rig and am currently building my 34 foot cat design which has to do two things - tackle blue water for limited amounts of time and fit into the English canal system. It's also designed for economy, for those without a lot of the folding stuff.

    There are two rigs I'm looking at - biplane junk of 272 sq ft each and a junk ketch of 505 sq ft. The fore and aft is nicer at sea but on a cat, it's cramped as it requires mounting on beams and junks do like to be sheeted aft.

    The biplane does this nicely, sheeting back to the sternpost [double ender] but there really are issues. The first time I saw the Radical 8000 sailing
     
  8. hump101
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    hump101 Senior Member

     
  9. James Higham
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    Location: Manchester

    James Higham New Member

    Wharram maybe took it too far but he was for flexi, i.e. the gust would be absorbed through, as you say, Hump101, the stays, the beam, the whole structure. Earlier in the thread, I noticed a bit of stick between tightly rigged racers and loosely rigged cruisers, for want of a better way to put it.

    Both are right in their own way. For off the beach, direct sail to hull lift is no problem and translates into performance. In a cruiser, the slight delay in shrouds to hull and mast to beams plus a certain twist between the hulls [especially with tied beams] might sound horrible but they give a slight leeway in the way a tri does.

    My three beams are each two pieces tied side by side of 9" by 1" by 21'. There's not flex unless under downwards pressure [mast], hull twist and fore and aft but by then you'd have reefed and furled.

    Instant vertical which the biplane imparts is a bit like in a sports car - you feel every bump. For cruising, not sure you want that.
     
  10. El_Guero

    El_Guero Previous Member

    Becaris,

    You mentioned 'drag' increase of a free standing rig versus a rig with wiring.

    If you want to get into the 'engineering' google the differences between low wing aircraft and high wing aircraft. Your engineering considerations will be almost the same.

    High wing aircraft use the rigging approach, yes the rigging is often a tube in modern aircraft instead of wired - less maintenance, I believe.

    The real difference for an airplane, where drag is REAL, is the WEIGHT. Low wing aircraft can have the strength placed in at lower weight, because you do not need separate landing gear structural support. The weight savings is about 100 pounds in a low wing - not compared to a high wing. The high wing lowers weight BY REDUCING INTERNAL SUPPORT, and making the support external. And that increases their drag component greatly when compared to a low-wing plane.

    And if using a free moving mast, the masts are normally designed with a winglet like shape. The leading edge is turned into the wind. The mast designs I have read about have SIGNIFICANTLY lower drag profiles than traditional masts.

    Hope that helps.

    wayne
     
  11. El_Guero

    El_Guero Previous Member

    Buy a Garmin or other EFIS equivalent, and go glass.

    :D
     

  12. scape
    Joined: Jan 2012
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    Location: tri-state

    scape Junior Member

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