Main-less rig

Discussion in 'Multihulls' started by Spiv, Feb 10, 2008.

  1. Spiv
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    Spiv Ancient Mariner

    Hi Sigurd,
    Thank you for your continuing interest in this thread.
    I had a cat with a lowering mast, you can see pics here.
    One of these days perhaps I am going to play with a 40' cat again and build an 'A' frame mast for it.... who knows what the future will bring...
     
  2. Blokatos
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    Blokatos New Member

    Very interesting thread with lots of useful info. I too have grown a huge dislike for mainsails and here is a link with some good news for those looking to innovate:

    https://www.researchgate.net/public..._and_CFD_investigation_of_unconventional_rigs

    "6.CONCLUSIONS
    In the present paper an unconventional rig has been investigated in comparison with a standard sloop rig by means of wind tunnel tests. The traditional sloop yacht rig used as a reference is a Comet 51’a Vallicelli Yacht Design & Co 51 feet IMS cruiser-racer. Several unconventional configurations have been tested, all characterised by an “A” shaped stern mast without mainsail in single-jib and double-jib configurations. Aerodynamic data available from experiments have been used to perform some performance prediction at full scale by means of a VPP code. Both experimental tests and VPP calculation show that the double jib configuration with overlap gives the best performance and also the same configuration without overlap gives better results in comparison with the standard sloop solution. Numerical investigation have been carried out using RANS simulation in order to better understand the aerodynamic differences resulting from the experimental tests. Simulation results put in evidence a slat effect in the overlapping jibs configuration leading to more attached flow on the aft jib allowing for an higher pressure drop on the sailplan."
     
  3. brian eiland
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    brian eiland Senior Member

    Welcome to the forums Blokatos.
    Yes I found that testing to be very interesting as well. I posted references to it on several discussions on this forum, including this one:
    Wind tunnel and CFD investigation of unconventional aftmast rigs
     
  4. Blokatos
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    Blokatos New Member

    Hello Brian and thanks for the warm welcome!

    I was reading the whole thread and was so excited with this article/research paper that I totally forgot that this was my first post.:D
     
  5. oldsailor7
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    oldsailor7 Senior Member

    John Hitch had (or still has), a very successful catamaran, a main-less rig with multiple fore stays. 'Fraid I don't have a pic , tho' I'm sure someone else has?.:cool:
     
  6. UpOnStands
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    UpOnStands Senior Member

  7. brian eiland
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    brian eiland Senior Member

    Since those photos are on a 'for sale' list they will disappear soon. So I thought I would post a few of the rig photos
     

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  8. Spiv
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    Spiv Ancient Mariner

    Lets design a 42' cat "A" Frame mast

    Hello all interested in main-less "A" Frames,

    after nearly 9 years of discussions, we have all gained a fair bit of knowledge, so I think it is time to get down and design this mast!!

    Before I go any further, I invite anybody interested in developing this idea to contribute, especially designers, sailmakers, engineers, composite experts etc.

    I kindly ask to all of you who think this is not a good idea, to refrain from telling me that it will not work, that it will be too heavy, that it will not point high, that the Marconi rig is better and that since it has not been adopted by mainstream designers and sailors it is not a good rig, etc etc. I have heard it all before and to tell you the truth, I am sick of it.

    Now, the scope of this design is:
    1. have three permanently hung sails on three furlers (Parasailor or other spi, optional)
    2. mast on hinges so it can be lowered (forward)
    3. first sail on a prodder (horizontal A frame with net to walk on and hinges to pull up)

    Some variables could be:
    1. first two sails with parallel luffs? This complicates the mast as we induces bending forces. Is this complication and the extra strength required worth the benefits?
    2. wishbone pre-bend or straight masts? With pre-bend, we can make the mast thinner as it will resist compression and buckling forces better.


    • I see the first sail as a sail for light winds, say up to 15kn.
    • The second sail as the driving force, sail to be used up to 30kn as it is, furling after that. If we put the mast aft enough, it could be self tacking.
    • The third sail is the smallest and its tack will be on a strop attached to the two mast hinges, so it will not have to be disengaged when lowering the mast.

    Lets start with naming the three sails, then size them and, of course, lets consider the centre of effort, then we'll think about the mast.....
     
  9. Spiv
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    Spiv Ancient Mariner

    Some ideas:

    No1 - Alibi had a good idea for the self tacking jib: an arched cross beam that had also held the mizzen furler as well as turning the mast into a triangular section.

    No2 - An idea to increase tension on the forestay via an aft strut as proposed by Brian Eiland.

    No3 - Procyon had solid cross members to stiffen the mast.

    No4 - My idea of the pre-bent mast. Please ignore measurements on drawings, I made them for a 17m cat I had in mind a few years ago.

    No5 - Nice rig. Do we need a mizzen?

    No6 - Is this the same as No5 before shortening??
     

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  10. waikikin
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    waikikin Senior Member

    OK Stefano,

    I volunteer the names..

    The aft sail to be the "Scorpion" or "Hornet"- the sting in the tail..
    The middle or second sail to be the sweet & hardworking "Honeybee"
    The forward sail to be the "Mosquito" as it attaches to the proboscis and to milk the best out of lighter conditions.
    I'd be in favour of strait sided A frame, the inner forestay could attache to center of a crossmember in the A as a beam or to a simple bridle at the same point with a monkeyface then some runners/backstays at that/those points on the masts.
    The mast setup needs a cool name also like invert V air transmission or I.V.A.T.... maybe some acronym that spells a word?


    Jeff.
     
  11. jfraymond
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    jfraymond Junior Member

    W ishbone A ftmast S ailing P ole. :D:D:D

    Sorry couldn't resist. May have to try something like this on my little 14ft sharpie boat im building for fishing/trolling... quick fold down out of the way would be nice. could contour it to the actual shape of the boat.
     
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  12. brian eiland
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    brian eiland Senior Member

    Probable going to lose my internet connection for a few days very soon, as we have a big hurricane headed for the east coast of Florida (I'm in St Augustine at this time).

    Wonder if you might have started this project/discussion over on this subject thread that had a LOT of discussions of A-frame type rigs?
    http://www.boatdesign.net/forums/boat-design/wishbone-sailing-rig-1999-3.html

    I just went back thru that discussion thread looking at all the posting for details that have been experimented with. I made some notes of postings I wanted to remember and/or look at a second time. Perhaps I should publish those notes?
     
  13. UpOnStands
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    UpOnStands Senior Member

    something in CF
    the legs swivel around the top horizontal member to make installation easier
    the assembly can pivot forward if bridges are a problem
     

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  14. brian eiland
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    brian eiland Senior Member

    Double A-frame ?

    Something that just got posted on another forum. I've ask the poster if he might have some photos or a sketch.

    posted here: http://www.cruisersforum.com/forums/f48/smg-50-its-like-they-were-reading-my-mind-79822-8.html#post2228016
     

  15. Spiv
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    Spiv Ancient Mariner

    Jeff (waikikin), I always liked your sense of humor.... perhaps we could keep Scorpion, Honeybee and Honeybee as nicknames, but to have a technical discussion with several new persons coming on board later on, we should stick more to conventional names, perhaps Screecher, Genoa and Mizzen. However this Screecher of mine would be very much used downwind, perhaps goose-winged with the Genoa or with a twin sail on the same furler foil, so the name doesn't quite fit.

    jfraymond, I like WASP, if we end up with bent, pre-stressed masts.


    UpOnStands, I considered an horizontal member, but the torsion forces induced by the mizzen would be hard to predict, also there would be bending of the masts at the junction of the supporting struts hence the masts would need to be beefed up, engineering costs would increase....


    Brian, while I have participated on the Wishbone sailing Rig thread and learned a lot from it, I have not asked the group to actually start designing this mast, I thought since I started this thread, it would be more appropriate to do it here.
    Thank you for showing us the post by admiralslater, very interesting, would you PM him and see if he'd like to join us or do you prefer if I do that?

    I have considered two A frame masts, ketch like, the idea was to spread the sails horizontally rather than vertically.
    But then I thought that a long prodder and an aft mast, can carry a lot of sail for light winds and the three furlers be able to reduce sail in a jiff.
    However this idea of having them hinged at the same spot has a lot of merit:
    • the aft mast can give a lot of tension to the forestay
    • masts can be shorter (intracostal...)
    • the 'upside down' mizzen is a 4th sail probably very useful in light winds.
    Now we need help from a good sailmaker (are you reading MB?) ....
     
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