Mainsheet Systems

Discussion in 'Sailboats' started by BRZ Designs, Dec 30, 2011.

  1. BRZ Designs
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    BRZ Designs Junior Member

    Hello all,

    How does the mainsheet with no traveler work in the arrangement of the attached picture?

    I understand the one with the traveller, but the one with the blocks set as a triangle I never used.

    When would you use one or the other?

    Cheers
     

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  2. Stumble
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    Stumble Senior Member

    BRZ,

    The non-traveler mainsheet is really a pretty poor option. It is intended to give you some of the ability of a traveler but at a lower cost. In my experience you just get more complexity with no real benefit.
     
  3. michael pierzga
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    michael pierzga Senior Member

    Without a traveller in the main sheet system you rely on the boom vang to generate leech tension. It works. Many modern boats use this one part mainsheet on centre line, no traveller system , because it gives a clean safe deck layout.

    Make sure your vang, the gooseneck and boom is strong enough to handle the greatly increased loading Cariboni makes a popular no traveller system

    http://www.cariboni-italy.it/public/caritec/products/datasheets/magictrim.pdf
     
  4. PAR
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    PAR Yacht Designer/Builder

    A traveler is a handy item if you need that last ounce of energy from the main, but most cruisers don't sail at this level of "set", so it's just extra gear to break and maintain. If you're racing or enjoy getting the most from your mainsail, then a traveler is necessary, but if your idea of sailing requires a beer in one hand and a foot on the helm, as you relax and let the world go by, you don't need one.

    The lower sheet setup is pretty common and a split 4 part purchase. At least half of the tackle has some advantage to control mainsail shape, per tack, but it's not very precise, though it is simple and requires a lot less gear, so it's lighter and less costly.
     
  5. souljour2000
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    souljour2000 Senior Member

    My Columbia 29 MK II has end boom sheeting to a traveller just forward of the taffrail on a platform there which has a name that eludes me...there is a factory cunningham I want to call it...I had a traveller on the companionway threshhold of my Seafarer 24 that seemed well suited for racing and tensioning the leech but as I dont race it got in the way frankly a hell of a lot. I like where the traveller is on my bigger Columbia but that long boom sheeted only at the ends seems like it could "fold"in the middle if it werent tubular 306 aircraft aluminum that was probably simultaneously being used for wing spars at the aircraft plants near Costa mesa in 1966....in other words,,I guess it's robust enough..just want to know if it needs more mid-boom support in some way/shape or form if ever there's a blow and I have a couple reefs in the main...or just sailing in general I don't see how the current rig is in any way sufficient to create good sail shape...
     
  6. BRZ Designs
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    BRZ Designs Junior Member

    Stumble, Michael and Par,
    thank you for your inputs, do you know any books on the subject or a site explaining the different setups for Running Rigging?

    Souljour,
    In my opinion I would rather have an end boom sheeting than a mid boom. The most part of the effort on the boom are on the gooseneck and Main Clew, so having the sheet far aft would take it closer to the effort on the clew. Plus the forces on the end of the boom are smaller than in the middle of the boom "fulcrum effect".

    But I may be wrong, perhaps the Senior members can clarify it further.
     
  7. keysdisease
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    keysdisease Senior Member

    YES, :cool:

     
  8. michael pierzga
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    michael pierzga Senior Member

    You might have a look at the Harken site. In the past they had a very good primer on various sail handling systems /.

    End boom sheeting is desirable from an engineering point. If possible go for it. If you must move the sheet forward for ergonomic reasons, seat it under the number one reef.
     
  9. Doug Lord
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    Doug Lord Flight Ready

    =================
    Two great books on sail control: "Sail Power" (updated edition) by Wallace Ross and "The Art and Science of Sails" by Tom Whidden and Michael Levitt.
     
  10. philSweet
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    philSweet Senior Member

    If you have a midboom sheeting arrangement, the sheet controls sail twist and the traveller controls boom position. When pointing, the energy needed to control the traveller is a lot less that that needed to move the boom with the mainsheet. This is because of the stretch in the lines and the change in the sail's twist as you crank in the sheet. This extra energy can be minimised by careful engineering and materials selection, but for an average older boat, it can mean a lot of extra effort, and it gets worse the higher the sail's aspect ratio. Lacking a traveller, everything on the centerline gives the best windward sheeting and lowest energy penalty, but the difference between a centerline rig and the one pictured is very small, and any number of other considerations could favor that arrangement. I always carry a handy-billy tackle and rig it as a preventer. If I didn't have a traveller, I would also use it for close hauling. Quite a few cruisers rig twin independent mainsheets along the lines of the second photo. Still cheaper than a traveller, built in preventer, can be set to self tack, and can avoid the need for a mainsheet winch entirely for the smaller sizes (you can pull on the twin sheets alternately and really get some tension, twin 4:1 can effectively be 8:1, but slow.) Improved visability forward is a big plus when you get rid of the traveller.
     
  11. Stumble
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    Stumble Senior Member

    BRZ,

    Ideally the mainsheet controls only the leech tension of the mainsail, while the traveler controls the angle of attack of the sail to the wind. So the boom should, ideally, always be directly above the traveler car. This however is hard to do on anything other than fully optimized race boats, but it is the theory. As the traveler gets shorter, the mainsheet has to be used more and more to control the position of the boom relative to the wind since the traveler doesn't have the range to do so.

    On boats with only a centerline block of course only the mainsheet can control both the position, and the leech tension. This is a step away from performance but may be worth it on cruising boats where performance is happily traded for ease of use. The double block system you posted is an attempt to have the best of both worlds, where the off center blocks can be used only on the windward side, thus pulling the boom to windward instead of down as the boom approaches centerline of the boat. But to set this system up properly requires two sets of mainsheets one on either side of the boat, and honestly isn't much less than a cheep traveler system that does a better job, and works much more effectively.

    Doug posted some good books, and Harkens website has some great information on the set up of different sheeting systems. My advice would be to also read some of the racers books on sail trim. Appreciating you are not a racer, the fact remains that racers tend to be much better at sail trim than cruisers, and once you understand the trade offs you are making you can make a more informed decision.


    As for mid vs end boom sheeting... As a matter of physics, the further aft on the boom the sheets can be mounted the more mechanical advantage you have, and thus the smaller the loads will be. However there are often practical considerations like if you want to have to crawl over the sheeting system while hanging out in the cockpit, or while having dinner that often require moving the sheet forward.
     
  12. michael pierzga
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    michael pierzga Senior Member

    The reality is that you...or I...seldom use the traveler when cruising. I just reviewed hundreds of photos from our last 13, 000 mile cruise and they all show the traveller sleeping in the middle, mainsheet eased, boom vang keeping the leech tight. The traveller is never used.

    About the only time I actively use the traveller is upwind , close quarters, in puffy conditions or regattas.

    If I were you I would choose the mainsheet layout that best compliments the way you use your boat while keeping your cockpit clean, rather than fuss about the technical aspects of mainsheet systems.

    Very worthwhile to investigate the robustness of your boom vang and its attachments before modifieng your mainsheet geometry.

    This boat transmitts boom vang loads to the mast collar, not the mast wall. Very robust
     

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  13. BRZ Designs
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    BRZ Designs Junior Member

    Hi Michael,
    I am a Cruiser for sure but I do use the traveller quite often. I am happy with my regular endboom double ended traveller mainsheet.
    But I am studying boat design and my interest on Mainsheet systems an technical data is mostly educational and so I can offer options to my future clients according to what they would like to have on a boat.

    I am also new to the Forum and would like to thank everybody for their time and valuable information.

    Cheers all

    Have a Happy New Year!
     
  14. PAR
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    PAR Yacht Designer/Builder

    Welcome aboard Jean. Most of the time, the design's SOR will whittle down the main sheet options. Getting mechanical advantage as best as you can is the usual path in a cruiser, but racers are the other end of the spectrum.
     

  15. souljour2000
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    souljour2000 Senior Member

    The possibility of my 45 year old.... 11 and a half- foot boom folding like an umbrella is greatly exaggerated as I have realised from your comments and from seriously re-evaluating my boat's concerns....the specter of this happening to my neglected beauty is far less likely than some other un-toward events such as rudder failure (me boat has a rudder that is beginning to delam at the corners a bit..but there might be a little time for me to address it before it gets structural hopefully)) and I need to replace all the ubiquitous bronze thru-hulls that have taken on a lime-green colour...my mainsail is older but still fairly crisp and it's a good cloth thickness despite only one reef which I need to address...but the leech tension of that sail despite it affecting sail shape is probably a lesser concern than the above concerns...except for maybe the addition of another reef in the main which as far as my sail plan goes is my most critical upgrade right now ....anyways...carry on with the thread ...just armchair repairing as usual....enough about my old tub...
     
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