wingspar sail rig

Discussion in 'Boat Design' started by alan white, May 10, 2007.

  1. alan white
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    alan white Senior Member

    Not the best copy, but this sailing rig is one I mentioned once a ways back, before I knew how to do attachments. I also have a model of the rig, and pictures of that.
     

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  2. alan white
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    alan white Senior Member

    The design also incorporates a lifting keel, which passes between a bridle under the boom/mast connection. The forefoot drop allows the ballast to be tucked in when running. The boat could easily be trailered.
    It would be impossible to do this with any other rig because the keel foil sticks a good two feet above the deck. A later improvement (I did this a while ago) is the bridle replaced by a SS tripod (2 legs forward and one back.
    Also, the stay running from the mast base to the aft end of the spreader between the mast and the sail is replaced by a compression strut, eliminating the stay it crosses. The main reason is that a set of normal spreaders is located at the aft end of the single mast spreader (can't be seen in this drawing).
    The advantage of the rig is the part cut off on the picture. The wing-spar replaces a gaff. It is foil shaped in section, looks like a banana. The depth of section allows a curvature at the top, a spitfire wing shape, making all leading edges aerodynamically clean (the lower edge is hanked to the luffstay). The upper sail area is fully effective, the same as is usually achieved with battens (this particular one has battens too).
    The sail can reef by dropping the wingspar to sit atop the boom. The wingspar has attachments at two locations. Just below thespreaders and just below the masthead. The top attachment has a release, and the gaff/wingspar drops onto the boom when struck by letting go the throat halyard. The mast, being forward, is just a round pipe about 2/3 as tall as would normally be needed. Being shorter, it could be shrouded at the halfway point (backswept). Then its diameter could be quite small.
    Another advantage of this rig is that the boom can overhang the stern, no runners are needed, and the boom can be run right out to a full 90 degrees.
    When struck, the rig is less subject to windage, similar to a gaffer.
    The light mast, even on a much bigger boat, would be easy to drop at sea for inspection, repairs, bridges, etc., if hinged at the deck at the bow (which, by the way, is the strongest part of the boat to put a mast, but usually a bad place to attach shrouds. In this case, they are swept back to the widest part of the boat).
    The jib has to slip around the mast more than usual, like a genny does. However, there are NO fittings or spreaders in the way, so it's not a problem (even with a genny).

    A.
     
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  3. alan white
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    alan white Senior Member

    This is the model
     

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  4. alan white
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    alan white Senior Member

    I'd welcome any comment from those who are familiar with rig design. The advantages of the rig must outweigh any disadvantages for it to be feasable.
    the stiffness of the gaff is in question. Otherwise I don't see any other cons.
    The gaff itself could be diamond-stayed. I have thought about that. carbon fiber strips (side to side) would help too. The fore/aft dimension might be 10" on a 16 ft boat, and the width at the widest might be 2", the idea being a teardrop section to allow free flow at the luff. My fifteen foot gaffer has a maximum section in the middle of its gaff of 1 1/2", and the boat carries 155 sq ft of sail. 2" would then be adaquate, I think, especially if carbon fiber were oriented within the laminate in athwartship strips (the rest could be foam). I would like the spar on a sixteen footer to weigh no more than 10 lbs.

    alan
     
  5. frosh
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    frosh Senior Member

    Hi Alan, although I am not familiar with with rig I am interested in modern derivates of the gaff rig and have built a James Wharram style wingsail.
    Yours is a little more complex then either a traditional bermudan rig and traditional gaff rig so there need to be payoffs. I would consider it a promising enough design to construct a prototype for a 16 ft sailboat, but be prepared to make modifications later, as your first version is very unlikely to be the optimum version. In particular I love the idea of the banana shaped carbon wingspar. Make sure that you introduce significant taper in this spar, especially in the lateral dimension, and it will become automatically gust responsive if you get the dimensions just right. Also a very nice aerodynamic solution for the mainsail leading edge. Do you have a conventional rig available to be able to test for comparison purposes? Good luck and keep us posted please.
    Good luck, Sam
     
  6. alan white
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    alan white Senior Member

    Hi Sam,

    Good points. I have since simplified the rig somewhat. Actually, if you consider the one shown is very short and count the stays, it has no more complication than a marconi rig. A set of upper and lower shrouds, a backstay (I call it a luffstay for obvious reasons), a forestay, and the two crossing stays between mast and luffstay are in later configurations not shown replaced by a single compression post.
    Ah, but the simplicity: Reef in any sail position as if reefing a jib with a boom(no expensive ball bearing cars), no runners (comparing now with gaffer and square tops/battened sails), no expensive and high tech mast (this one is round or square in the case of wood-- it doesn't care about air flow to a leading edge), no crane to lower the mast (its probably half the weight and 2/3 the length), no mast compression structuring (the luffstay works against gravity---- the weight of the ballast is pulling down), and finally, no bosen chair gear, since the mast, even on a larger boat, can be dropped to deck level (without overhanging the stern) in a few minutes by simply unhooking the forestay and hinging it on a tabernacle (similar to what could be done with a catboat, except with a far lighter mast. Lighter because a catboat would have to have narrow shrouding angles and probably wouldn't be hinged anyway for fear of losing a shroud--- I wouldn't hinge a catboat mast so far forward, and if further back, it would overhang the stern when dropped, probably exactly where you want to get to.
    Regarding the wingspar itself, it seems that idea has never been properly developed. All other configurations have a mast lower down, and in the case of gaffers, that portion of the mast has always been thick to stay in column because dropping the gaff or locating spreaders precludes the kind of simple construction gaff rigs are chosen for. Why have a gaff if it requires the same high strength tracks and cars and spreaders and diamond stays as a marconi rig?
    Throughout the history of sailing, the mast location directly in front of the mainsail has caused no end to expensive high tech solutions. Masts have become very expensive as a result and still they are not as efficient at the leading edge as jibs made 500 years ago. Some have tried to get high aspect using a wire all the way up, but the tension is necessarily enormous to keep it straight, involving all kinds of hardware and wide staying angles (my staying angles are wide too, but because the masthead is 2/3 the height of the sail, they allow the mainsail to be in the middle of the boat where it belongs. Further, the greatest unsupported span of my rig is one third of the sail height due to the aforementioned compression post. It could have one third the tension of a wire luff going all the way up, and still sag off no more than that type. Rig tensions in my design are more along the lines of what a gaffer sees, and we're really talking about luffstay and forestay tensions The mast can have some nice athwartship diameter now, same as fore and aft, so it can stand some serious compression anyway. Nither will it push the keel down or pull the stern(no backstay) or the bow up because the mast is in the bow and the bowsprit transfers compressive loading to the tabernacle and the bobstay pulls from the bottom of the bow.
    I've also considered a 16 ft test boat, a class boat maybe, to race against with same sail area. Its really a matter of finances! I bought a whole gaffer on a trailer for what I would have to pay for a sail for the wingspar rig. Modifying that would be no problem insofar as mast and hardware go, but the sail is a real expense--- curved and unusual, which gets sailmakers talking big money.
    The taper of the wingspar is exactly what I had in mind, and shows in most drawings.
    Thanks for your interest. Sam, and I hope others will comment, especially with criticsisms. There may be something I'm missing. The design is maybe 6 years old now, and someone should build it. It should be thoroughly analyzed from an engineering standpoint first (I wouldn't, but it's my design--- I'm a seat-of-the pantser). There are so many knowledgable people here who could analyze it.
    Anyone's welcome to use it, of course. It would really be a thrill to see it done. I have dozens of good drawings showing all details of fittings, configurations of sloops, cats, ketches, reefing, and so on.
    Alan
     
  7. MAINSTAY
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    MAINSTAY Junior Member

    Alan,
    Your rig does have several advantages over the typical sloop rig. With no mast wind shadow at 1/3 the luff and reduced shadowing of the rest of the luff your rig should get more drive from the wind. And its shorter spars may be less stressed, and easier to build and handle. I am impressed.
    How are the mods to the 16-footer coming? Keep us posted.
    Larry
     
  8. Buildboats
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    Buildboats Senior Member

    Very interesting Alan... how about a unstayed round or rotating foiled carbon section to hold the wing gaff aloft?
     
  9. Buildboats
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    Buildboats Senior Member

    I could see trying this on one of my cats Alan... please send me some more info, thanks.
     
  10. OldYachtie
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    OldYachtie Junior Member

    Why make a spar wing shaped when you can make the battens wing shaped?

    Tom Speer's page shows a wing shaped mast ( http://tspeer.com/Wingmasts/teardropPaper.htm )and an almost flat sail. The same assembly could be made reef-able if you just made it with full-length rigid battens with a hinge where the wing shape meets the straight batten. You don't even have to change the drawing! You use a junk type sheeting system to induce the camber, and get all of the handling benefits of the junk rig combined with the aerodynamic benefit of the wing mast.

    See http://dunnanddunnrealtors.com/Catamaran.html to see this idea illustrated.
     
  11. Buildboats
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    Buildboats Senior Member

    Yes I agree OY, I have always liked junk rigs and the rig in each hull is also my preferred location. I thought there might be a issue with shapped leading edges when it comes time to drop the sail. I suspect the leading edge will fold some how? That interest's me and would like to learn more.
     
  12. OldYachtie
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    OldYachtie Junior Member

    Hi, BuildBoats-I'm not sure I understand the question. My rig is basically a junk sail with wing shaped forward batten sections. It would fold up the way any junk sail does when you furl it. It is a more aerodynamic version of the swing-wing rig, which could be seen on the woodenboat board, if it weren't down. This link http://voilesdejonques.free.fr/bateaux/bateaux.php?page=navigants shows the catamaran "Pho" which has a "Swing-wing" rig.
     
  13. OldYachtie
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    OldYachtie Junior Member

    The "Gallant rig" is an example of a wing shaped rig, and it furls just like a junk sail. IMHO, it has two drawbacks-no hinged flap, and no sheetlets to the batten ends.

    See: http://www.svaphrodite.bostekanesthesia.com/
     
  14. SeaSpark
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    SeaSpark -

    Do you think about canting the rig to weather like a windsurfer to create upward lift?
     

  15. Pericles
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    Pericles Senior Member

    SeaSpark,

    Thinking about your question re canting the rig to windward as on a board, my experiences when doing that were, either I got a dunking to windward as the breeze died, or I would not sheet out enough before bearing away, so I'd get hauled up by the harness and dumped high over the bow into the sail. Either way, the event was over in a second. :D :D :D :D

    I am not sure your idea of creating upward lift is going to warrant the sky rides!:p :p

    Pericles
     
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