From: Mike Crawford

To: harryproa@yahoogroups.com.au

Sent: Monday, May 23, 2011 10:52 PM

Subject: [harryproa] Swing-wing rig

 

Ben,

  The swing-wing is a soft wing sail, essentially a junk rig supported by snowshoe-like wishbone frames to give the sail a double-skinned airfoil surface for its leading edge. 

  Because it works like a junk rig, it's easy to reef -- just let the halyard down another segment, pull on the new downhaul, and you're there.  With a portion of the "wing" in front of the mast, it's at least partially balanced.  Because it has a great leading edge that naturally orients to windward, it doesn't suffer the questionable upwind performance of a junk.

  The design is by Bertrand Fercot, implemented on his Wharram Tiki 30.  He reports that his boat tacks easily and sails faster than a standard Wharram Tiki 30.  Details are at:

   http://wharrambuilders.ning.com/profiles/blogs/sailing-with-pha-tiki-30-n119-1

  Kim and Rudolph aren't really related to the design.  I just like to mention them because they're the ones who convinced me it's a great idea.  Kim is the person who first mentioned the design in this forum, and Rudolph is the person who pointed out a lot of benefits that I wouldn't have noticed otherwise.

  The original discussion can be found here:

    http://au.groups.yahoo.com/group/harryproa/message/7314

---

  For a quick summary, it's the only soft wing sail I've seen that:

  - Can be raised and reefed with a single halyard,

  - Can be reefed or stowed simply by letting out on the halyard and tugging on one of the downhauls,

  - Can use soft heavy-duty sailcloth because the wishbones, not the sail, create the shape,

  - Automatically shapes itself to the wind without hydraulics or additional control lines,

  - Has the added benefit of the low sail/sheet stresses of a junk rig,

  - Delivers the partially-balanced forces of an easy rig,

  - Reduces those forces further by creating a double-skinned airfoil,

  - Eliminates both the boom and sail track, which are noticeable expenses once you include all the attendant hardware, and

  - Uses a fixed mast (no bearings!) and thus: an easier mast to build, erect, and remove.


Cons:

  - Not as efficient as a solid wing,

  - Definitely requires some labor for the creation of those wishbone frames,

  - Not as established as other designs that have been tested for years,

  - Will therefore likely require some experimentation, and

  - May be tough to use as a schooner rig; it looks like those mainsheets need to be lead aft, and not just to the windward cockpit.

---

  Personally, I'm largely sold on this design if I go for a single mast.  I love the efficient shape, lack of many moving parts, and lower cost (if you don't count labor and experimentation).


        - Mike




bjarthur123 wrote:

 

this is the first i've heard of kim and rudolph's swing-wing soft wing sail. can you provide a link? thanks.

ben

> If you're serious about keeping expenses down, another option is the
> swing-wing soft wing sail described by Kim and Rudolph. One mast, no
> boom, no rotating bearings anywhere, no sail track.

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