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
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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.
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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.