Subject: [harryproa] Re: Swing-wing rig |
From: Mike Crawford |
Date: 5/26/2011, 9:28 AM |
To: harryproa@yahoogroups.com.au |
Reply-to: harryproa@yahoogroups.com.au |
Ben,
While both the Omer and Swing-Wing have similar shapes on the
outside (with Omer looking a bit better, actually), there are some
notable differences in the implementation, both in terms of design
complexity and sailing complexity:
- Three panels. Omer uses three sail panels: forward, aft
port, and aft starboard. You can see them in this image with the
sail stowed: http://www.omerwingsail.com/lib/8887033.jpg
- Reefing. Because of this three-panel design, reefing
requires hauling down and tensioning three separate sections.
That'is a lot more time-consuming than reefing a junk rig, where you
let off a halyard, allow the weight of the wishbones to drop the
sail, cleat the halyard, and tug the downhaul. Having read Ann
Hill's description of her ability to single-handedly raise and reef
the junk rig sails on Badger, even in a storm, I find this most
impressive.
- Hardware. The three sail panels require four sail
tracks, with the cars to go with them, and the structure required to
support those tracks out there away from the mast, as well as the
battens/frames shaping the sail. The swing-wing requires just a
mast and the wishbones. Much less to build and take care of. The
wishbones could be wood, glass, carbon, whatever. And while they
may eventually fail or rot, you could patch them up anywhere in the
world with local materials. Try that with battcars...
- Piston-controlled. Omer uses an electric or hydraulic
piston to adjust the boom/sail angle on every tack: tack,
introducing more parts, complexity, and effort during tacking.
Also, a potential point of failure in terms of sailing efficiently
if the piston stops working. The Swing-wing will just flop over
with the force of the wind, no hydraulics required.
---
Of all the soft wingsails proposed, the swing-wing is the only
I've seen that deals with raising, reefing, and tacking, without
resorting to extra mechanical devices. No computer, hydraulics, or
electrics required, and when it's down, there's zero risk of the
boat sailing on its own while moored.
It's also the only wing sail I could see myself being comfortable
handling when a squall picks up out of nowhere. Drop. Done. Raise
a bit. Done. Even my wife, who weighs 105 pounds, could do it
easily if I were injured or incapacitated. That means a lot if we
want to go any distance that will require one of us to single-hand
the boat for hours at a time while the other sleeps.
Assuming Omer's polars are correct, and it can exceed true wind
speed with relatively little sail area and heeling moment, the soft
wing is a serious improvement over a single skin. Even if the
swing-wing is only half as good as the Omer, it would be a most
impressive rig (again, especially when you include its low cost,
complexity, and ease of use).
- Mike
bjarthur123 wrote:
thanks for the info. i'll book mark it. seems similar to omer's wing sail:
http://www.omerwingsail.com/
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).