Robert,

  Thank you for posting the omer link.

  I had written this design off over a year ago because larger designs use either electrics or hydraulics to induce camber.  I would not want a rig that depends upon either system on every tack or shunt -- too many things to go wrong. 

  On smaller boats the site says the camber can be induced by a hinge at mid-boom, though, so perhaps there are other options.

  As long as we're theorizing, do you think the auto-camber could be done on something the size of a larger Harry with a bruce number approaching 2.0?  Some thoughts:

  - Strong hinge. 

     I suppose the loads are known, so perhaps there's nothing preventing the design of a really beefy mid-boom hinge that would auto-camber in most winds.  Perhaps with a continuous-loop control line to force camber when the wind is really light.

  - Hinge with vang. 

     There could be a strong hinge as with the previous idea, but with some sort of vang system to carry the bulk of the vertical load, eliminating a lot of torsion from the boom.  The vang would take up extra space below the boom, and would somehow have to expand and contract to allow the mid-boom hinge to swing from one side to the other (a fixed vang would make this impossible), though, and that is definitely a design wrinkle.

  - Wide boom with traveler. 

     It would look a little funky, but you could have a twin-boom extending aft like a thin pie slice, with a curved traveler at the aft end that attaches to the mainsheets.  The boom itself would definitely have a major vertical flange/wall on its outer edges, essentially being two booms in one.  Whichever flange/wall is windward would then handle the vertical loads on each respective tack.  The
would then automatically migrate to windward with the force of the mainsheet (with the boom taking vertical loads).  This obviously makes for a larger and heavier boom, but:  a) at least the weight is not high aloft, and  b) the width of the boom might add a nice end plate effect.  You could also have a line on the traveler to force it to windward

---

  Today I'm pretty excited about the wide boom with traveler.  It's about as simple as you can get in terms of shunting, number of moving parts, and system design.  It wouldn't have the low loads of the junk setup, but it also wouldn't have the extra parts and drag from the sheets.  [I'm not arguing for or against the junk -- I'm just excited about a modified Omer at the moment].

  It would be great to have noticeably more lift and less drag than a standard sail, all while sailing at a 10-degree angle of attack instead of a 20-degree angle.

  This could be the super-fast-yet-simple una rig that I've wanted all along.  And if not this, then the swing wing, which is obviously tried and proven.

       - Mike



 
robertbiegler wrote:

 

--- In harryproa@yahoogroups.com.au, Mike Crawford <jmichael@...> wrote:
> But I actually wasn't thinking about a whole new system.

I found a link to a soft wing sail that its designer calls "ready for production": http://www.omerwingsail.com/

The flexible batten for the aft portion of the sail doesn't work with junk-style sheeting, for the reasons others have already explained. It does work if you set up your soft wing like a standing lug, as Chapman did in the 1960s. There is information on this rig in old AYRS publications.

Another alternative is to use rigid bent battens and let them flip along their longitudinal axis. Nils Myklebust has published drawings in the latest JRA Newsltter, and plans to make his next sail that way.

Jeff Doyle developed another soft wing, based on what a Chinese man told him about his grandfather's invention. I can't find Jeff Doyle's article on the web, but it was published both by AYRS and JRA. I also have a copy of the 2002 version of the article.

Regards

Robert Biegler

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