Subject: Re: [harryproa] Re: Swing-wing rig
From: Micha Niskin
Date: 5/26/2011, 10:39 AM
To: harryproa@yahoogroups.com.au
Reply-to:
harryproa@yahoogroups.com.au

 

Mike,


David Tyler's Tystie rig (the updated version) is a ketch, but I don't see why a schooner wouldn't work. Being able to get sail area forward of the mast is very nice for a proa, and not easy to achieve with other rigs. He settled on a sheeting arrangement that leads the sheets for the upper panels to windward (he has two sets of upper sheets, port and starboard), but he doesn't really lead them very far aft of the foot of the sail, at all. In the pdf you can see some interesting things also, like the extended upper batten to prevent fouling of the sheets when hoisting or lowering.

The other rig I'm interested in is the high-aspect, full-battened, standing lug schooner. These rigs like to have a bit of rake to the masts, though, which isn't possible on a proa, but otherwise seem to be well suited. The rig provides a good amount of sail area with a low center of effort, the running rigging is simple (only a single halyard, no separate peak and throat), the spars are short and lightweight, and there is no sail track or slides to jam. I'm not aware of any high-speed craft with either of these rigs, though, so the real performance is hard to predict.

I think that having simple, unstayed, non-rotating masts is a huge benefit in terms of design and construction effort, which more than makes up for the added complexity of the sail and running rigging, I expect. I guess one downside to non-rotating round section vs. rotating airfoil mast would be more windage under bare poles. I wonder if it would help to rig some kind of ribbon or hairy fairing that you could hoist to reduce the induced drag of the round section mast? That also begs the question of why we don't see racing yachts with ribbon fairings on the standing rigging?

On Thu, May 26, 2011 at 9:45 AM, Mike Crawford <mcrawf@nuomo.com> wrote:
 

Micha,

  I also like the use of multiple sheets to deal with twist.  That should cut down on excessive twist without the huge stresses on sheets and sail cloth that you'd see in a normal high-aspect high-roach main without a backstay.

  Sometimes I debate adding the rotating boom as you suggest.  It's a bit more complexity and expense, but it should make tacking and shunting easier from the cockpit, and also provides a nice fixed place to drop the sail while reefing or stowing.

  That said, I stand corrected on the junk's suitability for a schooner rig.  Never having seen a schooner junk up close, I had assumed that the sheets had to be lead as far aft as they are on Fercot's Tiki.  That angle may be ideal for reducing sheet loads and wishbone/batten stresses (or maybe not), but it looks like the ideal is not necessary.  Also, Fercot ends up combining his his multiple sheets into just two per sail, so it's not as complex as it might seem at first glance.  You could even combine those two into one, perhaps at the expense of having to use a winch more often.

  After reading Rudolph's update on the origin of the rig, I browsed across these photos of Badger (junk schooner) and Tystie (swing-wing schooner):

    https://picasaweb.google.com/108735432675049110317/Badger#5518116655093321266
    https://picasaweb.google.com/108735432675049110317/Tystie#5519151842438542050

  Neither one has the sheets on the forward sail lead past the aft mast.

  So, maybe a schooner could indeed work, particularly with the extra step of that rotating boom.

  Imagine the speed of two wings, combined with the lower heeling moment of wings and lower COE of a schooner...

  Maybe it's not perfect.  But what excites me is that it's something I could try, and perhaps fine-tune, without a huge R&D and equipment budget.  The allure of a better airfoil definite has its draw.

  Personally, though, I'd have to go with a higher-aspect shape that looks more like an efficient wing.  Tystie and Pha might work well, but the sail profiles challenge my notion of a pretty boat.

        - Mike



 

Micha Niskin wrote:
 
I like how the swing-wing deals with twist in the leech (the "chinese" sheeting arrangement). The omer wingsail seems more complicated. I was thinking that you could adapt the swing-wing for use on a proa, and still keep the chinese sheeting arrangement. This is the configuration I imagined: Unstayed, round-section mast, wing sail as in Mr. Tyler's Tystie. The mess of chinese sheets would be led to the outboard end of a boom under the sail. This boom would have jaws or a gooseneck at the inboard end and be free to rotate independently from the sail. Thus, I think you'd be able to set the chinese sheets relative to this lower boom, and then have your mainsheet that you'd use to adjust the angle of the whole sail rigged to this boom and run to the cockpit. When shunting you'd be able to leave the complicated web of chinese sheets fixed relative to the boom, and use the simpler, conventional, secondary mainsheets to get the sail over to the other tack.

On Wed, May 25, 2011 at 2:17 PM, bjarthur123 <bjarthur123@yahoo.com> wrote:
 


thanks for the info. i'll book mark it. seems similar to omer's wing sail:

http://www.omerwingsail.com/

ben


__._,_.___
Recent Activity:
Visit Your Group
.

__,_._,___