whatever happens when rotating and changing camber it is hydraulically driven on the larger test boat. Luc
--- In harryproa@yahoogroups.com.au, Mike Crawford wrote:
>
> Jerry,
>
> Thanks for going through the detailed analysis and sharing/recapping.
> Since harryrproa is the only list I follow, this is a big help.
>
> It does look as if there could be two lines to adjust the camber.
> Since they say "easy camber trim" instead of "automatic camber trim",
> this would be my first guess.
>
> However, there's another possibility. It also looks as if the luff
> might automatically rotate slightly to windward as the boom is pulled to
> windward. That could happen all by itself with a lot of wind on the
> sail, and then assisted by manually rotating the mast a few degrees if
> the wind is light.
>
> This would explain why the luff moves as the boom moves when they show
> the boat at the dock from 34s to 36s. Unless they have a crew hand out
> of sight pulling strings while the fellow on camera moves the boom, but
> I'd hope they wouldn't be intentionally misleading like that.
>
> The illustration doesn't look to be too helpful because it appears to
> be from the old Omer design that used a cylinder to help maintain
> camber. Unless there's a cylinder below decks that helps to rotate the
> mast to one side or another, the way the gas-charged cylinder in a Hoyt
> jib boom pushes it forward once you get it pat the center line. That
> would be neat.
>
> Ahh, speculation.
>
> It looks as if that particular sail would be about 2' high when filly
> stowed. In fact, I'd bet that it would be compact enough to convince me
> to go with a woven dacron, pentex, or dyneema instead of mylar -- I
> question how long mylar will last if it gets that crinkled up each time
> you stow or reef the sail.
>
> ---
>
> What matters most to me is seeing this sail in action. As recently as
> last week I was completely on the fence about whether to go with a soft
> wing sail or a normal fully-battened main on a wing mast with track.
>
> The single-skin sail seemed to be the path of least resistance, but I
> also think it would be really nice to:
>
> - Go with a fixed mast instead of a rotating mast -- less expense
> and complexity, fewer things to break and maintain. Maybe add a
> rotating boom to handle vertical loads, maybe go with the junk rig
> system for even more simplicity.
>
> - Skip the sail track and slides.
>
> - Have round bare poles so the boat sails itself less in a crowded
> mooring field.
>
> - Gain the efficiency of a wing.
>
>
> This new Ori sail would do all that. It might not be perfect, but it
> works really well, and is nice additional proof of a useful soft wing sail.
>
> I'd probably have to go with the junk-rigged-wing, though. That top
> crossbar adds weight, windage, and complexity I'd like to skip. I'd be
> especially worried about shock loading that T joint during gusts in a
> lumpy sea -- there's just less stress and less to go wrong with a
> straight pole.
>
> But I'm particularly cautious, and thinking about getting stuck out in
> a storm far from land, and am not necessarily the target market.
>
> In any case, I'm very excited to see how the sail works with those
> nice flexible battens. I'm convinced that a wing sail is workable. I
> think it might even allow me to skip the schooner rig and just go with a
> single sail, which would be wonderful for tacking up an inlet.
>
> - Mike
>
>
> Jerry Barth wrote:
> >
> >
> >
> > Mike,
> >
> > We already had a big discussion on the multihulls list about this
> > but I'll recap. I did a frame by frame view of the video on my big
> > monitor. They are very careful not to show much of the top inside of
> > the sail. If you look at the still pictures on the site you'll notice
> > there are four halyards going up to the crossbar. One goes to the
> > front of the sail, one to the back to raise and lower it. The other
> > two go from the deck, to just aft of the mast on the crossbar. From
> > there they run down to the top of the sail, to what I think are blocks
> > on either side of the top of the sail. Those are the dark areas in
> > the video. From the blocks it looks as if they go to the front of the
> > sail where there is probably a prod that moves right or left to adjust
> > the leading edge of the sail. On the bottom of the sail the bottom
> > most rib is a set of two half sections, one from the mast aft and the
> > other from the mast forward. Just below the forward section is
> > another prod that moves the leading edge. So they have control of the
> > leading edge of both the top and bottom of the wing. Then you'll
> > notice that the intermediate ribs have a pivot point/hinge where the
> > battens are attached. It looks to me that to adjust the camber they
> > move the nose and with the flexible battens the whole sail takes the
> > right shape. Things I wonder about is if it is better to rotate the
> > whole mast as they did, or to make just the crossbar at the top
> > rotate? How high is the stack when the sail is fully down?
> >
> > Jerry Barth
> >
> >
>