The swing wing looks a cross between a camber induced sailboard sail and a humpback whale fluke- both good pedigrees. I like the lack of rotating mast bearings, a more balanced sail than a soft wing gaff, and more spread out stresses with low leech loads.
I am concerned by extra drag of all those lines, but in spectra they can be pretty skinny and no more than jiffy reefing and less than stays. A wing mast can be built lighter with less carbon and with simpler moulds than a tapered round section one.
The mast for the swing wing should be similar to the soft sail so I can make up my mind later.
--- In harryproa@yahoogrou
>
> Rudolph,
>
> You make a strong argument for the swing wing. No rotating mast
> bearings, no boom, no worries about mainsail tension, and lower loads
> would all be great things. As would the efficiency of a wing sail,
> which is the primary reason to look at the swing wing in the first place.
>
> I was fascinated by junk rigs a while back after reading Annie Hill's
> book, but then stopped paying attention when I read of several people
> getting junk rigs and then abandoning them because of their upwind
> performance. I understand that the Hill's cruising habits made the
> upwind performance less of an issue, but I've got a lot of upwind
> sailing to do on each trip where my boat will be moored, so I can't
> ignore that limitation.
>
> The swing wing design, though, should take care of any upwind worries,
> and should be faster than a standard rig on a reach. Alternately, it
> should have less drag for the same amount of lift, and therefore lower
> loads for the same boat speed.
>
> If the sheeting can be simplified in terms of what needs to be
> cleated, while still keeping the benefit of multiple sheets on the sail,
> each with smaller loads, this could be quite an impressive sail.
>
> Now that I look at the PHA photos again, I can see that only two lines
> on each side are sheets, and neither has a winch on it. It's possible
> that the two lines are actually the same line, and can be pulled
> together when taking in a lot of slack, an individually when there's
> more force on the line. I can't tell.
>
> I'd been thinking of complexity and failure points in terms of numbers
> of strings, frames, and battens. But now that you mention the
> strengths of the swing wing, I can see that's only part of the story.
>
> Getting rid of rotating mast bearings and eliminating boom stresses
> also adds to simplicity, as does the elimination of the jib. Spreading
> the same load over multiple sheets could actually reduce opportunities
> for failure, as would the lower stresses on the mast due to the
> efficient foil shape. Getting rid of the need for all that mainsail
> tension would also be a great thing in terms of reliability.
>
> My hat is off to Bertrand Fercot for implementing the rig and testing
> it for years.
>
> Thanks Rudolph and Kim for explaining more details, and Gardner for
> continually revisiting questions and forcing a discussion.
>
> However, I'm still hoping not to be first in line with this one.
>
> - Mike
>
> //
>
> Rudolf wrote:
> >
> >
> >
> > Hi Mike,
> >
> > I would say the Wharram would be cheapest, and worst performer.
> >
> > The big wing mast would be much more expensive then the others. It is
> > the highest stressed rig in the comparison.
> >
> > The swing wing is a junk rig with the low loads and lots of sheets.
> >
> > Junk rigs are great as they have a way of dividing the loads so that
> > there are no high stressed parts.
> >
> > So it is not the absence of a boom that makes them cheaper, but the
> > uncomplicated way of building the parts.
> >
> > I am sorry to say I never saw such a rig in real life but I expect it to
> > be very docile when sailing and feathered.
> >
> > There are junk sail sheeting diagrams around showing multiple sheetlets
> > being diverted through blocks ending up in one single sheet. That could
> > solve the complexity when shunting.
> >
> > Safest on a mooring in a big blow is to lower your mast, and that could
> > probably be done with this rig as you don't need a rotating mast.
> >
> > But I think it is more important that when sailing the swing wing will
> > be much easier to reef because high stress rigs with full battens will
> > always bind on the mast. Although I must say that BD's ail comes down
> > quite well.
> >
> > Efficiency is not defined by the number of sheets on the sail, but the
> > ease of use combined with performance.
> >
> > The shape you can have with this type of rig is great, and will be
> > better in time.
> >
> > Because the sheets are lightly loaded they are easy to adjust, probably
> > can be arranged so they don't need much attention.
> >
> > Hoisting this sail would be a matter of pulling a rope tying it off and
> > that's it. On many (small) boats you are working a winch just to get the
> > main up. Tensioning it is loud enough for everyone within a hundred
> > metres to hear.
> >
> > That also has to do with efficiency, and wear.
> >
> > In the end the low stress stuff will outlive everything else. And
> > probably without much loss of performance.
> >
> > Again this is based on second hand information, but the Chinese sailed
> > with these rigs when we were floating around on tree trunks...
> >
> > regards,
> >
> > Rudolf
> >
> >
> >
>