Sorry about the formatting on the last message.
I worry about what will happen with a dynarig during a shunt when the
wind picks up.
With an una rig or easy rig, you can go completely neutral by
loosening the mainsheet and allowing the rig to weathercock. At any
time, at any point of sail. This is one of the reasons why I'm a fan
of a proa with an unstayed rig; no matter what you're doing, you can
quickly stop dead with a neutral rig, and/or back up.
With the dynarig, the full area of the sail goes perpendicular to the
wind during a shunt. That might not be a big issue in moderate winds,
but if you get a gust at that moment, especially if the ww hull is on a
wave, the results could be most unsavory. Even if you don't get
knocked down, that's a lot of stress on the rig when the boat isn't in
a position to defuse that stress by sliding leeward.
An illustration of this is at:
http://au.groups.
The group discussed this a bit last summer, but I don't recall anyone
offering a logical argument as to why the dynarig would be safe in this
situation. There were opinions about it not being a problem, of
course. Todd was most in favor of the rig, and said that it was not a
problem during his many tests (which were a great addition to this
group; I'm sorry he's not yet participating again).
The Maltese Falcon can deal with this in one of two ways. Either:
a) turn only one mast at a time -- it's a huge ship, and can easily
handle 1/3 of the sail area going perpendicular to the wind, or b)
press a button, furl the sails, turn the masts, and then press another
button to unfurl.
Given that a fast/light/inexpens
Then there are the issues of weight aloft, concentrated points of
stress at the battens, added complexity, and less-convenient furling.
I'd love the efficiency of a double-sided sail with perfect camber,
but my spending will likely vote with a system that is much simpler.
It's hard to beat a mast with a bolt rope luff for sheer simplicity and
ability to repair damage one's self. Reliable track and slides/cars
follow closely behind.
- Mike
Gardner Pomper wrote:
>
> Yes, I do keep coming back to the dynarig. It is appealing. I am,
however, concered about how it will behave if caught aback. I hope to
build a small one for my test proa this summer (if I ever get the
rudders and crossbeams built).
>
> I have thought that if the dynarig battens where flat horizontal
plates, wide enough to go around the mast, then a slot could be cut in
them allowing the whole sail to cant away from the wind, putting the
center of pressure aft of the mast. It would seem that would make the
sail auto feathering.
>
> All the arguments about weight aloft, mast stiffness and weight
and complexity still argue against the dynarig, though, so I am firmly
in the undecided camp.
>
> - Gardner
>
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