Subject: [harryproa] Re: Sunday sail
From: Mike Crawford
Date: 2/20/2006, 4:29 PM

<<all this looks as if the schooner rig efficiency is much less than the one of the una rig.>>

  That's tough to tell at this point.  That second sail obviously isn't contributing a whole lot past 16 knots, but once such a small non-planing boat goes past 16 knots, there could be other limits at play.

  The trick would be to get a taller una rig and then see:  a) where the boat's top speed lies, and  b) how it compares to the schooner in light wind.  The schooner's extra sail area, at lower apparent wind speeds and higher apparent wind angles, will probably then register.

  The big question would become reefing versus dealing with two sails.  A tall una will be great in low winds, but will require more changes to increase and decrease sail area as conditions vary, when compared to the lower center of effort of the schooner.  The schooner will require more effort on every tack.

  The una rig clearly would require less effort to shunt, and that means a lot.  If the boat does have a limit past which it isn't likely to be pushed, it makes a lot of sense to skip the second mast and save the time and effort required to rig it and tend it.  When trailering an Elementarry, sailing it, and trailering it back home, the effort savings could contribute noticeably to the day's fun.

       - Mike


dominiquebovey wrote:
all this looks as if the schooner rig efficiency is much less than the
one of the una rig. My feeling is that the forward sail disturbs the
rear sail to the point the latter could actually be almost only drag
and no propulsion. This assumption could be supported by the fact the
una-rigged proa seems much less constrained in sailing ("flies over

I would really be interested to see an easy rig compared to the una,
but I am starting to think it might not be much more efficient than
the una. But hey, in racing even 0.1kn is something. On class C wing
masts you almost always have "deflectors" in the wing mast leading
edge, to force the air going faster on the extrados (depression side)
of the wing. In an easyrig the jib plays this role.

--- In, "Rob Denney" <proa@i...> wrote:
> G'day,
> Went sailing on Sunday in Elementarry to assess una rigs vs
schooners.  15 knots of breeze, solo, with 11 sqm/118 sq' of sail.
This is half a Tornado sail area but the sail itself probably less
than 75% as effective due to the mast and the set up.
> Simply amazing.  It is a different boat. Flies over the water rather
than trying to force it's way through it.    Steered itself, the bows
were up upwind and top speed was not a lot different to the schooner
rig (16.4 knots max, vs 16.8 with the schooner in similar conditions).
Followed a Tornado upwind, was pointing as high, but going slower.
Quicker than a racing Hobie 16 reaching.   Not many other boats were
sailing.  Not much sea, but occasional large wakes from powerboats.
Handled with aplomb, although wet if the beam hits the wave top.
> I steered using only the aft rudder which was similar to steering a
conventional boat, the forward location making up for no daggerboard,
the oversize rudder making up for the lack of lever arm.   Shunting
was very easy (a nuisance going to leeward to lift and lower the
rudders), never got close to getting into irons or caught aback. 
Downwind, it just got up and went.  Occasionally buried the bow, but
did not slow it down.    It is now definitely a boat anyone could sail
solo and one which I look forward to teaching my 4 year old daughter
how to sail on.  Should also be able to look at the gps while sailing,
rather than only the max speed at the end of the day. 
> Interestingly, I only flew a hull once or twice the whole time (too
lazy to get off the windward hull, too amazed by how comparatively
easy it all was to bother with pushing the limits), which suggests
that the rig is under utilised, something supported by looking at it.
A new wing mast will help this.  I was going to increase the una rig
sail area, but think I will go with the same area, but with a wing
mast, maybe forward raked to reduce sheet loads.  Also building a
single rudder setup so I don't have to raise and lower them each shunt.
> The single rig is quicker to rig and derig; An hour and a half from
arriving at the ramp to sailing, but at least half of this was one off
jobs that needed doing.  Also easier to right after a capsize and 4
grand cheaper.
> I am not a lot wiser about how long boats should be for a given sail
area, but am pretty certain that it is much longer than they currently
> I think this was not so much a comparison between schooner and una,
more between lots of sail and less, although 2 is definitely twice the
effort of one. 
> Apologies for cross posting.
> regards,
> rob

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