Todd,
One thing that might help the discussion is getting clear on some
of basic criteria.
You're right in that there's a lot to be said for the pacific proa
design where you've got a lightly-loaded windward hull just skimming
the water.
There's an argument that the righting moment from a 60/40 windward
hull will allow you to create enough drive to overcome the
additional wetted surface area, but let's put that aside for a
moment. I don't have the software to prove or disprove this
position, so sor the sake of discussion, let's just assume the
pacific proa is more efficient.
If you don't mind continually manning the sheets and adjusting
balance, the pacific proa is going to be a very fast and elegant
sailing boat. I agree with you completely, or almost completely, in
this instance. If you add a dynarig to the equation, you'll have a
very sweet boat, as you've demonstrated with both your models and
your full-size proa.
---
But what if you can't continually balance the boat and adjust the
sheets, or alternately, want the option of not having to do these
things?
This can happen on a full-day daysail if:
1. You hit a squall before getting back to land and need time to
reef or furl the sail in very high winds and high seas. It actually
is possible to unexpectedly get hit with huge winds that don't give
you much warning, especially if the sky is not clear and there's no
associated black-cloud thunderhead associated with the wind burst.
People have gone from ten knots, to seventy knots, back to ten
knots, in a span of a few minutes.
2. You need to eat, drink. or pee, but don't want to stow the
sail.
3. You need to take multiple bearings with a sighting compass and
locate yourself on a chart. This takes both hands, and sometimes
has to be done repeatedly if you don't have a chartplotter, or if
your chartplotter fails, and you're either in unfamiliar waters or
in fog. It's not realistic to stow the sail every time you want to
verify your location.
4. You become injured or seasick, and can't handle boat balance
and sheets the way you could if you were in perfect condition.
5. You become incapacitated and a less-experienced guest has to
pilot the boat (and/or furl the sail in high seas and winds).
7. You want to take out several people who have little or no
sailing experience, and can't count on them to help with balancing
the boat, particularly if some of them are not agile.
8. You've simply been at the controls too long, need to rest, and
either let the boat do some of the sailing and/or have someone less
expert than yourself take control.
And while all of these *might* happen on a daysail, one or more
eventually *will* happen when cruising.
---
What then?
I'd argue that these situations would call a proa with a sail that
feathers into the wind, and completely depowers, without any input
or control, when you release the sheets, and which carries a good
amount of weight to windward in order to keep the boat upright when
hit with gusts and waves at the same time.
To me, the question is: how do we improve on the harryrpoa design
given these criteria?
It's not which design is the fastest, or most elegant, given a
good captain and agile crew, but which design is fastest and safest
once you add in the eight situations above.
I don't think that Rob has solved everything, but having said
that, I don't know how to improve upon what he has done. But with
your experience and intuition, you might be able to find ways to do
even better.
So, what would you do to make things faster, more elegant, and/or
safer for a lazy safety-conscious wimp like myself?
And I mean that question, too. You design and build fast boats.
If there's something faster/lighter/cheaper out there that takes
care of the above criteria, I'm seriously interested.
- Mike
--- On Sat, 1/1/11, tsstproa <bitme1234@yahoo.com>
wrote:
From: tsstproa <bitme1234@yahoo.com>
Subject: [harryproa] Re: Hull slenderness ratios ww hull lengths
To: harryproa@yahoogroups.com.au
Date: Saturday, 1 January, 2011, 5:21
I know it probably sounded like a really simply
question that one obviously could have answered him/her self. But
coming from a Pacific proa stand point, regardless of windward hull
length. Your adding to the over all weight of proa by having a
windward hull large enough to support weight of stuffs and crew.
Would that be a logical conclusion?
Never thought of Robs windward hull as having a wide waterline beam,
just large structure with large amount of volume.
I tend to believe making windward hull as high as possible in length
to beam ratio for the given length and weight to be carried for a
given draft. Especially for the smaller craft. To compensate for
shorter length.
Haven't run the displacement for what draft numbers, but running a
WW hull 4.26m/ 14' length with a waterline beam width of 25.4cm
/10'' gets you double your 8/1 for a 16.8/1 length to beam ratio.
Pushing it to 16'L x 12''w gets you greater weight carrying ability
on a little wide waterline beam with a 2'' increase from 10'' to
12'' with a 16/1 ratio or keep the 10''wlb for 19/2 ratio, just a
thought. Whats your load out on extended cruising and the weight
when just out for a day sail on windward hull? +/-
Todd