I would guess an empty boat may have that approx. ratio. More hull build in ww hull and deck etc offset by rig and rudders in lw.
But then when loaded with gear, food, people etc then it is much more biased w to w.
That is ths whole idea.

--------------------------------------------
On Fri, 8/6/18, Björn bjornmail@gmail.com [harryproa] <harryproa@yahoogroups.com.au> wrote:

Subject: Re: RE: [harryproa] Harryproa hull length and shape
To: harryproa@yahoogroups.com.au
Received: Friday, 8 June, 2018, 7:37 PM


 









I've read posts from Rob on
this mailing list that the target is ~40% of the weight to
windward on cruising proas. But I might have misunderstood
something. Might be with an empty boat? So with the crew and
gear it has more than 50% to WW?I guess you can move

around gear and crew if you want to optimize for the
conditions. 40% would
still be a lot more than on other types of proas with the
rig to leeward.



To
always have more than 50% on the short hull doesn't
seems like a good idea. If there is not much heeling force
in the sails (light conditions or sailing downwind), that
hull will produce a lot of drag (short and heavy). Also,
sailing downwind in a strong breeze with a lighter LW hull
doesn't seem like a good idea to me, then the boat will
have lower margins to pitchpole.
I was in Portugal to have a look at
Robin Wardes boat, Kleen Breeze, two years ago, while it was
still in the boatyard. He put a lot of heavy gear in the LW
hull. Like the battery bank, washing machine, e.t.c. He was
also talking about this 40% ratio, while we were looking at
all the stuff in the LW hull.
And to me, it makes sense. Let's
say we put 50% in both hulls, and targets the same length to
displacement ratio on the short hull in light winds, and on
the long hull in strong winds. Then the long needs to handle
100% of the displacement, and the shorter 50% of the
displacement. Then the ratio of the lengths will be cubic
root of 50%/100% = 0.5^(1/3) = 79% of the length. And that
is quite a long WW hull. If we assume that there is always

some heeling forces in the sails, and also put less weight

in the WW hull, the WW hull can be shorter, with the same
length to displacement ratio. So let's say 40% WW
weight, and 10% of the total weight resists the heeling
forces. Then we get 0.3^(1/3) = 67%, which is more or less
what Rob is using. Again, this is assuming the target is to
have the same length to displacement ratio on both hulls. A
cat might not be the best design, considering this, since
the LW hull gets more loaded while heeling. So if the boat
is light, the WW hull is unnecessarily long (extra wetted
surface, friction drag). And if the boat is heavy, the LW
hull is short and draggy (wave drag).
Don't see it as an issue with a
slightly lighter WW hull than 50%, since you can get both
high RM and a light WW hull, by just increasing the beam. If
RM is kept constant, the load on the beams will stay the
same. But the beam loads are always lower on a Harryproa
than on a cat boat with a stayed rig in the middle of the
beams.
There is also a
difference between the light racing boats, and the heavier
cruising boat, imo. For racing, the weight of the crew is
large compared to the weight of the boat. The crew is always
active, and will move to leeward when the conditions or
point of sail calls for it. So the sum of the crew and the
WW hull can be more than 50%, and the WW can still be very
short, like 50% of length. But I think on a cruising proa,
the weight of the crew has little significance, and you need
to distribute the gear so you have maybe 40-50% in the LW
hull, depending on its length. But if you want to have more
margins of safety while sailing into a strong wind, I guess
you can move some heavy gear from the LW hull to the WW
hull.
That is my
thinking, anyway! =)

On Fri, Jun 8, 2018 at
12:34 PM, Doug Haines doha720@yahoo.co.uk
[harryproa] <harryproa@yahoogroups.com.au>
wrote:















 










Yeah, not sure
what Bjorn was meaning there.
50% of total or 50% of movable
gear/stores ?








On ‎Friday‎, ‎8‎ ‎June‎
‎2018‎ ‎06‎:‎32‎:‎25‎ ‎PM‎ ‎AWST,
'Peter Southwood' peter.southwood@telkomsa.net
[harryproa] <harryproa@yahoogroups.com.au>
wrote:






 









Note that a
harryproa is specifically a “weight to windward” proa. 
More than 50% in the windward hull is almost a defining
feature. Cheers,
Peter
 From: harryproa@yahoogroups.com.au
[mailto:harryproa@yahoogroups.
com.au]
Sent: Friday, June 8,
2018 10:14 AM
To: harryproa@yahoogroups.com.au
Subject: Re: [harryproa] Harryproa hull
length and shape
  
I
think the most interesting lesson here was the fact that the
height of the rig has such as an importance if there is a
wind gradient. So on boats where the height of the rig
increases during heeling, it really increases the heeling
moment due to stronger winds higher up. On harryproas or
normal keelboats, the windstrength decreases from the first
degree of heel. The logic is confirmed with math.
 I
don't think its good design to put more than 50% weight
in the WW hull, because then that hull needs to be almost as
long as the LW. More beam and a lighter WW hull (Rob says
40%) would be better. But I think this isn't really the
point here, to look at the static numbers. It's very
easy to change same parameters, which will shift shift
either curve up or down.. What I thought was interesting was
the shape of the curves. It's just like Rick says, the
proa has less heeling moment at higher angles of heel, and
the cat the opposite.
 Take
this one for example, with a very large gradient (Hellman =
0.6)https://pasteboard.co/HoUBtOO.
png
 The
harryproa has positive righting moment all the way to 45°
in this case. I can image that when sailing in an
archipelago with islands covered with trees, or in a lake
surrounded by trees, the wind has a high gradient. So in
this case it would be almost impossible to capsize the proa,
but the heeling cat will reach stronger winds which has been
less blocked by the trees, and will need a really fast
reaction by the crew to stay rightside up.
 
 
 
 On
Fri, Jun 8, 2018 at 6:49 AM, Doug Haines doha720@yahoo.co.uk
[harryproa] <harryproa@yahoogroups.com.au>
wrote: 
I
would submit that in general, if you can build you hp for
say $20,000 and can go out and sail twice as fast as boats
that cost similar and only get matched for pace by $100,000
boats then you are the comparitive winner overall.

------------------------------
--------------
On Fri, 8/6/18, '.'
eruttan@yahoo.com
[harryproa] <harryproa@yahoogroups.com.au>
wrote:

Subject: Re:
[harryproa] Harryproa hull length and shape
To: harryproa@yahoogroups.com.au

Received: Friday, 8 June, 2018, 11:42 AM


 













| It is hard to say: assuming
all other things being equal.
Obviously the
hp can have most of its total weight in ww
hull, whereas cat has to keep it 50/50.

|So the argument can't
really begin on an even keel.



Doug makes a
good point. Perhaps i missed something too,
but it looks like you made the HP a cat, to
make it fair.



Also, and this might be a
language thing, but we don't
want fair.
We want accurate, don't we?



Not that the
thought experiment was not great. Thanks for
it, and I am still chewing on it. Neat to see a
physical
representation of the vectors.



Rob, a few posts ago, said cats use weight, and
hps use
width, which is lighter and cheaper.
I think it's fair
to object to
normalizing weight and width.



Perhaps add a
third boat. A typical, non normalized HP?
Still constrained by the same weight/cost?



To visualize the more realistic comparison?











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