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.

Maybe i have lost something in the thread, but you can argue atlantic v hp, but cat v hp is altogether different.

I do see the point that thr rig will want to pull boat further over because of its weight. This must be insignificant though compared to force on sails pushing it over.

Doesn't seem like a big factor.

Whatabout overall bea, providing relatively more stable boat because of localized sea and waves effecting heel.
I mean a small set of waves coukd bump a boat up to a significant heel angle, especially if on a small beamed cat.
Better to have wider and lighter boat, so irregularities in sea state are less of an effect.

Doug
--------------------------------------------
On Thu, 7/6/18, Björn bjornmail@gmail.com [harryproa] <harryproa@yahoogroups.com.au> wrote:

Subject: Re: [harryproa] Harryproa hull length and shape
To: harryproa@yahoogroups.com.au
Received: Thursday, 7 June, 2018, 11:41 PM


 









I think though that the weight
of the rig should be considered in this equation. On the
harryproa, the rig to leeward will decrease righting
moment.
I made a simple
Excel sheet to investigate.

My
assumptions were a 1000kg proa where 100kg is in the
beams/trampoline, and 100kg in the rig/sails, which would
fly a hull at 10 degrees. You can see the rest of my
assumptions in the pictures below. 
I found out that if we don't
consider wind gradients, the weight of the rig is the
dominant factor here. So if all else equal, the boat with
the rig to leeward (harryproa) will have less righting
moment margins. Because the heeling moment (with a constant
wind), is the same in both cases, if you think about
it.
But then I added
some math to include wind gradients, and then the results
aligns well with your words. Because then the height of the
rig impacts the sail forces due to the wind gradients, and
the boat with the rig to leeward produces less heeling
moment at high angles of heel. But it depends a lot on the
wind gradients (hellmans exponent) of the
location.
I'm sure
you have done similar calculations, but I'm sharing my
results here for others.
This is results without wind
gradients (Hellman = 0):
https://pasteboard.co/HoO0esk.png



This
is results with some wind gradient (Hellman = 0.2):


https://pasteboard.co/HoO1vdC.png



This
is results with an even higher wind gradient (Hellman =
0.4):


https://pasteboard.co/HoO1Ogd.png
So in this case, the harryproa would be
less likely to capsize, imo, despite having less stability
while just starting to fly a hull. So that is
interesting.
I have
very little experience reading the wind and judging the wind
gradients, but a guy I'm sailing with claims he has
observed that the wind some days is completely calm on the
surface, while there is still a decent wind some meters up,
indicating a high gradient (and hellman exponent), I
assume.
This is the
table from Wikipedia. 

locationαUnstable air above open water surface:0.06Neutral air above open water
surface:0.10Unstable air above flat open coast:0.11Neutral air above flat open
coast:0.16Stable air above open water
surface:0.27Unstable air above human inhabited areas:0.27Neutral air above human
inhabited areas:0.34Stable
air above flat open coast:0.40Stable
air above human inhabited areas:0.60



Not
sure what we typically have on the lake where I sail, or on
the coast to the ocean, or how you judge
"unstable" or "stable" air, in this
context. But if it is a windy day, where you are
more likely to capsize in the first place, my assumption is
that the air is unstable, which would give a lower hellmans
exponent, so less of and advantage to the
harryproa?But then you could just increase the
beam of the harryproa, I guess, since there is no rig load
on the beams, so the beams could be both longer and
lighter.

Doug, good point about the windage
of the WW hull flying. The hull will expose the same area on
both the cat and the harryproa, if we continue to consider
as many things as possible equal. That area might add more
heeling moment than the blocked sail though. But on the cat
it will block less of the sail, so better for the
harryproa.
Björn
On Thu, Jun 7, 2018 at
12:30 PM, Chris Purkiss chrispurkiss@bigpond.com
[harryproa] <harryproa@yahoogroups..com.au>
wrote:















 









The heeling moment on a cat increases until the
windward hull is out of,the water then it starts to decrease
after that. A harry proa is the same as soon the windward
hull is clear of the water then heeling moment starts to
reduce.  All the calls are done assuming the windward hull
is just clear of the water.

Chris
PurkissM. 0428755749
On 7
Jun 2018, at 7:37 pm, Björn bjornmail@gmail.com
[harryproa] <harryproa@yahoogroups..com.au>
wrote:
















 






Rick, you wrote (in another
thread):"

An interesting feature of
the harryproa configuration with regard to heeling is that
the heeling moment reduces as the boat heels.  A cat with
the mast in the middle or on both hulls has initial increase
in heeling moment when one of the hull lifts. 
"
Why does the heeling moment
reduce on the harryproa, but increase on the
cat?
On Fri, Jun 1, 2018 at 1:30
AM, Rick Willoughby rickwill@bigpond.net.au
[harryproa] <harryproa@yahoogroups.com.au>
wrote:















 









My first flat panel hull V14 taught me a
lot about section shape.  My V11 hulls were the fastest up
to that point and they had round sections.  The V14 were
constant flare flat panel.  For the same weight the design
data indicated 3% higher drag.  However the lowest drag
length was about 15% shorter than the round section and that
results in a weight saving.  In operation the V14 hull was
definitely faster, and by a significant
margin.
With regard to the
24 hour record, that boat was a V11 version 7.2m long with a
round section.  The record was set in 2008 but broken by a
surfski in 2015.
The fellow
who set the record in 2008 has built one of my V16 hulls
with the aim of retaking the record.  The V16 hull is the
first version to use the variable flare generated by the 32
parameter shape function using GODZILLA (Michlet). The new
hull is shorter, lighter and faster at target power level of
110W.
The link has a
video showing the plug built to make the female
mould:https://www.dropbox.com/sh/2tc
yk3y7drpwr2d/AACctJy1zD2FMDkG4 fCykWzya/PlugVids20151107?dl=
0&preview=VID_20151107_ 200302698.mp4
This link has a video of the boat
with Greg operating at 110W giving some commentary on speed
and other aspects of tuning the boat:https://www.youtube.com/watch?
v=0QrdEu1-zSc
As
it turned out he did not go to LA as he could not muster the
support needed for the attempt there.  He did try on the
Calgary dam but weather and the short course affected his
average speed.  I do not know if he plans to have another
go this summer.  The 2008 record was set on Whitefish Lake
in Montana.
 
On 1 Jun 2018, at 3:44 am, mcrawf@nuomo.com
[harryproa] <harryproa@yahoogroups.com.au>
wrote:
I'm
predisposed to agree with Rick Willoughby on the flat
bottoms for two reasons:   a) The flat bottoms work better
with intelligent infusion than a half-circle (meaning: I
will eventually be able to afford to build the boat), and 
b) One of Rick's designs for a human-powered pedal boat
held the 24-hour distance world record at one point.  



































































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