[Alberg30] Positive Stability Range

[John Birch]

"The Desirable and Undesirable Characteristics of Offshore Yachts" has a
screening formula. That formula was applied to about 50 different yachts by
Practical Sailor about 12 or more years ago. The A-30 came in second being
marginally beaten out by the Ludders 44. The A-37 came in fourth. The
threshold was to have a screening number as far below 2 as possible. The
A-30 was 1.6, the A-37 1.62.

Both meet the Characteristics of a Suitable Offshore Yacht.

That measure, the roll screening formula, was to determine the propensity of
a vessel to come back up (right side up) in the event of a knockdown or
roll.

Regards,

John  - Sunstone

----- Original Message -----
From: "Gordon LACO" <mainstay at csolve.net>
To: "Alberg 30 public list" <public-list at alberg30.org>
Sent: Wednesday, March 05, 2003 12:34 PM
Subject: Re: [Alberg30] Positive Stability Range


> on 3/5/03 10:19 AM, George Dinwiddie at gdinwiddie at alberg30.org wrote:
>
> > Alfredo wrote:
> >> Greetings,
> >>
> >> Does anyone happen to know the positive stability range of the Alberg
> >> 30?
> >
> > Back in 1994, Jack Hornor estimated the positive stability range to a
> > bit under 120 degrees.  Judging from the graph he gave out, I'd say
> > about 118 degrees.
> >
> >> Also, I know the total working canvas area of our boats. But, what's
> >> the area of just the main?
> >
> > The sailplan (http://www.alberg30.org/boat/A30sailplan.jpg) shows a
> > figure of 221 sq. ft. for the main.  The fore triangle is 189 sq. ft.
> >
> > - George
> >
> Hello mates -
>
> I am surprised at a figure as low as 120... last year I was up to my hips
in
> a problem involving a sailing ship whose Limit of positive stability was
> under 100.  In the course of working on that issue I came across material
in
> Machaj's "Seaworthiness - the forgotten factor" that indicates "dangerous"
> yachts having numbers under 130, (yachts lost in the Fastnet of '79 are
used
> as examples - Grimalkin had an LPS of 125) and yachts of our type - narrow
> with full keels having numbers of 160 degrees and more.   When you say 120
> degrees - what are you refering to?  When I say 160, I mean that I expect
> the boat to still have a righting force that will return it to an upright
> position.
>
> Gord
> #426 Surprise
>
>
>
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