[PUP] Objectivity in boating publications

[Brian Smyth]

Hi John,

Thanks,

But really, it isn't that big of a deal. To me, I can't understand why
anyone wouldn't be willing to give THE OWNERS this data??? After all, when
you buy a boat, surely you have the right to know the design parameters.

The stability booklet will tell you if the vessel is stable under all
expected loading conditions, as well as damage stability and down flooding
if required.  Unfortunately, there are very few stability criteria for
"yachts".  The closest we have are ISO stability criteria A thru D, but
unless you really understand how these criteria are derived, it means little
to the owner. Basically the last page of the booklet is a "pass/ fail"
statement.

However, our procedure is to do a "light ship" inclining experiment, and
then, knowing the tankage, the full load condition is calculated.  This
gives you your stability for all states in between also, but again it is
something that needs interpretation.

The cost of producing a stability booklet, is roughly $1500.00.  A small
price to pay for piece of mind!

Hope this helps....

Brian



-----Original Message-----
From: John Marshall [mailto:johnamar1101 at gmail.com]
Sent: Thursday, September 17, 2009 1:11 PM
To: Brian Smyth
Cc: 'David Evans'; 'Passage under power'
Subject: Re: [PUP] Objectivity in boating publications

Brian,
	Your willingness to put your data out there, both modeling data and

empirical tests, is encouraging and hopefully will motivate other
manufacturers. Its crazy to me that this info is so readily available
for sailing passagemakers but as soon as we move to passagemaking
under power, then most of that data disappears, to be replaced by the
largely meaningless A/B ratio and similar.

	While sailboats run their model all the way to the limit, it makes
little sense to run the model for most powerboats beyond 90 degrees of
inclination. The house is in the water then and the model changes
abruptly -- you either have windows intact and lots of buoyancy from
the house, or the windows break and you fill with water and go down
like a rock. I would like to see the model run at both light ship and
heavy ship weights.

So kudos to you and the Pathfinder 48 for putting the data out there.

John Marshall
Nordhavn 55-20 Serendipity