Posted by Dave_Benjamin (dave_benjamin@…>)
You shouldn’t need polars to figure out that the sails need tweaking
or trimming. It’s all theoretical anyway. Most boats are laden down
with supplies, spares, and other crap. Most time cruising is spent
with autopilot or vane engaged. Frequently a reef is tucked in to
keep the boat from getting overpowered. I’m sorry but a cruising
sailor needs polars about as much as a fish needs an umbrella. If
you’ve ever sailed on a boat crewed by mostly professional racing
sailors I think you’d probably agree with me. That kind of sailing
is pretty far removed from what most Freedom owners are up to.
— In freedomyachts2003@yahoogroups.com, “Fred Molden”
<fredmolden@…> wrote:
What a polar lot can tell a cruiser is if he is operating the boat
up to its potential in a given wind speed and angle. This would
maximize the VMG and shorten travel time. For example the polar may
show that the boat in a 10kts breeze at 45 degrees apparent wind
should be able to go 7kts through the water. If your speed is only
6.5 kts then you can tweak to improve speed. Polars are usually
under ideal conditions and represent a maximum speed possible.
----- Original Message -----
From: Larry Kraus
To: freedomyachts2003@yahoogroups.com
Sent: Wednesday, March 15, 2006 9:10 AM
Subject: Re: [freedomyachts2003] Re: Numbers
Thank you for the explanation. As a weekend cruiser, I need to
get to a destination at a approximate pre-appointed time. So VMG is
also my interest.
LK
Dave_Benjamin wrote:
Polars are a numeric expression of boat performance in a
graphic
format. Totally worthless for cruising boats IMHO. The polars
give
you an expected speed based on true wind speed and direction.
So if
there's 12 knots of breeze at 40 degrees off the port bow a
polar
chart would tell you that you should expect xx knots. There
are a
multitude of variables that can effect performance.
What I'm concerned about on a cruising boat is VMG (velocity
made
good)toward the destination, ride comfort, and safety. Most of
us
sail shorthanded and don't push the boats as hard as we can.
If
anyone wants to spend the money you can have a set of polars
developed for your boat or depending on which Freedom you have
some
polars may already exist.
--- In <freedomyachts2003@yahoogroups.com>, Larry Kraus
<kracherlandl@> wrote:
>
> What's a "polar"?
>
> Larry Kraus
>
> jerry_magic1 wrote:
>
> > --- macks011 wrote:
> > > With
> > > reference to sailboat performance, speed over ground is
meaningless.
> > > Speed through the water is the criterion.....the
reference by
> > > which we judge the performence of our sail set, the
knotmeter
is the
> > > instrument of choice.
> >
> > Good point. I should not be relating hull speed to SOG.
I’d
look at
> > the knotmeter reading if it worked more than 3% or 4% of
the
time, but
> > it is usually fouled with grass or something -- even
though I
> > installed a new transducer two years ago. Got tired of
going
into the
> > water to free the impeller wheel only to have it stop
spinning
again
> > after a couple of hours. Maybe the speed equipment will
be more
> > reliable when I switch from Datamarine to Raymarine
instruments.
> >
> > As a cruiser, I've always been more interested in time
calculations
> > from point to point and GPS is great for that, but I too
would be
> > interested in seeing the polars on these boats.
> >
> >
> >
> >
> >
> >
> >
> >
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