[Rhodes22-list] Toys for Rhodes

[Roger Pihlaja]

Jeff,

There are transom-mounted transducers for the knotmeter/log/water
temperature and also some installations of the depth sounder transducer
wherein the sensor is bonded to the inside of the hull with epoxy.  Without
going into the technicalities of these installations, neither type works
particularly well.  To the best of my knowledge on the subject, both types
of transducers will give the best accuracy & sensitivity (greatest measured
depth) if installed in properly located and oriented thru-hulls.  A
below-the-waterline thru hull is no big deal.

Roger Pihlaja
S/V Dynamic Equilibrium

----- Original Message -----
From: <JSusanj at aol.com>
To: "The Rhodes 22 mail list" <rhodes22-list at rhodes22.org>
Sent: Monday, May 17, 2004 11:38 AM
Subject: Re: [Rhodes22-list] Toys for Rhodes


> How do the sensors that must be in the water attach?  Are they in
through-hulls?  I have always been reluctant to add holes to the bottom of
the boat as they are a possible source of leaks but the log would be very
useful.
>
>
> Jeff Susanj
> s/v Sweet Medicine
> Florissant, MO (temporarily)
>
>
> In a message dated 5/14/2004 6:19:36 PM Eastern Daylight Time,
cen09402 at centurytel.net writes:
>
> >
> > Doug,
> >
> > OK, realizing I'm probably going to provoke an argument, here goes...
> >
> > 1st of all, complete disclosure.  Dynamic Equilibrium's electronic
> > navigation aids consist of an Autohelm ST-50 tridata instrument and a
> > Magellan GPS 2000 handheld GPS unit.  The ST-50 tridata combines a
> > knotmeter, log, depth sounder, and water temperature sensor into one
> > package.  The ST-50 is no longer in production.  The replacement
Autohelm
> > unit is called the ST-60 tridata & it has essentially the same
functions.
> > My ST-50 tridata has been in service since 1993 and my GPS 2000 since
1996.
> > The ST-50 has been totally bulletproof.  The GPS 2000 got dunked by a
wave
> > in the cockpit once in 1998.  Despite the waterproof rating, water got
> > inside the GPS 2000's case & it failed within 10 minutes of the dunking.
> > Magellan repaired the unit under warranty & it has lived inside of
ZIPLOC
> > plastic bags ever since than.  By today's standards, the GPS 2000 is
> > obsolete.  It's slow, with sufficient memory for only 100 waypoints.
> > However, it does show one's present position, average speed, plus
distance,
> > bearing, and ETA to the next waypoint.  Dynamic Equilibrium also has a
> > Danforth bulkhead mount ship's compass/inclinometer and an Autohelm
ST1000+
> > Tillerpilot.
> >
> > So what do you envision doing with your Rhodes 22?  If all you plan to
do is
> > daysail within sight of land; then, you don't need any instruments.  If
you
> > envision being out of sight of land, sailing to unfamilier ports of
call,
> > &/or possibly being caught out in fog or at night; then, the above
> > complement of functions plus a good set of compass bearing binoculars &
> > minus the autopilot are, in my opinion, about the minimum requirement.
You
> > need to be able to plot compass, GPS, and dead reckoning (DR), fixes on
a
> > chart.  A log (total distance) is more useful for plotting a DR fix than
a
> > knotmeter because it is difficult to maintain a consistent speed while
> > sailing.  Unfortunately, the low cost knotmeters like the SR Mariner
models
> > you cited do not include a log.  You will find the knotmeter will be
> > marginally useful for helping you learn how to optimize your sail
trimming
> > skills, but not for much else.
> >
> > The depth sounder is very useful for following a certain bottom contour
in
> > fog or at night in order to stay a certain distance offshore.  It will
also
> > provide early warning when you are approaching landfall - often many
miles
> > before you can see land.  A depth sounder with an anchor alarm is a
useful
> > feature if you plan on spending any time on the hook.  An anchor alarm
will
> > sound to wake you up if the depth below the keel changes from more than
a
> > +/- threshold from a setpoint water depth, presumably because the anchor
is
> > dragging.  This function is also useful for tacking up a narrow channel.
In
> > this case, the alarm will sound to warn you that it's time to come
about.
> >
> > The water temperature sensor has turned out to be more useful than I
would
> > have imagined when I 1st got my ST-50 tridata instrument.  Of course
it's
> > primary function is as a swimming comfort indicator.  But, it's also
very
> > useful for locating warm currents such as river outflows even miles
> > offshore.  It's also quite useful for fishing.
> >
> > The 1st instrument you should buy is a good ship's compass & a set of
> > compass bearing binoculars.  The 2nd instrument is a handheld GPS unit.
> > After that, there are lots of options.  The fishfinders provide a nice
> > complement of depth, water temperature, and fish sensing functions.
> >
> > You will be disappointed with the SR Mariner KT-5 knotmeter.  Either get
an
> > instrument with both a knotmeter & a log or don't bother.
> >
> > By the way, do you actually know how to plot a fix on a chart using
various
> > methods and do you understand the rule of the road and other boating
safety
> > concepts?  If not, then you should spend your money on a basic
> > navigation/boating safety course before doing anything else.  The US
Power
> > Squadron offers a pretty good course.  You should do this before you put
the
> > boat in the water!
> >
> > Roger Pihlaja
> > S/V Dynamic Equilibrium
> >
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