[Rhodes22-list] Depthsounder

[Roger Pihlaja]

Jim,

When I installed the depthsounder on Dynamic Equilibrium, I had many of the
same questions as you.  So, I asked Stan at GBI for his recommendation re
tranducer location.

As per Stan's instructions, I mounted the transducer on the starboard side
just inboard of the ice box as close as possible to the keel.  The inboard
edge of my depthsounder transducer is tangent to the point where the hull
shape transitions from the flat "garboard" area to the tight radius fillet
to form the vertical keel.  I wanted to have quick access to the backside of
the transducer.  So, I mounted a 6" diameter Beckson screw-in inspection
deck plate in the cabin sole right above the transducer.  My transducer is a
thru-hull installation.  So far, the installation has been absolutely
bulletproof & has never leaked a drop.  I never lose the bottom return echo
signal on either sailing tack + it always stays submerged in bubble-free
water.  The transducer is located well inboard of the trailer bunks.  I've
never had a depth sounder transducer/trailer interference problem while
trailering the boat in dozens of launches/recoveries & thousands of
trailering miles.

There is a couple of fundamental problems with mounting locations up forward
of the keel, like in the head area.  The R-22 hull has a pronounced deep-V
shape anywhere forward of the keel.  Echo sounder transducers do not
transmit & receive outside of a fairly narrow cone.  If you mount one of
these transducers on an angle, such as would be required up near the bow, it
may work fine on one tack or while motoring in level trim.  But, when you
get over onto the opposite sailing tack & the hull heels over, the
transducer will probably lose the bottom return echo signal.  The hull shape
in Stan's suggested location is much flatter & thus is not subject to this
affect.  In addition, the water flow over the transducer is much more likely
to have entrained bubbles when mounted close to the bow, especially on the
sailing tack wherein the transducer is lifted closer to the surface of the
water.

There is only about 6' of hull separating possible mounting locations
forward of the keel & Stan's recommended location.  Anyone that thinks such
a short distance is going to keep them out of trouble in rapidly shoaling
water doesn't know how to properly use a depthsounder.  At 4 knots, the 6
foot forward mounting location translates to about 0.9 sec extra warning
time! Of course, the transducer may not be getting a bottom echo return
signal, so you may not get any warning at all.  I'd much rather have an
absolutely reliable transducer mounting installation than worry about such a
trivial amount of potential extra warning time.

Roger Pihlaja
S/V Dynamic Equilibrium


> -----Original Message-----
> From: Jim Connolly [mailto:jbconnolly@speakeasy.net]
> Sent: Monday, February 17, 2003 12:43 PM
> To: Rhodes-List; Rhodes 22 List
> Subject: [Rhodes22-list] Depthsounder
>
>
> I am at home waiting for blizzard conditions to develop this afternoon.
> Forecast here is for less snow than MJM, but still enough (10-24").
> Fortunately, I went to the boat show yesterday. ;-)
>
> I've been thinking about depthsounder installation and transducer
location.
> I didn't see anything about this in the FAQ, but recall having discussed
it
> on the list.
>
> I've never been a fan of transom mounted depthsounders, but they are quick
> and easy, and usually cheaper.  I recall some have mounted them inside the
> cabin, potted in epoxy and shooting through the hull, but where did you do
> this?  What type of trasducer did you use (e.g., does it make a difference
> whether you mount a trasnducer intended to be transom-mounted or
> through-hull in this manner?  Are there portions of the hull bottom that
are
> less-suitable for thie (i.e., cored)?
>
> Ideally, I would like to mount a relatively inexpensive transducer
somewhere
> forward of the keel in a safe location in a locker or beneath the deck.  I
> would also like to keep it simple and inexpensive.
>
> BTW, on my last sailboat, I used the keel as a depthsounder.  I figure the
> R22 deserved better.
>
> Jim Connolly
>
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