[C320-list] Knot meter cleaning.... In water?

[Dave Rabinowitz]

i, too, tired of cleaning the knotmeter impeller.  The GPS Speed Over
Ground (SOG) was just fine for me, but the numbers were too small to read
(GPSMap 478) from my side seat, and as pointed out, the "true wind"
calculations were missing.  Sooo, what I did was install a CruzPro SOG1 (
http://www.cruzpro.com/sog1.html ).  This little box takes the SOG data from
the gps (on the NMEA 0183 output) and converts it to "paddle wheel" pulses.
So the knotmeter (and the other instruments) thinks there is a working
paddle wheel out there, allowing true wind and other things to work. It fit
right in the instrument housing, no problem.  You have to be a bit careful
with the wiring, but it isn't difficult.

Now i can see my speed on the knotmeter, and have true wind functionality.
Yes, purists will argue that SOG is not speed thru the water, and they would
be correct.  However, when trimming sails, or just looking and going "hey,
we're doing 5 knots with just the main", it all works out :-)

dave
wind chill


On Sun, Aug 23, 2009 at 1:24 PM, Jack McDonough <mcdonough5 at verizon.net>wrote:

> Warren:
>
> I don't know about Chesapeake Bay, but in New England ocean water our knot
> meter (hull #914) works only about 15 percent of the time, mostly after I've
> pulled the transducer and cleaned the impeller. And even when it's working,
> I don't believe it. The GPS shows SOG numbers that are always one or two
> knots higher than the knotmeter reads. (OK guys, please no e-mail telling me
> that SOG is different, etc. etc.) I prefer to believe I'm going faster. I
> think one problem with the system is that the impeller is too small and,
> therefore, gets gummed up more easily and frequently. The knotmeter on our
> Cape Dory 30 failed, too, but with nowhere near the frequency of the 320.
> And the CD had a larger impeller.
>
> jack
>
>
>
>
> ----- Original Message ----- From: "Warren Updike" <wupdike at hotmail.com>
> To: <C320-List at Catalina320.com>
> Sent: Sunday, August 23, 2009 7:48 AM
> Subject: Re: [C320-list] Knot meter cleaning.... In water?
>
>
>  Welcome to the Chesapeake Bay. After 5 years, this Spring I finally
>> stopped
>> trying to keep my speed transducer working. Though I cleaned it, replaced
>> the wheel, and painted it, it only worked for about a week. On the older
>> boats it's not so easy to pull it as it is inside and under the V-berth
>> cabinet. Plus, it has no internal valve to slow the water, plus the bilge
>> fwd of the mast does not drain to the pump. All problems that seem to have
>> been addressed in later models.  Bummer.
>>
>> So, with a GPS or chart plotter, why do you need boat speed anyway?  Well,
>> it's necessary to compute tide direction and speed, and to compute true
>> wind
>> if you have such an instrument. My wind inst. only works twice a season
>> and
>> then only for about 5 min.  Who needs tide info on the Chesapeake: it's
>> always running against you anyway. So, I concluded I don't need the
>> headache
>> of a speed transducer.
>>
>> On the matter of what fouls the paddle wheel, it's a mixture of surface
>> crud
>> and critters. The surface crud is a sad indication of the health of the
>> Bay.
>> The critters are testimony to the proclivity of life in waters that reach
>> above 80 deg. in the Summer. The turbidity of the water is such that, at
>> least above the Bay Bridge, it will no longer pass the tree-step test (how
>> many steps of the swim ladder can be seen once deployed.) My heart breaks
>> to
>> realize how bad it has become and how little political will there is to
>> address the problems; but, I must not turn this into a political drama
>> more
>> than it already is.
>>
>> Warren & Pattie Updike
>> Catalina 320, #62, "Warr De Mar"
>> Middle River, Chesapeake Bay
>>
>>
>>
>> -----Original Message-----
>> From: Brad Kuether [mailto:bkuether at comcast.net]
>> Sent: Saturday, August 22, 2009 9:00 PM
>> To: C320-List at Catalina320.com
>> Subject: [C320-list] Knot meter cleaning.... In water?
>>
>> Hello everyone,
>>
>> Well the Chesapeake has already claimed it first victim on my boat.  The
>> paddle wheel for the knot meter stopped turning.  I was thinking I could
>> dive on the boat in shallow water (would have to buy a mask, etc)
>> OR possibly pulling the knot meter while its in the water....  (of course
>> plugging the hole for a bit.
>>
>> Any thoughts on this, besides "be careful not to sink" ?
>>
>> If its possible and does the water just drain to the bilge?
>>
>> Thanks for any guidance.....
>>
>> -Brad, Mary, Monica, and Jarod
>> "Independence"
>> 2004 Catalina 320 Hull 1006
>> Middle River, MD
>>
>
>