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

[Andrew Santangelo]

Wow...

This is an interesting discussion and something new to me.

When on the Great Lakes the ONLY time the knot meter failed was when  
the boat yard broke it!  We will see how the knot meter functions over  
time in SFO harbor.

I do like know the True Wind, VMG and currents.  Also, the knot meter  
is rather instantaneous with its data - there is a lag with a GPS.

Also, knowing the true wind allows me to gauge the sails I want to  
use.  Sure, I can approximate with the apparent wind, but it is nice  
to know the true wind.

Also, I found knowing the VMG, currents and their direction helped in  
planning a course to sail.

It all boils down to situational awareness - the more information you  
have, the more you can plan.  NOW if you are out for a purely fun  
sail, the basics are only important. But for racing, extended cruising  
and navigation I would prefer to have as much knowledge as possible.

Best Regards,
Andrew

C320 "Dawn Treader"
#333

On Aug 23, 2009, at 1:34 PM, Dave Rabinowitz wrote:

> 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
>>>
>>
>>