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

[John Frost]

When we got our new MKII, I went out in quiet still water and ploted  
SOG vs knotmeter reading to pick my correction factor. I found that  
the correction factor varied linearly with speed. It appears that the  
efficiency of the paddle changes with speed. I picked a conversion  
factor that made the knotmeter spot on at a typical sailing speed


Sent from my iPhone
John


On Aug 23, 2009, at 8:22 PM, "Jack McDonough" <mcdonough5 at verizon.net>  
wrote:

> Stephen:
>
> Thanks for the suggestion. I'm sure you're right. But I've been  
> sailing for 25 years and I'll be 75 if I live through the end of  
> September.
> The SOG on my GPS is good enough for me. I guess I'm what you'd call  
> a lazy sailor.
>
> It is a Raymarine unit, by the way. And I haven't the foggiest  
> notion of how to calibrate it. Mostly I'm concerned about having a  
> couple of good books and a sufficient amount of scotch aboard.  
> Sailing, for me, is not a competitive sport.
>
> I don't mean to be a smartass. I do appreciate your offer of help.  
> Really. Thank you.
>
> jack  #914
>
>
>
>
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>
>
> ----- Original Message ----- From: "Stephen Cox" <scox at timmin.com>
> To: <C320-List at Catalina320.com>
> Sent: Sunday, August 23, 2009 4:15 PM
> Subject: Re: [C320-list] Knot meter cleaning.... In water?
>
>
>>
>>>
>>> ....................... 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.)
>>> ...
>>
>> If its consistently different allowing for current, then you need  
>> to adjust
>> the calibration. Assuming its Raymarine that's easy enough from the  
>> display.
>> (Don't know about other brands).
>>
>>
>> Stephen Cox
>> Tegwen #1141
>
>