[C320-list] Calibrate Knotmeter
Adam Weiner
esquirecatering at rcn.com
Sun Oct 1 19:53:31 PDT 2006
Russ, why wouldn't the SOG on the GPS show the effect of tweaking as
well? In a few moments of time the current (or other factors) won't
change. (Tides won't effect speed, only current.) For example, today
we adjusted the sheet on the spinnaker and I watched the speed climb
from 3.6 to 3.8. We tweaked in the sheet some more and the speed
dropped to 3.5 so we let the sheet back out until 3.8 was reached again.
-----Original Message-----
From: c320-list-bounces at catalina320.com
[mailto:c320-list-bounces at catalina320.com] On Behalf Of russgm at yahoo.com
Sent: Friday, September 29, 2006 1:41 PM
To: C320-List
Subject: Re: [C320-list] Calibrate Knotmeter
my approach to the knot meter is that it is not speed, never has been
speed and never will be speed, BUT it very importnat. Becuase You use
it to determine if you are tweaking things correctly, lets say it shows
4.9 kts, then you trim this, pull that etc, and all of a sudden it shows
5.5kts, you know you did something right, so you use it as a sail speed
reference, something that SOG can't provode becuase of the numerous
varibales involved such as tides etc...One of the things I have done is
experiment with towing my dinghy, how far back is the proper distance to
have the least impact on speed, pull it in, check kts, send it out a
biot, check kts, send it out more check again etc... -russ monaco
----- Original Message ----
From: Orlando.Duran at AveryDennison.com
To: C320-List <c320-list at catalina320.com>
Sent: Friday, September 29, 2006 4:05:37 PM
Subject: Re: [C320-list] Calibrate Knotmeter
Stan,
Oh, I agree with you on that point...you need to perform a calibration
at some point and using the gps is probably the easiest...my point is
that once that initial calibration is done, the twain will rarely meet..
OD
"Stanley
Rogacevicz"
<SROGACEV at holycr
To
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Sent by: <c320-list at catalina320.com>
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g
Subject
Re: [C320-list] Calibrate
Knotmeter
09/29/2006 12:53
PM
Please respond
to
C320-List
<c320-list at catal
ina320.org>
The reason I - had to - calibrate my knot meter was because it was
wrong at delivery. Full throttle in flat calm and slack tide was 5kts
while the GPS was giving me my correct speed of 7kts Over Ground and
Through the flat non moving Water..... so the only way to correct the
knotmeter was to do the' best' re-calibration I could by using the GPS
speed as a reference in flat water at slack tide at the middle of the
knot meters scale. Stan formerly "Christy Leigh" #656
>>> <Orlando.Duran at AveryDennison.com> 9/29/2006 3:35 PM >>>
Since these two instruments are used to measure different types of
'speed', they should almost never have the same reading...trying to
calibrate so they read the same is a useless process.
OD
"Stanley
Rogacevicz"
<SROGACEV at holycr
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Sent by: <c320-list at catalina320.com>
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Subject
Re: [C320-list] Calibrate
Knotmeter
09/29/2006 12:26
PM
Please respond
to
C320-List
<c320-list at catal
ina320.org>
As the other Stan says.. It's not a linear adjustment... the 1, 2 or
whatever adjustment number you use seems to be a factor in the
calculation not just a plus or minus. So I'd say the best speed to do
your adjustment at is around 4.5 - 5k to minimize your error .... unlike
I did my first time at 2k because it made the math easy with the known
distance run I was doing.... accurate at 2k or 3k but waaay...off at 5k
or 6k - useless. Stan formerly "Christy Leigh"
>>> Stan <ola7442000 at gmail.com> 9/29/2006 2:31 PM >>>
I gave up a long time ago. It's not a linear adjustment. i.e. On my
boat between approximately 4.5 - 5.5 Kts. it matches the SOG. Below 4.5
its reads low. Above 5.5 it reads high.
I'm not really sure how this can be as the the little spinning wheel is
sort of a generator. The faster it spins, the higher the voltage it
will put out. The output voltage is scaled to Kts. It should be a
straight forward calibration, but it is not. As I said, I gave up. I
just use the SOG since I'm on a lake.
Stan
"Our Little Amusement" #744
PS Moving to Las Vegas tomorrow. The boat will follow in Jan. or Feb.
depending when I get a slip at Lake Mead. (4-5 month waiting list)
On 9/29/06, Irv Grunes <igrunes at comcast.net> wrote:
>
>
> Guys,
> Have gone crazy trying to understand the manual on calibration of
the
> knotmeter.
> Have not been able to decipher it.
>
> Can anyone describe is some detail the process so that the knotmeter
will
> read the same as SOG over still flat water.
>
> Ours has never read correctly.
>
> Irving Grunes
> Isle of Wight #851
>
>
>
>
>
--
Stan
C320 "Our Little Amusement" #744
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