[C320-list] Boat Speed

[belairlk at aim.com]

Please explain relation of knot meter to correct boat trim, I'm not familiar with difference to GPS sog.
 
Thanks,
 
Len  
 
-----Original Message-----
From: Orlando.Duran at AveryDennison.com
To: Catalina 320 List <C320-List at catalina320.com>
Sent: Tue, 25 Apr 2006 15:16:03 -0700
Subject: Re: [C320-list] Boat Speed


Well, if you do any sort of racing--PHRF or Cruising--you cannot ignore knot 
meter, that's the only way of knowing if any trim/adjustment is working. A knot 
meter, correctly calibrated, is just as accurate but used for a different 
reason. Igonoring a knot meter completely will never allow you to have your boat 
in correct trim...

cuba libre 2
--------------------------
Regards,
OD

Sent from my BlackBerry Wireless Handheld



----- Original Message -----
From: C320-List-bounces
Sent: 04/25/2006 03:09 PM
To: C320-List at catalina320.com
Subject: Re: [C320-list] Boat Speed

I totally ignore the speed instrument, and rely on GPS sog  (speed over ground) 
readout on chartplotter at the helm which I understand IS accurate (unless 
satellite changes orbit or you're suddenly over the Marianas Trench).  Wonder 
how many 320's have GPS at this time?
 
Len
Aqua 5 #1070
 
 
 
 
 
-----Original Message-----
From: Walter burnett <selkie2003 at yahoo.com>
To: C320-List at catalina320.com
Sent: Tue, 25 Apr 2006 14:56:23 -0700 (PDT)
Subject: [C320-list] Boat Speed


All,
   
  It occurs to me the many variations in reported boat speed is likely due to 
variations in the speed sensor calibration, or lack thereof.  The only accurate 
way to calibrate the boat speed sensor is by timing multiple passes ata a 
constant speed through a measured course in slack water and opposite directions.  

Average the runs, calculate the speed and compare it to the readout for a 
correction factor to enter into the display. The more and longer the runs, the 
more accurate the calibration.
   
  In my experience the speedo out of the box can be off as much as 25%.  I 
suspect most boat dealers don't make any effort to calibrate the instruments 
before delivery and many skippers either don't know or don't bother. 
   
  Walter
  Selkie #887

        
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