calibrations

[Falcon71]

What is the best way of re-calibrating an ST60 speed log....any offers?

 

[stamfordian]

hi,
dont know that type of speed log but could you do it with gps ,i use gps as a speed indicater as my speed log was defuncked long ago.cruise at say 8n by gps and compare

 

[tcm]

can you "calibrate" these? I mean, 10 knots is x turns of the twiddly thing, 20 knots is 2x turns, and that's that. Reliable actual speed over ground is off the gps. Every time you leave the boat you should replace the twiddly thing in the speed thingy in the bilde with a mule or dud, so it doesn't get barnacles on it. Here's one I left in the water quite a lot with barnacles on it that reads 20% ish lower than actual speed. When selling the boat, the speed/log is a thing that yoiu point to and everyone says ah yes as tho it's very useful indeed. If sailing, the log is useful for judging if tightening that rope was a Good Idea or a Cockup, cos the speed goes up or down, altho the tide may have just turned and anyway we're still losing and it's your turn to make tea. Alright, beer becos there no gas.

 

[trev]

The trouble with using GPS for calibrating an impeller driven log is that the GPS gives speed 'over the ground' whereas yer log is meant to give 'speed through the water'. OK to try it at slack water in good weather I suppose, but anyway an impeller driven log aint ever going to be spot on.

Trev

 

[burgundyben]

Quite right

I think that the boats log is meant to read speed thru the water also, I think, that most logs can be calibrated by rumaging about in the settings, I think you are supposed to take the boat in both directions through a measured mile with a transit (two posts not a van) at each end and using the elapsed time work out the average speed, compare that to the reading on the log when you were doing it and adjust accordingly.

But, f*ck it, lets all use GPS as its easier and we dont want to know how to use our kit properly, that would be a raggie/ragpot thing to do.

GPS/Autopilot...destination. Bosh.

P.S. Only measured mile I know of is the one in Southampton Water, and the one from my house to Whyte Hart but that seems incorrect as its further on the way home......



burgundyben, coolest of men, by all I'm called, cool burgundyben.

 

[sjnewport]

i hope this will help you can get manual to down load for adobe acrobat reader,at
raymarine.com

 

[miket]

Best bet is to follow the manual !!

I actually read mine recently (most unusual) and it had a section on just that.

 

[Falcon71]

Nope, that's apparently gone walkies. I've asked the usual questions, what's it called, what's it look like, when did you last see it, have you looked properly in the concertina file where everything like that is supposed to be? etc. But thatnks anyway.

 

[Deleted User YDKXO]

Once you've read the manual find a measured distance such as the measured mile between Poole and Weymouth (look on the chart) and do 2 runs in both directions to cancel out the tide effects to find an average speed and adjust the log accordingly. Log should read speed thru water not speed over ground

 

[petem]

The electronics man under the PHYC will order a new one for you. Be warned that he will also relieve you of a tenner when it arrives.

 

[petem]

I guess that hull shape will affect the speed of water over the twiddly thing and therefore the head unit needs to be calibrated electronically.

On sea trials (when selling) use the GPS if running with the tide to give a high figure and the log when running against the tide.