Calibrating Speed and Log

[msimms]

Looking to calibrate my B&G Network Quad at the weekend. The manual recommends three runs between two fixed points at least 100 metres apart (seems quite a short distance to me). Anyone got any favourite places for performing this kind of calibration where there are objects of a known distance apart? Somewhere around Chichester would be good.

Also what speed would you tend do the calibration at?

Cheers

Mark

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[tome]

Mark

There's a measured 0.5 mile in the Emsworth Channel which I use for log calibration. There are two sets of yellow posts with X tops on Hayling (nearly opposite Marker on the Thorney side) which when brought into transit mark the start and end. 100 m sounds far too short to me!

I usually do the calibration at 5/6 knots (sailing boat) - you are limited to 8 knots by harbour byelaws.

Good luck
Tom

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[Deleted User YDKXO]

Trouble with calibrating at 8knots is that the calibration could be way out at 25knots which I guess is your normal cruising speed or thereabouts
There are 2 posts between St Albans Head and Durlston Head (just west of Swanage) which are a measured mile apart which you can use to calibrate your log. Probably much easier though is to measure your speed (must be in a straight line) on a GPS receiver and do 2 runs in reverse directions to negate tidal effect over about 1/2 mile and calibrate your log to the average speed given by the GPS. Best to do it in calm water and clear of traffic because you need to keep going in a straight line because the GPS measures speed over ground whereas the log measures speed over water hence need to do 2 runs in reverse direction

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