Skipper’s tips

Calibrate the sounder

Calibrate your sounder to accurately reflect the depths marked on your charts – not the
water under your keel

Thank goodness today’s echosounders can be set to remove the ‘depth below transducer’ factor. Charter operators seem to set theirs to ‘depth below keel, plus a little bit for safety’. I’m sure their reasons are based on bitter experience, but this makes me feel distinctly patronised.

A sounder is not just a last-ditch guardian against going aground. It’s also a navigation instrument. Every time I fix my position on a paper chart, the automatic follow-up is to check the depth to see if the charted plot and the sounded reality stack up. Where tide is relevant, I have a reasonable idea in my head of height, or I can quickly read the tidal graph made up before I started. With the sounder set to ‘depth of water’, the check is then instant. In fog, if all else fails and I’m left with only compass and sounder, it’s ‘depth’ I want to compare with the chart, not how much may or may not be under my keel. With the readout set to ‘below keel’ there’s always an additional factor to add. ‘A bit extra for safety’ increases uncertainty. It isn’t safe at all. And as for knowing when I’m going to run aground, if my boat draws 1.8m, she’ll stop when that’s what the sounder says.

Cut some slack

When mooring to a drying pontoon, do as this skipper has and leave some slack in your lines

Drying out alongside a pontoon, it’s vital to remember that the relative height of your boat may end up lower – or higher – than it was when she was afloat, so leave some slack in your lines when you make fast. I once lost a cleat when I tied up tightly, only to return from the pub and find the pontoon had stayed sitting high on the mud while I sank into a nice hole left by a predecessor.