What is the issue?Draft restricted vessels have to have careful tidal calculations to figure out when there is sufficient draft to enter or leave a harbour. This may involve some laborious planning with a current tide book in conjunction with various secondary port offsets from sailing Almanacs and the use of occasional tidal curve.
Why address this?Anything that assures sufficient depth without the necessity to do complex tidal calculations makes navigation easier.
How to address this?If you have a designated berth in a harbour calculate the tide once and look out for a natural tide gauge in the vicinity. If the tide calculation is correct use the marker from that point onwards to indicate when you have sufficient depth.
Sailors have been using simple measuring poles or "tide staffs" since time immemorial and continue to operate today. If you look about you might find one that is just coming awash when there is sufficient draft for your vessel to clear a channel or obstruction. Of course, channels may silt up or alter and fill after a gale, so there is some variability but having a mark and making allowances will help let you know when to drop the moorings without having to make complex calculations.
Photo: Pom Angers
The same principle can be used when entering a new port or harbour. If you take a mark on the way in you at least know when it arrives at this point where you have sufficient draft to exit again.
With thanks to:Michael Harpur, Yacht Obsession.
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