November 18, 2013

Pay attention to the tides

I’VE NOTICED that many beginning sailors pay less heed to tidal currents than they should. I guess that in these days of reliable, powerful auxiliary  engines, tides don’t come into their calculations much. Tides are regarded as being irrelevant, or at most, a little irritating.

But even if you could rely implicitly on your engine, you should know about the huge effect tides can have on a boat under sail alone — because sooner or later your trusty engine might develop a hissy fit and thumb its nose at you.

So, let’s say there’s a nice steady breeze and you’re making 6 knots through the water. If a 3-knot current is flowing against you, you’ll make only 3 knots toward your destination. If that same 3-knot current is flowing with you, you’ll make 9 knots toward your destination. If you’re not impressed by the difference between 3 knots and 9 knots (or three times the speed), you should be.

Tidal currents vary tremendously from place to place and time to time, so, if you sail, you badly need to know what the current is doing to you. You can get that information from annual tide and current tables for your area, either in book form or from the Internet.

It’s no good trying to guess. Looking over the side or spitting in the water isn’t going to tell you which way the current is going, or how fast. But a GPS receiver will indicate your speed and direction over the ground. By the simplest arithmetic you can compare this with your speed through the water, either taken from your regular speed indicator or estimated by shrewd guess, to find the speed of the current.

So, if your engine has the sulks, work the tides. Anchor until the worst is over, or work the close-shore reaches where counter-currents and back-eddies often prevail.  Tides come in two varieties. They’re either for you or agin you. Make sure you know which is which.

Today’s Thought
The ebb will fetch off what the tide brings in.
— Thomas Fuller, Gnomologia

“Boy, I’m always grateful I wasn’t born in France.”
“How come?”
“My French is so lousy they’d never understand me.”

(Drop by every Monday, Wednesday, Friday for a new Mainly about Boats column.)


biglilwave said...

John, I'm detecting a parental tone along with your review of sailing 101 in your last couple blog entries.
Have you been witnessing some lack of seamanship lately?

John Vigor said...

No, just hoping to illustrate the advantages of simplicity. We have taken a very simple sport and made it very complicated in one way or another. I have always advocated simplicity where possible. That's all.

John V.

Paul Mullings said...

My late Grandfathers mantra was always "Make The Tide Your Friend" practise that and you can't go wrong!