Recently a friend pulled my leg about my insistence on the skipper always knowing where he is when in pilotage mode. “The trouble with you”, he grumbled, “is that you're often more worried about where you're not”.
He didn't just mean missing the pub, either, though that's one of the better known hazards of tidal yachting. He was referring to my love of clearing bearings. And he's right. I do love 'em.
I first learned about clearing bearings when I joined a cadet training ship as a watch officer. The skipper, who I swear had two brains - one to run the ship, and one to answer the cadets' continual questions - had a thing about them too.
He had the ability to take the ship into places I wouldn't have risked - running dog legs between rocky entrances, or turning at precisely the right point to round an underwater obstruction.
He would station a cadet at each binnacle - one on the port side of the bridge, and one on the starboard - point out a particular rock, or a light, or even the end of an island, and tell one of them: “If that light bears less than 210 degrees, tell me. If I don't reply, you've got my permission to throw something at me.”
His ability wasn't magic. What he was doing was training us to use clearing bearings. A good clearing bearing, like a good transit, will keep you in safe water. The absence of a good clearing bearing will mean you will be continually worried.
Look at the entrance to Rocky Bay. The water looks wonderfully flat, but just under the surface at high tide, or just above it at low tide, are some nasty rocks on either side of the entrance channel. Happily, someone's put a clear water mark right in the middle of the bay, so if you steer 210 degrees towards it, you should be fine.
But sometimes it's not possible to steer such a precise course. Leeway, or the tide, or just bad pilotage, may set you off course by five or ten degrees. When do you need to start worrying? Is five degrees OK? Will you be OK if the island bears 220? What about 195 degrees? Is that safe?
Without a clearing bearing, just about any variation from 210 is going to start the adrenaline pumping, because the only thing you can know for certain is that you are off course. You won't know whether you are safely off course, or whether you are about to run into something nasty.
But plot a couple of clearing bearings, and you will know exactly when to start worrying. In the case of Rocky Bay, provided the clear water mark doesn't bear more than 230 degrees, or less than 180 degrees, you are in safe water. Any more than 230, and you have to take action fairly smartish. Any less than 180, and you are at risk.
So now you know that you have a window of 30 degrees either side of your 210 safe course. The safe course is Not Less Than (NLT) 180, and Not More Than (NMT) 230. Like the white lines at the side of the motorway, a good clearing bearing will tell you precisely when you're about to run onto the hard shoulder.
Provided you have something immovable to fix on, you can create a clearing bearing for just about any situation. A light, a buoy, or even a transit of two bits of land - all sorts of things can be turned into clearing bearings. When you get used to them, you'll find they pop into your thinking as you look at the chart of an entrance, or a narrow passage.
If you've got one either side, like those in Rocky Bay, you can even tack between them, knowing that as long as you go about before you cross the clearing bearings, you'll be fine. It's quite something to watch a yacht tacking up a narrow entrance where there be dragons on either side! He's probably working on clearing bearings too.
Richard Thomas holds a Commercially Endorsed RYA Yachtmaster and Cruising Instructor (Sail) certificate. He runs his own delivery business, www.yachtmovers.co.uk and is available for deliveries, assisted passages, own-yacht tuition, and yacht management.
