On the Water

1.Tides and CurrentsWork with them or they’ll work against youBy Peter NielsenPart of the fun of sailing is learning how to work tides and other currents to your advantage. Sure, you can roll up the genoa and turn on the engine if you’re caught in a foul current, but then you’re a powerboater. It’s much better to know when and where to expect contrary

1.Tides and Currents

Work with them or they’ll work against you

By Peter Nielsen

Part of the fun of sailing is learning how to work tides and other currents to your advantage. Sure, you can roll up the genoa and turn on the engine if you’re caught in a foul current, but then you’re a powerboater. It’s much better to know when and where to expect contrary currents and come up with a plan of action. Tide tables are available for every section of our seacoast and should be an essential part of your cruise planning; there are also some good online resources, like tidesonline.com.

Tidal streams sweep along the coast and up rivers, eddying around in bays and estuaries, reaching considerable heights in some places and modest ones in others. During spring tides (when the moon is full or new), currents can race along at 5 knots or more around headlands and 3 knots in other areas. They demand respect.

Currents from dead ahead or dead astern affect only your passage time or your comfort level; as anyone who’s sailed in the Gulf Stream will know, situations where the wind opposes the current can work up nasty, confused seas. (The type of wind-against-current conditions you’re likely to experience along most stretches of coast are unlikely to be dangerous, but are still best avoided.)

Currents that set across your course provide more of a navigational challenge, as they push you one way or the other. I’ve sailed with people who were enslaved by the Cross Track Error (XTE) display on their GPS, seeing and feeling nothing but the need to keep the boat bang on the rhumb line. Sometimes this matters—for instance, in a channel with dangers on either side—but more often it does not. Unless you are being set radically to one side of your track, it is pointless to worry about XTE when your destination is 20 miles or more away, because tidal currents can quickly change in direction and intensity.

Better to look at the big picture and work out if the current that will push you 2 miles off track in the next 4 hours will then push you back the same distance in the following 4 hours. This is where a tidal atlas earns its keep; it helps you play the game hour by hour, adjusting your course in accordance with the increases or decreases in current and boat speed. Just as nature abhors a straight line, so does a boat in tidal waters. If you just sail your course and make no allowances for tides, hourly plots over the course of a long daysail or overnight passage will show a sinuous curve as the current pushes the boat first one way and then the other. This is no big deal in open water, but close to the coast you may be set into shoals or other dangers. The current often sets into bays and inlets, and you need your wits about you when you’re close to shore.

When you are working out your tidal strategy, remember that the dream scenario is to arrive up-tide and upwind of your destination. There is nothing more demoralizing than having to sail the last few miles against an increasing and contrary current.

Many of us sail boats with small outboards or even no engine at all, and fighting a foul current in light wind is no fun. If the weather is calm, it may well pay to anchor and ride out the foul tide, or at least the fiercest three or four hours of it. This can be a frustrating experience if you are in a hurry to get home, but sometimes there is no alternative.

2. Coping with Fog

You can learn to sail blind

By Tom Cunliffe

Not long ago I was sailing out of San Francisco with an ex-army diver. He recalled a training exercise in which he had free-dived to 20 feet in near-zero visibility to retrieve an object from the seabed, then had to swim back to the surface before he drowned. Weighted to neutral buoyancy and with only one breath to sustain him, he could easily have lost track of up and down. Very like the emotions we feel in fog, I thought, except that a diver has to cope with three dimensions instead of two.

“So what do you do?” I asked.

“You breathe out a little and see which way the bubbles go. Unless someone switched off gravity, that’s got to be up!”

This led to a discussion of the sudden fog that can appear most anywhere, but especially in New England or San Francisco. On our way back in through the Golden Gate to Sausalito, we discussed what we would have done had the notorious fog rolled in, shutting down visibility to 50 yards. We’d need a navigation strategy fast, but first we’d need to secure our immediate safety (see sidebar).

Fog strategy

If you have a good idea of your position, you have four options when confronted by fog.

Go out to sea Your crew may not like it, but this is often the safest choice, especially if you don’t expect the fog to last long and shipping is light. If it isn’t, you won’t want to be out there if/when it starts to blow.

Anchor in the shallows This places your boat in safe water that’s not deep enough for a serious commercial vessel. It’s also often unchallenging as a navigation exercise, so if your GPS isn’t working, it could well be the best answer—best, that is, if the medium-term forecast is promising.

Carry on regardless In these days of reasonable navigational certainty, this is often a sensible option on a passage in open water.
Work into a safe haven If it looks like the fog will persist, this is everyone’s favorite. The crucial question is how you’re going to find the chosen refuge without hitting a rock or being run down.

Piloting tactics
We’ve decided to go for broke, and a number of alternative safe destinations are mooted, but some major issues soon become clear. We have GPS, but no chartplotter and no backup. The performance of the boat’s unit to date suggests that failure is unlikely but, as Captain Biff Bowker, late of the schooner Brilliant once remarked, “The floor of the ocean is paved with the bones of optimists.” We therefore decide to develop a plan that doesn’t need electronics, although we’ll augment it with GPS navigation if all goes well.

Crossing the harbor entrance (see Chart A), would be a memorably bad idea. Not only is there a high probability of shipping, but Mile Rocks would be hard to find unless we could be certain of the horn, and we wouldn’t want to be hanging around in that shipping lane. Fortunately, Plan A keeps us on the northern side. Here’s how it goes.

It’s slack water now, so we can steer 115T from the vicinity of the IDR buoy until we’ve run 31/2 miles on the log. We’ll pop in a waypoint there to help us along.

That would put us somewhere near the Bonita channel entrance, but we won’t go down the middle. We want to avoid the fishing traffic there, and we want to securely update our positon by soundings, in case we lose our GPS. (In bad weather, when the bar is all white water and the Bonita channel is a death trap, we would need a different strategy.)

Instead, we’ll steer something like southeast until we find the edge of the Four Fathom Bank (the Potato Patch, Chart B) with our sounder after about 11/2 miles. That heading will keep us out of the precautionary area, and it doesn’t matter where on the bank we come onto soundings, because all we have to do is turn to port and run east-northeast along the 6 fathom line. We’ll lay a waypoint at the ideal spot, but we won’t worry much if we don’t go there.

As the contour line leads us east and then southeast, we’ll probably hear the whistling buoy near our next waypoint, but we must resist the temptation to go for mid-channel. Instead we hug the 6-fathom line past nun 4 until it swings southerly toward the waypoint at the red-green-red buoy southwest of Point Bonita (Chart C).

Here Point Bonita (horn 2) will be blasting in our ears and maybe the red-green-red buoy with its whistle too, but even if we’re stone deaf, we’ll know when our line starts taking us southwest. That’s the time to peel off and steer south until we find 10 fathoms.

Now we follow the 10-fathom line in past the red-green-red buoy waypoint. By hugging this contour we’re outside the horrors off Point Bonita—not a nice place. We’ll plot a waypoint on top of the lighthouse and make sure we never get closer to it than 0.3 mile (600 yards). That will keep us outside the rocks 250 yards off the point, as long as we concentrate. Without GPS it’s the sounder or nothing. In either case we’re also clear of the shipping lane. The line of soundings will take us close in to Point Diablo (next waypoint) with its unmistakable horn. We’ll see that for sure, but it’s steep-to and, compared with Bonita, comparatively innocuous.

From Diablo, the 10-fathom line takes us all the way to the Golden Gate Bridge outside any obstructions. It passes within 100 yards of the odd rock, however, and the 20-fathom line is close outside, so 15 fathoms might be a sensible compromise.

Note the waypoint just inside the bridge and another a half-mile on, right outside Horseshoe Bay (Chart D). Once under the span—we’ll hear the mighty diaphone on our starboard bow even if we can’t see it—the visibility could well improve enough for us to work back to our berth. If not, and we’re running low on nerve, we can stay on our friendly contour and follow it northward past Lime Point until we reach Horseshoe Bay, which we’ll see for sure. By this time, we’ll probably have had enough, so we’ll probably cruise in and ask the Presidio Yacht Club for one of its visitor’s slips.

3.Crowded Waters

Power gives way to sail, right? Yes and no..

By Peter Nielsen

Forget about killer waves, violent storms, or whale attacks. The most nerve-wracking aspect of coastal cruising is dealing with shipping. All skippers should be able to quote chapter and verse of the navigation rules—the International Regulations for the Prevention of Collision at Sea (Colregs)—but always bear in mind that these rules are not to be followed blindly. The unofficial Rule One should be: Might Is Right. You may theoretically have right of way over a 100,000-ton container ship, but you would be a fool to try to enforce it.

There are also situations where shipping has right of way over sailboats, such as in marked channels in the approaches to ports. Since these are to be found near many of our major sailing centers, you’re likely to have regular close contact with commercial shipping. A Vessel Traffic System (VTS) is a network of traffic lanes called Traffic Separation Schemes (TSS). A TSS is not to be trifled with; 1,000 yards or more across, its two lanes are divided by a 500-yard-wide separation lane. Ships over a certain tonnage are required to stay within the lanes, but many smaller commercial vessels are exempt. This is what makes negotiating a TSS tricky for us small-boat sailors; you have to deal with not only the behemoths proceeding in orderly fashion along the lanes, but an ever-changing number of coasters, tugs, trawlers, and others that flit about at will and seemingly at random. This leads to close-quarters situations that can be anything from slightly tense to downright terrifying.

A TSS will be clearly marked and charted, so there’s no excuse for blundering into one unaware. The first written rule is that you should cross a TSS at right angles to the traffic flow; the first unwritten rule is that you should scoot across as quickly as possible, even if it means firing up the engine. The Coast Guard recommends you ease into or leave a lane at a shallow angle, so as to be better able to gauge the speed of approaching or overtaking ships. Often there are Inshore Traffic Zones (ITZ) adjacent to a TSS, and sailboats can use these without penalty. It should go without saying that you shouldn’t anchor in a TSS, but unfortunately such acts of crass stupidity are not unusual.



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