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post #1 of Old 08-02-2001 Thread Starter
Sue & Larry
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Sailing in Fog

Fog can roll in before you know it, bringing with it serious effects on your navigation.
You're sailing along, enjoying a beautiful afternoon and having one of the nicest Saturdays you can remember when suddenly—whameverything changes. A thick, wet, and chilling fog rolls in unexpectedly and totally surrounds you. Now, you can hardly see two boat lengths in front of you, never mind see where the shore is. Can you find your way safely back to the dock?

It doesn’t matter if you’re in a small sailing dinghy or on board a mega yacht, the chances of finding yourself in a disorienting fog one day are probably greater than you might think. Many areas of North America are prone to this annoying sight inhibitor, and sometimes a perfectly innocent little sail can turn into a scary experience if you are not properly prepared.

Fog can develop anywhere and any time the air temperature and the dew point are within three degrees Fahrenheit of each other. While the Northeast and Northwest coasts of North America are best known for their frequent heavy fogs, they don’t have exclusive rights to the stuff. Occurrences of the same thick air are not uncommon much further south on both coasts. On a sail from Los Angeles to Catalina Island off the coast of California one time I was very surprised to find almost zero visibility when we were only halfway there. Several times, when sailing down the Intra Coastal Waterway on the East Coast, we’ve encountered heavy fog in areas such as North and South Carolina, Georgia, and even in the heart of sunny Florida.

You don't have to be in Maine to become entangled in fog, it can happen almost anywhere in the coastal US.

Larry and I have just sailed from Bermuda to Nova Scotia and are finding that fog is heavy on our minds these days. In fact, it’s all too often dripping off our noses. We knew we would be encountering some fog when we made our summer plans to cruise Nova Scotia, but so far we’ve experienced considerably more than we were counting on. Ninety miles south of Nova Scotia we were greeted by a solid bank of fog that stuck with us, thick as could be, for the next 15 hours it took to make landfall. Actually, there must be another term other than "making landfall" when you do it in the fog, because we never actually saw any land until we were well inside the harbor at Shelburne.

Since then, we’ve traveled in fog on many days. We’re getting to the point where we’re actually quite comfortable in it. The navigating part, that is. I still can’t seem to bundle up warmly enough to counter the chilling effect that fog has.

Being prepared in advance for a sudden onset of fog can make your first experience in near-zero visibility a lot less intimidating. There are several tools that you should have onboard, and some basic rules of the road you should know to help you make your way safely to your destination or back to your own dock.

"Being prepared in advance for a sudden onset of fog can make your first experience in near-zero visibility much less intimidating."

When the fog rolls in, your dead reckoning skills will likely be put to the test. If underway, try to confirm your position visibly before you loose sight of land. If your original destination requires delicate navigation, change your course for a harbor that’s easier to enter, or one that incorporates major aids to navigation and/or sound signals on buoys. Or, reverse course altogether and return to your more familiar homeport. If you are totally unprepared to move in the fog, anchoring until it clears can be an option, provided you are not in a busy channel or well out to sea.

For the most basic navigation in fog, you’ll need a detailed chart, a compass, a sound producing device, a VHF radio, and a good set of ears. It’s also a good idea to hoist a radar reflector in your rigging, if one is not already part of your standard equipment.

Often times, simply dropping the hook and waiting out the fog is the right course of action as the authors did here.

If you decide to press on, reduce speed, and if possible, position a crewmember on the bow as a lookout. A good rule of thumb is to adjust your speed so that you would be able to stop in 50 percent of the distance of your visibility. The rules of the road mandate specific sound signals in restricted visibility for vessels 12 meters (39.4 ft) and larger, whether moving or at anchor. The rule for smaller boats is more lax for some odd reason, but they are still required to make some sort of sound. To us it makes common sense for all boats to make the same signals. (See sidebar for specific Sound Signals.)

As you proceed, listen carefully for signals made from other vessels and for clapper bells and/or horns from nearby channel markers. Not all boats out there are going to be using proper sound signals, so also listen carefully for the sound of approaching boats. If you hear a vessel’s fog signal forward of your beam, reduce speed further, and proceed with great caution until you perceive that you’ve cleared the other vessel. Reducing speed is very important, as the direction from which a sound is coming can be quite confusing in the fog.

In areas of frequent commercial traffic, it’s important to closely monitor your VHF radio for information about vessel movement and position reports. For an added measure of safety, you can broadcast your own position, heading, and speed on VHF channel 16, or another frequency monitored by the commercial traffic in that area. For example, "Securité, Securité, (pronounced Say-Curitay) this is sailing vessel Serengeti, entering the inbound shipping lane at marker 12A on a heading of 064 magnetic at a speed of four knots. All concerned traffic, Serengeti is standing by channel 16."

Fog has the effect of bending sound waves and making it difficult to discern the origin of a particular sound, like a bell buoy or foghorn.
It might seem strange to you, making these "blind broadcasts" of positions at first, but it may contribute greatly to your safety one day, as sailboats don’t reflect radar signals very efficiently. You can be sure that the commercial traffic will be making the same type of position reports among themselves.

If you live in, or plan to sail or cruise in areas of frequent fog, you’ll likely want to include some additional electronics onboard to assist you in further substantiating your position and the location of other vessels around you. With GPS and the magic of satellites, you’ll know your exact position at all times. You can confidently plot your course on paper, and safely avoid any hazards along the way. Your GPS will not, however, help you avoid a collision with other vessels.

For collision avoidance, radar becomes your most useful tool. It provides you with eyes-on-the-water when you can no longer see. Other boats, buoys and the shoreline all show up clearly and give you fair warning of what to expect. And by interfacing your GPS and radar, your radar will indicate graphically to you where your next waypoint should appear.

"When you hear the clang of a bell buoy it's reassuring to identify it on the chart and see it’s reflected image on radar."
Electronic charting software running on a laptop or a chartplotter can provide you with an even greater amount of data to further pinpoint your position. Having the above electronics onboard in poor visibility is like having incremental layers of information that build upon and complement one another. It’s reassuring when you hear the clang of a bell buoy and can identify it on your paper chart, see it’s reflected image on the radar, and view your boat’s exact position relative to the buoy on an electronic chart.

Although we have included and use this equipment on Serengeti, we are aware of the limitations of relying too heavily on any single form of information. If you lose power for any reason, none of these electronics are going to help you get safely back to shore. With this in mind, it’s still important to always maintain your current position on a paper chart.

We recently became especially glad for the above electronic assistance when we entered Halifax harbor, a busy shipping port. While approaching the outer edges of the harbor with a luxurious one-mile visibility in light fog, we were delighted to see eight racing boats making their last tacks towards the finish line of the annual Marblehead to Halifax Race. We also noted a couple of other cruising boats around, a number of fishing boats, and one large container ship inbound to Halifax. A few minutes later, the curtain came down and we were completely fogged in—with no sign of boats, channel markers, or shoreline.

"Great!" sighed Larry. "Here we go again, and this time we know half those racing boats don’t have radar and there’s a container ship out there." Another drop of water rolled off his nose.

Commercial traffic is only one of the hazards that crop up when fog creeps into the picture.
Larry scooted below to the nav station and turned on the radar while I maintained a vigil at the helm, slowed our speed and made regular sound signals with our air horn. After up-dating our position on the paper chart, and confirming our speed and heading, Larry then double checked our position on the GPS chartplotter and on the electronic navigation software that was already up and running on our laptop computer. With this accomplished, he could report to me above, with confidence, our exact position and let me know what targets he saw on the radar. We continued to monitor these targets as we progressed and could soon determine whether they were other boats or channel buoys.

Working together as a team, we were easily able to proceed with our long approach into the busy harbor although we could barely see past our bow. We didn’t come across any of the race boats, but did have to maneuver carefully with some of the commercial traffic, including that large container ship.

"We’ve got the container ship 30 degrees off our starboard bow at four tenths of a mile. We need to slow down and turn to port." Larry called up excitedly from the nav station. He then hailed the ship on the radio to confirm their exact course and speed. As it turned out, they had slowed to six knots, and were in the process of picking up the harbor pilot. We adjusted our course accordingly and were just able to make out their looming silhouette as we passed safely behind their stern.

With the container ship well ahead of us, we continued on our way into the harbor with fog so thick that it appeared our forestay was literally cutting its way through. Our course led us up a very narrow cut called the Northwest Arm, but we never saw land. We were happy to finally drop anchor. Our radar, GPS, and electronic charting software proved amazingly accurate and were extremely welcome additions.

Our fog stories don’t end with our safe arrival at the end of the Northwest Arm. Just a few days later at the insistence of the incredibly friendly members of the Armdale Yacht Club, I competed in the Nova Scotia Women’s Keelboat Championship that was being hosted by the club.

I joined one of the teams aboard a Soling. The girls were a little surprised when I showed up Saturday morning armed with a compass, a whistle and a vhf radio. I told them I’d already experienced Halifax harbor’s finest, and wanted to be ready for it. I was secretly concerned that if we found ourselves in fog and were to experience a wind shift, without compass onboard and pre-determined bearings, we wouldn’t know which way to sail.

Sue was greeted with surprise when she went aboard for a day race with a compass, a whistle, and a handheld VHF radio.
As it turned out, soon after the start of the Sunday race, we found ourselves in the middle of the racecourse with sometimes as little as a single boat length of visibility and zero chance of finding any of the race markers. With plenty of weekend traffic in the harbor along with the other race boats and a few commercial vessels, I knew it was important to pull out that whistle and start making regular sound signals. By using the compass, we were easily able to make our way back to the Race Committee boat after the race was abandoned. Although we had no close calls with other boats, we did have a close-encounter of an unexpected kind. Two magnificent Minke whales surfaced three times within 50 feet of our boat to say hello. In a breathless wonder I thought—there’s even beauty to be found in the fog.

Today, after several weeks of seemingly non-stop sailing in fog, Larry and I have noticed a strange effect it’s had on both of us that we did not anticipate. We’ve found a certain exhilaration in successfully navigating through its murky and chilling clutches. With each buoy passed, vessel avoided, and harbor blindly entered, we’ve experienced a new sense of self-confidence and know that we’ve built upon our seamanship skills with each and every additional foggy mile logged. It really just takes proper preparation, and a little bit of practice. But dress warmly, you’ll appreciate it.

The Sounds of Safety

In times of restricted visibility, if you can’t hear another vessel, you might not know that they’re out there. That’s why in US waters, specific requirements apply to vessels in various situations. Here’s how they break down:

Sailing Vessels Underway—One prolonged blast followed by two short blasts. Signal is repeated at intervals of not more than two minutes.

Power Driven Vessels Underway (this includes a sailboat when under auxiliary power)—One prolonged blast. Signal is repeated at intervals of not more than two minutes.

Vessels at Anchor—Ring a bell rapidly for five seconds at intervals of not more than one minute.

Vessels Aground—Use the same sound signal as vessel at anchor. Additionally give three separate and distinct strokes on the bell immediately before and after the rapid ringing of the bell.

Vessels Restricted in Ability to Maneuver—One prolonged blast followed by two short blasts. Signal is repeated at intervals of not more than two minutes. (**Note, this is the same sound signal as for a vessel under sail)

Vessels less than 12 meters (39.4ft) in length are not required to make the above-mentioned signals. But, if they do not, said vessel should make some other efficient sound signal at intervals of not more than 2 minutes.


Suggested Reading:

Installing Radar by Sue & Larry

Light Lists, Lighthouses, and Visible Ranges by Jim Sexton

Sailing to San Francisco by Liza Copeland


Last edited by administrator; 12-14-2007 at 04:10 PM.
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