Four hundred degree compass explainedJan 1, 2003
|From Ocean Navigator #107 |
First let's look at some numbers. Large port capacities are quoted in tens of millions of 20-foot container units. The typical container these days is a 40-footer. So if there were 100 such ports in the world, the total port capacity would probably be less than one billion units per year. There is no evidence of a general lack of port capacity, so the total number of containers shipped is equal to or less than that number.
Industry spokesmen have been quoted as saying that 99.99% of container freight arrives undamaged. The corollary is that one in 10,000 containers is damaged. The top number of containers lost over the side, then, would be in the hundreds of thousands per year. But, in fact, damage can come in many forms short of loss overboard. Leakage and dropping come to mind. So, if they share the total equally, the maximum total of overboard containers drops into the tens of thousands, annually and worldwide. Then, drift studies have been performed on container cargoes lost in the Pacific. Typically the contents of four out of five containers can be identified. So one out of five remains intact, either afloat or sunk. This drops the total into the low tens of thousands or even thousands per year worldwide.
I recently took a walk on the beach in northern California and on three beaches with less than a mile of total length, I estimate that 1,000 pieces of driftwood were visible. Of this total, probably 10 were sizable enough to damage a yacht in a collision. Almost all had the bark scoured off by tossing in the surf. In other words, they had not simply been washed down a river and left on the beach. They had been to sea for some period of time. Now, with roughly 30° of latitude between the tree line in Alaska and southern California, that gives us more than 1,000 miles of beach, or on the order of 10,000 dangerous logs that have been washed ashore. Does this represent a greater number than would be floating? Hard to say. And would their range be limited to coastal waters? Also hard to say. The coastal current sweeps westward into the Pacific gyre, again, at about 30° north, in the vicinity of southern California. If those floating logs only equaled those beached, the number for the northeast Pacific alone would approximate the top numbers for cargo containers worldwide, and in a much more limited geographic area. Nor is North America the only geographic area in which driftwood is likely to be found.
Containers are lost in storms. Storms are normally winter phenomena on most routes. Logs dislodged by erosion are also going to go adrift in winter. Rain, floods and erosion are also winter phenomena. Logs that go adrift from log rafts are another issue. Along the coast of Alaska and British Columbia it is common to transport logs as floating rafts, hundreds or thousands of logs, by tug. Logging is done from spring to fall, but mostly in summer. Why does it matter? Well, yachting in extratropical latitudes is a summer activity. Logically, logs originate on shore and will sooner or later become waterlogged and sink. Therefore, in mid-ocean you are less likely to hit one than in coastal waters.
Logs or containers are most likely to lie lengthwise in the trough of the sea. It is the lowest energy configuration. Therefore, if you are also abeam to the sea, close-reaching in a sailboat, then any collision will be a glancing blow. I collided with an oil drum in the Santa Barbara Channel in that fashion. There was no more damage than a new blue stripe on my topsides just above the waterline that came off with polish. A collision when going downwind would be a different matter.
Of course, aside from containers, logs are just one other possibility for collision. There are also whales. Whales are fortunately at least equally interested in avoiding collision as you are, which is helpful. But they sometimes also fail to keep a sufficiently good lookout. In the eastern north Pacific we have gray whales, sperm, fin, humpback, some blues, and orcas. The total number, again, is probably in the tens of thousands, grays alone being on the order of 20,000. The mechanism of collision is probably about the same as for inanimate objects, because it is generally believed that whales are only struck when asleep. Whale attacks are almost unknown. I once watched a sperm whale dodging to avoid an oncoming fishing vessel. Of course his antics resulted in some fairly interesting gestures and maneuvers on the fish boat. My closest encounter was probably with a gray. Running in Monterey Bay with the company of dolphins, I was dismayed at their sudden departure, until I saw the whale directly ahead and spun the boat upwind while he sounded. On the Santa Barbara race a few years ago one of the competitors hit a whale after midnight. It brought the boat, a Wylie 34, about 8,000 pounds sailing at eight knots or so, to a stop. The whale thrashed its flukes, flattening the stern pulpit and slapping the helmsman. The boat remained watertight and had no obvious damage beyond the pulpit. A carvel-planked wood boat might not have fared so well.
Still, it is worth considering that there are other things out there with which a collision is likely to be memorable, if not disastrous. The other things may be more numerous than containers.Edit Module