March 30, 2014

Debris in the oceans

HOW SAFE IS THE OCEAN for small yachts these days? Satellites looking for possible debris from Malaysian Airlines Flight 370 keep sending back pictures of scores of large objects floating around in the lonely Roaring Forties. So far, none of these objects appears to have come from the missing jetliner, though. It’s just random flotsam that makes you wonder what would happen if you ran into it in heavy seas on a dark night in a small yacht.

It is not easy to estimate how much of a threat this represents for the thousands of cruising sailboats currently working their way around the world. Much of this flotsam is too small to do much damage to a reasonably sturdy boat but unfortunately some of it actually is substantial enough to punch a hole through a wooden or fiberglass hull.

What we do know, however, is that energy equals mass multiplied by the square of the speed it’s traveling at. In other words, if you hit a large piece of debris at 3 knots, it will do x amount of damage to your boat. If you hit it at 6 knots, though, it will not do twice as much damage (2x); it will do four times as much damage (4x).

This makes a good argument for slow sailing boats, especially at night, because there is normally no hope whatsoever of spotting a dangerous piece of low-lying debris ahead of you on a dark night in the middle of the ocean. It also makes a good argument for something that cautious sailors used to do in the early days of yacht circumnavigations in the last century: tucking in a reef or two at nightfall to reduce speed and perhaps avoiding the need to flounder around trying to reef the sails in a sudden wind squall at 3 a.m.

There is already plenty of stuff in the water for a sailboat to hit without the airlines adding to the problem. Ivor Wilkins, a journalist living in New Zealand, ran into a whale one night in his yacht Thistledown.  Author Frank Wightman ran into a tree off the mouth of the Amazon in his sloop Wylo one dark night. And Lord knows how many people have run into semi-submerged steel containers. We know hundreds of containers fall off ships every year, and no small yacht is a match for one of those.

I don’t know of any modern skippers who insist on shortening sail at nightfall. There may be some, but I don’t think there are many. But perhaps there will be a few more now that the satellite searches we’re seeing on television every day make it obvious that charging through the dark seas at high speed at night is the equivalent of driving down the freeway while wearing a blindfold.

Today’s Thought
Allow time and moderate delay; haste manages all things badly.
— Statius, Thebais

Tailpiece
"How do you like your new mustache?"
"I didn't like it at first. Then it grew on me."

2 comments:

roeboats said...

Hi John,
I always put in a reef for the night and that was sailing up around 60ยบ north i.e.I didn't see as much flotsam as when crossing Biscay where I passed quite a few baulks of timber,pallets etc.
Keep up the good work, I always enjoy reading your blog.
Tiernan

Jack said...

Sailing a lot at one time up and down the east coast of Vancouver Isl, I came across quite a few submerged full length logs which I presume had got away from the logging operations. Without the cast from "Beachcombers" to salvage them, the call to those on lookout watch was "Lookout for tall seagulls " !
Jack