July 24, 2011

The downside of breakage

READERS OF THIS COLUMN are an inquisitive lot. By some strange coincidence, two of them have written asking why boats break on the downwind side.

I know what they mean. I have been in this business a long time. What they’ve noticed is that sailboats caught in bad storms often limp home with their portlights bashed in, or even part of the cabintop bashed in — but always on the side away from the waves.

There is a simple answer to this conundrum. When a boat is lying ahull, that is, broadside on to wind and waves without any sail up, the force of the wind on the mast and rigging heels her over, so that she presents her strongest surface to the force of the breaking waves bearing down upon her. Her cabintop and portlights on the windward side are therefore tilted over and partly sheltered from the breakers. It’s the strong rounded hull that takes the initial pounding.

But as the wind builds, and the plunging breakers with it, the boat starts to get lifted up and thrown down bodily, landing on the leeward side and putting enormous pressure on the deckhouse and ports. That’s where the damage occurs, on the downwind side, as my observant readers have noted. And that’s why bluewater cruisers should carry plywood covers that can be bolted over the portlights, especially if they are larger than normal. And they should be bolted on before the storm develops, of course, not after the damage is done.

Today’s Thought
Being in a ship is like being in a jail, with the chance of being drowned.
— Samuel Johnson

Boaters’ Rules of Thumb, #226
As a general rule, a backing wind in the Northern Hemisphere portends bad weather. A veering wind signals the approach of better weather, but probably only after some increasingly blustery weather in the short term. It’s the opposite way around in the Southern Hemisphere. And, in case you’ve forgotten, or never knew, backing is going back against the clock, or counter-clockwise. A veering wind is changing direction clockwise.

“You say the tow-truck guy charged you $50 a mile for towing?”
“Yeah, but I got my money’s worth — I kept the brakes on all the way.”

(Drop by every Monday, Wednesday, Friday for a new Mainly about Boats column.)

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