The key to heaving-to safely is keeping the boat directly downwind of the slick created to windward by her own drift to leeward. I can’t overemphasize how important this is. If a heaved-to boat forereaches fast enough to get out from behind the slick, heaving-to can actually become more dangerous than continuing to sail, because it is the slick that causes waves to break before they reach the boat. So getting ahead of the slick will result in waves breaking over the boat.
A Graphic Real World Demonstration
Some years ago Phyllis and I had this point forcefully brought home to us in a high pressure gale south of Bermuda. The winds were well in excess of 40 knots and significant wave heights some 20 ft (6 m) (confirmed by weather fax). As usual, we heaved-to and retired below to wait it out.
All went well for a few hours until we were hit hard on the weather side by a breaking wave. Keep in mind that a significant wave height of 20 ft (6 m) means that there are theoretically waves of 40 ft (12 m) out there.
I don’t know how big the one that hit us was, but suffice to say Morgan’s Cloud heeled to about 40 to 50 degrees and was pushed violently sideways. I suspect that a smaller boat would have been knocked down past vertical.
Also, Morgan’s Cloud is massively constructed of aluminum; in a boat less overbuilt I would have feared structural damage, particularly to the lee side. It is interesting that in such events it is usually the lee side of a boat that is damaged when it is slammed down against the water, not the weather side from the wave strike.
I spent the next half hour in the cockpit observing the boat’s behaviour. It soon became apparent that the substantial variability of the wind speed after the cold front passage, with lulls in the 20s to gusts around 50 knots, was the culprit.
(Generally, high pressure driven gales—when it keeps blowing hard, or even blows harder, after the cold front passage, as the following high moves in—have more variable winds than low pressure gales due to vertical instability in the air mass.)
The boat would fall off the wind during the lulls and then sail out of her slick with the next gust. Add the wrong wave at the wrong moment and BANG.
To make things safe we needed to slow the boat down and stop the bow falling off to leeward. However, the staysail was already rolled right in and the triple reefed mainsail centered, so we had done all we could with the rig to keep her bow up to the wind.
In the next chapter I will detail how we solved the problem.