August 7, 2012

Curing weather helm

NEWCOMERS TO SAILING are often surprised (and perhaps a little dismayed) when they discover that their boats suffer from weather helm. In their innocence, they never expected to have to pull their tillers up under their chins every time their boats heeled over in a puff of wind. Why, they ask, should a boat try to head into the wind just because the hull tilts one way or another?

Well, it’s not an easy question to answer, but here are some of the factors that cause weather helm on the average deep-keeled hull:

Ø Excessive beam, especially beam carried far aft

Ø A mast raked too far aft, or positioned too far aft

Ø The hull assuming an asymmetrical shape it heels

Ø Sails that are cut too full, or have stretched over the years

Ø The fact that when a boat heels, the center of effort of the sails moves farther out to leeward, away from the centerline of the boat, and thus has more leverage to shove the boat into the wind.  That’s why it’s usually advantageous to sail the boat as upright as possible.

Well-balanced boats have very little weather helm, and are more seaworthy than unbalanced hulls.  The problem is that unbalanced boats, such as the old International Offshore Rule racers, and the modern 60-foot racers,  are faster than balanced boats. That excessive beam carried far aft allows them to carry more sail. So their owners are prepared to take their chances, and strong, experienced crews help mitigate potential disasters.

The famous British designer, Laurent Giles, clung to the old philosophy that a yacht should have “the utmost docility and sureness of maneuvering at sea, in good or bad weather.”  He tried to design yachts that would maintain a steady course when left to their own devices, but respond instantly to the helm in heavy weather when there might be large seas to dodge. He also stressed that only a well-balanced yacht is capable of being left to her own devices, sailing, hove-to, or under bare poles.

In greatly simplified theory, the best-mannered boat would be a narrow-beamed double-ender under a low rig.  She should have similar areas immersed fore and aft so that the hull doesn’t dip at the bow or stern when heeling or rolling.

But yacht design is as much art as science, and naval architects don’t always get it right, not even the famous ones like Laurent Giles. The basic design factors for balance and seaworthiness are well known but there are too many pieces in the equation for every hull and rig to be perfect in all conditions of wind and sea.  Now and then, however, the pieces of the jigsaw fall into place, sometimes by sheer luck but more often by a lot of sweaty pushing and pulling, and a particular boat design earns a reputation for docility and easy handling in all conditions. Such boats are rare, but the newcomer saddled with weather helm will find that experience will eventually calm his beating heart. There  are many little tricks involving rigging, the setting of sails, and even the distribution of weight in the hull, that can ease the tug on the tiller or wheel.  It takes time to understand a boat but most of them will respond in the end.

Today’s Thought
Thus, thus I steer my bark, and sail
On even keel with gentle gale.
— Matthew Green, The Spleen, 1.

“Waiter, there’s a fly in my soup.”
(23) “Please don’t wave your spoon about like that, sir — you’ll frighten the poor thing.”

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


Anonymous said...

"Waiter, there's a fly in my soup."
(24) "Yes sir; all the 'fly in my soup' jokes have made him suicidal!"

Belinda Del Pesco said...

Perfectly timed post. I've been searching the web for detailed descriptions (and videos) of weather helm and it's affect on various hulls & sails, and this was very helpful. Much to learn still, but I'll keep reading and listening. :) Thanks.