February 19, 2015

Steve Sarsfield, a Bay Area sailing instructor and coach, contributed this article:

There is a lot of advice in books and articles about sail trim, tactics and strategy. It’s important to consider the origins of this advice. In particular, many advice books and articles are written by sailors who sail on lakes, or in parts of the world when conditions are different than on San Francisco Bay. I find a lot of confusion with my students about what can be effective because of the number of different opinions they have read or heard.

Often in lake sailing — and I sail on lakes — there are conditions where the waters are calm at night, and at a certain time during the day the wind starts blowing and the water is flat. This shifting medium breeze on flat water requires a certain style of sailing. Also, this wind, by the nature of the surrounding hills, changes in direction. This brings about the discussion of persistent and oscillating shifts. Add in the fact that there are no currents on lakes and the conclusion is that some of this good advice is not appropriate when sailing on the Bay.

Let’s start with oscillating shifts and that old mantra, ‘tack on headers’. While there are times on the Bay, usually in the edge seasons, spring and fall, when there are in fact oscillating shifts, my experience is that the Bay does not have this phenomenon to the extent that it requires always following this advice. On San Francisco Bay, what we have more of is what I’ll call oscillating velocity. The wind comes from more or less the same direction but, like the ebb and flow of waves, the velocity is always changing. Even in a blow the velocity is not constant. When this happens the result can be a velocity header, and it’s not time to tack.

When the true wind speed changes, the apparent wind angle changes. When the true wind speed increases, the apparent wind goes aft and this is a velocity lift; when it decreases it is a velocity header. On the Bay this requires sailing a sort of ‘S’ course. The person at the helm is not following the wind direction as much as following the apparent wind direction caused by the change in velocity.

I have a couple of tips for my students. One is ‘up slow and down fast’. As wind velocity increases and the apparent wind is moving aft, it is time to follow the wind direction higher. I call this ‘cheating up’, constantly sailing the highest angle possible while maintaining speed. Conversely when the wind speed decreases it usually is more abrupt and the response should be to turn the boat down to the new apparent angle. This must be done quickly to keep the boat speed up. Again this is not a header; it’s not time to tack. It is certainly not time to hold your course and grumble.

You should be glancing at the compass and/or the GPS to ascertain that these shifts are constant to some degree. Which brings us to another Bay phenomenon, which I refer to as geographic shifts. As you sail northwest toward Angel Island from Berkeley, for instance, there is going to be a persistent shift — if you want to call it that — as the wind bends around the island. This happens in many parts of the Bay, and it is not the purpose of this article to speak to that, except to say that these geographic shifts should not be confused with the kind of persistent shifts found on lakes and other parts of the world. Sailing toward the direction of a persistent shift is good advice if you’re sailing on a lake, not so much on the Bay.

Let’s get back to the velocity shifts. I mentioned two tips for sailing in these conditions. The second one is sailing ‘by the heel of the boat’; if you’ve never heard of this technique it means that helming is done in a way that keeps the heel of the boat constant. All monohulls are designed so that when the boat heels to leeward the boat tends to head up or round up. The opposite is also true. This is the source of the admonition to always sail with some ‘weather helm’. In the velocity shift, the increased wind speed causes the boat to heel to leeward. The decrease in wind speed brings the apparent wind forward and the boat starts to ‘stand up’. Meaning it has less heel to leeward. Here’s the tip. Pay attention to the heel angle at the mast. Go ahead, stare at the mast instead of the tell tales. The mast heel information is immediate and not as confusing as the telltales. Be aggressive, as the boat tends to heel more, head up to keep the heel constant. And as soon as the boat tries to stand up, turn down to maintain heel. Once you get into a rhythm, you can keep the boat’s heel constant. Remember that the drag on the hull and foils’ surface is what’s keeping the boat from moving fast. Constant changing of the hull and keel's appearance in the water is not fast.

Sailing by the heel is especially effective downwind. In light wind and chop it’s difficult to get the boat moving fast. When conditions are windy and choppy, this leads many to be uncomfortable downwind. As a wave moves under the windward quarter, the boat is heeled to leeward and as the wave moves to the leeward bow the boat heels to windward. If the helm is being moved to counteract the turning motion caused by the change in heel (described above), two bad things happen because the helm is reacting too late. First, turning the rudder sharply is slow. Remember that the rudder works by causing drag. Second the boat is rolling so bad the wind angle is never constant. Sail the heel. The mast will start to tilt before the boat turns due to heeling. It is subtle, but if you can steer the boat down slightly as the mast starts tilting to leeward you will counteract the rounding up before it begins while using less rudder. When the mast starts to tilt towards weather, head up. Now the purpose of this method is to keep the boat on the same heading. These rudder corrections are not meant to change the course but only to counteract the turning forces caused by heeling. Practice and you will find that the boat settles down, stays on course, and goes faster.

There are, of course, other elements to boat heeling, such as, crew position and sail trim. These are topics for another time. Give ‘sailing by the heel’ a try. I’m sure you’ll like it and it will improve your sailing.

See sfsailingcoach.com for more.

— Steve Sarsfield