Light Air Tricks

Sometimes frustrating, always challenging, learning how to plan for and execute light-air strategies is as fulfilling as it is critical to any long voyage

August 7, 2002

We were supposed to get the boat from Fort Lauderdale, Florida, to Plymouth, England, with the least amount of fanfare possible. The usual delivery rules applied: arrive alive, break nothing, move the boat safely in the shortest possible time. But the usual rules became somewhat distorted by mid-Atlantic when we were planted firmly in the grip of the North Atlantic subtropical high. The breeze faltered. Then, along with the few remaining clouds, it slowly evaporated. The sea’s surface became a mirror, shattered only when a bird gave up trying to fly on non-existent wind and glided softly in for a landing. The boat, a lightweight 50-footer, no longer bore a bone in her teeth; rather, it streamed a few paltry strings from the bow.

Normally, surrounded by 1040 mb of clear air, we would have resorted to the first light-air trick available to cruisers: We would have started the engine, concerned only about how long our fuel would hold out. In fact that time had come and gone, but this rocket ship had no engine.

Aboard a long-distance cruising vessel, fuel is a commodity that may rank in importance just below food and water. On a sailboat, your life may not depend on the level showing on the fuel gauge, but a lot of life’s conveniences do. And with no fuel docks in sight, that odious liquid needs to be allocated appropriately. First in importance, you will need to be able to generate electricity throughout the voyage. To run most vessels safely and responsibly, sailors rely on radios, running lights, navigation equipment, refrigeration and pumps that rely in turn on electricity. Second in importance, fuel provides propulsion — if you have an engine.


Probably, you will want to use auxiliary power when departing, entering an unfamiliar harbor or docking, or during an emergency en route. For efficiency, you may also want to employ your engine in light airs. The lighter the breeze, the more you may want the help of the Detroit spinnaker.

When beginning a delivery or cruise, I take readings of my available fuel using a sounding stick calibrated to the particular tank I am sounding. Fuel gauges may provide a useful reference — if they are working properly — but often they are not accurate enough to determine true fuel-consumption rates. The irregular shape of many tanks can cause false readings. A tank with a triangular section and pointed end down might appear half full when it is really only a quarter full. After powering for a protracted period of time, I am able to determine how many gallons per hour I am consuming to achieve a particular boat speed in those particular conditions.

As the voyage begins, I establish the boat-speed parameters under which I will sail and those under which I will power if the wind drops off. If I have selected four knots of boat speed as my lower parameter for sailing, once my speed goes under four knots I crank up the engine and power at a reasonably efficient motoring speed — say, seven knots. Each engine and prop will have a cruising speed and rpm that will optimize the mileage out of a gallon of fuel. If after 25 percent of the voyage I find I have consumed 35 percent of my initial fuel, I lower my sailing parameter to three knots of boat speed. Then, if after 50 percent of the voyage I have consumed 65 percent of my fuel, I again reduce my sailing parameter and will continue to sail until boat speed falls below 2 1/2 knots. Finally, if 75 percent of the passage is over and I find that I only have gone through 75 percent of the fuel, I may raise my parameter back to 3 1/2 knots of boat speed. Ideally, under normal circumstances, I would try to arrive at my destination with a reserve of at least five percent to ten percent of my original fuel capacity to allow for emergencies or the possibility that I may need to motor into harbor at night. Using this system, you will be able to power through the lightest conditions for a given fuel capacity, while reserving enough fuel to generate electricity and power all the way up to the dock. Watching the weather forecasts and anticipating light-air conditions will help you to project expected periods of motoring and adjust the scheme accordingly.


For extended passages, it may be necessary to take auxiliary tanks or jugs of fuel. These should be stored in well-ventilated areas and away from living areas to help maintain fresh air below. Containers should be stowed securely and lashed in place. Both tops and vent holes of auxiliary tanks should be sealed while not in use. I have found that running a heavy bead of silicon around the caps of auxiliary tanks and jugs helps to limit the fumes and keep the tanks from leaking. The bead can be peeled off like a rubber band when the fuel needs to be transferred to the main tanks. Transferring the fuel from a 30-gallon drum to the main tanks can be made relatively easy by using a small electric or hand pump. Naturally, gasoline provides its own set of problems. Its explosive nature requires that it be stored in a very well-ventilated, secluded area of the boat away from electric pumps, switches, appliances or stoves, preferably on deck in a safe, low-traffic area. One spark can end your voyage, even if you’re only a half mile offshore!

Our delivery sans engine demanded that we capitalize even on the smallest amount of sail power we could generate. Whether you’re motoring or sailing, the boat should be trimmed properly. Heavy items should be removed from the bow and stern to reduce pitching. Even in light airs and small waves, pitching adds to hull drag and disturbs airflow over the sails, which is even more critical at slow speeds than when the boat has power to spare. Additionally, you should reduce weight aloft and keep it as low as possible to minimize pitching and increase the vessel’s righting moment, which will provide an added safety factor in heavy airs. Keeping a spare anchor in the forepeak may be convenient while coastal cruising and gunkholing, but for an extended offshore passage with anticipated periods of light-air sailing, you might want to stow that weight in the bilge, close to the keel. Canned items and toolboxes should be stowed securely in lower lockers, keeping them dry and accessible while also lowering the vessel’s center of gravity. Upper lockers and bins tend to be less securely designed against contents spillage during a knockdown. Cans and tools hurled from unsecured upper lockers in heavy weather can be a serious hazard. A little thought can put a few hundred pounds of weight in a more desirable location for safety and efficient sailing.

As light air begins to fill in, you can shift some weight to leeward to help the boat to heel. Heeling the boat has a couple of advantages. First, the weight of the sails and boom help them to hang on one side, reducing the slapping of limp sails from an upright boat wallowing and rolling in the swell. Even the most even-tempered of us gets annoyed after days of listening to slatting sails, a slamming boom and rattling blocks. Even worse, shock loading of the sails, rig and gear during that light-air slapping can weaken gear and cause sails to self-destruct, blowing slugs off the foot of the main or blowing seams out of light-air sails. The second, and more important, advantage to heeling is that the more stable sails can now assume an airfoil shape that provides propulsion. Without use of a motor, your sails become your “engine,” and to get you anywhere, they need to work. In light air, they need to be gently coaxed. Heel the boat to establish their shape. Minimize pitching and don’t make sudden, jerky movements onboard, which cause the sails to flutter and lose what little efficiency they have at low speeds.


While sudden motions on deck can slow your momentum, below the waterline they can stop the boat like a hand brake. Driving in light air is a delicate art form. Turning the rudder too fast will stall the slow fluid flow across the blade. Avoid throwing the wheel all of the way over to the stops, which at low speeds only drags the rudder sideways through the water to the actual detriment of steering. Abrupt changes in course also can destroy the smooth airflow over the sails that you are trying so hard to maintain. Slow, almost understated motions with the wheel will allow the rudder to guide the boat into a new direction with minimal drag.

Your goal is to reach a particular destination which lies on a particular heading. If the apparent wind angle is only 30 degrees while pointed on that heading, you may be tempted to shoot straight for it, but if you are able to achieve only one knot of boat speed, you may be better to bear off to an apparent wind angle of 45 or even 50 degrees if you can achieve three knots or more of boat speed. Similarly, if running dead downwind toward your destination leaves you parked, consider coming up to a beam reach to generate boat speed and push the apparent wind forward of the beam. As the apparent wind direction moves forward, bear away slowly to achieve a more desirable course. You may not be able to sail directly to the waypoint, but your speed may move you closer more rapidly, increasing your Velocity Made Good (VMG). (See “The Tactical Navigator,” May 1995 and “How to Be a Tactical Navigator,” June 1995.) The idea is to close the gap between you and your destination in the most efficient manner rather than to labor along the shortest straight-line route. Determining your optimum choice requires some navigational skill and may require understanding the instruments and what they are telling you or a little about vector addition. But even without much navigational skill, it becomes readily apparent that, if one option is to remain on course but parked, you’d be better off 30 degrees off the rhumb line while steadily reducing the distance between you and your destination. You must close the gap as efficiently as possible. There is a balance between increased speed and compromised course. Going fast away from your destination is the least desirable scenario, unless there’s a substantial reason to do so.

One reason to alter course might be to use the weather to more advantage. Locally, winds often circulate under clouds. Most clouds that are not raining produce updrafts, sucking surrounding air toward them — the bigger and taller the cloud, the greater the effect. By easing over to a cloud bank, you may find more suitable wind conditions. If the clouds are particularly large, be prepared for sail changes. Line squalls can produce winds in excess of gale force. As you close with the clouds, you may be able to deduce whether there is wind under them by observing the sea surface. Is the coloration different? Are there whitecaps? Observe any streaks emanating downward from the clouds. Are they caused by sunlight shining through the cloud or is rain falling? If rain falls straight down, there probably is little wind. But if it falls at an angle, the cloud is traveling through the sky and dropping rain into a windless area or the rain is being blown sideways by wind. Study the direction the cloud is moving, and make a decision whether you might have better sailing conditions under the cloud.


For longer-range planning, you will want to study the weather forecasts. Try to move toward a more favorable weather pattern as it approaches without giving up too much ground toward your destination. Additionally, study the pilot charts and radio forecasts to consider how the ocean currents may effect your passage. As the wind provides progressively less and less of your distance made good toward a mark, a current can make up a progressively more significant percentage of your headway over the bottom.

Traveling from Fort Lauderdale to Europe, our ideal course would have taken us somewhat east of the Gulf Stream if we had only considered the wind direction. As the wind dropped off, however, it became obvious that we would have been far better off if we had stayed in the Stream, gaining between three and five knots of current on a course slightly to the west of our destination. Also, along the Florida coast, we might have been able to pick up some diurnal wind shifts. As land heats up during the day, air over it rises, drawing toward it a sea breeze; as it cools at night, the breeze shifts and streams off the land.

Sail handling becomes extremely important in light conditions. Ease halyard tension to the point that any more easing will cause wrinkles to begin to form along the sails’ luffs. Ease off the mainsail outhaul as well. Don’t overtrim the sails; rather, ease them out to the point of luffing. Watch also the telltales on your jib. You may want to introduce more twist by moving the sheet leads aft until all of them break and stream at the same time. Pull up the traveler a bit and ease off on the mainsheet to match the mainsail’s twist to the jib’s. These adjustments help to create a fuller shape in the sails and power them up for the slower, light air, similar to changing the profile of an airplane wing as it slows to come in for a landing by rolling out the flaps. Full battens will help to predetermine the shape of the main in these light conditions, but they must all be cambered on the correct side. After tacking in light conditions, I occasionally have been forced to go aloft to “kick tack” the battens. Sometimes partially dropping and rehoisting the main will accomplish the same task.

As the light wind shifts around, take care to avoid pinching. Steer the boat a little “wide” if necessary to maintain and build momentum in shifty conditions. It’s better to keep the boat moving and building speed than to pinch toward a course, causing the boat to stand up, luff its sails and kill what little speed there is. In light airs it takes a long time to settle back into the groove. Also realize, however, that building speed and bearing away from the apparent wind has its limitations. Some of that “wind shift” is caused by building speed rather than a shift in the true wind direction. When you have achieved a speed and course that maximize your rate of closure with your destination, stop bearing away; otherwise, more speed will only take you away from your goal.

Keeping your sails flying may be frustrating at times. Ironically, often a smaller sail is more stable in light conditions. Increased sail stability can translate into improved boat speed. Consider setting a staysail in lieu of a larger genoa if the genoa is too heavy to stand up in the light air. If the boat continues to wallow and it appears that the slapping main is in danger of blowing the slugs off the foot, even think about putting in a reef. With a reef, there are no slugs to destroy, and the main may still generate some power when the boat is occasionally stable. But if nothing works to keep the main going into self-destruct mode, drop it, stow it on the boom and guy off the boom to keep it from slamming until conditions improve. Preserving your equipment is not only the financially responsible, but also crucial to maintaining your ticket home when the wind begins to build again.

As the light air persists and patience begins to dwindle, keep the faith. The breeze will return, even in the doldrums. Look for ways to make the time useful and enjoyable. Have cooking contests, take a swimming break, hold parties at which everyone must make a present for another crewmember, or even try to wrap up those jobs that weren’t completed before departure. Maintaining crew morale will help to pass the time, and as a dividend the crew will be more efficient at sailing the boat when they’re on watch. And not least important, you’ll have fun. Light air — it’s not all bad, after all, even without an engine!

Bill Biewenga may have learned to manage light airs, but he is s no lightweight. He’s logged over a quarter million miles, moving boats of all types and descriptions across oceans and doldrums around the world. He frequently contributes to Cruising World.


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