A well-sailed boat can develop a great speed advantage; … so it is not unusual to see the largest race-winning leads developed in the lightest of conditions. Greg Fisher in When the Going Gets Light. . .
Sitting on the low side, trying to go fast in light air can be very frustrating. Dave Perry confessed that, for him, the only good thing about sailing in light air is you can usually go barefoot. However, light air is inevitable, and going fast becomes easier if you concentrate on a few specific techniques.
In this article, we collect tips for light air boat speed in cat-rigged non-spinnaker boats, with an emphasis on upwind sailing.
In When the Going Gets Light. . ., Greg Fisher uses the phrase “retain the precious attached flow across the sails.” Attached flow is indeed precious. In light wind, a small increase in air flow leads to a relatively large increase in boat speed. Even if there is flow, it’s no good unless it stays attached to the sail. Detached flow reduces lift and increases drag.
Once you understand the importance of flow, you can see the relationship between a variety of techniques. You can even devise your own techniques. Here are “flow” tips I have found useful for sailing in light air.
Generate Apparent Wind
In light air, concentrate on speed, not pointing. Speed gives you apparent wind; in other words, flow. Trying to point high is counter-productive. You may think you’re pointing well, but you will be going slow. This reduces apparent wind and makes your sails less powerful. It also reduces flow over your underwater foils, making them less effective.
Every boat has an optimum upwind sailing angle for each wind speed. As the wind speed decreases, the optimum angle to the true wind increases in order to maintain apparent wind. Big boats have polar diagrams and calculate target boat speeds for each true wind speed. In small boats, we go by feel. For very light air, a basic rule of thumb, according to Greg Fisher, is to bear off more than you think you should, and then bear off five degrees more.
The same principle applies downwind. Generate apparent wind by reaching up and then try to maintain that flow as you bear off. Reach back up as soon as you lose the flow. More on this in a future article.
Keep the Leech Open
In light air, the wind is strongest at the top of the mast and decreases as it nears the water surface. To take advantage of this stronger wind, be sure that the top of the sail retains attached flow. If the upper leech is hooked in too far, we say it is “closed.” With a closed leech, the slow-moving air won’t stay attached and the sail will stall.
The top batten and the leech telltales are good indicators of leech position. If the top batten is angled to very far windward, the leech is closed. If the leech telltales stay behind the sail, the leech is stalled.
Here are some tips to keep the leech open.
Heel the Boat to Leeward
Commit your weight to the leeward rail and hike. This lets gravity pull on the leech to leeward and open it up. Heeling also reduces the wetted surface area of the hull. Both of these effects are huge for upwind boat speed.
Experiment with Mainsheet Tension
The weight of the boom and the tension in the mainsheet pull down on the leech and tend to close it. Turn off your mainsheet ratchet and experiment to find the tension at which you are sheeting the sail adequately without closing the leech. Every change in wind speed requires an adjustment. Watch your leech telltales for clues.
Experiment with Traveler Position
On some boats, it may be beneficial to pull the mainsheet traveler to windward in very light air. This reduces the downward pull on the boom, letting you sheet in with less chance of stalling the leech. As the wind comes up, be sure to move the traveler back.
Stay in the Groove
In light air, steering accurately to stay in the groove is just as important as proper sail trim. Sail too high for your trim and the flow over the windward side is ineffective. Sail too low and you stall the leeward side of the sail. Unfortunately, it’s harder to steer by feel in very light air. I have found two good aids to help find the sweet spot.
A forestay telltale provides a good “ballpark” reference when you are sitting on the low side. Place it low enough on the forestay so you can see it under the boom. In light air in an MC Scow, you are close to the groove when the forestay telltale is pointing at or just outside of the leeward sidestay. Use this as a first reference for steering and then adjust from there by feel and other indicators.
Lightweight Sail Telltales
Sail telltales provide the most accurate indication of the groove, especially for sailors that haven’t developed a well-tuned feel. In sloop-rigged boats, the helmsman steers by the jib tellltales. In cat-rigged boats, telltales placed 15-20″ behind the luff take the place of the jib telltales.
For sailors that use sail telltales to find the groove, light air poses a challenge. Typical yarn telltales don’t respond in light air. When sitting on the low side, it’s hard to see the telltales on both sides of the sail.
In light air in an MC Scow, I have found my best upwind performance by using a ribbon of fluorescent 1/2-ounce spinnaker cloth on each side of the sail, positioned about 20″ behind the luff, slightly above my head height. The light spinnaker cloth responds well in the lightest of winds. The fluorescent color is visible from either side of the sail. A quick spray with teflon keeps them from sticking to the sail.
The leeward telltale is the best guide. If it is fluttering away from the sail or toward the luff of the sail, the sail is stalling, reducing lift and creating drag. Steer up until it just starts streaming toward the leech. I pay less attention to the windward telltale. If I am just above the stall point on the leeward side, I know I am sailing in the groove.
There are other factors that affect light air boat speed. We’ll mention them here and provide more detail in future articles.
- Sail fullness: deeper sails generate more power, but also make it more difficult to retain attached flow. We’ll break this topic down in a future article.
- Subtle changes: slow-moving air is surprisingly easy to disturb with movement of the boat or sails. Once you get things set, make changes smoothly and only when necessary. Concentrate on feeling the boat.
- Steering without the rudder: moving the rudder slows you down. Learn to steer with subtle changes in angle of heel, sail trim, and weight placement