If you have watched the America’s Cup in recent years or have been following the developments in hyrdo-foils, you may not be surprised at the comparison. Maybe it’s because I’m a bit of an aviation buff, but I think there may be a different and useful comparison to draw. Consider this: The lee shore for a sailboat is the ground for an airplane. Both vessels will “fall” to their respective ground if they fail to maintain lift.
Take Off
As soon as you unmoor a sailboat, you could consider it “airborne,” sails or not. I am fond of repeating, “the safest decision a sailor can make is not to leave the dock.” Same for an aircraft. It is safest as long as it’s well attached to the ground. However, neither sailboat nor airplane is much use on the ground. A prudent aviator or mariner decides to depart this safety with care and consideration. Are conditions favorable for launching into the wild blue yonder?
The Importance of Angles
The angle of the wings relative to the airflow on either craft is key to performance. A sailboat controls this by adjusting the sails’ angle to the wind, either by sheeting in or out or changing the boat’s heading. A pilot must manage the same. The proper angle is controlled through the pitch, bank, and roll of the plane. Regardless of the craft, the angle of airflow-to-wing is key. Too shallow, and instead of a sail, you have a flag. Too sharp, and you have a stall. Neither results in lift.
Climbing
Once we’ve thoughtfully committed to leaving the ground, it’s time to start making space, whenever possible, between our vessel and the lee shore. Climbing upwind is the “climb out” for an aircraft and the reason they climb so steeply after takeoff. If we’re going to fly, fly high. Why? The space between the plane and the ground is problem-solving time, as is sea room between a sailboat and her lee shore. The lee shore may be a dock of boats 5 feet away, a beach 100 yards away, or a continent 1000 miles away. Wherever it is, we need to be as aware of where and what it is as a pilot is aware of his altitude and type of terrain below. For both vessels, safety increases with every moment they spend climbing.
When a sailboat is working its way upwind, it behaves similarly to an aircraft climbing in altitude. Climbing in this way is technically and energetically challenging. The plane is working against gravity to increase the height above ground, requiring more energy than merely maintaining altitude. Meanwhile, a sailboat is working against the wind. Every bit of wind that is not generating lift on the sails creates drag against every other part of the boat. The wind also drives wind waves, and when sailing upwind, these will be smacking against the bow of the bow, sapping energy from the ship.
Lift is the force that works against all the drag and gravity and allows for the upwind climb. A failure of lift for either craft means an immediate descent and a diminishing of their safety buffer. The plane will descend toward the ground; the boat will drift downwind to her lee shore. Any sailor that has had her engine quit in a windy marina has experience with this.
Level Flight
On a sailing boat, we know this as a beam reach. The sailboat is sailing across the wind, the wings are in lift mode, and the vessel is neither climbing upwind nor falling downwind. It is neutral in terms of its windward/leeward movement. For a plane in level flight and a boat on a beam reach, each can expect to achieve greater speed than while climbing.
Descending
There are many reasons either vessel may wish to spend some hard-earned altitude: traffic, weather, or the decision to land, to name a few. Both would be wise to do so with an eye toward the impact on their margin of safety. Both can expect to gain speed more quickly in a descent. The wind and waves, previously dragging on a sailboat as it beat to windward, are now allies driving it downwind. The gravity a plane worked so hard to overcome now aids in the descent.
Landing
I like to think of landing as the graceful merging of vessel and earth. For both kinds of craft, the name of the game is to manage the energy remaining such that there is enough to get it to the destination and no more. Too little or too much, and we land either too short or too long and may suffer damage. As such, the arrival back to earth takes careful planning and momentum management. Prudent sailors and pilots have go-around and alternative landing locations planned ahead of time.
Variations in Lift
A plane can increase lift by altering the aircraft’s speed and the wing’s size and shape. Wing size and shape are controlled by deploying the flaps and slats along the wings’ trailing and leading edges. This increases the surface area and the draftof the wing. Secondly, a plane can use its engines to increase the airspeed over the wing’s surfaces.
A sailboat has similar options. It, too, can increase the draft of its sails by easing the foot of the main or headsail. A sailboat can also seek greater wind speeds if it is underpowered or less if it is overpowered. Like a plane, the faster the air moves over the sails, the more lift it generates. Similarly, if the available wind speed is too great, a sailboat can decrease its sail area by reefing (shortening) sail, or deploy larger and lighter sails should the wind speed be insufficient.
Lift-generators
If you understand a little something about flight, you probably already know a lot about sailing as well, and vice versa. When casting off use the same care and attention you’d expect of a pilot, and enjoy the many happy miles under your keel.