A sail is a wing standing on its end
Sailing downwind is easy to picture: the WIND pushes and the boat goes. Everything interesting happens when a SAILBOAT travels across the wind or towards it. Trimmed to the right angle, the SAIL curves like an aeroplane wing turned on its side, and the air flowing round it pulls the boat forwards rather than shoving it.
That creates a second problem, because the same force is also trying to push the boat sideways. The KEEL — a heavy fin hanging under the HULL — resists sideways movement while barely slowing forward movement, so most of the push becomes speed instead of drift. The weight down there does another job too: it levers the boat upright again when a gust leans it over.
Going upwind by zig-zag
Nothing can sail straight into the wind. Point at it and the sail simply flaps, in what sailors call being caught in irons. Most boats manage about 45 degrees off the wind, so reaching a harbour that lies directly upwind means tacking: sail at an angle, swing the BOW through the eye of the wind, sail at the opposite angle, repeat.
The strange part is that a boat can beat the wind that is pushing it. As it speeds up it creates a headwind of its own, and the sail works on the combination of the two — so modern racing boats lifted clear of the water on foils travel several times faster than the breeze. The outright sailing speed record now stands above 60 knots.
Why speed is measured in knots
The KNOT still carries its own instructions inside the name. Sailors measured speed by throwing a weighted wooden board over the STERN on a long ROPE with knots tied along it at fixed spacing, then counting how many knots ran through their fingers before a sand timer emptied. Knots per glass became simply knots.
One knot is one nautical mile per hour, and the nautical mile is neater than it sounds: it is one minute of latitude, a sixtieth of a degree. A navigator can measure distance on a chart straight off the latitude scale printed up the side, without converting anything.
An anchor does not hold by being heavy
Dropping the ANCHOR straight down and hoping for the best would not hold a dinghy, let alone a yacht. An anchor works by digging in: the flukes bite into sand or mud and bury themselves, and the harder the boat pulls, the deeper they go.
That only happens if the pull is sideways rather than upward, which is the job of the chain. Sailors let out five to seven times the depth of water, so a long stretch of chain lies flat along the seabed and drags the anchor horizontally. Too little chain and the pull lifts the anchor out, which is how boats end up drifting quietly out of the bay at three in the morning.
The oldest trophy in sport
Competitive sailing keeps some very long arguments running. The America's Cup began with a race round the Isle of Wight in 1851, won by a schooner from New York, and it has been fought over ever since — making it the oldest trophy in international sport, older than the modern Olympics.
For most sailors the appeal is quieter than that: a small YACHT, a CAPTAIN who is also the entire crew, and a VOYAGE that depends on reading water and sky. Our boats puzzle covers the engines and the working craft; this grid is the half that runs on weather.