Interactive · Points of sail
A sailboat can hold almost any heading — every direction but the narrow cone straight into the wind. And even that one it reaches, not head-on, but by tacking. Drag the wind, steer your course, lift the keel, and watch why.
The engine · airflow & pressure
Dead downwind, the sail is just a wall — air piles up behind it and shoves. Turn across the wind and it becomes a wing: the flow races over the outside face (fast, smooth, low pressure) and crawls along the inside (slow, high pressure), and that suction is what pulls the boat. Slide through the points of sail and watch the flow switch.
The sail is a wing: airflow across its curve makes lift. The keel (bolina) stops the boat sliding sideways and turns that lift into forward drive — lift it and the same force just shoves the hull downwind. Straight into the wind the sail luffs and pressure falls to zero; bear away and it fills again. To reach a point dead upwind you cambar — zig-zag across the wind, arriving on angles because the straight line was never on offer.