Sailing upwind: planning your tacks properly

Why everything takes longer upwind

No sailing boat can sail straight into the wind. A cruising yacht close-hauled usually sails 40 to 50 degrees to the true wind. This smallest angle is called the pointing angle. The tacking angle, the angle between the courses on starboard and port tack, is twice that: with a pointing angle of 45 degrees you tack through 90 degrees.

If the destination lies dead upwind and you sail at 45 degrees to the wind, the distance sailed is about 1.4 times the straight-line distance (1 divided by the cosine of 45 degrees). At 50 degrees it is already just over 1.5 times. On top of that, a boat sails more slowly close-hauled than on a beam reach, and every tack costs speed.

Leeway: course through the water is not course over ground

Close-hauled, the wind pushes the boat sideways to leeward. For a cruising yacht this leeway amounts to a few degrees, more at low speed, in a short sea or with a shallow keel. In addition, anyone sailing hard on the wind pinches and loses speed, so in practice you bear away a few degrees.

In Sailseer both effects are contained in the leeway value: the tacks lie at pointing angle plus leeway to the true wind. The default depends on the boat type (small 10, medium 7, large 5 degrees).

VMG: how fast you close on the destination

When beating, what counts is not the speed through the water but the speed towards the destination, the VMG (velocity made good). It is the boat speed times the cosine of the angle between the course and the direction to the destination. A boat doing 5 kn at 45 degrees to the wind makes around 3.5 kn to windward. Sailing a little lower and faster can bring more VMG than pinching; the polar diagram shows where the optimum lies.

How many tacks, how long the boards

Mathematically the distance is the same whether you make two long boards or twenty short ones. Still, there are differences:

• Every tack costs time until the boat is up to speed again, more so with a small crew or in a rough sea.
• Long boards out to the edge of the area are a gamble: if the wind shifts, you end up on the wrong side and have thrown away a lot of distance.
• If you stay within a band around the direct line, you can respond to wind shifts. If the wind heads you so that you point less well towards the destination, tacking usually pays.
• Coastline, shallows, restricted areas and traffic separation schemes limit the boards. Under COLREGs Rule 10 you cross a traffic separation scheme as nearly as practicable at right angles to the direction of traffic, rather than beating up inside it.

Current on the tacks

If the stream runs with you against the wind, you make good progress over the ground, but wind against tide builds a short, steep sea. If it runs against you, it can eat up your VMG entirely. It often pays to time your departure so that the stream turns before the beat begins. More in the guide Tides and tidal streams.

Comfort on the beat

Upwind the sea comes from ahead: if the waves are between one and just over two boat lengths long, the boat pitches and buries its bow, while a short sea slams against the hull. For each leg, Sailseer rates how the sea runs on the course in four levels from calm to very rough.

How Sailseer plans tacks

Sailseer does not add a flat surcharge for upwind legs but lays out real tacks:

1. The route gets waypoints: start and end of the leg and the distinct corners in between (from a 10 degree bend and 2 nm apart).
2. For each pair of waypoints, the wind in the first hour at the waypoint where the boat currently is applies. If the next waypoint lies closer to the wind than your boat's pointing angle, the boat beats; otherwise it sails the route itself.
3. The tacks follow fixed courses (pointing angle plus leeway to the wind) with as few tacks as possible within a band around the straight line to the next waypoint: 20 per cent of the distance, 0.5 to 2 nm on each side. Each board is at least 0.5 nm long, shorter only where the water leaves no other choice, for example at a harbour entrance.
4. No board crosses land, water too shallow for your draught, or a restricted, warning or protected area that the leg does not cross anyway. No tack is placed inside a traffic separation scheme.
5. The time comes from the polar diagram at the angle actually sailed, with wind for each place and hour, tidal stream and tack loss. The engine never runs upwind.

If there is no room in the water for tacks, Sailseer calculates with the VMG under sail and gives the reason. The tacks are available as GPX. If you want to motor, switch to the direct route with “Upwind”. Try it with your boat on the map.

Tacking aid in navigation mode

Under way, the tacking aid in navigation mode calculates the same tacks from your boat's position: which tack you are on, the course and the next tack up to the next target on the route. It recalculates every 30 minutes, at every tack and whenever you are off the planned boards. If you wish, it uses the wind on board, entered by hand or taken from the boat instruments; its influence fades over three hours. There is no off-course alarm on the boards.

Your boat's polar

Sailseer calculates with the polar diagram of a 34-foot cruising yacht, scaled to your planning speed. Under “Close-hauled and beating” you set the pointing angle, leeway, tack loss and close-hauled speed at 6, 10, 15 and 20 kn of true wind. From a GPX track of earlier trips, Sailseer estimates how fast your boat sails by comparison and suggests close-hauled values; the track is not stored. With boat instruments connected, a polar is built from your own measurements.

Tacks are a plan based on the forecast and a depth grid, not navigation. Official charts, the marine forecast and warnings take precedence, and on board you decide according to the wind you actually have. Whether a beat is worth it at all is covered in the guide Weather window.