2 min read · Updated 18 June 2026
A racing yacht's instruments measure wind, boat speed, depth and heading, and a processor turns that raw data into the tactical numbers crews actually race to — true wind, velocity made good, laylines and performance targets. Modern racing is sailed as much to these numbers as by feel, which is why the electronics are a core part of a boat's technology.
The sensors
A handful of sensors feed the system:
- Masthead wind unit — measures wind speed and angle (the apparent wind the boat feels), mounted at the top of the mast to be clear of disturbed air.
- Boat-speed sensor — a small paddlewheel or sonic sensor in the hull measuring speed through the water.
- Depth sounder — water depth under the boat.
- Electronic compass — the boat's heading.
- GPS — position, and speed and course over the ground.
From raw data to useful numbers
On their own, those raw measurements are only part of the story. A central processor combines them to calculate the figures that decide races:
- True wind speed and direction (computed from apparent wind, boat speed and heading) — see apparent wind vs true wind
- Velocity made good (VMG) — progress directly up or downwind, the key upwind/downwind number, explained in what is VMG
- Laylines — when the boat can fetch the next mark
- Performance against polars — how the boat is going versus its theoretical best
Polars and targets
Polars are a model of how fast the boat should go at every wind angle and strength — its performance benchmark. Loaded into the system, they give the crew target speeds and angles to aim for. The displays then show current speed and angle against those targets, so the helm and trimmers can see at a glance whether they are extracting the boat's full potential, and the tactician and navigator can base strategy on hard numbers rather than guesswork.
Decision support, not autopilot
It is worth being clear: in fully crewed racing, people steer and trim — the electronics inform, they don't drive. The instruments turn what the boat and the wind are doing into numbers the crew can act on, fast. Reading them well is a skill in its own right, and it is a big part of how modern crews sail consistently to their boat's potential. For the rest of the language, see the sailing terms glossary.
Frequently asked questions
- What instruments are on a racing yacht?
- The core sensors are a masthead unit that measures wind speed and angle, a boat-speed sensor in the hull, a depth sounder, and an electronic compass for heading, alongside GPS for position and speed over the ground. A central processor combines these to calculate derived numbers like true wind and velocity made good, which are shown on displays around the boat.
- What is the difference between the raw and calculated instrument data?
- The sensors measure raw values — apparent wind, boat speed, heading, position. A processor then combines them to calculate the numbers crews actually race to: true wind speed and direction, velocity made good (VMG), laylines to the mark, and performance against the boat's polars. The raw data is measured; the useful tactical numbers are computed from it.
- How do crews use sailing instruments?
- Crews steer and trim to targets. The instruments show the boat's current speed and angle against the target speed and VMG for the conditions, so the helm and trimmers can tell instantly whether they are sailing the boat to its potential. The tactician and navigator use true wind, laylines and trends to make strategic calls about where to go on the course.
- What are polars?
- Polars are a model of how fast a boat should sail at every wind angle and wind strength — its theoretical best performance. Loaded into the instrument system, they give the crew target speeds and angles to aim for. Sailing 'to the polars' means matching that benchmark; consistently beating or missing it tells the crew how well the boat is going.
- Do the instruments steer the boat?
- No — people steer the boat. The instruments inform the crew, who make the decisions. (Many boats do have an autopilot for delivery or short-handed sailing, but in fully crewed racing a person is always on the helm.) The electronics are decision-support: they turn what the boat and the wind are doing into numbers the crew can act on.