On a sailboat, the wind sensor (speed and direction) is installed at the masthead. Perched high up, it suffers the effects of the wind (that's what we ask of it!), but is strongly disturbed by the movements of the boat. Heeling, pitching and swell propel the masthead at high speed.
To understand, imagine a sailboat at anchor on a windless day with a 1-metre swell. The movements induced at the head of the mast cause the wind sensor to move in the air, which then measures a speed and an angle. The period of a 1 metre swell can be around 7 seconds. That is to say that in 7 seconds a fixed point on the water will have undergone 2 wave crests. Our boat will therefore have dived towards the trough of the swell then reared towards the next peak before starting again. Her masthead will have circulated through the air at good speed, recording first a headwind then a tailwind..
By installing a 3-dimensional accelerometer inside the boat to measure these boat movements, NKE manages to "de-noise" the apparent wind. It subtracts in real time all the accelerations of the boat that disturb this measurement.
A specific algorithm has been developed for the HR Processor (the brand's top-of-the-range control unit). For it to be relevant, it is also necessary to install a high-performance wind sensor at the head of the mast. NKE has moreover improved its wind vane anemometer sensor. It is equipped with a new reel, the lightest, and the windvane blade has been redesigned. It has been fitted with a high-resolution digital decoder to obtain a sensitivity now close to a tenth of a degree.
Having a more accurate wind reading acts primarily on the autopilot. The result is more precise steering (performance gain) and, above all, fewer helm strokes and therefore reduced power consumption. (NKE speaks of 50% less consumption).
In red the information of the anemometer, in blue the same corrected information
Used on the Vendée Globe IMOCA boats or even for the America's Cup, the Apparent Wind Monitor will be available to the general public from May 2017.
