The elite racing models have been developed by the worlds top racers and olympic sailors.
The tactical scales and quick readability give a critical advantage. The cone shaped card with gimballed lubber lines has a main steering scale on the horizontal part and a tactical scale on the vertical edge of the card. Detecting wind shifts may be the tiny difference between winning and losing. Silva's tactical scale grades from 0-20 and the figures correspond on port and starboard tack. If the reading on starboard tack is 2 the reading on port after tacking should also be 2. In this way you only have to remember one number, this is a great benefit in triangular course sailing where racers need to watch the wind shifts, rather than their actual course.