If, for example, a boat is running at, say, 4 knots before a true wind of 10 knots the effective wind acting on her sails to drive her ahead is only 6 knots.
Ukuba umzekelo isikhephe sibaleka ngokwesantya esibekiweyo esingu-4 phambi komoya wokwenyani wesantya esibekiweyo esingu-10 umoya onguwo osebenzayo kwiseyile zawo ukuziqhubela phambili uzakuba ngu-6 wesantya esibekiweyo.