Lift generated on a foil is directional, and when applied to sails one can say that the lift moments generated at any one point of the surface of the sail will be at 90 degrees to that surface (although the amount of lift generated will depend on the velocity that the sail is travelling through the wind and the displacement of the wind at that point) therefore one can calculate the amount of lift at any given point of the sail AND ITS DIRECTION. In the case of the working sails the direction that the lift can be adjusted (in the vertical plane) while sailing is relatively limited, but in the case of a spinnaker there is quite a large degree of “vertical” directional adjustment available for the use of that lift generated I.E. by letting the foot of the spinnaker be set further forward the lift generated by the spinnaker can be directed more “upwards”. In so doing reducing downward pressure on the bows. The best comparative example is to a “parachute” or better still a “Para glider” where lift generated is DIRECTED to give both lift upwards and forwards.