Sailing boat variable stress hollow mast - with internal pressure strips tightened from outside using threaded screws

The hollow mast is made from aluminium, or light alloy, or from suitable plastics. One edge has an open groove in whih the sail is threaded. The inside faces are fitted with pressure strips (2) running up the mast and secured by screws (3) tightened from outside the mast. The selective tightening of the screws up the mast alters the tension in the mast and sets its optimum flexibility. This allows bes use of the sail shape. The strips are held on elastic mountings, so that the screw heads are always pulled flat into the mast. The strips do not add appreciably to the weight of the mast.