is usually done by application of a glue or elastomer providing a connection that is tight and flexible the same holds for the coupling of the other blades with each segment a second alternative for the design of the joint between two segments as shown in fig2 is illustrated in fig7 it is similar to that of fig6 with the differences that the engagement of the two segments 8 a and 8 b is done by force and that the provided coupling also works in a direction corresponding with the radius of the circle formed by the ferrule and that in both directions as with the design of fig6 i the right end of the segment 8 a has a general profile in the shape of a u201c u u201d of which the opening is directed toward the other segment 8 b with which is to be joined the base of the u201c u u201d being formed by the portion 11 a corresponding with the profile on the side of the back of blade 4 the two branches of the u201c u u201d being straight lines and each possessing a recess 13 a u2032 the insides of the branches are however at an angle here relative to the median plane.