Abstract: According to some demonstrative embodiments of the present invention there is provided an apparatus for adjusting the flexibility of a fin of a waterborne vessel comprising at least one movable and/or rotatable component adapted to be positioned in one of at least two different positions, a first position and a second position, wherein when said component is positioned at said first position, said fin exhibits a first degree of flexibility, and when said component is positioned at said second position, said fin exhibits a second degree of flexibility, wherein said first degree of flexibility is greater then said second degree of flexibility.

Abstract: The invention is a fin for surfboards with a variable stiffness function. This is accomplished by means of a central disc that can be rotated to give different degrees of mechanical support to the fin when rotated to different angles, thus providing variable flexibility.

Abstract: The invention is a fm for surfboards with a variable stiffness function. This is accomplished by means of a central disc that can be rotated to give different degrees of mechanical support to the fin when rotated to different angles, thus providing variable flexibility.