Apparatus for the stabilizing of the direction of travel of watercraft, specifically a sword or fin for sailboards

An apparatus for the stabilizing of the direction of travel of watercraft, specifically a sword or fin for sailboards having a guide plate extending from the bottom side of said watercraft into the water, which guide plate has a symmetrical airfoil profile cross-sectional shape,

• comprising two independently from each other flexibly deformable side walls defining the profile of said guide plate, the shape of said side walls in the prestressed condition due to their internal elasticity corresponding to an optimal profile for low flow velocities, which said side walls are designed such that they are deformable in accordance with prevailing pressures which change due to velocity of flow and/or due to angle of flow thereagainst;
• said flexible side walls being mounted to a relative to the direction of flow leading edge of a rigid center wall, said flexible side walls abutting solely due to their inherent elasticity laterally at the area of the trailing edge described by said center wall of said apparatus, said side walls defining together with the two oppositely located surfaces of said center wall two substantially closed void spaces or cavities, respectively, inner bracings being provided at said center wall whereby a limitation of a minimal profile is achieved.

An apparatus for stabilizing the direction of travel of watercraft comprising a guide device extending from a bottom side of the watercraft and having a longitudinal axis, a leading edge, and a trailing edge, said guide device comprising:

• two independently from each other flexibly deformable side walls defining a profile of said guide device, said side walls being joined at said leading edge and free from each other at said trailing edge, said side walls having sufficient internal elasticity to hold their trailing edges adjacent said axis while allowing individual and asymmetric deformation of portions of said side walls between said leading edge and said trailing edge in accordance with prevailing pressures against said side walls solely due to velocity of flow and/or solely due to angle of flow thereagainst, and a rigid center wall aligned along said axis, said leading edge of said side walls being joined to a leading edge of said center wall, said trailing edges of said side walls only resting against a trailing edge of said center wall, said portions of said side walls defining together with two oppositely located surfaces of said center wall two substantially closed void spaces or cavities, respectively.

An apparatus for the stabilizing of the direction of travel of watercraft, specifically a sword or fin for sailboards having a guide plate extending from the bottom side of said watercraft into the water, which guide plate has a symmetrical airfoil profile cross-sectional shape,

• comprising two independently from each other flexibly deformable side walls defining the profile of said guide plate, the shape of said side walls in the prestressed condition due to their internal elasticity corresponding to an optimal profile for low flow velocities, which said side walls are designed such that they are deformable in accordance with prevailing pressures which change due to velocity of flow and/or due to angle of flow thereagainst;
• said flexible side walls being mounted to a relative to the direction of flow leading edge of a rigid center wall, said flexible side walls abutting solely due to their inherent elasticity laterally at the area of the trailing edge described by said center wall of said apparatus, said side walls defining together with the two oppositely located surfaces of said center wall two substantially closed void spaces or cavities, respectively, said void spaces being filled in part by a compressible material.