GB2181102A - Flexible propulsive fin-mechanically mounted - Google Patents

Abstract

A flexible fin arrangement, when coupled to a prime mover, provides a means of propelling a displacement or submersible body through a liquid. A flexible fin (or fins) 10 are mounted on the end of a radial arm (or frame) 11, the other end of the arm providing a pivot 12 about which the prime mover can exert a semi-rotary reciprocating movement, thus moving the leading edge of the fin 20 through the liquid in an arcing movement, similar to a fish's tail fin movement. <IMAGE>

Description

SPECIFICATION Flexible propulsive fin-mechanically mounted This invention relates to a flexible fin, used as a means of propulsion in a liquid.

Flexible fins used as a means of propulsion in a liquid-normally water-are usuaily associated with the rubber "flipper" as used by swimmers. These are worn on the feet, the fin extending beyond the toes and a kicking action of the legs achieving thrust in the manner of a whale's tail fluke. The present invention allows a flexible fin or fins to be attached mechanically to any suitable displacement body or submersible in order to propel that object through a liquid.

According to the present invention there is provided a flexible fin arrangement comprising a flexible fin (or fins) securely mounted by the leading edge to the free end of a stiff radial arm (or frame) and inline with it, the fixed or other end of the arm providing a pivot. The flat section of the fin lieing in the same plane as the axis of the pivot. The arm is provided with means whereby it can be swung about the pivot.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawing in which: Figure 1 shows in perspective, the flexible fin arrangement fitted to a twin hulied craft.

(One hull has been omitted for clarity).

Referring to the drawing this example comprises a twin hulled craft 15 on which the occupant sits in a semi reclining type seat 1 7 facing forward midway between the hulls, each foot resting on a pedal 14 connected to, and on either side of, the vertical shaft or pivot 12.

The shaft passes through a bearing and housing 13, the housing so formed as to provide a flange by which it is bolted to the structure 16 connecting the two hulls. Fastened securely to the base of the shaft is the fixed end of the radial arm 11, the arm extending rearward, approximately parallel to the water surface.

The fin 10 is securely fastened by its leading edge 20 to the free end of the arm, extending rearward and inline with the arm, its top edge positioned just below the water surface and approximately parallel with it. The flat section of the fin lies in the same place as the axis of the shaft. A method of steering the boat is provided by a rudder 19 and hand lines 18. The hulls must be so arranged that the arm is free to swing through an arc of approximately 60". The length of the arm and the area, shape and flexibility of the fin are matched to achieve maximum efficiency for the specific usage. The fin can be moulded in a polymer, or cut and shaped from a suitable sheet material and used singly or 'sandwiched' as shown. Thrust is achieved by anternating foot pressure against the pedals thus inducing an arcing motion at the leading edge of the fin.

1. A flexible fin arrangement comprising a flexible fin (or fins) securely mounted by the leading edge to the free end of a stiff radial arm (or frame) and inline with it, the fixed or other end of the arm providing a pivot. The flat section of the fin lieing in the same plane as the axis of the pivot. The arm is provided with means whereby it can be swung about the pivot.

2. A flexible fin arrangement as claimed in claim 1, wherein the radial arm (or frame) is of sufficient length and stiffness so as to transmit the desired energy input to the leading edge of the fin (or fins) in order to achieve thrust.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (2)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Flexible propulsive fin-mechanically mounted This invention relates to a flexible fin, used as a means of propulsion in a liquid. Flexible fins used as a means of propulsion in a liquid-normally water-are usuaily associated with the rubber "flipper" as used by swimmers. These are worn on the feet, the fin extending beyond the toes and a kicking action of the legs achieving thrust in the manner of a whale's tail fluke. The present invention allows a flexible fin or fins to be attached mechanically to any suitable displacement body or submersible in order to propel that object through a liquid. According to the present invention there is provided a flexible fin arrangement comprising a flexible fin (or fins) securely mounted by the leading edge to the free end of a stiff radial arm (or frame) and inline with it, the fixed or other end of the arm providing a pivot. The flat section of the fin lieing in the same plane as the axis of the pivot. The arm is provided with means whereby it can be swung about the pivot. A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawing in which: Figure 1 shows in perspective, the flexible fin arrangement fitted to a twin hulied craft. (One hull has been omitted for clarity). Referring to the drawing this example comprises a twin hulled craft 15 on which the occupant sits in a semi reclining type seat 1 7 facing forward midway between the hulls, each foot resting on a pedal 14 connected to, and on either side of, the vertical shaft or pivot 12. The shaft passes through a bearing and housing 13, the housing so formed as to provide a flange by which it is bolted to the structure 16 connecting the two hulls. Fastened securely to the base of the shaft is the fixed end of the radial arm 11, the arm extending rearward, approximately parallel to the water surface. The fin 10 is securely fastened by its leading edge 20 to the free end of the arm, extending rearward and inline with the arm, its top edge positioned just below the water surface and approximately parallel with it. The flat section of the fin lies in the same place as the axis of the shaft. A method of steering the boat is provided by a rudder 19 and hand lines 18. The hulls must be so arranged that the arm is free to swing through an arc of approximately 60". The length of the arm and the area, shape and flexibility of the fin are matched to achieve maximum efficiency for the specific usage. The fin can be moulded in a polymer, or cut and shaped from a suitable sheet material and used singly or 'sandwiched' as shown. Thrust is achieved by anternating foot pressure against the pedals thus inducing an arcing motion at the leading edge of the fin. CLAIMS

1. A flexible fin arrangement comprising a flexible fin (or fins) securely mounted by the leading edge to the free end of a stiff radial arm (or frame) and inline with it, the fixed or other end of the arm providing a pivot. The flat section of the fin lieing in the same plane as the axis of the pivot. The arm is provided with means whereby it can be swung about the pivot.

2. A flexible fin arrangement as claimed in claim 1, wherein the radial arm (or frame) is of sufficient length and stiffness so as to transmit the desired energy input to the leading edge of the fin (or fins) in order to achieve thrust.