VARIABLE RESISTANCE WATER SKIS WITH VARIABLE RESISTANCE PADDLES The characteristic feature of variable resistance water skis is that their bottom side (being in contact with water) during the movement of the ski on the surface of water in one direction (forward) produces a minimal resistance on the water, whereas with the change of direction to opposite (backwards) the resistance becomes a lot greater which, while alternate movement of one leg is sliding forward and the other one backward, enables pushing against the water and moving forward. In the model design it was achieved by installing on the bottom side of each ski a series a row of transverse plates, in relation to the axis of the ski, made from material of negative buoyancy, which with the forward movement of the ski and resistance caused by water close (minimum resistance in water), and with the change of movement to opposite and with the resistance of water they open up to 90 ° and position themselves vertically in relation to the bottom of the ski, therefore resistance grows dramatically.

Description of figures.

Fig. 1. Cross section of variable resistance water ski on the level of attachment of one of the movable plates.

A-the ski B-attachment socket for axis of movable plate C-the axis of movable plate D-the movable plate in the raised position-minimal resistance in water E-stopper of movable plate opening-holds the movable plate in the vertical position in relation to the ski Fig. 2. Cross section of variable resistance water ski on the level of one of the movable plates.

D-the movable plate in the open position (down) -resistance in water is maximum Fig. 3. Schematic figure of variable resistance water ski. Side view.

The arrows show the direction of movement of the ski in water.

D-movable plates raised during forward movement. Resistance in water is minimal.

D1-movable plates in the open position (down) which is vertical in relation to the ski. Maximum resistance in water.

Variable resistance paddle for the variable resistance water skis is in practice comparable with the role played by standard winter ski sticks.

They enable pushing against water (forward movement), changing direction of movement and keeping balance. Blade of the variable resistance paddle is made of movable plates which during movement of the paddle in one direction are raised due to water resistance-in that case blade of the paddle is open and resistance in water is minimal. With the change of direction to opposite they swing back by up to 90° and assume vertical position in relation to water surface-in that case blade of the paddle is closed and resistance in water is maximum. In order to facilitate the use of the paddle its blade is of such positive buoyancy that it floats freely under water surface. In the model design the movable elements of the paddle's blade are made from material of negative buoyancy and are attached horizontally on the carrying frame and the required buoyancy is achieved by attaching floats to the blade. The paddle with the operation described above may be used instead of a traditional paddle, e. g. in a row-boat.

Nevertheless its application is indispensable for the use of variable resistance water skis to which purpose it has been designed.

Description of figures.

Fig. 4. Open blade of variable resistance paddle (movable plates raised)-minimal resistance in water.

F-frame of the paddle's blade G-axis of the movable plate H-movable plate I-socket for axis of movable plate J-stopper of movable plate opening-its purpose is to hold the plates in such position that during the movement of the paddle in the opposite direction they close in the same required direction thus making solid whole K-closed stopper of the last plate-for the other plates this function is performed by the top edge of the next plate L-shaft of the paddle M-active joint with a positioning blocking joining the shaft with the blade and which enables their relative positioning at the required angle N-float of the paddle Fig. 5. Closed blade of the variable resistance paddle (movable plates down) -maximum resistance in water.

Fig. 6. Schematic figure of variable resistance paddles operation for variable resistance skis use.

Fig. 7. Schematic figure of variable resistance paddles for a row-boat use (without floats).

The variable resistance skis and paddles described above were constructed in accordance with the shown figures. They proved to function well in practice. The variable resistance water skis ought to be characterized by displacement and dimensions adjusted to the weight and height of the person using them. The assumed application of the variable resistance skis with variable resistance paddles is recreation and sport, opportunity of summer practice for winter skiers and occupational therapy.