Dolphin Address 35
August 12th 2005
Life in the water has its adaptations. In DEA 27 I described the remarkable water repellent ness of the dolphin's skin. The photographs in 'Dusty water' bear witness of this. The following subject may require a little more of your spatial imagination.
Like gravity has a decisive influence on the human condition and the resistance of air is a generally negligible factor, this is kind of reversibly true for the dolphin. The body of the dolphin is streamlined to move through the water efficiently. It minimizes water resistance. Generally she drives herself in length and the pointed rounding of her beak 'opens' the water that further flows by with a minimum of slackening eddies. Moreover the peduncle (or tailstock) is flattened on either side so it can be moved up and down with minimal water resistance. The leading edges of the pectoral fins and the fluke are rounded, again to facilitate passage.
For the dolphin gravity plays a part of minor importance. This is almost cancelled out by the buoyancy that results from her water displacement. The Archimedes effect. Sometimes we lay face to face at the surface and then she lets herself sink straight down without any movement of the fins. I am not sure how she does this, but I think she decreases her body volume by pulling in her chest. Her body weight remains unchanged but her buoyancy diminishes just enough to make her sink.
The very same water resistance that she conquers with her streamline, she needs as a push off for her propulsion. In a flowing movement she tilts her fluke in the up and down stroke. Thereby she pushes herself off against the water resistance. The waterwing and the monofin make use of the same principle. The dolphin harmonizes an apparent contradiction: she utilizes the resistance for propulsion. It is of course incalculable, but to inspire the imagination one might estimate that if we would know how to deal with gravity like this, we effortlessly would be able to jump over a house.
When she accelerates it becomes apparent how inside the length of her body she has yet another way to push off. The fluke moves simultaneously up and down with her pectoral fins. I like to compare this with the moving of a heavy case. When you push that away with your back against the wall, you can exert much more power than without a wall. She like takes the wall with her. This is also one of the properties of the waterwing. By its resistance in the up and down direction you can put more power in the monofin and/or reach a higher frequency of strokes.
Once her body is moving the dolphin uses her pectoral fins and her fluke to steer and to break. This you can roughly compare with a car that steers with both fore- and rear wheels. Thus she can choose her trajectory to extreme precision. Also she tilts her body sometimes in a curve, shifting her fluke out of the horizontal position and letting it effectuate sideways.
She breaks by more or less positioning her pectoral fins across the swimming direction and by holding her fluke in down stroke position. This way she can even swim backwards by pushing water forward.
Finally she can use the sideways flattened peduncle by pushing water backwards, much like a fish does.
Except for an enormous propulsion power the dolphin commands an arsenal of finer locomotion. Her streamline is so absolute that she can move through the water almost without resistance under any desired angle. Years ago this inspired me to the following lines:
I lay myself in the arms of gravity
the water carries me and my body smiles.
How lovely it is to be a dolphin.
She comes the closest to my ulti mate.
Jan Ploeg, Meadow Fanore, August 12th 2005
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