July 18, 2016

Current and speed over ground

HOW OFTEN have you heard a boat owner say: "I need more power to fight the current.  I need a bigger engine."

Whenever I hear that, I know this is not a true sailor talking. This is a land person, not a water person.

Land persons know about power in cars. More power enables a car to go uphill faster. With enough power and low-down torque, you don't even need to change gears.

Land persons appear to equate a boat struggling against a current with a car going up a hill, which is something a natural-born water person never does.

Water persons are blessed with a natural affinity for sensing the speed and direction of their craft. They can "feel" movement that they can't see. Something deep down inside tells them they're also going sideways or even backwards when it looks as if they're going straight ahead.  They know without ever having to think about it that the thin sheet of water they're sailing in is often moving with respect to the ground beneath it because of a tidal stream or an ocean current.

They know when they are steaming upstream against an ebbing river that the current they're fighting is not the same as a hill on a highway. Their speed through the water does not decline, as an underpowered car's does with respect to the road. It's the current that robs them of speed over the ground, not the lack of engine power. Always presuming, of course, that the engine is capable of pushing the boat at hull speed.

A bigger engine is not going to help, unless it's a whole lot bigger, because it takes an enormous amount of extra power to make a displacement hull exceed its hull speed by even a small amount.

This whole business seems to be quite difficult for land persons to comprehend, but I expect the manufacturers of new, more powerful engines are quite happy to let them remain ignorant.  And the water persons are quite happy, too, knowing that the land persons will always be the lubbers they suspected them to be.

Today's Thought
Our knowledge is a little island in a great ocean of nonknowledge.
— Isaac Bashevis Singer, NYT 3 Dec 78

 "Hey buddy, I thought you had a date with that blonde tonight."
"Yeah, I did."
"What happened?"
"Well, we went to her place and sat around and chatted and then she put on some quiet music and changed into her lingerie and lay down on the sofa. I guess she was ready to go to sleep. Then she turned out the lights — so I came home. I can take a hint."

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