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

Tailpiece

 "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."

Pay attention to the tides

I’VE NOTICED that many beginning sailors pay less heed to tidal currents than they should. I guess that in these days of reliable, powerful auxiliary  engines, tides don’t come into their calculations much. Tides are regarded as being irrelevant, or at most, a little irritating.

But even if you could rely implicitly on your engine, you should know about the huge effect tides can have on a boat under sail alone — because sooner or later your trusty engine might develop a hissy fit and thumb its nose at you.

So, let’s say there’s a nice steady breeze and you’re making 6 knots through the water. If a 3-knot current is flowing against you, you’ll make only 3 knots toward your destination. If that same 3-knot current is flowing with you, you’ll make 9 knots toward your destination. If you’re not impressed by the difference between 3 knots and 9 knots (or three times the speed), you should be.

Tidal currents vary tremendously from place to place and time to time, so, if you sail, you badly need to know what the current is doing to you. You can get that information from annual tide and current tables for your area, either in book form or from the Internet.

It’s no good trying to guess. Looking over the side or spitting in the water isn’t going to tell you which way the current is going, or how fast. But a GPS receiver will indicate your speed and direction over the ground. By the simplest arithmetic you can compare this with your speed through the water, either taken from your regular speed indicator or estimated by shrewd guess, to find the speed of the current.

So, if your engine has the sulks, work the tides. Anchor until the worst is over, or work the close-shore reaches where counter-currents and back-eddies often prevail.  Tides come in two varieties. They’re either for you or agin you. Make sure you know which is which.

Today’s Thought

The ebb will fetch off what the tide brings in.

— Thomas Fuller, Gnomologia

Tailpiece                                                             

“Boy, I’m always grateful I wasn’t born in France.”
“How come?”
“My French is so lousy they’d never understand me.”

^{(Drop by every Monday, Wednesday, Friday for a new Mainly about Boats column.)}

How power corrupts

I CAN'T BEGIN TO COUNT how often I have heard the owner of an older displacement sailboat 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 down.

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

Tailpiece

 "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 nightie and lay down on the sofa. Then she turned out the lights — so I came home. I can take a hint."

(Drop by every Monday, Wednesday, Friday for a new Mainly about Boats column.)