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Old 08-27-2013, 07:28 AM   #32
ApS
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Lightbulb Physics—It's the LAW...!

Quote:
Originally Posted by ITD View Post
Interesting theory APS, how much will my 26 foot bow rider affect the speed of the current?
It's not a theory, and it can be measured—but first—think of it this way:

If 100 cubic yards of "fill" were added to the channel bottom, would the speed of the current change?

Now take the displacement of all the boats in the channel, and think of that as "fill"—but at the top.


The more engines a boat has—the deeper the "V" of the hull—all that displacement has to be "displaced" to somewhere else—effectively, narrowing the channel.
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To measure the effect of your boat, put your GPS in a Styrofoam cooler, and float that GPS down a measured course—say, a hundred feet. Record the speed of the current. Then anchor your 26-footer in the channel, and measure the current with the same floating GPS device. You can expect the GPS to record a faster speed. Apply that reasoning to a large number of boats: that they're in motion is insignificant.

If the channel were narrow enough, you can see even a canoe can affect current speed. (And why I advocate starting one's boating-experience with a small boat—even building one—not jumping in with an over-sized boat).



Quote:
Originally Posted by VitaBene View Post
You are not saying that a 40' cruiser will change the speed of the current in the Weirs channel in any appreciable way, are you?
It would, but not to the same measure as a 40-foot rowing scull. It's displacement that counts—not length.
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