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ContinuousWave: The Whaler GAM or General Area
Shark Week on Discovery
|Author||Topic: Shark Week on Discovery|
posted 08-13-2001 10:10 AM ET (US)
I was watching shark week last night when they mentioned that the roughness of a sharks skin enabled it to travel through the water more efficiently (I always wondered why they were not slick or slimy). In fact they stated the US submarines have adapted the use of a rough surface on the exterior of the hulls in order to make them more efficient. It was also mentioned that some racing yachts also use a rough surface on the bottom of the hull. Does anyone know the science behind this? Is anybody out there using this technique on their Whaler?
posted 08-13-2001 10:30 AM ET (US)
Thanks for your update, now I can return all of the paint remover I was going to use on my mottled bottom paint!
posted 08-13-2001 10:43 AM ET (US)
I have heard 2 different opinions on smooth bottoms. 1 is if you wax(slimy)the water beads like a car hood and the air bubbles slow you down. 2 is waxed bottoms are more efficient. I believe in the do not wax theory because it saves me time.
posted 08-13-2001 11:04 AM ET (US)
the micro-turbulence engendered by water friction is decreased when it remains confined in the grooves of sharks (skin)..same theory should apply to boats..keep in mind a sharks "skin" is like your beard..smooth toward your tail (bone) and rough toward your head. Isn't mother nature a genius? :)
posted 08-13-2001 11:18 AM ET (US)
The whole purpose is to increase laminar flow, and reduce turbulant flow. On experiment on subs used the "goo gun," which squirted viscious goo out of the bow of the sub to increase top end speed. There was a news report in June of a Russian rocket propelled torpedo which used the same technology.
Very cool stuff.
posted 08-13-2001 11:53 AM ET (US)
BS - Air bubbles slow you down? Try running through water, then run through air. Which is easier? Easier means less friction, which in turn means faster. But I like your no wax theory for the same reasons you stated.
posted 08-13-2001 12:12 PM ET (US)
Water beading on a waxed surface is created by friction. Ergo, waxing below the waterline is creating undue friction. Racing sailors will use nothing but one of two methods for finishing below the waterline: wetsanding and teflon. A lot are wetsanding their teflon applications.
In all of the one design racing I've done over the last 30+ years, I've never seen a race decided by the boat's wetted surface. Of course, no one will deny that they'll do whatever is necessary to win or gain an advantage, and still be legal.
posted 08-13-2001 01:20 PM ET (US)
I always though water beads on a car because of the surface tension of the water is stronger than the friction between the water the surface. I don't think that there could be much friction between the water and the surface when I recall how quickly the water runs off the surface when you drive down the road.
posted 07-02-2003 01:25 PM ET (US)
"I always though water beads on a car because of the surface tension of the water is stronger than the friction between the water the surface."
This is correct. as to a rough surface haveing less friction, that is not true. A sharks skin is faster not because it is rough, but because of its particular SHAPE. Water molecules moveing against other water molecules have less friction that against MOST other surfaces. Therefore if a surfaces SHAPE promotes water to adhere to it instead of traveling along it or pushing against it, then the MOVEING water is traveling along a "skin" of water and not the object itself.
posted 07-02-2003 03:02 PM ET (US)
Do you guys remember the last summer olympics? All of the swimmers, male and female traded in their speedos for "sharksuits" that looked like overalls. The idea was that the rougher skin grabbed the water better, they also scuff up their hands on the cement before diving in, and shave their body hair right before a race so as too leave their skin rough. Now I can understand why a swimmer would want the rough surfaces to push hrough the water but I can't understand why a rougher boat bottom would increase speed.
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