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Which boat is faster?? Hypothetical ?

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Old 01-24-2003, 11:01 PM
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Question Which boat is faster?? Hypothetical ?

Two Cats, both identical power, weight, drives props, trim everything the same.
Boat 'A' runs a marked course for one mile, flat water conditions, zero wind.
Boat 'B' runs the identical course for one mile, flat water, but a 20 mph head wind kicks up.

Which boat is faster?

1)The racer states; "Boat 'B', my cat is faster into a head wind, this causes lift, thus making the boat faster."
2) A Physics instructor states "Boat "A", allthough there may be lift, it still takes more energy to push a boat into a head wind." If you take this to an extreme and had a 100 mph wind, the boat would get plenty of lift, but the wind does not contribute to the lateral energy needed to push the boat foward."

So What boat is faster? Who is right, the racer or the physics instructor?????

Last edited by Fast Shafts; 01-25-2003 at 04:00 PM.
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Old 01-24-2003, 11:04 PM
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I think the boat "A" is faster and the physics instructor is right.
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Old 01-24-2003, 11:11 PM
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I agree ,
Boat A would be faster If the speed was there .
 
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Old 01-24-2003, 11:18 PM
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The "B" boat may be faster since the water is no longer flat;
the drag maybe lower
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Old 01-24-2003, 11:22 PM
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Okay, so they are not identical
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Old 01-25-2003, 12:15 PM
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You need to add in the chop factor that causes less water resistance. When Iím cruising at 70 Ė 80 on flat water and go around a bend where I head into the wind and a good chop, I pick 2 - 4 mph. Iím sure the cat guys in Cincy run into this all the time.
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Old 01-25-2003, 03:53 PM
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In the "hypothetical' model, the only thing that changes is the head wind.
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Old 01-25-2003, 04:05 PM
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Dont some cats run faster with a head wind while some run slower?
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Old 01-27-2003, 12:15 AM
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I have heard of cats running faster into a head wind also. The happens because the headwind packs more air under the boat, creates more lift and less resistance.
I think if the boat is set up perfectly to begin with it should be able to pack enough air under it already to get max lift, so the head wind wouldn't matter.
In the case of a perfectly set up cat, it should be faster down wind. I think Perfection is very rarely achieved though. Its also going to depend on the wind resistance and aerodynamics of the boat in question. It might be faster with a 10 mph headwind that packs X amount of air, but a 30mph headwind might create too much wind resistance and make the boat slower.
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Old 01-27-2003, 03:11 AM
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Quote:
Originally posted by Griff
Its also going to depend on the wind resistance and aerodynamics of the boat in question. It might be faster with a 10 mph headwind that packs X amount of air, but a 30mph headwind might create too much wind resistance and make the boat slower.
I agree.

Iím sure that not all makes/models have the same Cd (Coeffient of drag - both aerodynamic and hydrodynamic).

When the hydrodynamic drag is reduced as the tunnel packs air and it becomes less than the aerodynamic drag on the boats frontal area (deck leading edge, sponsons, windscreen/canopies, etc.), only then can a speed benefit be realized.

One problem is aerodynamic forces are proportional to the square of the speed. Obviously, that means you quadruple the drag as you double the speed. The faster you go, the tougher it is to overcome and I would presume there is a theoretical limit to any efficiency gained.
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