Cat Length question
Theoretically, shouldn't a 38' Cat be able to pack more air underneath than a 37' 9" Cat assuming everything thing else is equal? I realize we're talking about a minuscule difference. But is there any reason the boat that's 3" shorter would be faster if everything else was equal?
Looking for technical responses please. No BS, No polotics. Please. |
Re: Cat Length question
Okay, I'll play. Theoretically a 37'9 1/2" boat could have less wetted surface in the water and be faster-overcoming the decrease in possible lift. Remember that most boats only have a fraction of the hull wetted-esp cats. Assuming a 2 foot wetted surface at speed the 2.5 less inches would have a much greater effect than 2.5 inches of a lift area that is 30 plus feet long. So there ya are...thanks for playing.
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Re: Cat Length question
The width, height and funneling of the tunnel will also effect the amount/velocity of the air underneath the cat.
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Re: Cat Length question
Originally Posted by insptech
Okay, I'll play. Theoretically a 37'9 1/2" boat could have less wetted surface in the water and be faster-overcoming the decrease in possible lift. Remember that most boats only have a fraction of the hull wetted-esp cats. Assuming a 2 foot wetted surface at speed the 2.5 less inches would have a much greater effect than 2.5 inches of a lift area that is 30 plus feet long. So there ya are...thanks for playing.
but to answer the question, tunnel length and boat length aren't mutually exclusive...a longer cat won't pack more air unless it has a longer tunnel....and if a longer cat has a longer tunnel, it also has more weight to lift now... kind of a viscous circle... |
Re: Cat Length question
I don't know where the 2.5" is coming from, whether it's the tips of the sponsons or the transom which would affect the tunnel and airfoil, but either way we're talking about a difference of 0.5%. Say it is in the tunnel area, lift and drag behave linearly with surface area as defined by L (or D)=1/2 * rho * V^2 * S * Cl (or Cd), where rho=density, V=velocity in fps, S=planer area in sqft, and Cl=coefficient of lift (or drag). Again, 0.5% differences...maybe.
After running a quick CFD comparison, I see no appreciable difference. |
Re: Cat Length question
Originally Posted by CigDaze
I don't know where the 2.5" is coming from, whether it's the tips of the sponsons or the transom which would affect the tunnel and airfoil, but either way we're talking about a difference of 0.5%. Say it is in the tunnel area, lift and drag behave linearly with surface area as defined by L (or D)=1/2 * rho * V^2 * S * Cl (or Cd), where rho=density, V=velocity in fps, S=planer area in sqft, and Cl=coefficient of lift (or drag). Again, 0.5% differences...maybe.
After running a quick CFD comparison, I see no appreciable difference. |
Re: Cat Length question
Is being 3" short going to give ANY advantage? Does it have ANY disadvantage?
PS - Hello to my old friends Uncle Teddy :evilb: and Nick :drink: |
Re: Cat Length question
Originally Posted by Sean H
the 2.5 inches in question is overall boat length from tip of sponson to the top of the transom... there is no set length for tunnels...
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Re: Cat Length question
Originally Posted by MarkMathews
Is being 3" short going to give ANY advantage? Does it have ANY disadvantage?
PS - Hello to my old friends Uncle Teddy :evilb: and Nick :drink: |
Re: Cat Length question
Life is good.
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