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Aerodynamics on cats?

Old 01-27-2003, 12:24 PM
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Default Aerodynamics on cats?

There was a thread a few months back regarding aerodynamic lift on cats, ground effect, lift, angle of attack, etc.
Anyway, I was wondering how much additional lift you could generate with a wing at the bow between the sponsons. It seems to me that a front wing and tunnel tab extension could be a good way to generate a little more lift for a heavy cat (ie. chris cat).
Specs: 4' wide, 1' long, variable angle, 100mph top speed.
Gary
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Old 01-27-2003, 09:45 PM
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i think you have a good idea but how would you test it also i wonder if that part of the boat would support that kind of stess lifting up from that point
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Old 01-27-2003, 10:54 PM
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They make them for drag boats to keep them from blowing over. Just the opposite.
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Old 01-28-2003, 06:42 AM
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Rough calculation.

Max wing CL ~ 1.0
100 mph q = 25 psf
area = 4' x 1 ' = 4 sq ft

max lift = 100#

CL=.7 (70#) would be a more practical value.

-Greg
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Old 01-28-2003, 08:25 AM
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Thanks for the info Greg. 70 lbs probably is not worth it for the lift alone. May be useful as a trimming devise. Dont unlimited hydros run a variable forward wing?
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Old 01-28-2003, 12:18 PM
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Yes, but they are really set up to plant the nose suddenly, and also "spoil" the airflow over the rest of the hull(deck) to kill off the lift from the main hull body, which you can do by giving a quick kick to the wing and letting it's wake dump over the deck.

Lift varies as the square of speed, so 200 mph is 4 times the force. Still not much for an 8000# offshore, but quite a bit for a 1500# hydro. If you go to multi-element sections like the top fuel cars do you can get the CL part of the equation up to about 2.5, but at a lot more drag.

-Greg
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