Need help with Fluid Mechanics equation

I am trying to design a "fin" for my water rudders for my experimental
floats. I need the equation for the amount of forces exerted by water
going 0-50mph on a flat surface at right angles to the water flow. It
would be dependent on the speed of the water, the depth of the fin and
the angle of the fin to the water. I am hoping one of you tech types
in homebuilt might know how to find this equation. The reason I want
the equation, and not just the answer, is I want to be able to fool
around with location of this fin to find the best spot. I have a
degree in Electrical Eng, and had a course in statics, but I never
took Fluid Dynamics. Hopefully the equation is not too complicated.

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-----water flow--- |-----Need force F
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side view of fin

Doug