steeply angled they are, you could use elementary aeronautics equations
for flat plates. The lift is proportional to the angle of attack (angle
to roof plane, I suppose, here), and the center of pressure is 25% back
from the leading edge. The lift is something like 2 x pi x alpha x
stagnation pressure. That's only good for angles up to about 25-30
degrees if I remember correctly, then the plate will "stall" and it
starts to look more like a drag element with Cd approaching 2. A first
year aero book, like Bertin & Smith (Aerodynamics for Engineers) covers
the basics if you're willing to wade through - or gloss over - the N-S
equations to get to the simplified answers for your case.
Jordan
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