Tony Goetz wrote:

> The test section is a 17" cube. It's a suck down tunnel, with the diffuser
> opening up to te 27" diameter of the 1/4hp fan we have. We're not entirely
> sure how fast it should go, but a rough (very rough) estimate is 40mph. We
> finished the diffuser Friday and hooked up the fan. Now we can truthfully say
> that our project sucks! We're quite happy with it. Building a pitot tube is
> not out of the question, but being sure it's producing accurate outputs is
> kind of questionable. I'd be very interested in the designs you've built and
> how they work.
>
> I'm a bit uncertain about linkages for measuring the forces acting on the
> models, though. We're planning on at least testing a few wing sections, which
> are seemingly easy if mounted on a lever protruding out the side of the test
> section. Still, it would be nice to have a few complete models to test, and I
> do'nt know how good that setup would be for them. Searches online haven't
> revealed much regarding how professional wind tunnels mount test articles.
> Can you lend any advice in this area?
>
> On a side note, if anyone's interested, I've built up a typical WWI airfoil,
> based on an Albatros D.V wing, and will also make sections of general
> aviation, airliner, laminar flow, and high speed wings to investigate their
> characteristics at low speeds.
<some stuff snipped>

Tony, As far as the pitot tube... Run the pitot through the wing so
that the open end is flush with the "upper surface". Connect it to a
tube with water and slowly bring up your "airspeed". You should see the
water in the measuring tube start to rise as the pressure decreases over
the wing surface. Your measurements in inches of water should be pretty
accurate. Then at constant "airspeed" you can vary the attack angle
of the wing and measure the variance of the pressure over the wing.
The kids should be able to figure the forces based on the mass of
the water lifted in the measuring tube.

Jim

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