In article ,
brian whatcott wrote:

Alan Baker wrote:

I have never noticed the fabric lifting on my wings, however I have
seen the fuel siphon out of a wing tank due to an improperly applied
fuel cap.
And greater pressure in the tank than outside of it...

/snip/
So, yes, the greater pressure inside the tank is pushing the fuel out.

Hmmm...it probably goes more like this: there's a 100 mph? wind past an
open port, with some venturi effect certainly, but plenty of
turbulence. If you beat up the surface with a gusty blow, it gets
wavelets which can lap the filler and blow out the fuel.

How about it? It still doesn't change the physical reality that air
doesn't *pull* on the wings.



You're still singing the last hymn, Alan.

We are now discussing how an open tank, with a 100 mph wind blowing over
its top, can lose its fuel over the top. Do you think the tank has
GREATER pressure due to the venturi effect of the airflow?

No. I think that the venturi effect lowers the pressure below the
pressure that already exists in the tank. Contrary to what the PP wrote,
a tank cannot be sealed if you are to pump fuel out of it. If it were
the pump would have to work against a rising pressure difference as it
removed fuel from the tank. Hence we know the tanks pressure must be
allowed to equalize.

If the pressure over an open filler is less than that in the tank -- and
assuming the filler is not simply pulling from the air/fuel vapor
mixture, then it will pull fuel from the tank if the pressure difference
is sufficient to lift the fuel the from its level in the tank to the
level of the open filler.

But it is being *pushed* out by higher pressure inside, not pulled.

--
Alan Baker
Vancouver, British Columbia
http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg