Way back when I was in engineering school studying aero- and fluid
dynamics (and when a 15" Regina sold for $350.00), I amused myself
by figuring out what the maximum velocity of the wind-sheet out of
an organ pipe's flue would be, given reasonable wind pressures of
4" to 6".

I was shocked to find that it could achieve 70 miles per hour, just
short of hurricane force!   And human lung pressure through a straw
can make a tiny tornado!

This lends credence to the statement made recently, about the upper
lip edges of wooden pipes being eroded away by decades of "dirty" air.

Mike Knudsen