"Joseph Gwinn" wrote in message
...
In article ,
"Vaughn" wrote:

[snip]
Here in Florida, 90+% of the homes are built to the strict S. Florida
building code which (I believe) is based on surviving a 120 MPH wind, which
is
only a mid-sized Category 3 hurricane. With a Category 4 hurricane you can
expect "...extensive curtainwall failures with some complete roof structure
failures on small residences". I believe a rough rule of thumb is that
damage
doubles for each additional 10 MPH wind speed. A class five hurricane has a
minimum wind speed of 155 MPH! You do the math.

Aerodynamic forces (lift and drag) vary as the square of wind speed, so
going from 120 mph to 150 mph raises the forces by a factor of
(150/120)^2= 1.56 to one.

Thanks, but I did not say that the force doubles for each 10 mph, I said
that damage (measured I suppose in $) doubles. I have heard this repeated by
meda weather people numerous times, and cannot offer a specific reference. I
can, however, mention two factors at work he

1) At a certain speed the wind starts picking up debris and flinging it against
structures. Lower than that speed and it does not generally happen. This is
why the South Florida building code now requires doors and windows to be missile
resistant (the famous 2 by 4 cannon).

2) Once damage to a structure starts, it tends to multiply quickly. One
breached window can result in the eventual loss of the structure.

Vaughn

Ref: http://www.av8n.com/how/htm/4forces.html

Joe Gwinn