What would be the windload on a 30 ft height by 21 ft wide pylon sign.
How far into the ground would 14" sq tube post go?
Karen

I can't tell you exactly the specs. But on a telephone pole the rule of thumb is the heght divided by 10 and add 2 feet so 20 foot 10 goes in twice = 2 feet and add 2 more feet. I'am not an engineer. You have a big kite there. Sorry but have a nice Holiday

What you need to do is calculate the EPA, Effective Projected Area, for windloading, and then learn what the average wind speed in the location of the sign.

Start here, and do a web search for Effective Projected Area for other sites to help you.

Calculating Effective Projected Area (EPA) (http://www.sabresitesolutions.com/towerDocs/EPA.htm)

Pressure per unit area may be calculated by
p=1/2*a*^V
Where, p= pressure per nuit area in Psf, a= sprecific density of air and V= velocity of wind in MPH.
This further shortened as p=0.00256*^V.
This pressure multiplied by area of the element exposed to wind in SqFt, Cd = Coefficient of drag, for flat area is considered as 1, may give the force exerted by wind in Pounds on the sign board.
More the height more the speed of wind.
Bala