The material used in the
construction of Jewell Windmills is ASTM A526 grade sheet steel.
The Ultimate Tensile strength ranges from 42,000 – 54,000
psi. The blades and tail vane is constructed from 16 gage (0.059”
thick) steel, twice as thick as the 20 gage (0.0359”)
used by the original windmills! The blades actually increase
in bending strength by a factor of 4 when the thickness doubles!
This is definitely advantageous in a hailstorm! The framework
utilizes 11 gage (0.1196”) steel and most other components
are 14 gage (0.0747”).
A Galvanized proactive layer serves two
main corrosive protective functions; Barrier and Sacrificial
Protection. The barrier protection refers to film that stops
oxygen and corrosives from reaching the steel surface. In addition
to the barrier, the application of zinc supplies a ‘sacrificial
anode’ for protection to the steel. Zinc has a higher
electro-chemical potential (more active) then steel. When zinc
and steel are in contact in an electrolyte, the zinc corrodes
in preference to steel which is protected. It is this feature
that enables zinc to protect steel at cut edges.
The heavy Z700 galvanized protective
coating used on Jewell Windmills is the thickest commercially
available! Z700 designates that 700 grams per square meter of
zinc is applied to the steel (both sides combined). This is
nearly triple the Z275 (G90) coating thickness you would find
on galvanized Roof and Siding applications and even heavier
then the Z610 coating on corrugated steel pipe culverts!