I'm setting up a new tower with an F-12 C-31XR (effective area 1 sq. m)
mounted 200mm above the thrust bearing, and a Delta-240 (effective area
0.4 sq. m) mounted 2m above that. I've calculated the total moment at
the thrust bearing (including mast drag) as 1517 Nm for 160 km/hr wind
speed. For 40mm schedule 80 pipe (OD 48.26mm, ID 38.1mm), the required
yield strength is 225 MPa. The local steel supplier stocks this tubing
in two material grades, 304L and 316L. They have similar yield strength
(310 MPa for the 304L, 300 MPa for the 316L). 316L is a chrome/moly
steel, while 304 is a plain chrome stainless. The manufacturer says the
316 provides better corrosion resistance in marine environments; however
this is not important as I live 500 km from the coast. Is there any
reason to go with the chrome/moly 316, which is about twice the price,
instead of the plain stainless 304?
Many thanks and 73
Andrew ZS6AAA
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