[TowerTalk] ridge top derating factors

[Lonberg, Hank]

Dave:

There is no "right de-rating" factor. What you might do is to research
similar geographic locations that have weather data available. Call the NWS
and see what they have. I think they also have a web sight. Look for
locations with similar terrain layouts in California and use that as a basis
for the design wind. On the Oregon Coast it is not unusual to use 120 mph as
a design wind velocity depending on the type of installation and local
geography. I would think a 100+ mph velocity would not  be out of the
ballpark. 

Hank / KR7X P.E.


	-----Original Message-----
	From:	Curtis, David B [SMTP:david.b.curtis@intel.com]
	Sent:	Wednesday, April 12, 2000 12:14 PM
	To:	TowerTalk
	Subject:	[TowerTalk] ridge top derating factors


	EIA-222-F lists Mariposa county California as an 85 mph county, 85
is lowest
	possible.

	But... I have a ridge-top location. Therefore, I need to derate for
wind
	acceleration over the ridge. I've read Leeson's book and done some
other
	research, but it is not straight forward and I couldn't convince
myself that
	I know how to calculate the correct derating factor. So, my question
to the
	group: How can I arrive at the right derating factor?

	73, Dave N6NZ


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