[TowerTalk] Wind Surface Area estimates

[Gene Fuller]

Unless you're a Sam Harris disciple (if it stays up more than a year it was 
over designed), it's hard to be too cautious when you consider the possible 
combination of factors such as ice and wind, resonances, pulsing gusts, etc. 
That's why I designed my LP for 100 mph with 1/4" of ice and threw in an 
extra 10-20% safety factor. It  would be impossible to design that way if 
you had to be commercially competitive but the LP has been up a for 12 years 
and I sleep well on those windy nights, at least one of which was reported 
to have been 75-100 mph.
Gene / W2LU

----- Original Message ----- 
From: "Jim Lux" <jimlux at earthlink.net>
To: "Gary Slagel" <gdslagel at yahoo.com>
Cc: "TowerTalk" <towertalk at contesting.com>
Sent: Friday, March 09, 2012 2:21 PM
Subject: Re: [TowerTalk] Wind Surface Area estimates


> On 3/9/12 10:32 AM, Gary Slagel wrote:
>> Shoot... using the .707 figure for 45 deg I'm back right at the worst
>> case scenario. Where does the .707 come from?
>
> cosine (45 degrees)
>
> That's the projected area in the direction of the wind coming from 45
> degrees off axis.
>
>
>
>> I was using a simplified version of windload calcs from the force 12 web
>> site that goes something like '..wind load is either the total element
>> wind load OR the boom windload, whichever is the larger resistance to
>> the wind....'.
>
>
> That's probably not a very valid approach.  Some sort of "projected
> area" is more valid, but neglects the skin friction along the axis of
> the tube.
>
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