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Re: [TowerTalk] Guying a self-supporter

To: towertalk <>
Subject: Re: [TowerTalk] Guying a self-supporter
From: Steve Maki <>
Date: Sun, 09 Nov 2008 18:48:13 -0500
List-post: <">>
jimlux wrote:

>> I wish I could justify the purchase of one of the finite element 
>> analysis programs, but I know they're not cheap...

> There are lots of free FEM programs out there.(FeLT and GRAPE spring to 
> mind)  The real challenge is in having the expertise to effectively use 
> them. Also, free usually implies non-user-friendly interface (for casual 
> users).. just like for NEC.
> And, just like for NEC, the devil is in the details.  Are you going to 
> model the details of the bolted joints or use some reasonable 
> approximation? Are you going to model the L section as a simple beam 
> with specified parameters, or actually the details of the L.
> It's much worse with structural FEM than for ElectroMagnetic.. In EM 
> modeling, it's a conductor with specified properties, and generally 
> isotropic, and there's no concept of "bending".  In structural, a beam 
> has torsional, bending and shear, and they're different in all 
> directions and coupled to boot.
> There's a reason that introductory texts talk about idealized beams with 
> uniform cross section in axial compression, tension, or simple bending 
> or torsion only.

I took a look at those two, and it's obvious there would be a steep 
learning curve.

I'd like to have one of the custom tower packages, like Tower, 
RisaTower, or Guymast, but they start around $3k. I imagine these 
programs are like EZNEC in that they are elegant GUIs on top of a 
standard FEM engine.

Steve K8LX

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