[TowerTalk] Self-supported tower designs

[Máximo EA1DDO_HK1H]

Hi all,

I am thinking to build a self-supported tower for my HK1H´s station.
The tower could be around 25 meters high. Four sides
Thinking in something like this;

http://3.bp.blogspot.com/_umpsa6tUB2I/SoPi1PjpbtI/AAAAAAAAABk/9DQ2BrH3jek/S660/PANORAMICA.JPG

or this one;

http://farm1.static.flickr.com/98/383631062_89cc03d2f0.jpg

What I need is a design layout to know what size pipes to use.
Anyone knows where can I found them?

Thanks

73, Maximo - EA1DDO & HK1H