Towertalk
[Top] [All Lists]

## [TowerTalk] Antenna surface area

 To: [TowerTalk] Antenna surface area kr7x@gte.net (Hank Lonbeg) Sun, 10 Jun 2001 10:11:20 -0700
 ```Time Out everyone: All this talk about integrating and double integrals has given me a head ache. As defined in the Building Code I know the most about ( the UBC), the surface area exposed to the wind is the plane projected area normal to the wind direction under consideration. For a flat plate of W width and L length with the W dimension normal to the wind the projected area is the width W times the length L. It is really that simple. A cylindrical member of diameter D and Length L has a projected area of L X D. Any modifiers to the projected area are used to describe the effects of shape and size(the Reynolds number or Froude number) to the air mass moving over the particular element. At the normal range of element sizes and distances between elements it is safe to assume that the elements do not shade each other and that the total projected area is the sum of the elements and any connnection items that have an normal area in the same direction. The same is true for wind normal to the boom which might have a shape factor coefficient because it is of large enough diameter. (The UBC uses 1.0 for elements less than or equal to 2" in diameter and 0.8 for cylindrical elements large than 2" in diameter.) This method is used not only for towers but is used for buildings and other structures to determine their design loads. You must remember that all these loads are approximations of the real world and are not exact numbers. Use the most significant digit analysis and realize that any wind load numbers you come up with are really only significant to the nearest 5 or 10 pounds anyway. What the manufactures need to do is to publish the antenna areas as the projected area to the nearest 0.5 Square foot and be done with it. It really makes no sense for them to publish wind load information in Pounds Force at some wind velocity because they normally don't publish the height and method of calculation and other assumptions for that load. It is meaningless without the additional information. In reality considering a triangular open trussed type tower system, unless it is extremely short, the wind load on the tower is the largest force in the system, not the wind load on the antenna. The absolute antenna load is most important for the selection of the mast materials and size and of course the load capacity of the rotor. 73 and happy calculating Hank Lonberg P.E. / KR7X -----Original Message----- From: owner-towertalk@contesting.com [mailto:owner-towertalk@contesting.com]On Behalf Of Tod - Minnesota Sent: Sunday, June 10, 2001 8:33 AM To: towertalk@contesting.com Subject: RE: [TowerTalk] Antenna surface area Wasn't the original purpose of this discussion to allow someone to put together a tower and antenna system that would neither blow over in the wind nor be 'crushed' under its own over-designed weight? If we use equations that calculate forces and torques that are high (two times or even three times high), aren't we simply adding a safety factor to the overall design? It is really hard to work DX when you spend all of your free time calculating wind loading. At some point I would think we would have a sufficiently good set of equations and models to allow quick, safe values to be determined and then we can get on with the assembly, hoisting and maybe even use of the antenna system. Tod, KØTO List Sponsor: Are you thinking about installing a tower this summer? Call us for information on our fabulous Trylon Titan self-supporting towers - up to 96-feet for less than \$2000! at 888-833-3104 www.ChampionRadio.com ----- FAQ on WWW: http://www.contesting.com/FAQ/towertalk Submissions: towertalk@contesting.com Administrative requests: towertalk-REQUEST@contesting.com Problems: owner-towertalk@contesting.com List Sponsor: Are you thinking about installing a tower this summer? Call us for information on our fabulous Trylon Titan self-supporting towers - up to 96-feet for less than \$2000! at 888-833-3104 www.ChampionRadio.com ----- FAQ on WWW: http://www.contesting.com/FAQ/towertalk Submissions: towertalk@contesting.com Administrative requests: towertalk-REQUEST@contesting.com Problems: owner-towertalk@contesting.com ```
 Current Thread [TowerTalk] Antenna surface area, (continued) [TowerTalk] Antenna surface area, Bill Hider [TowerTalk] Antenna surface area,