[TowerTalk] Thoughts on towers suitable for my difficult location?

[Drax Felton]

If it's bracketed to the house then the house should already be on a stable foundation.  Why the expense of a PE  for a short 40 ft tower?  Use a hazer or tilt base and crank the darn thing down when a hurricane approaches.   

Sent from my iPhone

> On Oct 23, 2013, at 12:38 PM, "Your Name" <ks4tl at rodentranch.com> wrote:
> 
> I am trying to determine if it would be practical to safely install a 40
> to 50 foot free-standing or bracketed (not guyed) tower in my location.
> I would like to hear from anyone who has erected a tower in a similar area.
> 
> My location is Chincoteague Island, Virginia, Zip Code 23336. If I am
> reading the “three second gust speed” maps correctly, this location is
> in a 120 mph area on the Exposure “C” maps. However, the location is
> also about a quarter-mile from open water (an inlet off the Chesapeake
> Bay), so it is possible that it should be considered Exposure “D”. The
> location is flat and barely above sea level, with no significant
> features to obstruct wind.
> 
> The soil quality is about as poor as possible from a support standpoint.
> It is silty sand, and during the course of a year varies from dry/loose
> to completely waterlogged. It is also mildly salt-contaminated(from
> seawater flooding in 2012), and so rather corrosive. The ground water
> table is high - holes deeper than 3-4 feet tend to fill with saltwater.
> 
> One good thing: winters are relatively mild, frost depths never exceed
> an inch or so. Ice storms are rare. Icing would not be expected to
> exceed 1/4 - 1/2 inch at most, and ice storms have not been known to
> occur at the same time as high winds.
> 
> One final feature of the site: it is subject to tidal flooding during
> severe tropical storms and nor’easters. Every 2 or 3 years, the base of
> any tower at this site will be immersed for several hours in seawater,
> to a height of up to 4 feet. (Most houses here, if you are wondering,
> are elevated on pilings or perimeter walls.)
> 
> Guying of the tower is absolutely not possible. Bracketing to my
> residence (modern construction, concrete walls from the ground to four
> feet, frame above four feet) may be possible.
> 
> The total wind load of all equipment would be about 10 square feet.
> I would install either a K4KIO Hex-Beam, a 2-element Steppir Yagi, or a
> small tribander (Force 12 C-3S or similar) on the shortest practical
> mast at the top of the tower.  All of these have rated wind loads below
> 6 square feet. A medium-sized rotator (Yaesu G-800 SA or equivalent)
> would be used. I would probably also attach 1-2 fixed, omnidirectional
> VHF/UHF antennas to the tower. 
> 
> My initial idea is to simply overengineer - select a tower rated for 120
> mph at *double* my planned windload, and go up a step or two on the
> usual foundation size. I'm also inclining toward an aluminium, rather
> than steel, tower due to the saltwater corrosion issue.
> 
> Any thoughts would be much appreciated. I might end up turning to a
> Professional Engineer for final planning, but I'd like to check to see
> if this is even remotely feasible before I incur that expense.
> 
> Thanks,
> 
> Jeff / KS4TL
> 
> _______________________________________________
> 
> 
> 
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk