Anchoring for Small Wind Cross Section Tower

[TechnoShaman]

I'm planning on putting a lighted beacon up this year. I put one up last year but this year I'm planning on it being taller. Last year the beacon consisted of two sections of 10ft black pipe, so 20 foot tall. It was secured with two sets of guy lines on three sides, equally spaced 120 degrees, so 6 guy lines total. The guy lines were at the top of every 10ft section and the base was anchored to the ground. The Beacon has a pretty small cross section for wind, so there is not much force on the poles at the top. I used 24" x 1/2' rebar stakes with back ups, and welded rings that the ratchet straps attached to which hooked to 1" nylon webbing slings. This year, the mast will be welded steel pipe with three truss side bracing structures running up the entire length, and it will be 30 ft. tall with bolted steel plates joining the three sections together. My question was whether 36 inch x 3/4" concrete form stakes placed 20 feet out, with three sets of guy lines (again, one set for every 10 feet) would be sufficient anchoring for such a structure. I had also thought about backing the main stakes up with helical screw stakes for added safety. Also, the guy lines will be upgraded from the nylon webbing to 3/16" SS cable rope, with turnbuckles, thimbles, and crosby clamps, with steel shackles connecting the cables to the stakes and mast. Also, I was wondering if 3/16' cable rope is sufficient, or if I could get away with using 1/8" instead. Any advice/suggestions are greatly appreciated!

[TechnoShaman]

Here is a picture of the anchoring base, and the bottom of the truss/mast

[TechnoShaman]

Here are the concrete stakes I was planning on using. 3/4 inch x 36 inch, with welded rings on the ends.

[TechnoShaman]

Here is a picture of one 10ft truss section/mast

[GreyCoyote]

Very nice job! Love the base design.

My gut says it should work nicely, but without knowing the materials, dimensions, etc, it's really hard to predict ultimate performance. Got a friendly PE who could run the figures for you? That would be ideal. Failing that, can you keep folks out of the fall zone if it fails?

IHMO, those stakes should be fine, regardless if the structure itself fails. 36 inches of playa penetration should be plenty.

You might give the folks at BMIR a holler and see what they use.

[EspressoDude]

I have put up 30 ft flag poles several years. Pole is made of 3 ea 10 ft sections of 1.5" intermediate conduit (IMC) with threaded couplers. at each coupling inner reinforcement with 2 ft of fence post tubing. 3/8" Kevlar rope for guy supports. connecting points do wiggle slightly so put some teflon tape on to make it easier to take apart. anchors 2ft long 5/8 re-bar about 10ft from pole base

[some seeing eye]

I love the dilemma of the America's Cup sail races. They have access to the best engineers, materials and an almost unlimited budget. But the saying is, if it breaks you made it too light and if it doesn't break you made it too heavy.

Have to second Mr CG suggestion to get professional help. Maybe in your work, you employ them, or find a local engineering school. Get a feel for how mechanical-structural engineering works and how to use the software. Of course, engineer for wind.

I don't think the three side elements add a lot to the structure. With side loading for wind, more diagonal bracing in the tower vertical elements helps. Definitely visit BMIR and Camp Legba of you want hints for going higher. You find amateur radio towers for sale all the time, but not inexpensively.

Good for you for challenging yourself on playa projects!

[TechnoShaman]

GC, thanks! I do have a contact that is a crash test engineer that was suggested I run the numbers by for a professional opinion. The side rails definitely give it added structural support. before adding them the pipe could bend and now, I can secure it from one end out horizontal and it's completely rigid. Earlier today I made a second backup set of stakes to hole the primaries. Thanks for the suggestions and insight everyone.