Friday, August 28, 2015

Building a new Antenna at N6QW ~ Part 10

Placing the Concrete Base

 
We are victims of our past experience! Upon graduation from college (BSEE) I had to serve four years in the US Navy Civil Engineer Corps. That scholarship from the US Navy entailed a large payback -- four years of my life. During that four years I got to operate as DX from Midway Island (then KM6) but unfortunately no operation from South Vietnam during my two trips there.
 
As with all industries, workplaces or even the military there is certain acceptable and respected common language. Much of the construction  work of the "Seabees" involved concrete, and the proper terminology was "placing concrete" not "pouring concrete". The real subtle difference was that placing had an air of precision whereas pouring sounded like a "random spilling out" that literally went everywhere. So for my project, obviously involving precision and the "knack", I placed the hand mixed concrete into the homebrew form.
 
Don't get ahead of yourself -- allow three days of cure time before removing the forms and at least week before adding any load bearing structure. (Well I waited 1 day before removing the forms.)
 
A lot of effort was expended in assuring the form was level and that the anchor bolts were in the proper position. The bolts in the right position was accomplished by having the baseplate attached to the form during the pour. The leveling as another matter especially since the concrete shrunk a bit after setting. Anticipating this problem I insured enough thread was available so that I could have a nut on the underside of the L Bracket and thus enable a precision leveling using the nut much like a jack screw.
 
 

The Placing Sequence

 






Tribal Knowledge Tips

  1. Wait seven days to assure the concrete is fully cured before placing any heavy load on the base.
  2. Spray the bolts with WD-40 before placing the concrete -- the last thing you want is concrete in the bolt threads
  3. Spray WD-40 on the bolts while awaiting the concrete to cure. This prevents them from rusting.
  4. Once the final leveling is done then apply a "coax seal" to the bolts so that they don't rust.
 
 

Pete N6QW

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