On 10/7/11 10:28 AM, normn3ykf@stny.rr.com wrote:
>
> Thanks all for the contributions. The saddle sled is the type I'd
> need. My problem is getting it by code. I would have to have the
> windload and structural calcs done by an engineer to ensure that it's
> right. Code is crazy here. Any ideas?
>
> The issue is that the property needs a new roof. Installation of a
> crank up/tilt over tower is a large expense. The plan of the property
> does not lend itself well to do it. If it's easier and cheaper now
> to do the roof structure upgrade, get my array up at a decent
> altitude, so be it.
>
If you're installing a new roof, then the roofer should be able to
provide "hard points" that are properly flashed and sealed to mount your
external structure. You might look at how they do solar panel
installations, which have a similar need (and which have static and wind
load issues as well).
On a shingle/composition roof, the techniques are straightforward
(people have been putting things on roofs for centuries, after all). On
a tile (or concrete) roof, it's a bit trickier, especially if you want
it to look nice and not provide a pleasant home for vermin to live under
the tiles, but still, it's a pretty standard thing.
After all, they bring waste water vents and various stacks for water and
air heaters up through the roof. They're not load bearing, but they have
the same sort of sealing issues.
What you might do is look at your expected loads, and then specify that
you just want a piece of something like UniStrut stubs sticking up
vertically through the roof which can carry, say, twice that load.
After the roofing job is done and signed off, you put your tripod up
there and bolt it to stubs. That separates the "roof structure design
and construction" process from the "antenna support structure design and
construction" process.
I daresay, one might be able to be a bit clever and assert that the roof
stubs are being installed to support a Over The Air Reception Device
(OTARD) (surely, you need to receive those fringe stations with a
massive TV antenna and multiple DBS dishes, right?). That would get the
approval process for the stubs and structure separated FAR away from the
amateur/communication antenna regime, which seems to always raise the
hackles of some folks.
A consulting Engineer could do the load calculations for your proposed
satellite antennas in a few hours.. spend the few hundred bucks if needed.
Then, you might need another or the same Engineer/Architect to do the
calculations and design for your roof structural mods (or to say that
you don't need mods).
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