donovanf@starpower.net wrote:
> It sounds like you're planning on full sized 40 meter elements, they will
> be about 75 feet long with your severe taper. Irrigation tubing only has
> only 0.040 inch wall, I expect it to fail in the first strong breeze.
>
> Its surprising that you plan to use such a strong boom, an excellent
> choice for this large antennam, but you plan unreasonably thin wall
> elements that would be marginal even for a 20 meter Yagi.
> W3LPL
Actually, irrigation tubing is at least 0.050 inch and heavier grades
are available. I have made 30 foot unguyed verticals out of it that
survived very high winds (>70 MPH). I'm think your Yagi plan
might be OK, as long as you are not going to experience ice or
hurricanes. The rating is 28,000 PSI, you can calculate the
wind survival using the usual tools. The main issue with thin wall
tubing is to avoid mounting it in such a way as to encourage buckling.
Rick N6RK
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