[TowerTalk] Yagi Materials

[Steve]

Hi Mike, sound like you have quite the ambitious project on your hands. If you
want to fit 2" fiberglass to 2.75" id tubing just find a peace of 2.75"X3/8"
tubing or have a piece machined for you and use it as a bushing. As for the
insulator at the coils I would go for 3/4" fiberglass rod. I don't know the
yield strength of 2" fiberglass rod but check to make sure that it is close to
the yield strength of 3" 1/8" wall tubing. I would recommend that you chamfer
the edges of the aluminum tubing where it contacts the fiberglass to minimize
stress risers. The best way to test the strength of the 2" fiberglass rod is to
make up a test piece with 3" aluminum tubing and put it in a vice and try
bending it to see if the aluminum bends first or the fiberglass breaks. Don't
forget to paint the fiberglass or wrap it with tape to protect it from U.V.


gl with the project es 73, Steve

Mike Wetzel wrote:

> I am attempting to build a shortened 80 meter beam.  I am going to use coils
> and am patterning it from the M^2, 3 element 80.  I have found 2" fiberglass
> rod (used to insulate 3" x .125 wall tubing from the boom) anyone know what
> the bushings are made of that go from the 2" o.d. of the fiberglass to the
> 2.75" i.d. of the 3" element tubing?  Wish I could find fiberglass rod that
> was 2.75" o.d. but it doesn't seem to be manufactured.  McMasterCarr only
> shows 1.5" fiberglass rod available (so I felt lucky to find the 2" rod
> locally).
>
> Also the coils made by W6ANR uses some sort of material like Delrin (but not
> Delrin I asked David but he couldn't remember what the material was) to
> support the coils, I was thinking of using fiberglass rod at that point but
> don't have any idea as to the strength of .75" solid fiberglass, any help?
>
> Thanks,
>
> Mike W9RE
>
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