NoSPAM wrote:
"JIMMIE" wrote in message
...
I came across an old single LPDA TV antenna in the trask. It was
pretty much FUBAR except for a coupe of feet of boom matrial and a few
insulators. My XYL is into making models and castings and she can make
a mold of the insulators easy enough. I was wondering if anyone knew
of a good casting material that would be compatable with the
requirements to build a single boom LPDA antenna to form the
insulators. She is not usually concerned with strength or UV
resistance so she couldnt help much on this part.

Epoxy and polyester resins come to mind. If you are rebuilding the TV
antenna and not adding significant weight, these should work well. Use
the low viscosity resins sold in quarts, and not epoxy glues.

For added strength, consider adding chopped fiberglass strands. For
reduced weight, glass microballoons may be added to the resins. They
are extremely light with a specific gravity of 0.18 to 0.25 depending on
the manufacturer. Phenolic microballoons are also available.

For ultraviolet protection, a small amount of titanium dioxide may be
added (1 to 5%), but the microballoons will do a fair job alone.
Painting the finished insulators with acrylic paint (Krylon®) will also
provide good UV resistance.

Many marine supply stores carry these resins, the chopped fiberglass,
and the microballoons. Be extra careful with the polyester catalyst
(typically methyl-ethyl-ketone peroxide) as it is extremely damaging to
the eyes.

Good luck with your project.

73, Dr. Barry L. Ornitz WA4VZQ
[transpose the digits to reply]

Where do you buy the titanium dioxide?
73,
Tom Donaly, KA6RUH

"Tom Donaly" wrote in message
...
NoSPAM wrote:
For ultraviolet protection, a small amount of titanium dioxide may be
added (1 to 5%), but the microballoons will do a fair job alone.
Painting the finished insulators with acrylic paint (Krylon®) will also
provide good UV resistance.

Where do you buy the titanium dioxide?
73,
Tom Donaly, KA6RUH

I was sent 10 pounds from a friend at DuPont, one of the larger
manufacturers of titanium dioxide. For small quantities, I would suggest
contacting a local paint manufacturer, or artist supply store. The pigment
is used in many ultra-bright white formulations. Note that titanium
dioxide has a high dielectric constant between 85 and 110 depending on the
ratio of rutile to anatase. So to minimize detuning effects of the
insulators, use them only at low impedance points of the antenna.

73, Dr. Barry L. Ornitz WA4VZQ
[transpose the digits to reply]

On Sun, 25 Jan 2009 18:31:31 -0800, "Tom Donaly"
wrote:

NoSPAM wrote:
"JIMMIE" wrote in message
...
I came across an old single LPDA TV antenna in the trask. It was
pretty much FUBAR except for a coupe of feet of boom matrial and a few
insulators. My XYL is into making models and castings and she can make
a mold of the insulators easy enough. I was wondering if anyone knew
of a good casting material that would be compatable with the
requirements to build a single boom LPDA antenna to form the
insulators. She is not usually concerned with strength or UV
resistance so she couldnt help much on this part.

Epoxy and polyester resins come to mind. If you are rebuilding the TV
antenna and not adding significant weight, these should work well. Use
the low viscosity resins sold in quarts, and not epoxy glues.

For added strength, consider adding chopped fiberglass strands. For
reduced weight, glass microballoons may be added to the resins. They
are extremely light with a specific gravity of 0.18 to 0.25 depending on
the manufacturer. Phenolic microballoons are also available.

For ultraviolet protection, a small amount of titanium dioxide may be
added (1 to 5%), but the microballoons will do a fair job alone.
Painting the finished insulators with acrylic paint (Krylon®) will also
provide good UV resistance.

Many marine supply stores carry these resins, the chopped fiberglass,
and the microballoons. Be extra careful with the polyester catalyst
(typically methyl-ethyl-ketone peroxide) as it is extremely damaging to
the eyes.

Good luck with your project.

73, Dr. Barry L. Ornitz WA4VZQ
[transpose the digits to reply]

Where do you buy the titanium dioxide?
73,
Tom Donaly, KA6RUH
I use http://www.acp-composites.com/ACP-CAT.HTM

John Ferrell W8CCW