"ml",.

I apologize if I offended you, but your comments were so poorly written that
it was difficult to understand entirely just what you intended to say.

You suggested using the same methods used to preserve telephone poles. I
discussed both the older methods as well as present day methods of wood
preservation. Wood preservatives and sealers, such as creosote,
pentachlorophenol, and chromated copper arsenate are far too toxic to use.
But more importantly, they are also _very_ poor from an electrical
standpoint in the _original_ application, i.e. for use on wood dowels as
ladderline spreaders. I also clearly stated why boiling the wood dowels in
paraffin wax, as done by oldtimers, did a better job electrically than than
creosote. Previous posts I had written already covered the safety aspects
of using hot paraffin, especially its flash point temperature., and the
extreme danger of skin contact with the hot wax.

You then mentioned that _plastic_ is _a_ way to go. You did not mention
which plastic as this is extremely important in the original application.
Polyolefins (polyethylene, polypropylene) are extremely poor in outdoor use;
they can fall apart quickly if exposed to bright sunlight. Polyamides
(nylons) fare a little better but they too are soon damaged by the
ultraviolet in sunlight. They are also damaged by acid rain.
Polyoxymethylene (Delrin) is quite sensitive to halogens in acid rain.
Polycarbonate and acrylonitrile-butadiene-styrene (ABS) plastics have good
ultraviolet resistance only if stabilizers and absorbers are blended in;
they have good chemical resistance to aqueous acids and bases, but they are
quite prone to solvent attack. Polytetrafluorethylene (PTFE, Teflon) and
other fluoropolymers have wonderful electrical properties (superb insulation
resistance, low dielectric constant and loss tangent) as well as high
ultraviolet and chemical resistance, but most are subject to cold flow and
have poor temsile strength. In other posts I discussed acrylic and
polyester plastics that are inexpensive, have good UV resistance and good
electrical properties. I also discussed polyvinyl chloride and chlorinated
polyvinyl chloride plastics. I didn't bother to consider polyimides
(Kapton) as the cost would have been prohibitive. Suggesting "plastic" as
you did without specifying which particular composition is essentially
useless information. I gave my suggestions and the detailed reasons why I
would pick certain plastics. I did not specifically mention cost except
with the suggestion of plastic coathangers, but as an engineer.cost is an
important consideration for virtually all my decisions. It was certainly a
consideration for the original poster --why else would he ask about using
wood?

Of the three methods of protecting wood in this application. as queried by
the original poster, I plainly stated that urethane varnish would be my
choice. I also explained why this would be preferred over shellac and
paraffin wax. I further suggested which specific plastics would perform the
best for the original application of transmission line spreader.

In the future, you should be far more clear in your writing if you really
want people to take your suggestions seriously. You also need to be far
more specific in your suggestions.

Again I apologize if I offended you, but I still stand by my earlier
postings. If it bothers you, you can always filter out my posts. I
certainly do this for a few of the people found here who espouse
pseudoscience and refuse to defend their claims with either mathematics or
experimental evidence.

73, Dr. Barry L. Ornitz WA4VZQ




"ml" wrote in message
...
Guess no spam didn't read my post fully

I also acknowledged that using oil was bad , thats why i then stated
that plastic is a way to go

but it can't be poor per say because the original post asked for
comments on wood, so we gave comments on wood


he also asked about plastics he got comments on plastic

also acknowledged was some pro's and cons

only the user and his applications and desires will determine what
is 'best'



In article ,
"NoSPAM" wrote:

"ml" wrote in message
...
In article ,
"Hal Rosser" wrote:

Thanks, Barry on helping to wake up my recollections. I had forgotten
that

{snip}

find some of that oil they soak telephone poles in then coat it
w/sealer

ultimately wood prob wont last as long as some good plastic
and
i guess would be heaver stressing the wires more

it will prob still hold more water than a smooth plastic
dunno

and prob not have as good insulative prop's but might be moot

I consider this a poor suggestion for a number of reasons...

Several methods of wood treatment have been used over the years. The
three
main methods used to be pressure treatment with creosote,
pentachlorophenol,
or inorganic arsenic salts. These were generally replaced by chromated
copper arsenate. Other treatments involved copper napthenate, zinc
napthenate, and tributyl tin oxide. All of these methods provide fungus
protection and some limited moisture protection.

Creosote, as used for treating wood, is generally coal tar creosote.
This
material is distilled from coke oven tar and it contains polycyclic
aromatic
hydrocarbons, phenols, and cresols, all of which are quite toxic and most
are either proven or suspected carcinogens.

Pentachlorophenol is registered by the Environmental Protection Agency as
an
insecticide (termicide), fungicide, herbicides, molluscide, algaecide,
disinfectant, and as an ingredient in antifouling paint. Stated simply.
it
is toxic to just about all life.

Chromated copper arsenate, at one time, was the most widely used wood
treatment. Hexavalent chromium and arsenic in any form are both
extremely
toxic, so newer treatments were developed including ammoniacal copper
quaternary. The EPA lists this as a general use pesticide and it is far
less toxic than chromated copper arsenate. Other newer wood treatments
used
today are based on borax and other borate salts. These too are less
toxic
than the older copper salts.

The oil treatment that "ml" refers to is most likely creosote. However
creosote or any other of the treatments described above will not make the
wood a good electrical insulator for use as spacers in open wire
transmission line. Raw wood or wood treated with any of the metal salts
shows a high dielectric loss. Even pentachlorophenol is not very
suitable
as its dielectric constant is around 8 to 10. But then the wood itself
usually has a radio frequency dielectric constant around 10 or more too,
even if completely dried. Increases are seen at frequencies below the
MHz
region, and with increasing moisture. The loss tangent of wood also
increases rapidly with moisture content.

The reason that old timers boiled their wood dowels in paraffin wax was
twofold. The first was to completely dry the wood, and the second was to
provide moisture protection. The preservation of the wood against fungus
or
termites was generally inconsequential for use as spacers in transmission
lines.

Polyvinyl chloride and chlorinated polyvinyl chloride plastics are
moderately lossy at radio frequencies but are far better than wood in
this
respect, and I have seen them used with homebrew transmission lines.
However, from the standpoint of RF losses and ultraviolet radiation
damage,
acrylic plastics are my choice as true ladder line insulators.

One suggestion I have is to look at cheap plastic coathangers. These are
about 1/4 inch in diameter and are not vinyl coated wire hangers.
Several
insulators can be cut from a single coathanger. Since you can often buy
these hangers for around $1.00 for ten; a few dollars could provide a
good
number of insulators. If you don't like the color, spray paint them with
Krylon or another acrylic paint. White will provide the best ultraviolet
resistance. I would limit my wire size to 16 Gauge or smaller as this
plastic is quite brittle.

73, Dr. Barry L. Ornitz WA4VZQ