Dennis Vernacchia wrote:
> I have a semi ancient 440 mhZ old F9FT long boom Yagi for 440 MHz
> ( Many elements on a 10 or 12 foot boom )
>
> The Driven element which is a folded dipole has separated from it's cracked
> black plastic insulator
> and a piece of the insulator is MIA
>
> The insulator used to be molded right around the N connector feed point
> which the driven element is soldered to.
>
> What would be the best type of Epoxy I could buy at say, Home Depot or a Ace
> Hardware store that will
>
If there's a marine store in the area, or possibly you can find it
elsewhere, pick up a "West System" Epoxy Kit and some mill fiber. If
you can find a piece of mill fiber, just get a small piece of fiberglass
cloth and cut into small 1/4" or smaller pieces. These are easily
separated into the individual fibers. Start with a small batch of epoxy
and mix in enough fibers to make a paste. (lots of fibers, a little
epoxy) It might take some practice to get it right, but a mill fiber
mix is strong. Be careful if you mix very much epoxy as this is an
exothermic reaction when it cures. The cure time and speed at which it
cures depends on the amount mixed. More means faster AND hotter and
getting it on you during cure is like getting hot melt glue on you.
Initial cure (when it gets too stiff to work as a paste) IIRC takes
about 15 minutes but can vary widely with the above conditions as well
as temperature (warmer means faster)
No special techniques are required to make the patch or apply and shape
the material but working with fiberglass and epoxy does take a little
practice. Some of us take more practice than others<:-)).
Make sure the pieces to be repaired are clean and roughed a bit with
sand paper. I cut a piece/strip of plastic from the container that
electrical tape comes in. Any good PE should work. I round the end and
it makes a good tool by sanding to apply the material as well as shape
it. After the "fix" reaches full cure (about 24 hours, or less) you can
grind, sand, or cut the patch. One of the little high speed grinders
works well as does a small sanding block.
REMEMBER this contains fiberglass which will be in the dust from working
on the patch. Wear a dust mask and do not breathe in any of the dust.
Like working with fiberglass insulation its a good idea to change
clothes after getting in the dust.
> adhere to the old ubiquitous type black plastic insulator AND the round
> flanged body of the N connector,
> for a temp repair til I can machine a new insultor ( Round-To-Its are
> getting scrcer around here ! )
>
>
If you have the tools to machine a new insulator you might want to
experiment and make a split mold to make a new, professional looking
insulator. DC4 or 5 compound, or even Johnson's spray wax or Carbuna
wax make good mold release agents.
One added thought: if you can get the pigment (as long as it's not
carbon black) adding a little to the mix can even give a part that looks
like the original.
One other thing to remember is fiberglass and epoxy is not strongly UV
resistant so you might find some additives, or just give it a couple
coats of clear Krylon after full cure.
73 and good luck,
Roger (K8RI)
> 73, Dennis N6KI
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