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Re: Secondary construction



Original poster: "BunnyKiller by way of Terry Fritz <twftesla-at-uswest-dot-net>" <bigfoo39-at-telocity-dot-com>

Tesla list wrote:

> Original poster: "Paul Benham by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <Paulb-at-woodanddouglas.co.uk>
>
> I am soon going to build my first secondary.  I will sand the tube to
> remove the writing on it, but should I then varnish it before I wind it?
>
> Thanks,
>
> Paul.

Hi Paul....

Im supposing that you are using PVC tubing....    varnishing /
polyureathaning it before winding isnt
really needed BUT it wouldnt hurt at all ( in fact it will help a little if
you do pre coat it)

here are some caveats about secondary work...

if you pre coat the form try winding it while the coating is still a bit
wet   this helps with displacing
the air that would be "trapped" between the windings if you didnt pre coat...

if you decide to wind the form after everything is totally dry, when you
apply the coating you will see
very small bubbles appear from under the wire ...   you may apply a second
coat of varnish/ PU while the
first coat and bubbles are still damp/wet

another method to remove the bubbles is to support the coil assy. in a
horizontal position and use the end
of an electrical sander to "vibrate" the bubbles to the surface   ( use the
sander on the end of the tube
preferably at the base)

and the final method of a clean coil with minimal bubbles is to thin out
the varnish/PU a bit to allow good
penetration under the wire ( but this has a tendancy to cause runs and
drips as it dries)


Scot D