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Re: Need Coiling Advice



Hi Tom,
        You wrote...

>           I am building my second generation secondary coil. It is a six
>           inch acrylic tube. I will be winding it with 22ga magnet wire.
>           My question is this: Do I need to apply a layer of epoxy on
>           the bare coil form before I begin winding? Any help would be
>           appreciated............

I'm replying because although conventional wisdom says no, I'm in two 
minds about it. The reason is that I have two coils wound on clear 
tube, and I noticed after several coats of varnish that the close 
winding prevented the varnish from penetrating the windings. I guess
it wouldn't matter if the tubes were perfectly round, but in the case 
of one of those coils, the tube was fabricated from sheet and is not. 
The result was that some of the windings were not nested against the 
tube and left airgaps behind the turns which made a heavy outside 
coating a bit superfluous. The next time I try a trick like that I'll 
give it a couple of coats first and wind while the stuff is still 
soft. I also found the non-penetration of varnish between the turns 
to be a bit worrying but decided that the enamel insulation on the 
wire would be OK for the voltage gradient at the worst spot (bottom).
    I also think that as long as the coil is never overcoupled 
(flashover territory), heavy varnidhing is unnecessary.

Malcolm