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Re: [TCML] Poly thickness



jhowson4@xxxxxxxxxxx wrote:
All this talk of putting poly on coils has got me wondering (how many
coats of poly is enough) i recently wound a 3" by 24" secondary with
some #28.  first i coated the form with 1 coat of poly.   then i
wound the coil.  Then I put on 4 more coats of poly.  is that enough?
I ha\ve not had any problems with it yet.

jay howson _______________________________________________ Tesla
mailing list Tesla@xxxxxxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla


Hi Jay,

There are many folks who successfully run their coils without using ANY
polyurethane or epoxy coatings over their magnet wire. Others have used 10's of coatings. The coating helps to hold the wires in place (important if your secondary is subjected to wide temperature variations). Otherwise, it's more of an aesthetic thing: how pretty do you want it to look, and how patient are you...

If you do decide to coat your coil and want it to look really great, I'd recommend coating it with a two-part polyester (good) or epoxy (best) resin instead of applying lots of individual coatings of polyurethane varnish. It's much less work and provides you with a superior appearance. You'll need to continuously rotate your coil form while applying the coating, and you must continue rotating until the coating cures to avoid getting sags.

Apply the coating in a dust and bug free area - and don't apply at night
in the summer under bright lights (don't ask me how I know). A beautiful water clear epoxy or polyester coating will enhance the appearance of your coil, will help smooth out the E-field near the wire surface, and may even provide some protection against wire damage for primary-secondary flashovers or racing sparks. The downside is that the polymer surface tends to develop a persistent surface charge that can "zap" you long after the coil has been powered down.

Bert
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