Hi Mike,There is an electrical difference regarding the base used, but it's been so long since I looked it up that I don't remember the details. The main reason I use it is simply because it goes on thick (but not too thick) and is very flexible (doesn't crack under normal stresses). Of course, it can be damaged (hit the coil with hammer and it will dent the coil and over stress the coating). The main difference between polyurethanes and marine spar varnish is the flexibility. Polyurethanes are used for hardwood floors, table tops, etc.. where spar varnish is used on boats where the wood will flex and which gets a fair amount of sun (so better UV properties). Of course the UV isn't an issue with our coils.
There are of course more expensive high voltage insulations which are great to use, but for the price and for the typical garage coiler, I think either polyurethane or spar varnish is in the price range and widely available at the corner hardware store. I personally prefer the marine spar varnish, but others may not.
When I do coat a coil, I lay the coil horizontal, let it turn slowly with a low voltage dc motor, and apply a coat. Then I let it spin until dry (to prevent runs). When it dries, I lightly sand and recoat until I get the finish desired. I usually like to have a smooth surface meaning I can't feel the turns as I rub my hand over the coil.
Take care, Bart Mike H wrote:
Bart, On the question of the coating that you discussed, Is there an electrical, or other performance behavior that has you preferring marine varnish? Or is it just a question of for the application, you want to make sure you coat things fully, and thus based on price, the marine varnish simply makes more sense with little to no downside? Thanks MikeConsidering our outer layer "coatings" (and I personally don't like polyurethanes but prefer marine spar varnish which to me is the best coating for the price), the coating itself protects outside issues that can cause turn to turn shorts, but the turn to turn voltage issue is dependent on the wire insulation. I've never heard mention a problem with that._______________________________________________ Tesla mailing list Tesla@xxxxxxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla
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