Original poster: "resonance" <resonance@xxxxxxxxxxxx>Another great coilform material is SDR --- stands for "sewer & drain". It's available at most plumbing supply houses. It is green in color and has a much thinner wall than the standard schedule 40 PVC tubing. Be sure to avoid anything that is black or dark gray in color. Additives may cause tracking.
This makes the sec coilform very light weight and easy to handle, transport, etc.
I prefer Dolph's AC-43 to coat my coilforms. It's a bit more expensive than the polyurethane, but it is specially formulated for large transformer manufacturers to coat their magnet wire windings. It provides excellent dielectric and tracking resistance. Tracking resistance is especially important in Tesla transformers as the windings are always stressed due to the high potentials across a short distance. It air drys fast and usually 2 coats can be applied in a single day.
I use 2 thick coats inside and outside prior to winding, and then apply 5 thin coats to the wire after winding. I do the 5 coats over a 3 day period to allow complete drying of each coat. I allow 9 hr. interval between coats. Setting in the sun helps a lot too.
I buy it in 5 gallon pails and sell it in quarts if anyone on the list needs some.
Dr. Resonance
Some dry the pipe while rotating it under heat lamps - the down side of PVC is that it is hydrosopic (absorbs water) it would seem to follow the thicker the pipe wall the more moisture path will be present. If it will fit in the oven set it on very low heat and let it dry out for awhile. Than coat the inside and the outside with a couple of coats (preferably on a "dry" day). This seals the water out. Wind the coil and coat it with three more layers of poly. This protects the coil from physical damage as well as raising the HV standoff. This seems like the standard. Richard Hull said he never coated his coils I believe.