Thanks for the comments, everyone!
I don't think the dielectric constant of material in the gap matters much here, but dielectric strength does.? At 2000V, I get a spark across the gap.? If the somewhat-humid air during that test has dielectric strength of 3kV/mm, then this means the gap is less than 2/3 mm.? I'll guess that it's about half of a mm.? It looks that way.
My RTV dielectric strength is probably in the 7-10 kV/mm range; much better than air and on par with "fish paper".? So after I put some varnish in there to prevent future shorts, I plan to put some RTV in the hole.? But as some have cautioned, the region certainly has some carbon or other oxidized materials around.? This means that if an arc were to try to form again, it might not matter what the hole filler is.? Therefore, I plan to insert some other material over the hole.? I looked up polyimide film (aka Kapton) properties and found that a single layer is good for at least 7.7 kV.? So I'll put in 1 or 2 sheets of that and hold it in place with PVC electrical tape (10 kV/mm).? Then I'll re-install the filament winding over the bulge.
I'll update on the outcome here!
Cheers
Halden VE7UTS
