big secondary forms

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

Casting about for ideas on inexpensive, but high performance, forms for a 
secondary around 18" (50 cm) in diameter and 6 ft (2 m) long...

Sonotube (concrete form) is an inexpensive starting point, but might have 
"evil" stuff in it that kills the Q, and there's no doubt it's hygroscopic 
(a HV "bad thing")..

But, what about taking the sonotube, putting 1 or 2 layers of 
fiberglass/resin composite over it (or, you don't even need glass, you 
could just use canvas as the fiber).. wait for it to cure (at least to the 
"tacky" stage).

Wind your coil.  Fix the windings with something (another layer of glass?.. 
urethane? glyptal?, etc)...

Remove the sonotube by scoring and water soaking it.



I think Greg Leyh did something like this for Electrum....


Questions:

How much fiberglass on the inside?  The windings themselves will provide a 
fair amount of strength. For more longitudinal strength, one could put some 
sort of insulating beams on the inside (fiberglass tubing or PVC pipe)

How would one make a mounting fixture for the secondary?  You could "glass" 
in a piece of 3/4" plywood in the bottom.  Ideally, one would want to be 
able to support the secondary horizontally as a cantilever attached only at 
the base (sort of a worst case...)

You're looking at around 30-40 pounds (15-20 kg) just for the wire.