Secondary Coil design

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

Original poster: "G by way of Terry Fritz <twftesla-at-qwest-dot-net>" <bog-at-cinci.rr-dot-com>

Hello List,

I have noticed a failure pattern in all of my secondary coils and am 
searching for a solution. Each one has had a failure within the 
bottom 25 turns (shorts between turns).During the most recent 
failure, I was watching the operation very carefully in a dark room 
and I am sure there wasn't any arc struck between the secondary and 
the primary, or even corona.

I have not noticed any other report of this problem. Has anyone had a 
similar occurrence?
I may try using a larger gauge wire toward the bottom to help deal 
with the higher current in this region. Is current even the problem?
Would using a larger gauge wire cause a damaging voltage gradient?
Is space winding the bottom turns a possible solution? (also- 
negative effect on coupling?)


Thanks!
Gregory

PS- I came across some construction trash dwv pipe labeled 'triple 
wall hdpe'. It is lighter than a thinwall pvc pipe and is a 
lower-loss plastic. Would the air pockets that exist between the 
layers cause a secondary coil to burn through, or last longer?