Re: sealing a cardboard tube?

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

Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz <teslalist-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>

Tesla list wrote:

 > Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>" 
<Beans45601-at-aol-dot-com>
 >
 > I just got sonotube (cardboard tube) from homedepot that I will eventually
 > wind my secondary coil on. I know first, to wype it down with an acholed
 > (is that a word?) rag. But, to seal it, what should I use?

Shellac varnish, polyurethane varnish, etc. But I would not bother
with this, unless you want to operate the coil in a very humid place.
Maybe better to let the cardboard "breathe".
Apply a coat of varnish over the finished coil, just to hold the wire
in place.

 > Also, they sell
 > circles that are (.5" wide, not sure...) made of mdf. They don't have the
 > size I need (or course), so I was thinking it would not hurt anything to
 > have an inch or two hanging over the side. I could get my friend too cut it
 > to the right size, but should I go trough the trouble? Could I use one of
 > these for the endcap for my secondary coil? And, would it be okay to use
 > metal screws to attach it to my sonotube?

It's not necessary to close the tube, and in the case of a cardboard
tube, useless, as a spark can easily punch through this material.
If you want to make a base for it, or something where to attach your
terminal. Little screws are not a problem.

The old coil seen here:
http://www.coe.ufrj.br/~acmq/tesla/oldtesla.html
uses a cardboard tube, not sealed, 70 years old, has the base made
of wood and iron, with several metal screws and nails, and a terminal
made of wood and brass that covers the top end. The secondary wire
enters the tube while going to the terminal. The secondary is too
long, and the primary is helical. Many of these things are seen as
big "no-nos", but the coil works perfectly well, at least within
the limits of the power supply used in the tests.

Antonio Carlos M. de Queiroz