Re: secondary coil form materials

["Barton B. Anderson" <tesla123-at-pacbell-dot-net> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Hi John, 

Coilers have used everything form PVC, polyethylene, to cardboard sonotubes.
They can all work well. If using a natural moisture absorbing form, always seal
it and coat it inside and out (this includes PVC). Local hardware stores carry
everything you need for coating. On forms such as sonotube, it's a good idea to
use a hard coating that goes on thin. Some even dilute the coating a bit with
thinner to help the coating soak in and penetrate the card board. I would add
that it won't hurt to apply a few coats of non-thinned coating on top of the
thinned coating if you do this. For the outer coating on top of the winding, I
like to use a softer coating such as Marine Spar Varnish (holds up well to
weather or stress changes that can cause hard coatings to crack). 

The thickness isn't important. Just as long as it's rigid enough to withstand
the the winding tension. Sonotubes are generally 1/8" thick and do just fine.
These tubes are usually used on larger coils. PVC's come in all sizes however
and is just as easy to get ahold of. 

Most people use what they can find. How you build it is far more important than
what you build it with (the secondary). 

Bart 

Tesla list wrote: 
>
> Original poster: "John Morawa" <morawaj-at-interaccess-dot-com> 
>
> Hello everyone, 
>
> Can anyone recommend a material for secondaries coils?  Something that can 
> be found in a 4"-6" diameter.  Normally I use PVC but I understand that it's 
> RF qualities are not that great.  Of the two which would be better, acrylic 
> or polyethylene?  Or is there something that is similar in $ but better for 
> secondaries?  Also, for a coil of that diameter, what is the minimum wall 
> thickness to keep it rigid enough to wind.  Is 3/16" ok or is that too thin 
> or thick? 
>
> Thanks for any comments, 
> John M.