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PVC, Re. Bert's response on Pyrex




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From:  Eleanor Flood [SMTP:eflood-at-bellsouth-dot-net]
Sent:  Wednesday, January 14, 1998 6:10 PM
To:  Tesla List
Subject:  PVC,  Re. Bert's response on Pyrex

Tesla List wrote:

 Heck even well
> > baked out cardboard tubing that is saturated with polyurethane and allowed
> > to dry under heat is superior to glass!
> >
> <SNIP>
> 
> Alfred,
> 
> Got to disagree with you a bit here, Alfred. The difference in
> dielectric loss between PVC and glass is really not all that great...
> and Pyrex (at about 30) is actually about 1/4 as lossy as PVC. Even soda
> lime glass is only 1-2X as lossy as PVC. While using glass, or PVC for
> that matter, as a dielectric in a Tesla Coil tank cap would be quite
> lossy, use of this material in a coilform is a significantly different
> application. PVC, although quite lossy, makes an excellent coilform due
> to it's excellent insulating properties after proper pre-treatment. Its
> dielectric loss properties have relatively little practical impact on
> secondary Q when compared to other losses in an operating system
> (streamers in particular...).
> 
> Jim, your Pyrex coilform will work just fine.. and may actually have a
> higher Q than if you wound it on PVC.
> 
> At no loss for words in Illinois...  :^)
> 
> -- Bert --

We are now using afore mentioned coated cardboard tubing for secondary
coil.  Planning a PVC one shortly. Note a reference to proper
pre-treatment. Please, how?  
Plan to make coil as open air as possible by cutting slots lengthwise in
PVC about 1/4' apart, this is just a thought, would it be worth the
trouble?
Any advise on use of PVC in this manner would be appreciated.
Thanks much.
H & E