Re: Ideal coil forms (was: Re: Sonotube's high RF loss!...yes or no?)

[FutureT-at-xxxxxxx (by way of Terry Fritz <twftesla-at-xxxxxxxxxx>)]

In a message dated 11/6/00 10:18:36 AM Eastern Standard Time, 
tesla-at-pupman-dot-com writes:

> Original poster: "Alex Crow" <user-at-alexcrow.clara-dot-net> 
>  
>  Hi Mark, All,
>  
>  I wrapped a skin of 1mm polystyrene sheet (the stuff modellers use, we 
call 
> it
>  "Plasticard" in the UK) around a wooden skeleton form, glued it at the 
seam,
>  sanded the seam flat, removed the skeleton and plugged the ends. This was
>  solely because I had great difficulty finding any amount of 6" PVC. 
However, 
> I
>  recently saw it mentioned (was it here?) that this is an excellent 
material 
> in
>  terms of RF losses and dielectric strength. I believe others have used it 
> with
>  good results. However, it is easy to split it at the ends if your plugs 
are 
> a
>  little too large - easily cured with a good slop of epoxy/PU.
>  
>  Alex Crow
>  

Alex, all

polystyrene is good as you say, but one thing i noticed about
it when I used it in tube coils is that any kind of arc causes terrible
burning damage to the form.  Polyethylene and polypropylene are
better to resist this burning.  Sometimes chemical tanks made of
these material can be found and used for a secondary form.  
Sometimes a plastic trash pail can be used too.

John Freau