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Re: Thin Foil
Reinhard and all,
You COULD make a rolled cap using thin cooking foil without using
extended foil construction. However, as you indicate, it is considerably
more difficult winding the thinner foil without tearing it or making it
wrinkle. The big problem is in termination.
Practically speaking, most cap builders who use thin foil end up going
to extended foil construction simply because its much easier to
mechanically terminate a batch of foil layers to a heavy electrical
termination than trying to do the same with a single layer of foil!
There is a secondary benefit as well. Thinner foil has higher sheet
resistance, so that using extended foil terminations tends to minimize
the series resistance (ESR) losses in the cap, while also reducing its
self-inductance. However, the biggest performance improvement comes from
using a low-loss dielectric (LDPE, HDPE, PP, PS) in the first place. Any
further performance differences between extended and end-terminated foil
will be difficult to distiguish once the sparks begin flying on your
coil.
-- Bert --
Tesla List wrote:
>
> Original Poster: RWB355-at-aol-dot-com
>
> Hello All,
>
> Bert wrote (in an email a while ago) kitchen Al foil is only recommended for
> extended cap design. Why is this ?
>
> Up to now I have been using kitchen AL foil in my caps with great sucess.
The
> only problems I have had were with the thin plastic sheeting (my emails a
> while back). However, this was due to the material not being PE.
>
> The reason I am asking is because thick foil (similar to the U.S. 0.010"
> roofing foil) is pretty expensive. It runs around $40 for 10 square
meters. So
> I would rather (if possible) go for the kitchen stuff. It takes a little
> handling care so that it doesn´t get wrinkled, but that is about the only
> negative thing I can say about it.
>
> Coiler greets from germany,
> Reinhard