Re: Toroid Design

In a message dated 12/23/98 12:17:02 AM Mountain Standard Time,
tesla-at-pupman-dot-com writes:

>  The right material is more like a thinwall
>  (0.005"?) aluminum bellows that's fairly stiff and is shipped somewhat
>  compressed. The 8" diameter material I purchased was about 2-2.5 feet
>  long, but would stretch out to about 7-8 feet. It will dent if you poke
>  it hard enough or drop the toroid, but otherwise is pretty robust. 
     I was wondering if anyone using the aluminum duct has tried filling it
with expanding foam insulation after the ends have been sealed.  I figure it
could be injected through a small hole punched into the toroid along the inner
radius so it would not be seen.  So far, I have been careful(or lucky) and
have not dented mine, but thought that this might make them a little sturdier
without adding too much weight to them.