Toroid Building - Update

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Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi Everyone,

As I stated earlier, I started filling in the corrigations of a 8x32 
toroid using Bondo.  I didn't get very far as I was getting too 
little coverage using bondo and the "work time" is way too 
short.  The mixture only is usable for about 4 minutes before it gels 
and half of that time is taken by mixing.  The sanding, although was 
straight forward, was taking way too long.

So...  I switched to grout.  Much easier to work with,  no toxic 
fumes, long work times, and best of all, no sanding required.  The 
grout takes several days to cure and can easily be smoothed using a 
wet cloth in the first 6 hours.  Water actually helps the cure 
process and clean up is easy.

For those that only want a smooth surface, I believe, this is the way 
to go.  The dent resistance has gotta be better than the "bare" AL 
duct tubing although, perhaps, not the best.  For those that also 
want more dent resistance, I see no reason that the result can not be 
covered with resin, followed by a bondo fill where needed, and then 
taped.  I plan to use grout to fill any defects and then maybe a lite 
sanding followed by varnish to provide a surface suitable for taping.

Gerry R.