Re: flexible ducting

[FutureT-at-aol-dot-com (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

In a message dated 8/6/00 3:03:36 PM Pacific Daylight Time, tesla-at-pupman-dot-com 
writes:

>  How did you join the pieces and what did you put in the center of it and 
how
>  > did that attach to the duct? I know it seems a simple question, but other
>  > input helps sometimes.

Kevin,

To join the ducting, I've used two methods which produce an almost
invisible seam:

Method 1:    Cut the ducting so that two ribs are left at the ends
instead of four.  Then drill tiny holes in the edge of ribs (about 6 double
holes around the diameter).  The double holes should be about 1/4"
apart.  Then put the ends together and make little "staples" using
#22awg buss wire.  Place the staples through the matching holes
at each end so the ends are held together.  Then fold down the ends
of the staples and solder them if needed to hold.  Since the staples
go though the ribs, they do not project above the surface of the toroid
and will be almost invisible.

Method two:   This method is easier, and looks just as good.  Cut
two pieces of 3/4" wood to the (minor) diameter of the toroid so it can
fit into the end of the ducting like a plug.  Prepare the toroid ends
as above, but don't drill the holes.  The edge of the wood should be
shaped to fit the curvature of the ducting as it arcs gently away
from the ends (A larger toroid will need less of this shaping).  If
you don't shape the ends, then the joined section will be straighter
than the rest of the curve of the toroid ( the entire toroid won't be
round when observed from above (or below).  When the wood is
the correct shape, it is glued into one end of the toroid.  When the
glue is dry, tiny nails are driven through the toroid at a depressed
area, using a punch so as to to squash any ribs, and driven into
the wood below for strength.  Next, the other end of the ducting
is placed over the wood and nailed to it the same way.  BTW, 
the wood projects 3/4" into one end of the duct, and 3/4" into the
other end of the ducting.  I forgot to mention above, but the two
pieces of wood are glued and nailed together to make the plug
1.5" thick before it is inserted into the ducting.

Using these methods, it requires careful inspection to find the joint,
and best of all, the sparks will not preferentially stream from the
joint (the sparks don't see it as a joint).

Cheers,
John Freau