Re: McMaster-Carr 12" aluminum duct for toroid question

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Original poster: FIFTYGUY-at-aol-dot-com 

In a message dated 10/31/04 7:01:42 PM Eastern Standard Time, FIFTY GUY
writes:

 > >  Also, I'm not sure how the piece that's ex-
 >  >  pandable to 30 ft. can have the same compressed length of
 >  >  30" as the 15 ft. expandable stuff.  Maybe a typo on McM-
 >  >  Carr's part?
 >
 >   I was wondering that myself.
 >   I just placed an order for 30' of the 8" size of your "#2" style. I'll
let
 > you know how it compares to the 4" and 6" stuff I've been getting from my
 > local Home Depot (and whether it's really 2-1/2' long when compressed!).

     I got in my 8" expandable aluminum duct and made an 8 x 36" out of it.
Here's my thoughts:
     McMaster-Carr listing the same compressed length of 2-1/2' for both
extended lengths of 15' and 30' is NOT a typo. I got their Part No. 
5525K47, which
is 30' extended. Cost $60.72, for those without catalog access. Comparable to
the pricing I got from our HVAC guy for similar duct (he would also have had
to special order it for me).
     It is simply "accordionized", so it compresses down quite tightly.
Accordion depth of about 1/4", which isn't very much. Seamless. Fairly 
stiff for the
material thickness. Covering might take a bit more foil, as the accordion
creases are relatively sharp and deep, but foil is cheap.
     NOTE: Struggle against any inclination to overextend the stuff. It will
buckle and leave nasty dents that are difficult to remove. I could get three
toroids 8 x 36" out of the 30' piece I got without straining.
     Extending it is a bit tricky, as it takes some force at even only 8" dia.
Perhaps the best way would be to clamp it at both ends around pipe, and pull
the pipes apart. Difficult to maintain a grip on with enough force while
extending.
     Not like the stuff I've been getting in 4" and 6" from Home Depot, which
seems closer to the Type #3 listed in your post. Note that Type #1 has a seam,
but I think it would be easier to cover as it has wide "plateaus".
     If you want to make just one toroid, you might want to try the Type #2,
but in the 15' length. It might prove smoother and easier to extend. The
cost/length is somewhat comparable.

-Phil LaBudde