[VAC] Re: Dent Removal

[wescott50@xxxxxxxxx (Bill Scott)]

Doug,  good question about the dry ice and dent removal.  I had to
scratch the noggin on that one.   Here's the theory.
When  sheet aluminum, like 2024  T3 is dented, the metal is unforgiving.
The dent or bulge, causes the aluminum to------------ "stretch and
expand", then the metal immediately "work hardens".  After the dent, the
area is slighty thinner in its stretched condition.  Like a ballon, it
stretches, but unlike a ballon , it does not shrink back into its
original condition, and it is "hardened".  Using "heat"  and/or "cold",
may help the aluminum to expand or contract,  slightly.  I have heard of
using a heat blanket, or a hair dryer, to warm the area and help it
become more flexible, so the dent can be "manipulated", then use the dry
ice to cool the metal so it will "shrink" and the dent will retract into
its almost original condition.  Using a torch   (like in sheet steel)
is not possible, because  aluminum will melt and oxidize at torch
temperatures.   In some conditions, like Paul Farley's Wee Wind, I think
he was able to just use dry ice, to shrink the dent, then pull it out
with a suction cup.   If the dent is "creased",  it is probably beyond
the stretching ability of the metal, and must be patched, or replaced.
I hope this explanation is understandable.  What one must visualize, is
the stretching and shrinking ability of aluminum.

Bill Scott
Charter Member and Membership Chairman
Washington DC Unit,  WBCCI   #3221
Our Homepage;  http://www.servintfree.net/wbcci-dc/