Stuart,
Thanks for the lead. I have ordered the book.

Stuart & Kathryn Fields wrote:

Gary: Fatigue Design of Aluminum Components & Structures, Sharp, Nordmark
and Menzemer, a chart, page 110, shows decrease in fatigue life due to
pre-cleaning as well as the affects of Alodine and a couple of different
thicknesses of anodic coatings.



Gary: The text that "Gary K" wrote in message
...

A 269A Hughes (and subsequent models) has some critical parts hard
anodized. I don't recall any parts with "normal" anodize.

Do you have any cites on the cleaning issue? I would be interested in
reading them.

Gary

Stuart & Kathryn Fields wrote:


aluminum control tube failed causing helicopter crash. The helo had an
anodized aluminum control tube that failed in fatigue with less than
400hrs. The loading was low producing stresses in the area of 460psi.
Discussions with anodizing folks say "Never anodize flight critical
components" Some research has provided data indicating that some
cleaners can also shorten the fatigue life of aluminum significantly.
I've seen gyrocopters with long anodized aluminum control tubes shaking
like your English teacher's No-No finger. The May 07 issue of
Experimental Helo has a more indepth article on this with pictures of the
helo before and after..
.