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Subject: Re: TWL: Aluminum Boat Problems in the News
From: George Randall (georandall@XXX.XXX)
Date: Thu Feb 21 2002 - 10:17:44 EST
quote
the problem is limited to a particular aluminum alloy, 5083 H321.
This is a relatively new alloy that was not widely used in
local boat building until very recently.
unquote
FYI - My 1975 (sic) copy of Marine Metals Manual by Roger Pretzer, pub
Int'l Marine Pub Co., Camden Maine ISDN 0-87742-055-6 lists 5083 H321 in
their table of Popular Marine Aluminum Alloys. It is the middle of 3
varieties of 5083 of increasing strengths, each having a different
'temper' designation, e.g.. H321.
For the lower strength variety of 5083 the "available forms" are "sheet
and plate" and the "usage" is "hull, deck".
For 5083 H321 the "available forms" are "extruded shapes" and the
"usage" is given as "bulkheads". Perhaps this particular 'temper' of
5083 is better used internally rather than in the hull plating.
Further, the number 3 in the H321 'temper' designation "is for aluminum
magnesium alloys only, because these will soften with age if they are
not cold worked and then stabilized by a low temperature anneal." Sounds
like one or two things could go wrong in the manufacture of this
particular alloy.
George Randall
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