Re: External stiffeners, paint, 'exotic' metals?

[Phil Nuytten <72020.572@compuserve.com>]

Hi, John:
        Please excuse me for jumping in on your exotic metals thread . .
.this is actually for "ALL":

John Brownlee's synopsis of working with titanium is absolutely right on
the money!! I particularly like the ' crotchety old lady to get out of the
shop'   . . .Ti is miserable stuff to work with  but nothing short of
miraculous once well-finished and in service. It is so damn tough, tho' . .
. very hard to roll or form because its 'spring-back' is much greater than
usual materials -  tears the heck out of carbide tools . . .highly
flammable in 'steel-wool' shaving form ( I first started working with Ti in
1984 - we used it for the knife-edge seals in the NEWTSUIT rotary joint -
the knife edges were machined to a high surface finish prior to being
diamond honed to a one micron  final finish- this produced piles of 'angel
hair'-like shavings - one of our German machinists was a heavy smoker,
always had a butt dangling out of the corner of his mouth, even while
machining . . the result is predictable!  He later said "Jeez, I thought
was the end of the world! " like a giant magnesium flashgun . .eyebrows
gone, forelock gone, and moustache so badly damaged it had to be put down!
. . . something to remember) 
        We (Nuytco) use rolled, welded Ti  for our battery pods when we
need to pick up a couple of hundred pounds of additional bouyancy.  One of
the real problems with a multi material sub is accelerated electrolysis
when the nobelest metal is large in size/weight relative to less noble
materials - we have to coat the Ti, - which is a real shame 'cause it looks
great when polished and doesn't corrode at all - or the mild steel hull
will fizz like a seltzer tablet, trying to protect the pods!
        We are currently building several elaborate combination lifting
frame/crash-bars  made out of Ti, for a customer who will be using the Deep
Workers 24 hours a day and doesn't want to get shut down by rough seas - by
being able to lift on the crash-bar assembly, they can use a hydraulic
knuckle boom handling system which can latch remotely, 'rigidize'
hydraulically, and they can 'pluck' the sub out of the water, even in
fairly ambitious sea-states. The resulting frame is about twice as heavy as
aluminum, but half as heavy as steel, using the same dimensions. But the Ti
is almost the same strength as steel (depending on the respective grades
and alloys) whereas the aluminum would have to be thickened to where it
weighed more than steel to have the same strength. Hmmm . . .I'm not sure I
said that very clearly, but you get the idea. 
        In short, titanium fabricated systems are extremely expensive
compared to more common materials,  primarly because of the high cost of
dealing with it as a fabrication material  . . .but once done, it is very
nice stuff, indeed, and there are specific applications where the result is
worth the increased cost and pain in the . . . !

regards
Phil Nuytten