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

["Marsee Skidmore" <heyred@email.msn.com>]

Another snotty feature of Ti is its relatively low Young's Modulus. Although
it's very "strong," it's not very "stiff." Corrosion resistance is a nice
feature, but I'm just not interested in leaving a submarine to future
generations. I'm hesitant to build devices that outlive my attention span.
There are a jillion finishing systems for steel, but the typical approach is
a phoshate "wash" primer, followed by an epoxy primer, followed by one or
more polyurethane topcoats. Yes, painting tends to push designs toward
simpler geometry. Hot dip galvanizing is a wonderful base for paint, and I
see it on bigger and bigger stuff every day. Zinc is getting more air play,
with Cadmium on the EPA's "Ten Most Wanted" list. I'll bet you could find
somebody to dunk a submarine in Zinc. :-o Joe
-----Original Message-----
From: Phil Nuytten <72020.572@compuserve.com>
To: INTERNET:personal_submersibles@psubs.org
<personal_submersibles@psubs.org>
Date: Sunday, March 28, 1999 2:41 PM
Subject: Re: External stiffeners, paint, 'exotic' metals?


>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
>