External stiffeners, paint, 'exotic' metals?

[Nathanael Henderson <jude@pconline.com>]

    It appears most subs have internal stiffening T beams, but I see a
number of references to external ones as well.   External beams certainly
have their appeal from the standpoint of internal space (and even some
ease of construction).  BUT, what do you do after putting on external
stiffeners?   How do you restore the hydrodynamic body shape to escape the
drag of exposed beams?  Putting on a second thin hull (perhaps with
internal ballast tanks, etc.) seems like the inevitable thing to do, but
then how would you maintain/rust proof the inner hull?
    Along those lines, is there any advice on how to treat the hull?  A
special type of paint?  Anybody up to hot-dip galvanizing a whole sub? :-)


     Materials.  Steel is cheap and easily worked, but what about aluminum
and titanium?   Aluminum would sacrafice some strength, but for a person
with money titanium seems like the gold standard for submarine material.
Besides the strength of titanium, it's almost complete invulnerability to
corrosion makes it a very appealing material.   Anybody know what
titanium costs in bulk and if it's unreasonably hard to work?  (The last
time I saw a price on titanium it was about $30 a pound, but that was for
wire, not plate/beam.)