O'Neill's aluminium vs. something else (was Aluminium can sub for st

> > "The welding of 2014 aluminum in 8 in. thick plates"
> And this is why it's only partially useful. It is very
> difficult to transform such material into anything
> remotely useful.

To what material are you comparing it?

> The expense, mass, and cost of the factory needed to do
> this would very likely make the concept uncompetative
> against other supply systems.

Other supply systems of what?

In case you are comparing hull aluminium alloy to some other source
of aluminium alloy (and aluminium alloy is not the same thing as
plain aluminium*), and in case material thickness is anticipated to
violate Minimal Cost Design, the RP-1 tank in the 1963 version of the
Sea Dragon is not necessarily made of 8 in. thick plates.
http://neverworld.net/truax/Sea_Dragon_Concept_Volume_3.pdf

"Elimination of all welding appears to be possible if the tankage is
constructed of multiple I/4 in. thick laminates, mechanically joined
and sealed with a soft metallic liner. Mechanical joint efficiencies
of over 94% are possible. The use of sheet materials under I/4 in.
thickness from guaranteed properties aspects, and the direct process
control techniques applicable to mechanical joiningmethods offer
distinct and immediate advantages in the construction of very large
pressure vessels. These advantages are pronounced where fabrication
is to be attempted in shops which do not have a history of aircraft
quality manufacturing experience."

Also, aluminium is easily machined with waterjets (abrasivejets) --
even pieces over one foot thick.
http://www.omax.com/materials_aluminum.php
http://www.google.com/search?q=waterjets+aluminum+%22bread+and+butter%
22

"Aluminum is often called the "bread and butter" of the abrasivejet
industry"

*
http://en.wikipedia.org/wiki/Aluminium

"The yield strength of pure aluminium is 711 MPa, while aluminium
alloys have yield strengths ranging from 200 MPa to 600 MPa. ...
Aluminium ... is ductile, and easily machined, cast, and extruded."