This is precisely why you should hire an engineer. If you only
look at strength, then your boat may fail. Stiffness is
often the governing criteria, and the spacing of frames,
bulkheads, stringers will have as much of an effect as
the thickness of the plating. Also the size of channel,
angle iron, etc will be different between aluminum and steel,
resulting in a whole new set of calculations. All these
dimensions are interelated, and making sure that things fail
in the right order is part of a good engineering analysis as well.

"boatdreams" wrote in message
...
With the emphasis on "approximately", aluminum has 60% of the strength
of steel. Algebra: 0.60 / 1.0 = 0.375 / x and x = 0.625 or 5/8"
Good luck,
Boatdreams

Techie wrote:

If a plan for a ship calls for 3/8" thickness in steel hull, what would
that be app. in Aluminium instead?