floating concrete horsies

[Dick Morrisson <rmorrisson@unidial.com>]

Dave,
After your comment on the 10 ton trucks on the old Roman concrete
bridges I recalled a more modern example of concrete used in a marine
environment.  There are two floating bridges in the Seattle area which
cross Lake Washington and carry trucks exceeding 30 tons every day.
These are supported on concrete pontoons and are very safe (except when
people leave inspection hatches open in high seas!).  The traffic on
these bridges probably exceeds 10,000 cars/trucks per day.  This would
be strong evidence of concrete as a viable floatation material with
plenty of payload.  They are of course very large and therefore don't
compare well with p-subs.  I think every material has its place when all
things are considered, we just have to be smart about it and learn from
our past (and everyone elses past) mistakes.  In my line of work
(engineering hydraulic and pneumatic systems) I have to evaluate new
ideas and materials very often.  I consider performance, cost,
appearance, maintainability, etc...  There is one term though which is
my favorate, "Robustness".  This is a vague term to some but to me it
means the ability to handle the unexpected as though it were an everyday
occurance.  In a p-sub this would get you back home to tell the story
instead of having it told about you.

Thanks for listening and may all your subs be robust!
Dick Morrisson