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Alan S wrote:  Navigation aside, there are many bridges that people all over the world traverse every day that were designed with slide rules, same with office buildings and similar structures.Of course, with structures, a few more yards of concrete can always be thrown in, or a bit more steel. For that "quick and dirty answer", I submit that the slide rule, stick or circular, still works, likely always will. Batteries not require being perhaps a singular virtue. Considering that the "stick" slide rule has two moving parts, the things are really quite amazing, or so they strike me, an old guy who is perhaps to easily amused.

Slide rules weren’t just used to design ground based items where the safety factor can be quite high, and the material can often be relied upon to ‘yield to fit’.  They were also used in the design of aerial vehicles where the safety factors have to be much less, or they’d never get airborne, and the light-weight materials need much more careful handling.  The well known author Neville Shute Norway (author of ‘On the Beach’) even used ‘Slide Rule’ as the title for his autobiography of his early days as an airship stress-man https://en.wikipedia.org/wiki/Slide_Rule:_Autobiography_of_an_Engineer  . 
As I remember, you were never 100% certain where the decimal point should go, and this led to the necessity for a quick mental estimate of what the answer ought to be, a precaution that’s sadly frequently missed now everyone relies on electronic calculators.  

I went through my postgraduate training in the early 70s when electronic calculators were just coming in.  All I felt able to justify buying was the simple CBM +-x/ model, but the enthusiasts were starting to buy the HP programmable models.  The old guard muttered that using them would make the exams too easy.  The staff in their wisdom provided more complicated questions.  DaveP