[Paddlewise] Strength, stability and (shudder) serviceability

These three words were drummed into my head in university.  In studying
structural engineering, we learned that these were the three criteria that
had to be met in any design.

Strength       - it shouldn't break
Stability      - it shouldn't fall over
Serviceability - it should meet its design objectives and satisfy the
                 needs of the users.

Strength is easy; we can develop analysis models and determine design
parameters that, with safety factors, give us the strength we need.
Stability is a bit trickier.  Buckling and such is difficult to calculate
and sometimes hard to prevent.  But it's doable.

Serviceability is a nasty.  There are, for all intents and purposes, _no_
deterministic parameters that define serviceable.  It is entirely a
subjective thing.  And in structural engineering and architecture, it
is the thing of lawsuits!

Recent discussions about the stiffness of kayaks have brought this back
to my mind.  John W. has commented (paraphrasing) "We know how to make it
strong, but don't know how strong to make it."  So by trial and error, we
find kayaks are reasonably strong, though some, who push limits, prefer
stronger.  Stability is similar - we can stiffen the kayaks to the point
that they won't fail by the deck or hull buckling.

But serviceability?  How do we define that?  I've said that I want a kayak
that is stiff enough to avoid oil canning and other hydrodynamics-spoiling
effects but any stiffer is too heavy and expensive.  Doug on the other hand,
wants stiff, _stiff_, STIFF!  Skin boat enthusiasts like their boats pliable
and sensually moving _with_ the water.

I think that to some extent, the stiffness issue is more a serviceability
one than anything else.  There is a degree of stiffness that is required,
but beyond that it's subjective.  Folks know what they want, but do they
know what they need?  I don't.  I haven't seen hard data to allow me to
judge the lower limits.  I know my kayak performs well enough.  I also
know I keep thinking of building a skin-on-frame kayak.  That will be
much more fragile than my current kayak.  I won't take it out in conditions
that I'd take my Solstice.  And I won't take my Solstice out in conditions
that Doug'd take his armour-plated Nordkapp.  So it goes.  But each will be
serviceable for _me_, since it suits my perceived needs.

When you view your current or prospective kayak, don't get hung up on the
limits of what is subjective.

Mike

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