[Paddlewise] Mind Experiments on a Cold Winter Day - Einstein was onto something

This weekend I stayed on the farm and did nothing; my wife and I are both
fighting off a nasty cold that has raced through our family and finally
caught up with Grandma and Grandpa. This forced downtime has allowed me time
to catch up on reading some of those paddling articles in the magazines. You
know, the stories you just don't have time for because you're busy packing
to go paddling or skiing, etc.

I usually don't get sick. This is one of the few advantages of getting
older; my immune system has finally figured it out. This time the virus
must've been a new critter because my immune system is busily making me
miserable while it iterates through the calculations required to nip the
next attack of this particular strain of virus in the bud. Meanwhile I'm in
my robe and slippers for two-and-a-half days and catching up on my naps.

There are other advantages to getting older (notice that I'm avoiding the
simpler form, "old"). I no longer lay awake worrying about dying young, for
instance. And the database of cute-young-things has grown to remarkable
proportions. It's just amazing how many attractive over... uh... 35 gals 
including both my wife, Sue, and my favorite paddling partner, Pam  there
are in the world; why I never noticed this when I was 25 remains a mystery
to me.

Um... where was I? Oh, yeah. So this weekend I found myself thinking a lot
about various situations encountered in paddling. Albert Einstein, who was a
theoretical and not an experimental physicist, often said that he conducted
"mind experiments" in which he tried to imagine how the universe would react
to different scenarios. Now, I'm no Einstein, but I can do much the same
thing  but simpler  with paddling.

As an example, this morning I started thinking about the mechanics behind
turning a kayak. We all know that we can edge our boats to make them turn
faster but most of us only learned to edge away from a turn. Motorcyclists
and skiers edge into a turn. Why do kayaks do it the other way around?

The mechanics of edging a kayak to make it turn faster are simple: basically
you convert the hull from an essentially flat surface with little rise from
end to end into a curved surface with rocker. The more you edge the more
rocker you get and the faster the boat will respond to the turning moment
imparted by your paddle blade. Since both sides of the kayak are curved
pretty much identically (you'd know it if they weren't) then theoretically
you can turn just as easily to the left by edging to the left (banking) as
you can by edging to the right.

Why we don't generally turn by edging into rather than away from a turn is
mostly due to two factors: 1) The bracing action of the paddle; and, (2) The
effect of the water the bow is moving through.

In the usual turn we edge away from the direction of the turn and use the
paddle on the lowest side of the kayak to propel the boat through the turn
and onto the new heading. The paddle in the water provides the brace to
stabilize our edge and helps keep us from toppling over. Meanwhile the
bottom of the boat, being raised, protects us from having the water (which
is acting as a current as we turn the bow through it) from moving onto the
side of the boat and having that weight topple us over in the direction of
the turn.

But there are situations in which you might want to do exactly the opposite.

For instance, when you are in one current and want to move into another
current an accepted maneuver is to run along the eddy line (the boundary
between two currents) and then turn the boat sharply through the eddy-line
and into the other current by edging the boat into the turn and using your
paddle in a pry (or ruddering) stroke to keep the turn going until you are
entirely into the new current.

Another situation is when you are on the face of a wave surfing down and
want to turn back up the wave and off the face. You'd edge towards the
direction of the turn (and into the wave-face) while using your paddle to
rudder your stern around. This would probably be really interesting in a
round-bottomed sea kayak and your "edge" might turn out to be more of a
side-slip. Remember that the water particles are move in a circular pattern:
up the back of a wave and down the face of a wave so that you would not just
be fighting gravity as you move across that wave-face.

Skiers talk about "carving" turns as they move down the face of the slope
and so do white-water kayakers. But the face of a wave is more akin to
trying to turn in a moving avalanche than it is to a static snow slope so
it's much more difficult for a kayak to get a "bite" on that surface than it
is for a ski to bite into the snow. This is why kayaks designed for playing
in waves and holes (a white water term) have hard edges and flatter bottoms.

Einstein was really onto something with his mind-experiments. There are all
sorts of scenarios you can run through in your head. How to safely move your
heavily-loaded kayak up a beach after landing; a better system of arranging
the load in your boat; a new and safer deck-line arrangement; night
paddling.... the list goes on. While those of us in the frozen north have to
wait to put most of these ideas into practice the southerners can go right
out and try them.

That's ok... I hear the cross-country skiing is pretty slow down there.


Craig Jungers
Royal City, WA
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