Re: [Paddlewise] Excessive Weather Cocking (or is it Fairy gliding with the wind)

"Michael Daly" michaeldaly_at_rogers.com wrote:

<SNIP>>>>>>>>>You seem opposed to wind ferries and my point is that they are
effective,
especially in conditions where the wind is not accompanied by significant
waves.  Paddlers have been using ferry techniques for a long time and
my own experience is that they make life easy.  You imply that the make
for more work.<<<<<<<

How can I be opposed to something that I can't avoid (at least if I want to
go somewhere in a kayak when the wind is blowing from the side)? You seem to
be implying that there is some advantage to be gained from this wind.
Without a good upwind sail and a deep keel, center board, or leeboard the
best you can hope to do is minimize your losses by choosing the best ferry
angle consistent with your goals. Your goals could range from minimizing the
strain on an injury, to minimizing total energy expended, to getting to the
take-out before a rapidly approaching thunderstorm. No matter what angle you
choose to cross you are to some extent subject to the effects of the wind
and the kayak won't be moving in the exact direction through the water that
it is pointed in, therefore by definition it is ferrying when going across a
wind.
The push you get in this sideways direction while ferrying is not powered by
the wind alone. On its own, the wind would blow you downwind. So where is
the energy coming from to make your boat move somewhat sideways in the
direction of your goal (if there is no current)? It looks to me to be coming
from the energy expended paddling against the wind to hold your position on
the line of your intended course (at whatever angle into that wind you
choose to adopt so as to best meet your particular goals). The steeper your
angle into the wind the more streamlined your craft will be to the wind and
this will make it easier to counteract the wind and remain on the course
line. You would need to apply the least effort resisting the wind to remain
on the line of your intended course if you point your kayak straight into
the wind. Unfortunately this heading doesn't move you any further along the
course line towards your goal. Going directly into the wind you would
ultimately expend an infinite amount of energy to never arrive at your
destination. This might feel good for a little while because you would be
expending energy at the lowest possible rate consistent with staying even
with the course line. Not only is your pointy-ended kayak most streamlined
to the wind at that angle but there is also no hull friction to overcome
when you are standing still relative to the water (other than due to yaw
from your off center strokes). The more directly you point your kayak
towards your goal (and still stay on your intended course, holding to your
line relative to being pushed downwind) the higher the rate at which you
would have to expend energy to do so. Not only does the wind have nearly the
whole side of your kayak to push against but you have to go much faster at
that shallow angle to stay on the course line because you must travel so
much further in a given amount of time (because time is a factor in how far
the wind drifts you to the side). The redeeming feature of this shallow
ferry angle choice is that you would get to your destination a whole lot
quicker (vs. not getting there at all going straight into the wind). So
while the rate of energy expenditure is higher in this particular case the
total energy expended would be lower. Of course it feels easier at the time
to not work as hard (by going straighter into the wind) but the catch is you
must continue this for so much longer that your total energy expenditure for
the trip may well be greater.
The effects of hull friction (and the other factors involved with drag--one
of which is the efficiency of the hull at the angle it is moving through the
water) as well as the limitations of the horsepower available and the
efficiency of the "engine" are going to determine which angle to keep your
kayak angled (to the wind) to be the most efficient in terms of total energy
expended to reach your goal. Nearly any kayak's hull is most efficient when
going in the direction of the pointy end, but at very slow speeds this
hardly matters. Trying to go too fast will increase the frictional drag (at
nearly the square of the speed) and eventually as speed is increased you
will bump into "hull speed" beyond which you would be using energy at an
unsustainable rate (because you are working against gravity as well as the
rapidly increasing friction at these speeds) and would be exhausted before
being able to go the entire distance to your goal. Somewhere in between
these two extremes will be the angle to the wind that allows you to use the
least total energy to reach your goal. For a variety of reasons most
paddlers will chose to expend more than that optimal amount of energy if it
significantly increases their speed without too great an additional strain
or energy cost. Much like the same choice a paddler makes whenever they
choose to paddle at a less efficient 3 or 4 knots rather than at say a much
more efficient speed of 1 knot or less.

I think another reason (besides the rate of energy expenditure) you may feel
you are working less hard to "wind ferry" at a steeper angle is because at
that angle (as you described) you did not have to spend a lot of extra
energy fighting the weathercocking tendency as you would have had to do in
order to keep the pointy end going more in the direction you wanted to
travel. This brings me back to my original point. It is better to have a
kayak that is neutral to the wind (when moving forward at a reasonable
speed) rather than one that weathercocks or lee-cocks because all known
methods of compensation for an imbalanced wind/water couple have costs that
can be measured in terms of extra energy expended to keep them pointed in
the right direction.

If offered the choice of waiting around (while you expended a minimal amount
of energy and protected your injury) or towing you, I would gladly have
chosen to tow you. That way you could have cut your energy expenditure and
elbow strain to near zero, while the group stayed together and also
maintained a comfortable and reasonable pace. I could probably use the
exercise.

Matt Broze
http://www.marinerkayaks.com


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