RE: [Paddlewise] Bad forward sweep

Hi John,

John wrote:
>I was always taught that a boat turned around it's center of flotation,
which is
>somewhere around your rear end!  You can't turn a boat without turning both
ends.

	While it's my belief that the boat actually turns around the boat/paddler's
center or gravity when at rest, descibing this as it's center of floatation
is close enough for me. With regard to turning the boat by turning both
ends, this is true *as long as the boat is not moving* but different forces
come into play when the boat is moving.

	When the boat is *moving forward* there exists a bow wave that has a
similar effect as pushing the bow deeper into the water, retarding any
tendency for the bow to move left or right appreciably. The first part of a
forward sweep is pushing against this bow wave and having little effect. The
middle part of the sweep cannot turn the boat either because the bow wave
again fights any effort to move the bow left or right. So the middle part of
the sweep tends to move you forward. But the last part of the sweep is
acting against the stern that is not "anchored" by a bow wave and may in
fact be in a wave trough. This makes it possible to pull the stern  towards
the paddle during the last phase of the forward sweep, in effect performing
a stern draw.

	A clear example of this can be seen by taking your boat up to speed, say
about 4 knots. Then try to turn the boat by doing only the first 1/2 of a
forward sweep. Count the number of 1/2 sweeps that are required to turn the
boat 180 degrees. Then perform the same test only this time use only the
last 1/2 of the sweep stroke. To keep things easy, try to do the turns with
no edging of the boat and be sure to take the last 1/2 of the sweep all the
way to the stern. Think hit the boat with the paddle. Most people find that
the boats turn with significantly fewer strokes when they use the last 1/2
of the sweeps compared to the first 1/2 of the sweep stroke.

	There are other people on this list, much more technically inclined than I,
that can do a much better job of explaining why this works. I only know that
it works and my own simple model that helps me understand why. Hopefully one
of our engineers will step in and correct/clarify my explaination.

Jed


***************************************************************************
PaddleWise Paddling Mailing List - Any opinions or suggestions expressed
here are solely those of the writer(s). You must assume the entire
responsibility for reliance upon them. All postings copyright the author.
Submissions:     PaddleWise_at_PaddleWise.net
Subscriptions:   PaddleWise-request_at_PaddleWise.net
Website:         http://www.paddlewise.net/
***************************************************************************