[Paddlewise] rocker etc.

Steve Scherrer mentioned that he prefered a boat that had a more neutral
response to heel. Over the years I have talked to a lot of people about this
and have found that most instructors and "experts" seem to prefer boats
responsive to heel and most casual paddlers prefered a boat with less
response. Flat water racing paddlers  that I interviewed during my CCA
project days all preferred minimal response.

For just messing about the more responsive boat prfovides a lot of
entertainment but for tripping Steve's approach makes more sense to me. .

There has been a lot of discussion about how and why boats turn. The basic
physics are simple - any unbalanced forces around the yaw axis of the boat
will initiate a turn and the rate and direction of the turning will vary
with the magnitude  and directions of forces which will vary thorughout the
turn. There are some coupled forces with heave and pitch but these can be
ignored for simple discussions. How and why different hull shapes affect
turning and course stability (resistance to turning) is much more complex. I
developed a program for this that worked reasonably well in a comparative
manner but did not allow automatic variation of the hull to attain a
specific goal. I abandoned the project as it was taking too much time to
develop and it seemed easy enough to achieve goals intuitively.

The math just boggled my mind.

I think that anyone with a keen interest in boat control using heel and trim
changes would find a study of freestyle canoeing and paddlers useful. Mark
Molina, Pat Moore, Charlie Wilson, Sue Plankis and others have probably
forgotten more about this than most people will ever know or care to know.
Pat has a video (not sure if he has a web site) and I think Mark may have a
web site and video. Interestingly, most freestyle canoes have round bilges.
Dave Yost, Pat Moore and Mike Galt, the designers with the most experience,
all prefer round bilge designs. No doubt a host of reasons and maybe they
all don't directly apply to kayaks but I have found that the same
hydrodynamic principles that apply to canoes have almost always applied to
kayaks without any modification.

I paddled a hard chine version of one of my round bilge designs last summer
and could hardly tell any difference so it seems that people should not get
hung up over a specific hull shape.

Cheers,

John Winters




***************************************************************************
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/
***************************************************************************