Re: [Paddlewise] Hard chined hulls

I agree with John Winters and Nick on this one. At one point John wrote:
"...so long as all other parameters were kept equal (hard to do)". Not only
impossible to do but we will get different results depending on which of the
other parameters it is that we choose to give priority to in trying to be
equal. For instance, if we keep the dimensions (or more likely) waterline
dimensions equal the chine boat will suffer greater wetted surface and
possibly a lower Prismatic Coefficient. Both may lower top speed. However,
if the factor we choose to keep equal is a more important one to the paddler
like "the stability curve" we may find that we can make the hard chined
kayak narrower (cutting its wetted surface and volumetric
coefficient--another important factor in speed) and end up with a faster
kayak that is just as stable as the rounded chine kayak. Since hard chines
can also help retard side to side and skidding motions the hard chine kayak
may feel even more comfortable to the paddler than the "equal static
stability curve" might indicate (allowing a hard chine kayak to be built
even narrower and faster--if we hold the "intimidation factor" equal for our
comparisons).

Hard chines by themselves don't really tell you much about how a kayak will
handle because many other factors in the design can overpower (or enhance)
the effects due to hard chines or rounded hull. Yes, hard chines will
probably reduce sideways skidding but so will a lot of "V" on the keel (or a
skeg or a fin keel on a round hull). Things are not so simple that you can
say one thing about a boat always has the same final effect. There is a very
complicated interaction of many factors that determine the many aspects of a
hulls performance. Everybody would like a simple straight forward answer to
"once and for all time, what does this do?", unfortunately, things are often
much more complicated. The trick in hull design is to understand the
environment and what tends to have what effects in that environment and then
blend that knowledge in a way that the hull does what you want it to do in
the conditions that the hull will be used in.

Some designers get lucky with a hull design even though they don't have a
clue what they are doing. If they then have enough sense to keep recycling
that hull design over and over with different decks and names on it they
might even get a good reputation as a designer based totally on their
initial good luck. Of course, if their reputation goes to their head, and
they design a new hull that sucks and/or start to provide us with the
benefits of their knowledge in books and articles then they leave themselves
wide open to bashing. My late dad always said something like, "Its okay if
some people think you are stupid. Why open your mouth and remove all doubt?"

Matt Broze
http://www.marinerkayaks.com


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