Subject: Re: baidarka stability/performance vs. flexibility
From: Tom Wainright (wainair@yahoo.com)
Date: Fri Dec 22 2000 - 00:12:07 EST
Good points, I think you would find the amount of flex
would be according to the preference and skill of the
individual paddler. I understand in the old boats of
the aluet they used Ivory sliders in the joints so
they would slide more freely, and that they would add
ballast to the bow and stern to magnify the undulation
of the boat in the waves to increase speed and reduce
paddling effort.I can't remember were I read these
things but I'm sure Wolfgang or Mr. Zimmerly would
have an idea. Tom
--- "Peter A. Chopelas" <pac@premier1.net> wrote:
> Jim brought up an interesting question about the
> rigid fiberglass baidrada
> vs. the skin on frame ones that Cory Freeman has.
>
> There has been a lot of literature published and
> much discussion (and
> speculation) on this and the Paddlewise lists about
> the affects of
> flexibility. I have recently had some off list
> discussions with another
> list member about flexibility and kayak performance
> and an idea occurred to
> me for which I would like the list members comments
> and input.
>
> I one of my engineering professors used to say that
> one experiment is worth
> a thousand expert opinions and I thought it would be
> easy enough to do such
> an experiment since kayaks are small and simple
> enough to build.
>
> My idea is this: get a couple of builders together
> to build identical
> baidarkas except for the frame stiffness, then get
> together with a group
> of paddlers with different experience levels and
> actually compare the
> performance under different paddling conditions.
> One hull would be fairly rigid and tight lashed,
> another flexible and loose
> lashed. All other dimensions, materials etc. would
> be as close to
> identical as possible.
>
> You would have to get at least two builders that
> want to build identical
> kayaks of course. But this would allow a side by
> side comparison in the
> same conditions.
>
> Another alternative would be to build a single loose
> lashed kayak and wrap
> it with plastic and duct tape and give it a tryout,
> then re-lash it and
> perhaps add some stiffeners to the frame, and again
> skin it with plastic
> sheet and duct tape and try it again. Of course you
> would lose the
> advantage of being able to try it out side by side
> but you would only have
> to build one experimental hull.
>
> You would also want to plan to have a number of
> different skill level
> paddlers trying them out and make fairly detailed
> notes on their
> impressions and conditions in which they used them.
> It also might be
> interesting to try a number of different stiffness
> of hulls; one really
> flexible, one medium, one stiff and one real rigid.
> I suspect there is
> likely a point where a hull being too flexible would
> be detrimental as well
> and this would help us locate where that point is.
>
> It would be interesting to learn which is better and
> end the speculation.
> If the experiment and results is well written Sea
> Kayaker magazine might
> publish it. And if done properly would end this
> constant second guessing
> and debates, it may even result in changes in
> factory kayak design.
>
> I suspect that there are some conditions that the
> flexible hull will out
> perform the rigid hull, and other conditions which
> are just the opposite,
> just like stiff and soft snow skis. I also suspect
> that if there was some
> way to maintain torsional stiffness and make it
> relative flexible
> longitudinally it would perform better than one that
> is both torsionally
> and longitudinally flexible. But I am just
> speculating.
>
> What do you think, any volunteers want to give it a
> try? I live in the
> Puget Sound area a little north of Everett (where
> Jim Mitchell lives), I
> was planning on building several skin on frame
> kayaks over the next year
> anyway, one for me and one for my wife. The more
> data points we collect
> the more meaningful the experiment will be. It
> might be fun to combine the
> get together with one of the kayak gatherings we
> have in the area. I think
> Cory is planning another skin boat gathering in
> Anacortes this coming March
> or April, it would be a good place to run the
> experiment.
>
> Anyone interested?
>
> Peter
> Arlington, Washington
>
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