Subject: RE: baidarka stability/performance vs. flexibility
From: Peter A. Chopelas (pac@premier1.net)
Date: Thu Dec 21 2000 - 23:16:18 EST
Bill wrote:
> Peter,
>
> To apply the results of the tests you propose, it might be useful to
> conceive of a way to measure and quantify looseness (tightness) so two
> people building the same design in different places can achieve the same
> level of stiffness. There should also be more then two values of
> looseness, however that might make the experiment more difficult.
>
I already thought of this, there are a number of simple ways to measure
flexibility that can be done in a shop with simple tools that who ever is
participating could set up so we are all measuring to the same standard. I
think was is also critical is dimensional control, so we are comparing
differences in flexibility, not hull shape.
> An alternative here might be to take the loosely lashed boat and tow it
> with a scale (to measure towing force) and compare this to speed (GPS?).
> This could be done on the same boat with different levels of tightness.
By
> conducting tests on several levels of tightness, you can determine if any
> effects you measure are linear or not and, perhaps, be able to recommend
an
> optimum level of looseness for that design. Of course, this is
optimizing
> for speed and not stability.
That would be interesting too though I was not so much interested in drag
and had not planned on measuring it. That would work, also measuring top
speed obtained with each of the paddlers in each hull. I was more thinking
of measuring the more dynamic performance (and something harder to
measure): like how controllable it feels in rough conditions, how it surfs,
how tight you can turning (I think a flexible hull would make a much
tighter turn), how easy it is to roll, directionally stability, roll
stability, etc.
These are harder to measure and some are totally subjective, hence the
reason to have a variety of paddlers give their impression. Jim claims the
skin on frame biadarka is much more "lively" (what ever than means, though
I can imagine it but I doubt it is measurable) compared to the identical
rigid fiberglass hull.
I think this would be a fun excuse to build another kayak and get a bunch
of paddlers together. We actually might learn something in the process.
Any volunteers?
Peter
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