Re: [Paddlewise] Your expertise needed again

-----Original Message-----
From: John Fereira <fereira_at_albert.mannlib.cornell.edu>
To: Alex Ferguson <a.ferguson_at_chem.canterbury.ac.nz>
Cc: PaddleWise_at_lists.intelenet.net <PaddleWise_at_lists.intelenet.net>
Date: Monday, June 21, 1999 7:01 PM
Subject: Re: [Paddlewise] Your expertise needed again



>  There are at least a couple of plastic boats that have welded
>  plastic bulkheads (the VCP Skerray RM, for one).  I understand
>  that foam bulkheads leak, but how long do they generally last
>  before they start leaking?  If it's only a year or two, that
>  would seem to be long enough to decide whether to fix it or
>  upgrade to glass.
When asked by a customer if the caulked in foam bulkheads were watertight
the designer and retailer of one model would answer that they were
"guaranteed to leak in a week". I may be a little out of date here but
nothing much sticks to polyethelene very long. How to you fix it once you
have decided to?

When I called one designer of a plastic kayak (same one) to asked if he had
changed the design. I was curious because when I retested it it now turned
about twice as fast and didn't track worth a darn anymore. He informed me
that the design hadn't been changed but that no two plastic kayaks of the
same model are the same. It seems the highest paid guy in the factory was
the guy who tried to wrestle them into shape once they came out of the mold
(all soft and rubbery) before they cooled ans stiffened up. Since then I
have retested my turning times on several plastic kayak models and while
none showed the extreme differences of that first one there was definitely
an inconsistency that was not there on retests of fiberglass models unless
there was a design change. Lesson: If you plan to buy a plastic kayak test
the very one you are thinking of buying, not just a demonstrator. Once you
buy it be very careful in storage not to hang it or set it in a way that it
can sag out of shape. This can be especially severe in hot climates or
locations. Do not store them in the sun either because the sun (as well as
ozone and breakdown products of natural gas--among others--I imagine) cause
the plastic to lose plasticizer more readily and this results in premature
brittleness. The life of even a well cared for plastic kayak is far shorter
than most fiberglass kayaks due to this plasticizer migration. Once a
plastic kayak that has become brittle cracks, trying to repair it is
probably not only futile but potentially dangerous because it is likely to
just crack again somewhere else maybe at an inoportune time. The "repairs" I
have seen done to plastic were grotesque. Severely damaged glass kayaks can
be made to look almost new.
While I have paddled some plastic kayaks that I liked a lot better than some
fiberglass ones I paddled the same day my general impression has been that
they feel "dead" as opposed to "lively". I'm not sure why but I suspect it
may have something to do with flexing and absorbing some of the energy of my
stroke. Also the heavier weight may contribute to the feeling of a lack of
acceleration when starting one up. My first thought is often  "am I dragging
something?" and then after looking back to see, I realize "oh yeah, plastic,
why do I forget to expect that heavy dead feeling and get surprised every
time."

The towing tank tests Sea Kayaker did back in 1986 suggest that there is
more drag on a plastic kayak than a glass one even when they are both new.
Once they get scratched up the difference becomes much greater because
roughness sticking out into the flow causes far more drag than the inward
(scratches and gouges) roughness that happens to fiberglass gelcoat.
There are some fiberglass kayaks that aren't much more expensive than
plastic ones that I like a lot better than any plastic kayak I've ever used
(but since I sell them maybe I shouldn't mention them by name as that might
seem too commercial--even though they are sold many other places as well as
by me and I have no other connection to the company.)

Comparing toughness between plastic and fiberglass is rarely done by using
the same weight kayak. A well made 78 pound fiberglass kayak would be
extremely hard to break. Rarely does a paddler need that kind of toughness
and most gladly trade some of it away for something they can lift onto their
car by themselves. Most sea kayaks made of plastic need to be thicker (and
therefore heavier) to get enough stiffness just to hold their shape.
Matt Broze
http://www.marinerkayaks.com

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