[Paddlewise] more on life of plastic and plastic boats

Dave Kruger wrote:
> 
> rdiaz_at_ix.netcom.com wrote:
> >
> [snip]
> > I wonder if some other factors should be added.
> >
> > Thickness of the material.  The walls of a polyethylene boat are of x
> > thickness.  That would likely mean that they would age a lot faster than
> > say the half inch thick high density polyethylene cross ribs used in
> > Feathecrafts.
> 
> Yup.  And, sea kayak hulls are normally thicker than the usual PE bottle's
> walls.
> 
> > Length of the material in conjunction with how much it is subjected to
> > flex.  I sense that polyethylene white water boats (except for the hard
> > knocks they get against rocks etc.) tend to last a bit longer than their
> > sea kayak counterparts because of the differences in length and amount
> > of flex.
> 
> Both valid points, Ralph.  I suspect thicker materials such as the Fcraft
> ribs will outlast you or me!  (Are they polyethylene?  I believe Folbot
> frames are a filled polycarbonate -- much more long-lasting than PE.)

Feathercraft uses HD polyethylene for cross ribs in all its boats except
the K-Light.  The K-Light uses polycarbonate.  Feathercraft also uses
polypropylene at the bow and stern pieces of their boats.

The polyethylene is cut on jigs using 1/2 thick slabs of the stuff (the
jig cuts do 2 slabs at a time to yield 2 sets of ribs).  The
polycarbonate, like that used in Folbots, is from molds.  Feathercraft
executes its ribs somewhat better than does Folbot.  The holes in the
polycarbonate in the Feathercrafts are all part of the molds where as
Folbot does some drilling in its polycarbonate.  Feathercraft strives
for rounded corners everywhere whereas Folbot's corners in places are
sharper.  In polycarbonate, any drilled hole and any sharp corner is a
potential weak point for cracks, fissures, etc.

Feathercraft uses polyproplene in the bow and stern pieces precisely
because it can take drilling and it flexible.

As you can see, choices of "plastics" fascinate me and how different
companies work in different ways with them. My interest in this has led
me to by chance run across the formula for determining the life
expectancy of a plastic boat.  This will help answer the question that
led to this string. Here is the formula:

Find the boat's Bartow coefficient (the average thickness divided by the
square root of boat length).

Establish the Lonval or longitude value.  To do this determine the
degree of longitude of where the boat is mostly used.  Use your GPS or a
map or chart to establish this.  Divide the sum of the degrees and
minutes of longitude by 3 to get the Lonval.

Consider the ROY G BIV factor, which is based on the color of the boat.
If the first letter of the boat's color is in the ROY field, the factor
is 3.  If in the BIV field, the factor is 7.  Boats in colors that begin
in G gets a 5.  So a green colored boat would have a ROY G BIV factor of
5, a red boat 3, a blue boat 7, etc.

Now divide the Bartow coefficient by the Lonval value and multiply the
result by the ROY G BIV factor.  That should come up with a close
approximation of
the life of the boat in terms of months of life expectancy.  Honest! 
:-)

ralph diaz


-- 
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Ralph Diaz . . . Folding Kayaker newsletter
PO Box 0754, New York, NY 10024
Tel: 212-724-5069; E-mail: rdiaz_at_ix.netcom.com
"Where's your sea kayak?"----"It's in the bag."
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