Re: [Paddlewise] Kevlar question

Scott,

>   It has been suggested to me that one can save weight in a Kevlar boat by
>foregoing the pigment in the hull. Is this true? 

Yup, but it doesn't work exactly like you think it does.  The pigment is
usually contained in some thickened resin, the part they call "gelcoat,"
applied to the outside of the boat.  A typical sea kayak would probably
have about three pounds of gelcoat on it.  The gelcoat acts as a cosmetic
and sacrificial layer only, adds no structural strength for it's weight.
If you are into cosmetics you'll want the gelcoat, but most of us buy boats
to paddle, not just look at.  

Gelcoat is on both fiberglass and Kevlar boats.  What it does is take the
scrapes and bumps that the strength members of the boat (fiberglass and
Kevlar would suffer if it wasn't there.  In the process it can gouge, star
crack, and chip, and flake off, etc.  That's better than the strength
members taking that abuse, but the glass and Kevlar don't abuse as easily
as the not strong gelcoat.  Gelcoat also looks pretty until it scratches
and starcracks, and chips.... which is soon if you bought the boat to use,
and not just look at.  Maybe some people take better care of their boats
than I do?  (almost certainly) 

Clear gelcoat is available and often used in Kevlar boats to let that
expensive Kevlar show through.  Sort of like the price tags on Minnie
Pearl's hats (or am I showing my age here?).   It does the same thing,
protects the strength members underneath (for a while), but doesn't look as
pretty cause you're looking through it at the stuff underneath.  Clear
gelcoat should have ultraviolet inhibitors in it as Kevlar is UV sensitive.
 Not bad though.  The surface of the Kevlar fibers darken with UV exposure,
which then blocks UV from getting to the interior of each fiber.  It's a
surface phenomenon only and us manufacturers don't worry about the
resulting insignificant structural losses, just the cosmetic effects, which
usually does take a few years.  

Boats with a "skin coat" rather than a gelcoat are available, though not
all manufacturers make them.  That's where the boat is made without any
gelcoat at all.  The Kevlar or the fiberglass is the outside of the boat.
Often more expensive cause the manufacturer has to do a really pretty job
of making the boat (pigmented gelcoat hides errors).  Same with clear
gelcoats, though.  The resin used for the skin coat can be pigmented,
usually at an insignificant weight penalty, though it seldome hides the
Kevlar very well, and may be pretty ugly if the Kevlar is the outside
structural fabric.  That's a color choice.  Ask the manufacturer of the
boats you are considering what the options are. 

Good luck,

Hank Hays
Lightning Paddles

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