Epoxy/Fiberglass Kayak Paddle Blades
Instead of curved plywood blades, I built blades from fiberglass.
I figured out how to lay up fiberglass blades. Find a clean 5 gallon bucket, cut the top & bottom off (epoxy doesn't stick to polyethylene), split it down the side, and lay it out into a nice, gradual curve. Screw it to a piece of plywood to hold the curve.
Cover it with about 5 layers of glass. This is a great place to use glass scraps trimmed off when glassing the hull or deck of your boat. You could also add a layer of fabric to the layup (ala Swift) and have cool graphics in the blade. Cut the blades to shape with a jigsaw, utility knife, or tinsnips. It works best to cut about 1/8" outside the line and sand down to the line.
Cut a curve in the shafts to fit the blade curve, and then use some thickened epoxy to glue the blades to the shaft. Cover the back of the blade/shaft joint with another 2-3 layers of glass - this really stiffens things up.
This photo
shows the first two blades I laid up--they're not pretty, but they've held
up so well I haven't replaced them yet. Notice on the top (right-hand)
blade, I miscut the glass blank when I was cutting out the asymmetric
shape--I accidentally cut two left-hand blades! A little bit more epoxy
and glass, and nothing but a thin white line to show for my boo-boo. I
had some strips of weatherstripping wrapped around the shaft for drip rings.
It worked well, but isn't too durable sliding against the roof rack of
my pickup. These blades are approximately 6.5" x 20" and have
proven to be very durable. I'll put some fabric in the layup of the next
blades I make like this, ala Swift paddles.
The blades and shaft were sanded smooth and varnished with spar varnish.
My next
attempt was to make some foam-cored glass blades. I carved pieces of Dow
BlueBoard into the shape I wanted. I covered the power face with a layer
of unidirectional glass, a layer of 45* bidirectional glass, and a layer
of 6 oz. woven glass. I then carved away the area where the paddle shaft
would glue on so that the shaft is glued directly to the blade rather than
the foam. The back was covered with a layer of 6 oz. woven. While laying
up these blades, I had some epoxy metering problems, so some of the glass
(on the back face) never fully hardened, so I just started using this paddle
in the not-quite-finished state. The power face was fully cured, so they
still work well. When the blades actually do give out, I'll just grind
them off and make some nicer ones on the same shaft. The white areas are
where water reacted with uncured epoxy. These blades are 5.5" x 21"--this
blade size and shape took some getting used to, but I really like it now.
I am thinking about making a foam form so that I can lay up dihedral blades. I'll take a piece of extruded polystyrene (pinkboard or blueboard), carve the negative shape I want, and fair and glass it. Once the glass is really smooth, I'll use that for the mold. I might even make a casting off of the mold and use it to press the layup between two mold halves for more fabric/less resin.