Configure the paddle's overall length to your body, measuring one full arm span plus the distance from your wrist to your elbow. Cut your cedar board to that length. Draw lines marking the width of the paddle's loom -- the thin middle section where you hold it -- at about shoulder width.
Turn the board onto its side, and mark the taper of the blade. Draw the centerline along the middle of the board's narrow side. Then draw a second line extending from the end of the loom, or handle, to a point 1/4 inch above the centerline at the end of the board. Draw an identical line on the other side. Cut the board along each line, creating a taper that concludes with a 1/2-inch width at the end.
Draw a centerline along the length of the board on its wide face. Draw two parallel lines, each of them removed from the centerline by 1/2 inch along the length of the loom in the board's center. These lines mark the loom's width. Cut, following the lines.
On the board's broad face at each end of the loom (which you have marked), draw tick marks one-quarter of the way in from each of the board's edges. Draw additional tick marks, showing the board's full width 4 inches from its end. Draw a line connecting the upper-side tick marks, extending from the end of the loom to a point 4 inches from the end of the board. Do the same for the lower side. Cut along the lines, giving shape to the tapering width for half the paddle. Repeat for the other side of the paddle.
Sketch curves, creating smooth, rounded edges on the broad face of the paddle at each end. Also, sketch the shallow S-shape of each blade's shoulder, where the loom joins the blade. Cut along the sketched lines with a jigsaw.
Adjust the thickness of the blade. Draw two parallel lines that are 3/8 inch apart, extending from the end of a blade to a point two-thirds of the blade's length. Then widen the lines so that they are 13/16 inch apart at the blade's root. Cut along the lines, giving shape to the blade. Repeat for the other end of the paddle.
Trim the corners along the length of the paddle, successively cutting away each corner's edge until each of them is rounded and smooth. The blade's roots should be oval. The blade's ends should be slightly convex. The cross section of each blade extending from the root to a point about halfway along the blade's length should be diamond shaped. Trim so that the changes in the paddle's shape flow together.
Sand the finished paddle, making sure to wet it to raise the grain before the final sanding.
Apply either epoxy resin or spar varnish on the entire paddle, providing a laminated finish. Allow it to set for 24 hours.