Nearing the end of the project, I still didn't have any paddles! After all the work done on the boat itself, it seemed like a crime to go and buy the paddles.
The first version, as described below, was built with ordinary, non water-resistant plywood. After many years of use, water finally seeped in between the plies, and a new version was necessary. I made the new version using string techniques, and increased the area a little.
Note that the original paddle served me very well! Using either marine plywood, or a better paint, maybe impregnating, would make the construction still very useful.
The form of the blade is as personal as tastes or colors. I tried to make sense of all the things I found on the 'net. Surface area was determined to be between 90 and 120 square inches. Finally, the design I made ended up with 105 square in., about 670 cm2.
The actual form is another discussion point. I didn't want to complicate things too much and settled for a slight curved form, but not hollow. I'm not dissatisfied with the result. It looks nice, and it does move the kayak forward!
Here's the diagram. (If you click on the image, you'll get a huge image. Save it on disk, and use it to print - it's scaled for 300 dpi).
Note that there is a newer version of the paddle available!
Here's the engineer again. I suspect you could simply make a round form. Lots of commercial paddle shafts are round.
Blades aligned or offset by an angle?
Another subject for discussion. It's easy to find paddles with the blades completely aligned (0 degrees offset) and any angle up to 90 degrees. The offset angle is somehow intuitive. It also necessary to decide if the left or right hand will be the 'control' hand (the paddle shaft slips in the other hand). First impression would dictate right control for right-handed persons. I have the impression it's the other way around (after actually following my first impression).
Round or elliptic paddle shaft?
I'm used to 'ergonomic' tools, so I decided to make the shaft elliptic too. That's quite a complication, as it will be necessary to make the left and right half of the shaft elliptic with a different angle. If in doubt, make it round.
Another complication. Actual length depends on the kayak model (height above the water), the pilot's physique, and, of course, taste!
How to construct the paddle shaft?
I made a rectangular shape of 34 by 30 mm. For the first version, I used pine, which is a little heavier. (Check with your supplier) I made a 3-layer sandwich, drilled the center layer with 13mm holes along the center (total about 1 meter long), to make the shaft lighter. Literature recommend 5 or 6 layers. I didn't have the patience...
These layers are glued together using epoxy. If you cannot obtain material long enough, glue them together using the 'scarf' technique - see pics.
To obtain the elliptic form, I cut the corners of the 30x34 mm rectangle using the measure from the drawing. Mind: only one half of the paddle shaft! The other half must be cut to reflect the 60 degree offset! (Check the dotted ellipse on the drawing).
At each side, I cut the paddle shaft to force the curve I wanted the blades to have. I couldn't find and easy way to press the blades into the form, so I drilled the blades at each side of the shaft, and used the tried stitch and glue technique!
The pictures are on the next page.
|(c) John Coppens ON6JC/LW3HAZ