The Sawdust Factory Presents
The "Bird's Mouth" Method for Hollow Shaft Single Blade Canoe Paddles
You know what really bites? When you present yourself as Mr. Expert, and then someone comes along and does it better than you. Ha ha, not really -- it's actually the BEST thing that can happen, and exactly the result I hope for most when I post these little how-I-did-it articles. Here's a perfect example:
The following was sent to me by Aljosa Rovan from Brezice, Slovenia, to tell me about a couple developments he came up with. In one, he works up his staves to create accurate octagonal cross sections, as opposed to the "traditional" lopsided ones I show. In all honesty, I doubt it will change anything I do, but it's still a great and wonderful thing to have options, so here you go.
Another bright idea is in answer to a direct question I asked back on Page 1 of this Bird's Mouth presentation: How to make straight shaft paddles using this method. The only part of it I disapprove of is that it's so elegantly simple and effective that now I feel like an idiot for not having thought of it myself. But it's really no no great hardship, for I am comfortable, through persistent practice, in feeling like an idiot.
And finally, I love his take on the handle!
So without further ado, here is Aljosa's note, ver batim, just as it was sent to me. Thanks again, Aljosa!
While surfing the internet, I came across Kurt Maurer's Sawdust Factory website where he explains the method of making hollow shaft paddles. I liked the idea and decided to give it a try.
Having worked in R&D for years, I always look for potential improvements. So I slightly changed the geometry of staves. The bird mouth is not symmetrical anymore. The long part of the bird’s mouth is as long as the stave is thick and the other one correspondingly shorter – see the sketch below. For those interested in formulae, the length of short part of the mouth equals where represents the stave’s thickness. Such staves make a better octagon when glued together – see the photos of both versions. This enables less sanding to get to a round (or oval) shape and even machining with a router (16mm radius roundover router bit in my case).
During a discussion with Kurt it turned out that this brings additional advantage – you can get to the shape in one pass of the saw, if you use a saw blade with thick enough kerf. I actually had the staves made by a professional, since I do not have a table saw and only later realized that the bird’s mouth can be made with a router (or on a router table) using a vee router bit. The professional did not have linden wood that I asked for, so he made staves out of beech and gave them to me for free saying it was his Christmas present.
Next, Kurt always makes bent-shaft paddles using this method and he challenged his readers to make a straight shaft paddle. That was the lure I bit into. I made the blade in a few steps. First I made a rectangular shaft extension from a piece of spruce wood and machined one end of it into an octagon. Then I pushed it into the hollow shaft and glued it in.
Next I glued two additional pieces of wood to get the paddle blank. The rest was the usual stuff – making an otter-tail template, cutting the paddle blank to an approximate shape with a jigsaw, routing it to exact shape using flush trim router bit, planning, sanding etc. At first I wanted to go for a traditional pear-shaped grip, but then decided to make a T-grip using a part of the hollow shaft – thus making visible what this paddle is all about.
Finally I coated the paddle with two layers of polyurethane resin that is supposed to survive occasional contact with rock.
Admittedly, my paddle has quite a few ''clumsy woodworker signatures'', such as scratches, resin runs and places where I fixed the surface with wood putty. In my defense I can only say that a) it was the first paddle I ever made and b) I was born quick and clumsy, so I blame it on my ancestors.
And now – I’m waiting for some nice weather to go for a wet test!
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Email Kurt Maurer at NGC704@aol.com