I wanted a yoke without pads for my 1930 OT 50-pounder – my carrying is usually quite shore -- from garage to car-top, and then from car-top to water (though the later can involve a few hundred feet), and I didn’t want padding that would rise above the sheer line, possibly complicating things like loading the canoe onto a car rack. If I were to be portaging serious distances ( a mile or more), I might consider a padded yoke, but this plain one has proved comfortable enough for my purposes.
I couldn't find a pattern, but the shape is fairly simple. I traced the outline of the existing middle thwart onto a piece of hardwood (ash, in this case) some ¾” thick, to copy the shape of the thwart ends and to get the proper length. I then drew the outline yoke center where my neck and shoulders go (after measuring my neck diameter and adding a couple-three inches). I cut the yoke out with a jig saw, eased the edges with a router, and then did additional shaping by hand, mostly with rasps and round surform and microplane tools. I dished out a bit the area where the yoke actually sits on my shoulders. The first yoke I made many years ago for my Mohawk Royalex canoe I made much too thick at first – about 1 ¼” – after some experience, I thinned it down to about ¾” which should be ample for any canoe that you are likely to want to carry.
The only important dimensions are the length of the yoke and the space for your neck. The first you get from your canoe, the second you estimate after measuring your own neck and shoulders, determining where on your shoulders you want the yoke to sit. Padded yokes usually allow for some adjustment of the padding.
There are more elegant shapes possible – I think of the yokes in Rollin Thurlow’s canoes -- but this basic shape gets the job done.