This is one part of the project for which there is surprisingly little guidance from Ian Oughtred in the plans or in his book on Clinker Plywood Boat Building. It would be great to have specific guidance on the length of oar and some design options with the plans that are tailored to the boat. Apparently some of his other designs might have that.
I started looking around at different plans out there. Pete Culler, Francois Vivier, John C. Harris (WB #240), Peter Helland Hansen and Wesley Reddick all of which have different sized and shaped blades in particular. I also used the Shaw and Tenney oar length fromula (Divide the span by 2, and then add 2 to this number, Multiply the loom length by 25, and then divide that number by 7. The result is the proper oar length in inches. Round up or down to the closest 6″ increment) and John C. Harris’s calculation ((Beam + Freeboard)+9)x1.34 and have come to the conclusion that I need 11.5′ long oars… whoa that is long.
I also consulted the Wooden Boat forum and found that Caledonia Yawl owners seem to have oars between 9.5′ and 11′ long and there is little consensus on what is the sweet spot. I’ve also really liked the solution offered by Harry Bryan to create a scarf that allows you to disassemble the oars into tow pieces (WB #229).
So my choice is to make 11.5′ oars out of sitka spruce that will have a scarf to disassemble. I can always shorten them if I find it to be too long. If I have the energy I may also make a second set of 9.5′ long oars that would fit on the floor boards on either side of the centreboard between the bulkheads. I figure it is always good to have a backup and 9.5′ might still be quite usable.
I’ve also been inspired by the Small Boats Monthly post on making oar risers for stand-up rowing.