-- Last Updated: Jul-05-13 1:18 PM EST --
I can envision a reason hatchet blades are better, after seeing them in action in some of the videos posted for this topic (some are posted on the other rowing thread too, I think). When I'm rowing, I notice that the shaft of each oar moves forward through the water, cutting a noticeable wake in the process. I see this to a much greater degree with the 8-foot oars of my guide-boat than with the 7-foot oars of my "pack boat". That's because the oar blade slips very little as the boat moves forward, so as the oar shaft changes orientation on its pivot point, the part of the oar that's between the blade and the boat "follows" the boat to some degree. The forward movement of the part of the shaft directly adjacent to the blade (and submerged), is less than the part that's closer to the oarlocks (and not submerged, thus producing no drag), but the forward movement of the shaft within the first 1.0 to 1.5 feet of the blade is significant enough to slice through the water a fair distance, I think close to two feet or maybe more if the blade is buried a little deeply (as would be the case when it's choppy). This really doesn't worry me at all for the kind of boating I do (I'm already much faster than a solo canoe, with far less effort too), but to a racer, that slicing action would be seen as worrisome drag, and drag which fights against the forward motion of that part of the oar shaft will also resist forward motion of the boat, though to a much smaller degree (to a smaller degree due to where it occurs on the lever arm). The hatchet-shaped blade puts the oar shaft right "at" the surface of the water rather than beneath it, so the shaft itself is not slicing through the water as it pivots forward around the blade location. I can't quantify the amount of drag that is eliminated, but based on geometry, it would be easy to calculate what rough percentage of the oar shaft's drag (with conventional oars) would translate into resistance against forward motion of the boat, and in principle, it's easy to see that the full amount of drag experienced by the oar shaft itself is far less when hatchet-shaped blades are used.
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