-- Last Updated: Sep-23-12 4:45 PM EST --
I'm not an engineer, yet I'm absolutely positive I can bore a forum with over analysis.
BTW, Carldelo, are you in NYC? Why did I think you were in CA?
I'm glad Ret-Dave entered the thread because I saw Aleut posts by him in old threads I researched, and I'm especially glad he mentioned the offset nature of the Aleut blade with respect to the shaft. I'm not sure anyone has mentioned that the Aleut seems to have a pointed tip rather than a flattish GP tip.
I think four things contribute to the perceived stability (non-flutter) when using the ridged side as the power face.
1. The ridge anchors the stagnation line, according to Carl. I only buy this when the paddle face is pulled flush to the water. If the paddle face is rotated around or translated along the X, Y or Z axes during a stroke -- sliced, pitched, angled, canted -- I think this ridge will cause unpredictable water flows that could even cause flutter. So, I assume an Aleut paddler learns to pull during a power stroke in such a manner as to maximize the stabilization potential of the ridge.
2. When a paddle face is offset from the shaft, the indented face will produce less flutter as power face than the flush face will. I know this because I have a straight shaft ZRE paddle with an offset blade with otherwise identical faces, which exhibits this exact phenomenon. Therefore, the blade offset on the Aleut may be contributing as much or more to the stability as the ridge.
3. This is speculation, but the pointy paddle end may cause less flutter upon entry than a flattish end. Many aboriginal and native canoe paddles today, for example, have pointed ends.
4. Subjective superstition and hooey. It seems obvious to me that non-fluttering canoe, Euro and GP paddles can be made without Aleut ridges, because they are all over the paddling world. The Aleut shape is the outlier. (Actually, I think all paddles flutter a little at some velocities, but the flutter can easily be controlled by grip.) Therefore, while Aleut paddlers can love their ridged paddles for all sorts of functional, aesthetic and historical reasons, I'm not convinced that these paddles offer any better stability or other efficiencies than many good non-ridged paddle designs do.
There -- I proved my opening sentence.