Metal or plastic?

I was with you up to the 'clearing the shear line' bit. For greatest impact I laid up some carbon fibre dustbin lids and attached them to an ovaled, hollow, unobtainium shaft. In order to get an efficient stroke with this setup I was forced into such severe wrist movement that I am forced to give up all paddling for several months. I have discovered that a Personal Water Craft (PWC) is much more efficient than paddling and no more annoying than my normal personality. I may never go back.