The dihedral illustration shows the flow of water off the dihedral of our touring blade designs. Notice how the powerface is angled from the center of the blade. This angle is called a dihedral. The dihedral angle concept comes from the discovery that a curved plane gives direction to the flow of water off the blade. During a forward stroke water builds up on the powerface of a non-dihedral blade. To expel this build up, a non-dihedral blade will flutter back and forth. Therefore, by adding a dihedral angle to the blade design, water is given direction to flow easily off the blade, minimizing flutter and the gripping effort needed to overcome the flutter.
* Decreased flutter also reduces stress on your wrist and arm.
From Werner Paddles.