The turbine blades are skewed in two planes, the angle of the hydrofoil section relative to the axis of rotation varies with the diameter of the blade. The slower moving profile near the hub has a correspondingly steeper angle.
The leading edge of the blade is curved to encourage entangled debris to slide off, this curve is a logarithmic spiral. It remains to be seen whether this arrangement will necessitate a greater clearance between blade tip and shroud.
Where the blade meets the hub (the blade root), the main consideration is an even transfer of load from the blade to the hub. Early configurations used an extrapolated hydrofoil profile projected onto the curved hub surface. The smoothest transition was found to be a loose ellipse composed of two intersecting radii. It has proved more reliable and expedient to rely on a mathematical description of the curves that define the blade surface. A significant proportion are exported from a numerical visualisation program (Scilab) for defining the surfaces in the solid modelling program (Solidworks).
