Blade Geometry Modelling

The crank (or ‘rake’), and the size and shape (planform) of blades have been modelled for use in the Paddle Comparison Tool. The wing cross section and blade twist were not modelled, as this was not practical with the resources available. (If we can’t measure / predict the impact on performance of changes to aspects of geometry they’re best left alone!) So as well as not being modelled in the Comparison Tool, these last two aspects are left as ‘typical’ (of wing geometry) on the current Physic blades. (Keeping these aspects of geometry ‘standard’, has the advantage of minimising the difference in ‘feel’ between typical wing blades and Physic blades).

Crank is the angle of a blade segment in relation to the shaft, and (unfortunately!) this varies constantly down and across wing blades.  Hence for comparison calculations an average of 5 measurements across the width, and every 1cm down the blade (typically around 250 measurements) were made for each paddle being ‘compared’.

For calculations comparing blade shape and size, the blade planform was used.  This is the projection of the blade shape on to a flat surface, with width measurements being taken (again) every 1cm down the blade.

Blade comparisons showed that changes in blade size / shape effect all paddlers ‘blade efficiency’ equally. But the effects of changes of paddle blade crank on efficiency are ‘paddler technique specific’. (Generally the, err, ‘less cultured your technique’ 😊, the more the performance gain!)