Turbocles on Rudders
We have been producing tubercle (or as we like to call them “Turbocle” ) foils together for the dinghy market for some time now.
The main advantage of applying tubercles to the leading edge is to delay the onset of stall for a particular rudder form for a minimal drag penalty for most existing boats with well-designed rudders adding leading edge projections will not give much benefit. However, what it does mean is that there is an opportunity to reduce rudder area and become more aggressive with foil sections at the design stage. Thus it is possible to significantly reduce drag at low angles of attack and relying on the anti- stall properties of the tubercles to give you the characteristics of a larger or less aggressive foil.
There has been a relatively large amount of research in this area as well commercially proven applications in wind turbines and related technologies where reduction of blade size for no loss of performance is of commercial benefit.
Most research clearly shows that flow separation pattern and surface pressure is dramatically altered by the tubercles when correctly applied. The tubercles function to generate vortices which help maintain lift and prevent stall at high angles of attack. For regions downstream of tubercle crest, separation can be eradicated almost to the trailing edge.
Needless to say we are looking at applications on a range of craft from the very large to the very small; such is the success of the projects where we have applied this technology I fear that we are starting to sound like a broken record when discussing rudder options with our clients!