At relatively low wind speeds, frontal area (i.e. cable diameter) plays a dominant role and therefore Future Fibres TSC is currently the lowest windage product available on the market.
However, "aero" is currently the centre of a lot of attention. So let's consider the facts aout aerofoils:
- 85% savings are technically available from an aerofoil section, over a circular section, but ONLY IF foil is aligned to the apparent wind angle.
- At apparent wind angles greater that 26 degrees a fixed aerofoil has more drag than a circular section and this increases exponentially with increased wind angles.
- By 33 degrees the drag of a fixed aerofoils is double that of a circular section.
- Under normal sailing/race conditions, studies have shown that average apparent wind angle is greater than 26 degrees and therefore a fixed aerofoil will add additional drag compared to a circular section.
Aerodynamic Drag =½ x Cd x ρ x A x V²,
Where = Cd = Drag coefficient, ρ = Density of medium, A = Surface area,
V = Wind speed
10-15 years ago, maximum downwind sailing speeds were 12-16 knots but with canting keels, fathead mainsails, asymmetric kites and much faster, planing hull shapes, Volvo 70's, Open 60's and racing super maxis are regularly exceeding 30 knots. Double the apparent wind speed and the drag quadruples! In a recent study conducted for Future Fibres, Juan K's office predicted a half day gain could be made during a transatlantic crossing on an Open 60 by reducing drag on lateral rigging by 85%.
Drag is therefore a significant frontier for development, however, what is clear is that fixed aerofoil standing rigging will, on average, increase aerodynamic drag. Rotating sections could provide significant benefits but their application requires a careful balance between increased weight vs drag reduction.
