No takers here then!

I guess I should have put 'Lance', 'Cervelo' or 'Powercranks' in the title, that may have got some response!

Well, the coefficient of drag of an aerofoil is about 10% that of a cylinder and so is all else is kept constant, you would expect the drag to be approximately 10%.

D = cD * ½ * rho * V² * Dia * L
D(round) = 1.2 * 0.5 * 1.224 * 11² * 0.025 * 0.4
D(round) = 0.9N = 92g
D (aerofoil) = 0.09N = 9.2g

So therefore approximately 83g drag saved. from memory, John Cobb said that 45g saved = 0.5secs/km.

Although there's 83g saved theoretically, I'd suggest it's more like 45g so you'll save about 0.5secs per km.

The old Vision site used to claim about 30 seconds over 40 Kms.