• Yeah that aerofoil has a fair bit of camber, so it produces lift at zero incidence hence wouldn't be a good choice for a a bicycle.

    It wouldn't be surprised if the aerofoil section used on bicycle frames is one of the NACA 4-digit aerofoils, so NACA 00XX range, probably a NACA 0012, where the '12' is the percentage of max. thickness to chord length.

    airfoiltools.com has a decent database of aerofoil properties here is the NACA 0012: http://airfoiltools.com/airfoil/details?airfoil=n0012-il
    Alpha represents angle of attack, which for a bicycle would be the yaw angle. If you assume the Reynolds number on the headtube of a bicycle is roughly 5x10^4, it should give you a good good idea of the aero properties of the section. You can also assume the CD of a cylinder is around 1 at this Reynolds number (CL is obviously 0).

    Should also remember the tubing on bicycles is three dimensions this isn't ideal and distributions of the aero coefficients over the span of the tubes will change. Also once the air reaches places like the downtube the air is already really turbulent and messy, so it's not quite this simple.

    If you want to work out the actual drag force that you need to overcome, you just multiply the drag coefficient by 0.5*1.225*velocity^2*surface area

  • It wouldn't be surprised if the aerofoil section used on bicycle frames is one of the NACA 4-digit aerofoils, so NACA 00XX range, probably a NACA 0012, where the '12' is the percentage of max. thickness to chord length.

    UCI bikes are regulated to a thickness of just over 30% of chord length measured perpendicular to the tube's long axis. Measuring chord the aeroplane way parallel to the direction of travel, that's about 25% for the head and seat tubes and about 15% for the downtube. Because the downtube has a lot of sweep in aeroplane terms, it creates what would be spanwise flow if it were a wing, so thickness:chord measured in the direction of the flow field could be under 10% at some points if the basic tube shape was as thin as is permitted.

About

Avatar for wjrh @wjrh started