Kit Car Aerodynamics

We are now in the second year of competing with our Kit car, and are about to build an more aerodynamic cover for our vehicle out of a aluminium frame and some shrink wrap that has been scrounged form a local boat transporting company. We are having a discussion at school and want to know whether it would be better to try and cover all the wheels, cover just the back wheels, or don't cover the wheels at all. All of our wheels have HIPS wheel discs on them and we will be looking for a teardrop type shape for the vehicle body. In the tests on simple computer models it appears we will not be gaining much by encasing the wheel, just a bit of a headache on the construction front. In my humble opinion we would be better having a smooth sleek body shape that lets the air flow round and off the back. If we cover the wheels we will be making the body shape too wide for the air to flow comfortably off the rear of the vehicle. Any advice would be very much appreciated.

Comments

  • edited December 2015
    A colleague of mine has wind-tunnel tested 20" bike wheels with and without covers - this was for the gravity racer version of Prometheus ( look up " lola " scottish carties on you tube ) - it reduced overall vehicle drag by more than 80 % -but the chassis was very very low drag anyway - on a typical gp car the effect would be a lot less 15 to 40 % depending on chassis aero - a good shape for the body is a symmetrical NACA laminar flow profile - blunt end forwards - just a poser for you , we calculated that with 4 x 36 spokes 20" wheels a spoke will pass the tarmac more than 7 million times in the old 4 hr format !! , regards Tigris
  • edited December 2015
    have a look at video clips i have just re introduced - I am currently racing the 3rd car to come off that mould ,
  • edited December 2015
    Remember that when running computer models, the wheels will be in a dead straight line, and likely flush with the bodywork.

    When steering, unenclosed wheels will protrude from the bodywork and disrupt the flow down the entire rest of the side of the car. This is where the benefits of enclosed front wheels are greater.

    However, the drag equation includes the Coefficient of Drag AND the frontal area. If you increase frontal area by 20% to decrease Cd by 10%. you are not doing yourself any favours.

    Cd is hard to calculate (especially as it changes when you steer), but frontal area isn't too hard. If you can't enclose the front wheels without massively increasing the frontal area, then its time to look at something different. The trugs and RR show that enclosed wheels aren't necessarily part of the winning formula in F24.
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