The aerodynamics of a kart

WHAT IS IT?

HOW DOES IT WORK?

IN PRACTICE

Aerodynamic efficiency is a development area that is becoming increasingly importat in karting. In fact, thanks to the application of new technologies, such as computational fluid dynamic studies (CFD), it has been demonstrated that by taking care of the aerodynamic aspects of a kart it is possible to obtain incredible results (even in the order of half a second less per lap), with few precautions and with costs that are sometimes negligible. On a practical level, the most evident developments are those that have involved the fairings, which have evolved from mere protective devices, becoming the main object that leads to the reduction of aerodynamic resistance, called "drag" (for further information, "Dossier | The evolution of kart fairings”).

Nowadays, even if to a lesser extent than in the past, the aerodynamics of karts are affected by the presence of the driver, in particular by the helmet, shoulders and arms: elements which increase the frontal section area and which generate very large areas of turbulence, which are the main cause of aerodynamic drag. Open wheels are another source of turbulence, even if in karts, unlike single-seater cars with open wheels, they remain partially within the overall dimensions of the fairings. The elements that contribute most to the aerodynamics of a kart are the front spoiler and the nassau panel (generally known as the "front panel"): in fact, the most recent developments have concentrated precisely on these elements.

The most evident developments in the aerodynamic field are those that have involved the fairings

1 di 2

The development of the front spoiler and the nassau panel have led to larger and more opaque shapes in recent years. Against a slight increase in the frontal area, they allow greater coverage of the feet, legs and front wheels, with a huge benefit in terms of reducing resistance. The side fairings have also evolved and are now thinner than in the past, to offer less impact surface to the turbulent air coming from the front wheels. In the example these enormous differences can be appreciated thanks to the comparison between [1] the first set of fairings produced by the KG Karting company in 1992 and [2] the KG 505 (approved in 2015) and KG 506 (approved in 2017) kits.

WHAT IS IT?

HOW DOES IT WORK?

IN PRACTICE

Even though there have been huge steps forward in aerodynamics, the kart-driver combination still generates, overall, a decidedly high drag. This is directly proportional to the aerodynamic resistance coefficient Cx (also called "drag coefficient") which for a modern kart is between 0.6 and 0.8 (to make a comparison, that of a car is around 0.3 ). The Cx is a dimensionless value and the lower it is, the less resistance opposes the motion of a vehicle. In karts, its variability is due to the different builds of the drivers, with a clear disadvantage for those who are taller. The high drag coefficient karts translates into greater resistance to forward motion and therefore a loss of power which could instead be used to reach higher top speeds.

Fortunately, the speeds involved in karting are not high, they rarely exceed 150 km/h, which is why the effects of such inefficient aerodynamics are not all that dramatic. In fact, the aerodynamic forces assume significant values only above 80-100 km/h, while below the forces involved are negligible. The only exception are Superkarts (i.e. karts equipped with engines with 250 cm³ displacements), which have fairings that completely cover the tyres and to a great extent also the driver and which therefore can drop to a coefficient of around 0.4/ 0.5. Although karts are by their nature aerodynamically disadvantaged, with a few tricks and with the most modern fairings, as we will see in the continuation of this article, it is still possible to optimise the trend of the air flows, with concrete improvements in terms of lap time, even of the order of half a second less on the fastest tracks.

CX COEFFICIENT: WHAT IT IS AND WHAT ITS VALUE FOR KARTS IS

1 The OTK Kart Group M7 front spoiler is one of the most advanced in karting, yet from the analysis of the distribution of the pressure coefficient "Cp" (a parameter that we will discuss later) it can be seen that the helmet is still one of the areas of greatest resistance aerodynamics in a kart. 2 The Superkart driven by Peter Elkmann, winner of the FIA Karting European Championship held at LE MANS in 2019. It is clear how the fairings of these karts are much more opaque and enveloping compared to racing karts with 125 cc engines (such as the OK or KZ ), in addition, the presence of a rear wing absent in the other classes can be noted.

THE AERODYNAMICS OF A KART