Efficient extraction of the air that enters the cockpit from the vents has been considered in many glider designs over the years but only recently has it been investigated further to understand the impact on glider performance. Most gliders have openings at the base of the rear of the fin to try and allow the air to exit the fuselage efficiently. Poor extraction leads to pressurisation of the cockpit causing air to escape around the canopy and through the control surfaces of poorly sealed gliders.