Introduction T HE parafoil is an aerodynamic decelerator that uses the concept of parachute and airfoil aerodynamics. The device has been used as a parachute for high-precision delivering of payload (military and civilian), to recover sounding rockets, for various tethered applications (to carry instrumentation for weather survey, air pollution measurements, radar tracking systems), and as recreational parachuting since the 1970s, as discussed by Nicolaides et al.1 and Knapp and Barton.2 All of these systems take advantage of the low landing speed and maneuverability of the parafoil. The invention is rather old, and it was used as far back as World War II for stabilization of supersonic vehicles by H.G. Heinrich, as reported by Meyer.3 The essential concept was that in addition to suitable aerodynamic resistance the parafoil had to provide lift, stability, and control, so that it could be used for high-precision landing. The technical literature in the field has addressed aerodynamics, performances, and longitudinal stability, from flight testing, windtunnel measurements, and theoretical models. Relevant publications in the field include the work of Lingard,4 who showed equations for the lift and drag coefficients from low-speed aerodynamic theory and discussed the effects of wind speed, geometry, and size of the parafoil. Other studies address glide ratio and rate of descent under various wind conditions, in addition to deployment/inflation mechanisms, warping, turn control, effects of rigging lines, and more. These analyses are not directly applicable. A summary of this literature is given by Matos et al.5 This paper discusses the low-speed wind-tunnel drag characteristics of parafoils. The devices tested are flexible (but not inflatable) strips of cloth that adjust to the conditions of the incoming wind and produce relatively large drag forces and little or no lift. Therefore, they are essentially aerodynamic decelerators with spanwise camber increasing with their length because their edges were tied at a constant distance. Ram pressure builds up on the side of the parafoil facing the freestream and creates considerable drag.