A study has been made of the flow past thin, inflated lenticular aerofoils at zero angle of incidence. The configuration is an idealization of the flow past long low inflated buildings when the effects of the earth's boundary layer are neglected. It is shown theoretically, and confirmed experimentally, that the non-dimensional tension coefficient in the inflated membranes comprising the aerofoil is a unique function of the internal pressure coefficient divided by the square root of the excess-length ratio. This applies for excess length ratios up to at least 0·05 which corresponds to a thickness-to-chord ratio, wind off, of 0·28. The aerofoil is found to become unstable at negative internal pressures corresponding to tension coefficients of approximately 0·4.

The theory has also been used to predict the shape of the aerofoil and the pressure distribution over it. With increasing wind speed at positive internal pressures, the membrane theoretically changes shape from a circular arc to a form involving inflexion points and in all cases the contours are symmetrical about the half-chord point. The non-dimensional membrane slope at the leading and trailing edges agrees fairly well with the experimental values. However, the measured pressure distributions show some fore-and-aft asymmetry and the maximum thickness is slightly downwind of the half-chord point. Nevertheless the comparison between theory and experiment is satisfactory for small values of the excess-length ratio.