Abstract : Wind tunnel tests were conducted on a shrouded propeller model in which the propeller diameter was varied for the purpose of measuring the effects of tip to shroud clearance. The basic model tested contained a four-bladed variable pitch propeller operating within a 0.50 chord/diameter ratio shroud. To assist in studying the effect of annulus area on tip clearance, two models having 0.30 and 0.40 hub/tip diameter ratio centerbodies were tested over roughly the same range of propeller tip clearances. Performance of the models was measured throughout a range of advance ratios from zero to roughly 2.20 at several propeller blade pitch settings at zero angle of attack only. Results are presented in the form of force and power coefficients and efficiency varying with propeller tip clearance and rotational speed for forward and static flight conditions.