Starr Truscott
Published: 1938
Total Pages: 586
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N.A.C.A. models 74, 74-A, and 75 were tested in the N.A.C.A. tank to determine their hydrodynamic properties and in the N.A.C.A. 20-foot wind tunnel to determine their aerodynamic properties. The forms of these models were derived from that of a solid of revolution having a lowe air drag, and the departures from the form of this low-drag body were the minimum considered to give satisfactory take-off performance. Model 74 has a rounded bottom with flared chines, a transverse step wit ha small fairing aft of it, and a pointed afterbody. Model 74-A has the same forme except for the removal of the fairing aft of the step. Model 75 has a pointed step and a horizontal afterbody derived from the form of the N.A.C.A. model 35 series.