Sec. 44.5 



FORCE AND FLOW DATA FOR HYDROFOILS 



77 



0.227, 0.329, and 0.453, respectively. The varia- 

 tions between the two sets of ratios were due to 

 the rounded ends of the planform of the assembly. 

 For rudders and planes having aspect ratios 

 materially less than 4, stalling should occur at 

 flap angles greater than those shown in Fig. 44. C. 



On page 105 of the Gottingen reference there 

 are given some data for a flap-type compound 

 hydrofoil in which the fixed leading portion lies 

 at an angle of attack a to the stream, and flap 

 angle ^(ksi) is applied to augment the lift, as in 

 diagram 2 of Fig. 14.U. 



In the late 1940's the National Advisory Com- 

 mittee for Aeronautics conducted an extensive 

 investigation of control-surface characteristics. 

 Its purpose was to provide experimental data for 

 designers and to determine the section charac- 

 teristics of various types of fin-and-flap (or 

 airfoil-and-flap) combinations suitable for use as 

 control surfaces. 



Two of the reports describing the results of 

 these tests are listed hereunder: 



(1) Riebe, J. M., and Church, O., "Medium and Large 



Aerodynamic Balances of Two Nose Shapes and a 

 Plane Overhang Used with a 0.40-Airfoil-Chord Flap 

 on an NACA 0009 Airfoil," ARR L5 COl, March 

 1945. This appears to be Part XXI of the report 

 series covering the complete investigation. 



(2) Riebe, J. M., and McKinney, E. G., "Medium and 



Large Aerodynamic Balances of Two Nose Shapes 

 and a Plane Overhang Used with a 0.20-Airfoil- 

 Chord Flap on an NACA 0009 Airfoil," ARR L5 

 F06 of June 1945. This is Part XXII of the com- 

 plete series. 



As applying to combinations of fixed plates or 

 fins and movable control surfaces abaft them, 

 K. E. Schoenherr gives a graphic summary [PNA, 

 1939, Vol. II, pp. 207-208] of data derived by 

 experimenters abroad and published in the 

 following references: 



(a) Cowley, W. L., Simmons, L. F. G., and Coales, J. D., 



"The Effect of Balancing a Rudder, by Placing the 

 Rudder Axis Behind the Leading Edge, upon the 

 Controlling Moment of the Motion," Tech. Rep. 

 Adv. Comm. for Aero., R and M 253, 1916-1917, 

 p. 154ff 



(b) Munk, M. M., "Systematische Versuche an Leit- 



werkmodellen (Systematic Tests on Models of 

 Control Surfaces)," Technische Berichte der Flug- 

 zeugmeisterei, 1917, p. 168ff. 



Fig. 44.D, adapted from Fig. 10 on page 208 of 

 the Schoenherr reference, covers a number of 

 cases of this kind, in sufficient detail to indicate 

 about what may be expected of elementary com- 

 pound assembfies. 



The results of somewhat similar experiments 

 made by T. B. Abell are to be found in his paper 

 "Some Model Experiments on Rudders Placed 

 Behind a Plane Deadwood" [INA, 1936, pp. 

 137-144]. The results of these experiments are 

 summarized by W. P. A. van Lammeren, L. 

 Troost, and J. G. Koning [RPSS, 1948, pp. 

 327-328]. 



Iqp is Distance from Leoding Edge to 

 Center of Pressure ond c is the Chord Length 



40 35 30 25 20 



f\no\e. of Attack a^, deo 



Fia. 44.D Graphs of Lift Coefficient and Center- 



of-Pressure Position fob Several Combinations 



OF Fixed Fins and Movable Blades 



