A TYPICAL MACHINE 183 



and take the following parts in the slip stream : fuselage, cock- 

 pit, windscreen, tail skid, fin and rudder, just half the tail plane 

 and elevators, all tail bracing wires, all centre section gap struts, 

 all chassis wires, half the chassis struts, all centre section bracing 

 wires, all centre section incidence wires, all tail unit control levers, 

 and all tail unit control wires. 



We will now work out these items of resistance, putting a 

 cross in the margin each time we arrive at a figure which will be 

 required for later reference. 



The fuselage has a maximum cross section consisting of 

 3 feet o inches x 4 feet o inches rectangular and a domed top 

 I foot 3 inches high. 



. -. a = 12 + 2 '6 = 14-6 



r- 



i = 2-5 x 14-6 = 36-5 . (X) 



The struts on the list are 4 centre section gap struts 



I inch x 4 feet o inches, \ of 2 front chassis struts 2 inches 

 x 2 feet 3 inches in front view, -J of 2 back chassis struts, 



I 1 inches x 2 feet 3 inches in front view, and 6 king-levers on 

 the tail I inch average x i foot o inches. 



We will take it that all these struts are of R. A. F. 4. z. section, 

 i.e. section B, page 80, with fineness ratio 4. 



.'. = 4x1 X4 + ^X2X2X2'25+^X2X I 7 5x 2*2 5+6x1 XI 



= 16 + 4-5 + 3-94 + 6=30-44; 

 and x = -215 



.-. r^ = 30-44 x -215 - 6-5 . . (X) 



The cockpit is i foot 6 inches wide. 



... r , = 7 x 18 = 12-6 . . . (X) 

 The " normal plate " items consist of the windscreen, 

 8 inches x 4 inches, and the tail skid, 6 inches x 2 inches. 

 .-. = -|xJ + ^xJ-= -2222 + -0833 = -3055 

 .-. r, = 29 x -3055 = 8-9 . . . . . (X) 

 The_/f and rudder area is 18*4 square feet. 



.-. ^ = -58 x 18-4 = 107 . ... (X) 

 The tail plane and elevator area is 83-4 square feet, and we 

 are dealing with half of it. 



... r r - 78 x ?p - 32-5 . . . (X) 



The wires in the list comprise 2 top front tail bracing wires 

 g-inch stream-line 6 feet o inches long in front view, 6 other tail 

 bracing wires J-inch stream-line 6 feet o inches long, 2 front 

 chassis wires |^-inch stream-line 4 feet 6 inches long, 2 back 

 chassis wires T V-inch stream-line 4 feet 6 inches long in front 



