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Aviation History
1916
1916 - 0076.PDF
speeds and angles of incidence. These are, it should be noted, monoplane values and in order to obtain corre sponding biplane values it is necessary to multiply them with the value for biplane spacing, which is, in turn, determined by the amount of stagger and gap. As the lift and drift coefficients given in the N.P.L. report are in " absolute " units the figures in the table compiled by me were obtained by multiplying these coefficients by v2 x 0-00238. In another table we are given the dimensions of the section expressed in terms of the chord, from which it is a simple matter to plot the full scale section for any length of chord. Let us now examine the area required to lift the machine at its maximum speed, which was to be Table of body items weights, and their distance from engine plate. For propeller and engine the sign is minus since they are in front of the engine plate, for all the other items the sign is plus. Distance from the wings have to carry their own weight before they lift the machine we must make an estimate of the weight of the wings before we can find the area necessary to lift the machine. From such data as I have available a fair weight to assume for wings would be -8 lb. per sq. ft. As a matter of fact, there is every reason to expect that we can build them for a slightly smaller weight and still maintain a sufficiently high factor of safety, and I have chosen -8 to be on the safe side. It therefore follows that the useful lift of the wings at 95 ft./sec. and 40 incidence = 5 91 x "85 — '8 = Table of lift, drift, lift/drift and centre of pressure coefficients OJ R.A.F. 6 section taken from N.P.L. Report. o o o O- Item. Propeller Engine Engine plate ... Bracing rods ... Longerons Former No. I ... „ II ••• Fuel and tanks Former No. Ill IV Controls Instruments Pilot and seat ... Former No. V... „ VI... „ VII... „ VIII... IX... X... XI... Tail piece Fabric Wiring Tail planes Total Weight I (lbs.). 18-00 121-00 8-oo 5"6o 12-00 3-2S 3-60 90-00 4-30 3-60 20-00 20'00 I7C0O 4-0O 2-78 2-41 2-13 2-0O 1-83 1 -58 4-00 9-00 9-00 25-00 543-o8 Engine Plate. - 1-04 - 0-42 o-oo o- 5o 6-oo I-10 30 17 90 5o 50 5o + 5 '5o + 6-oo + 8-oo + io-oo + 11-83 + i3'5o + 14-92 +16-00 + 16-83 + 7-00 + 4-00 + i6-oo Moment ( + )• 2-80 72-00 3/58 8-20 285-00 16-80 16-20 90-00 90-00 935-oo 24-00 21-25 24-10 25-00 27-00 27-15 25-30 67-00 63-00 36-00 400-00 Moment 18-70 50-80 - 2 0 2 4 6 s 10 12 14 16 18 S 2 •3.2 S£"o v s i-j *-* 0-003 0-074 0-173 0-275 o-354 423 496 564 593 605 550 •33 sfi'o £o| o- O' O' O' 0* O" •J O £ v C i-, <U tucL o u u a v « „ H *£ 3W 8 rj 5*3 S 0201 — 0165 4-5 0159 10-9 0193 14-3 0252 14-1 0329 12-9 0-0433 11-4 0-0545 10-4 0-0640 9-3 0-0875 6'9 0-1336 4-1 * Distance of c.p. from leading edge expressed in terms o-575 0-425 358 329 312 302 292 280 296 33° 15.S^- 023 043 074 097 115 136 154 163 171 0-180 0-190 of chord. Table of dimensions oj the plane section as decimal fractions of the chord. — 2,259-38 69-50 Distance from Leading Edge in terms of Chord. o •025 •°S •1 •2 •3 •4 Height above Chord in terms of Chord. Upper Surface. 0-005 •032 •044 •060 •074 076 •075 o- o- O" 0" (.)• O" Lower Surface. O-ooo 0-002 0-004 0-007 0-008 0-007 Distance from Leading Edge in terms of Chord. •5 •6 •7 •8 •9 I'D Height above Chord in terms of Chord. Upper Surface. 0-071 0-065 0-057 0*044 0*027 0-005 Lower Surface. 0-005 0-004 0-003 0-002 o-ooi o-ooo Table showing lift in Ids./sq.ft. of the plane section at various velocities and angles of incidence. In the last three columns the velocities are in m.p.h. (Monoplane Values). tt II Lift (in lbs. per sq. ft.) at feet per second. 40. 45. ; 50. 55. 60. 65. 70. 75. i 80, 85. 90. 95 100. 105. no. 115. 120. 125. 130. 135- 140. 100 m.p.h. |C 105 110 3 j§ m.p.h. m.p.h. Jj^ -2 o 2 4 6 8 10 12 14 16 18 20 22 24 o-on 0-28 0-64 1-04 i"33 1-56 i-88 2-13 2-25 2-28 2-08 I'90 i-8o 172 0-0140-02 ,0-36 |o-42 0-83 I 32 I-70 2-03 •38 2-70 2-85 2-90 2'04 2-40 2-28 2-18 0-97 t'54 11-98 \2'37 J277I3 !3'i54 |3"32J4 i3\35|4 S2-8o 12-67 f2-56;j 02 0-03 o •530-63 o •24! I-47 •98:2-34 55I3-O0 •95 3'59 '57;4'22 05.4-80 2715-00 •325-10 "954 "67 •6014-25 •4214-05 283-88 '"3 74 73 75 '54 •33 96 64 93 05 •50 00 76 •56 0-0410-040 o 86|o-99 2-oo!2-32 3-i8j3'68 4'>oJ475 4-90 575 6-51 6-85 6-93 6-38 5-80 5"52 5 "3o 5-5i 6-63 7'55 7-91 8-05 7-36 670 6-36 6-io 0*05 1 "26. 2-951 470 6-03 7'20 8-49 9-65 OO IO'IO IO I0'20 '34 "22 •92 9-40 7-6oj 8-5oj T 8-14! 7-80 0-06 1-42 3-32 S'4» 6-8o 8-io 9-53 io-8 n-4 11-5 10-5 9-60 9-13 873 0-064 1-59 373 5-91 7-60 9-10 io-6 I2-I I2"7 12-9 H-8 107 10*2 9-80 0-07 1-76 4-10 b-5S 8-40 IO'I u-8 i3"4 14-1 14*3 13-1 11-9 11-3 io-8 o I 4 7 9 11 13 14 15 15 14 13 12 11 oS '94 S3 •20 •27 •1 •o 7 •5 7 4 1 5 9 09 o 14 2 981 5 •92, 8 •2 11 •2 13 3 IS 09; o •33 2' '7' IS 18 8*7 4 ii5 7 |i5 2 >I4 48 •65 'i '3 6 8 6 9 '3 7 'O •4 10] O S3! 2 90 6 40! 10 'I 113 4 il5 9 fi8 8 !20 1 118 0-12 2-98 695 in 14-3 17-1 20-o 22'7 23-8 24'3 22-2 20'2 19-2 18-2 0-13 3'22 7-50 n-9 I5'4 18-4 2I-6 24-5 25-8 26-1 24-0 121-7 207 19-8 0-14 3-46 8-io I2'9 16-6 198 23 "3 26-4 27-8 28-1 257 '23-4 22-3 \M'3 0-15 377 8-8o 14-0 18-0 21-5 25*3 28-8 3o-3 30-5 28-0 25-5 24-2 23*3 0-168 4-15 97o I5"4 19-8 237 27-8 31-6 33'2 33-6 30-8 28-0 26-6 25-6 o-i8J 4-53 io-6 16-8 216 25-8 30-3 ' 34-5 ! 36-2 36-7 33-6 30-6 29-1 27-8 -2 o 2 4 6 8 10 12 14 16 18 20 22 24 65 m.p.h., or approximately 95 ft./second. At this speed, and at 40 incidence (the angle to which corre sponds the maximum value of lift/drift), the lift of R.A.F. 6 is 5-91 (monoplane value). By choosing suitable gap and stagger—when gap — chord an efficiency of about 81 per cent, is obtained, and by a stagger of 0-4 of chord another 5 per cent.—we may expect a biplane efficiency of about 85 per cent. As, however 4-17 lbs./sq. ft. Assuming that a sufficiently strong undercarriage for a weight of 50 lbs. can be built we have a total weight, less wings, of 593 + 4*17 — 142 sq. ft. For first estimates I suggest taking a chord of 4' 0'' and a mean span of 20' o". This gives an area of 80 sq. ft. for the top plane and about 70 sq. ft. for bottom plane, total 150 sq. ft. As weight of wings = 150 X "8 = 120 lbs. the total weight of machine = 76
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