I'.canis I,V and I, VI were cut out of I'MMIM I, IV us already 

 <lescribr<l. 'l In- wide \ ii mtii'ii ill tin' vain,- .'I tin- Ain stress and (if tin' 

 co.cflieient "I <-i undoubtedly duo to the f.iet that the amount 



nf tin- onipi,' ion at tin' central support ha- hern di*iv!;ai i|i>i| in tlic 

 calculations. If thi- compression is taken into account, and if it is 

 i-.-nni'-il tliat tin 1 ordinary tln-ory of flexure hnlds good for tin- whole of 

 thr etlcciive depth, it ha- IMTH shewn that the skin stresses in lh 

 sq. in. 1...-D1II. (i-Jiiit li.r r,,.;iin I, IV, (117(1 lor Beam LV, and 580C 

 fur Iiejim LVI . the variation in the magnitude of the stresses being 

 comparatively small. 



Further experiments will he nndu with new spruce beams. 



old spruce stringers were found to possess ample strength :md 

 stittiiess for the work they were designed to do. Th" experiments 

 _'ave : 



29.15 Ibs. a- the average weight per cubic foot. 

 1,189,800' " co-efficient of elasticity. 



3875 " " maximum skin-stress per s,j. in. 



The ii>l]owing Tahles A to V give the end deflections and in some 

 iix.s the deflections at points dividing the beam into four, six, or ciirht 

 equal parts, tin 1 distanc of these points fiom the ends b 'ing stated 

 at the beads of the coluinn>. 



Tables A to 1 show the deflections in inches of Canadian New 

 Douglas Kir l!e:nn- (1 to XXV) under gradually inerea^'d loads. 



TABLE A 



Inflections of Beam I at rinls. 



Breaking weight of Beam 1 = 45,000 Ibs. 



37 



