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BELL SYSTEM TECHNICAL JOURNAL 



of Curve 3 up to the \\" knot point with those of Curve 1 for 2" and larger 

 knots, would be the practical minimum section moduli for roofed sections 

 between pinholes. Accordingly, such a smooth curve was constructed and 

 is shown as Curve 2 in Fig. 4. The results of Calculations 1 and 3 for nom- 



KNOT DIAMETER- INCHES 



Fig. 4— Sections between pinholes. Section modulus of crossarm sections containing knots 

 of the sizes shown on the base line and located in damaging positions. 



inal and arm-end minimum sections were also plotted, and Curves 1 and 3 

 drawn for those sections. 



Roofed Pinhole Sections 



Two calculations were made for the pinhole sections: Calculation 4, in 

 which the knots were assumed to be located adjacent to the pinhole in a 



