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Hardwood Record — Veneer & Panel Section 



June 10, 1919 



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material, such as wing beams or propeller woods, which 

 tests to destruction subsequently, conducted with care, 

 have shown to be entirely suitable for use. 



Advance Rot 



In this connection, the question of "advance rot" as 

 affecting the toughness of the wood is of great impor- 

 tance. Even where there is apparently no evidence of 

 the actual presence of fungus, its influence has been 

 known to extend some distance into the otherwise sound 

 wood, altering the chemical condition of the cell walls 

 and causing the so-called "advanced rot." This condi- 

 tion is usually accompanied by a discoloration of the 

 wood, but other discolorations of an entirely harmless 

 nature als o frequently occur, and the discolorations of 

 certain fungi fade out entirely upon exposure to the air. 

 Very little is known concerning this subject and it is now 

 being carefully studied by the pathologists of the Depart- 

 ment of Agriculture. 



No Adequate Direct Tests Have Yet Been Devised 



It might be argued that an actual mechanical test is 

 the only accurate means of determining the suitablity of 

 a piece of wood for use; but here the difficulty enters that 



a mechanical test, to be entirely adequate for the pur- 

 pose, in some cases injures the part and renders it unfit 

 for use. A test made within the elastic limit of the ma- 

 terial will establish its strength up to the amount of stress 

 imposed, but it does not indicate what v/ill be the be- 

 havior of the piece if it is suddenly made to w^ithstand a 

 load considerably in excess of this amount. On the other 

 hand, a test made on an adjacent piece of wood fails of 

 its purpose, as the defect may be confined to the one 

 specimen and not occur in the representative piece tested. 

 This throv/s us back upon a visual examination based on 

 the intimate experience of the inspector, which after all 

 may prove to be the most effective way; but, at the pres- 

 ent time, it is far from satisfactory, and for certain pur- 

 poses the mechanical test within the elastic limit is prob- 

 ably preferable. 



The test to maximum load of struts that fall in the long- 

 column class is adequate to determine the load-carrying 

 capacity of the strut, and the test may be made without 

 any injury to the strut. Such tests, how^ever, cannot en- 

 tirely take the place of visual inspection. Visual inspec- 

 tion is needed in this case to detect defects which, while 

 not affecting the maximum load, would have a tendency 



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