Wood properties of finger-jointed southern pine

Wood from 11 batches of commercially manufactured finger jointed southern pine was examined. Specific gravity and rings per inch were determined for the two pieces of wood finger-jointed together in each board. The effect of a durability cycle on moisture was examined and the relationship between wood properties and strength of finger jointed test specimens was also examined. The mean specific gravity of 900 pieces of wood within 450 boards was 0.550 and the mean rings per inch was 6.49. On average, the two pieces of wood finger jointed together differed in specific gravity by 0.062 and in rings per inch by 2.49. The maximum difference in one board in specific gravity was 0.315 and in rings per inch was 13.19. Mean moisture content at time of test significantly increased by 5.66 percent for 2 batches, by 1.04 for one batch and decreased significantly by 1.34 percent for one batch following a durability cycle. The increases led to more unequal distribution of moisture and the decrease led to more uniformity in moisture between the two pieces of wood within the finger jointed specimens. For broken test specimens exhibiting greater than 75 percent wood failure, the strongest relationships were found between modulus of rupture and the average specific gravity (r2 = 0 .3047) and average rings per inch (r2 = 0.3352). For broken test specimens with 95 percent or more wood failure, a higher r2 of 0.44 was found. Coefficients of determination of 0.60 and 0.64 were found for specimens where fractures occurred equally between the wood fingers of the 2 pieces of wood.