A System for Controlling Warp When Kiln Drying Plantation-Grown Red Pine

Approximately 1200 board feet of 5/4 Number 4 Common red pine lumber were kiln-dried to test the effects of using three kiln schedules in conjunction with presurfacing and mechanical restraint to control warp. The lumber was cut from 10-inch diameter logs obtained from plantations in western Massachusetts. U.S. Forest Products Laboratory kiln schedules T11-B3, T12-B4 and T13-B5, designated mild, recommended, and severe, respectively, were used. Restraint was accomplished using 2 inch by 2 inch steel angle iron clamped in place with spring-loaded hooks that engaged the sticker opening. Stock for the presurfaced treatment was dressed two sides to 1-1/8 inch in thickness. The various system were evaluated on the basis of the total warp recorded. There was no one “best” way to control all forms of warp simultaneously. The use of a mild schedule (T11-B3), presurfacing, and spring-loaded clamps was most beneficial in controlling twist. This system was also effective in reducing the occurrence of bow, crook, and cup.

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