L-°l FOREST PRODUC TS LABORATORY t FOREST SERVICE U. S. DEPARTM1.M 01 AGRICULTURE VENEER CUTTING AND DRYING PROPERTIES TUPELO There are three commercially important tupelo speo Water hi pe l e (Nyssa aquatica), black tupelo (N sylvatica ), and swamp tupelo (N sylvatica var. biflora). Water tupelo and swamp tupelo, as the names indicate, are water-loving trees and grow principally in the fresh-water swamps and along the edges of streams and ponds in southeastern United States. Black tupelo, which has a much larger range, grows throughout most of the eastern half of the United States The wood of the various tupelos is similar, and no attempt to separate the species is made by commercial lumber inspectors The heartwood is light brownish grey, and the sapwood is nearly white Black tupelo and swamp tupelo sometimes have darker colored heartwood than water tupelo The wood is diffuse porous and has a close, uniform texture It has very inter- locked grain, which prevents it from splintering under heavy wear and makes it difficult to split— The interlocked grain tends to cause warp during the seasoning of the lumber _ The wood is rated as moderately heavy and moderately strong and hard Tupelo lumber is used principally for shipping containers, flooring, and furniture Rotary-cut tupelo veneer is used mainly for the interior plies of stock panels and for wirebound boxes Because of its light color, moderate strength, and resistance to splitting tupelo is a preferred box wood Some tupelo is used for pulpwood, railway ties, and cooperage Selection, Handling, and Preparation of Logs for Cutting One 1 6-foot and four 8-foot logs of water tupelo and a similar sample of swamp tupelo were used in Laboratory tests of the rotary veneer cutting and drying properties of these species This material was part of a shipment sent to the Laboratory through the cooperation of the Southern Forest Experiment Station -Betts, H S. Tupelo Amer Woods Ser . Forest Serv , U S Dept of Agr 1945. 2 McMillen, J M Kiln Drying Water and Swamp Tupelo Proc Forest Prod Res. Soc 1953 Report No 1766-9 > Maintained at Madison 5, Wisconsin in cooperation with the University of Wisconsin September 1953 Agriculture - Madison and the Mississippi Products Company. The logs came from Livingston County, La , in the Bayou Barbary Swamp 25 miles southwest of Hammond, La. They were reported to be of veneer or good saw-log quality. The test logs were from 1 5 to 31 inches in diameter at the small end. The specific gravity of the test material varied from 0. 31 to 0. 51; the lower value represented the sapwood from a swelled butt log. Judging from defects observed in the 10 test logs, fire scars, ring shake, and swelled butt logs should be avoided when selecting tupelo for veneer cutting. Tupelo veneer of moderate quality can be cut from bolts at room tempera- ture Bolts heated in water at 160° F. yielded smooth, tight rotary veneer 1/16 and 1/8 inch thick. A temperature of 140° F. at a core diameter of 8 inches can be attained in 8-foot bolts of different diameters by heating them in water at 160° F. according to the following schedules: Average log diameter Heating time Inches Hours 12 7 24 42 36 94 Veneer Cutting Burls were common in 8 of the 10 test logs. They did not seriously inter- fere with cutting, but sometimes rough veneer was cut in the short grain areas around them. Interlocked grain also resulted in occasional patches of rough cutting. Fire scars or shake occurred in two-thirds of the logs cut. They caused breakage at the lathe and a corresponding reduction in veneer recovery. Knots were not a big problem in the test logs. About one-half of the test bolts were cut almost to the core diameter before knots were encountered. When knots were encountered, they did not seriously interfere with cutting, nor did they degrade a large percentage of the veneer. Report No 1766-9 In general, good-quality veneer was cut from the tupelo test bolts that had been heated at 160° F by using the lathe settings_ given in table 1 Veneer cut from bolts heated at 200° F. was fuzzy and subject to "shelling, or separation of the springwood from the summerwood. Veneer Drying The heartwood of the swamp tupelo had an average moisture content of about 1 ! i percent, and the remainder of the test material had an average moisture content of about 145 percent. Temperatures of 250° and 320° F. were satisfactory for drying tupelo veneer in a small roller -conveyor dryer. Table 2 lists the drying schedules used For practical purposes, 1 /16-inch veneer both heartwood and sapwood, of water tupelo and swamp tupelo can be dried on the same schedule. Similarly 1 /8-inch sapwood veneer of both species can be dried on the same schedule. To obtain the most favorable drying schedules, however, 1/8-inch heartwood and 1/8-inch sapwood, and possibly 1 /8-inch heartwood of the two species, should be separated and dried on different schedules During drying the sapwood veneer of both tupelo species sometimes developed a dark-brown surface discoloration. This stain was shallow and could be sanded off. The heartwood veneer, but not the sapwood veneer, sometimes buckled slightly during drying Tangential shrinkage during drying to a moisture content of 2 to 4 percent averaged 5 to 7 percent of the green width. Veneer Yields The total yield of dry veneer from the 10 test logs was 2 percent greater than the log scale (International Log Rule) Approximately one-half of the veneer was of grade 1 or face veneer when graded according to Commercial Standard CS 35-49 for hardwood plywood The yield from the swamp tupelo was better in quantity and quality than that from the water tupelo. 3 —Fleischer, H. O. Experiments in Rotary Veneer Cutting. Proc. Forest Prod Res. Soc. 1949 Report No 1766-9 -3- The favorable veneer recovery indicates that some tupelo veneer could be used for such products as interior wall panels and furniture. Other Factors Tests on tupelo blocks indicate that good glue joints can be made with this wood _ Interlocked irregular grain, common in tupelo veneer, may cause tupelo plywood to warp more than plywood made from straight-grained species. -Truax, T. R The Gluing of Wood. U S. Dept of Agr. Bull No. 1500 1929 Report No 1766-9 -4- Table 1 --Lathe settings used to cut tupelo vent-i-r Veneer thickn- Knife angle Horizontal Vertical nose' : nosebar opening bar opening Inch 1/16 1/8 Degrees - Minutes 90 - 30 89 - 45 Inch 0^0 110 Inch 016 028 Table 2 --Drying schedules for tupelo veneer Veneer : Heartwood or : Temperature : Time in Final mois - thickness sapwood in dryer • dryer ture content Inch °F : Minutes Percent Water tupelo 1/8 Heartwood : 320 ; 30 2 - 4 Sapwood 320 : 18 2 - 4 Heartwood : 250 : 60 2 - 4 Sapwood 250 : 40 2 - 4 1/16 Heartwood 320 a 9 2 - 4 Sapwood : 320 : 8 2 - 4 Heartwood 250 : 18 2 - 4 Sapwood 250 ■ 16 : 2 - 4 Swamp tupelo 1/8 Heartwood : 320 24 2 - 4 Sapwood 320 20 2 - 4 Heartwood 250 50 2 - 4 Sapwood 250 40 2 - 4 1/16 : Heartwood 320 8 : 2 - 4 Sapwood 320 8 2 - 4 Heartwood 250 16 2 - 4 Sapwood 250 : 16 : 2 - 4 Report No. 1766-9 UNIVERSITY OF FLORIDA 3 1262 08924 4973