htX WOOD GOES TO WAR December 1942 L, // No. D1426 UNITED STATES DEPARTMENT OF AGRICULTURE FOREST SERVICE FOREST PRODUCTS LABORATORY Madison, Wisconsin In Cooperation with the University of Wisconsin WOOD GOES TO WAR-*- Bv CARLILE P WINSLOW, DIRECTOR In the popular mind this is a war of dive bombers and hiqh-speed armored divisions — vet this war of machines requires a larqer quantity and variety of forest prod- ucts than has been used in any previous war. As a matter of fact, this has been recoqnized by the Germans for a lonq time; thev put wood second on the list of essential materials — second only to steel — in planninq this war. Lumbermen are aware of the vast quantities of lumber qoinq into the construction of military buildinqs. However, it is likely that few comprehend fully the list of wood items demanded by war's insatiable appetite — wood for hanaars, scaffc inq, boats, wharves, bridqes, pontoons, railway ties, telephone poles, mine props, anti-tank barriers, shorinq, shippinq containers, and air-raid shelters; plywood, for airplanes, blackout shutters, prefabricated housinq, concrete forms, ship pat- terns, assault boats, ship interiors, truck bodies, and army lockers; fuel for qasoqenes, for trucks and tractors; pu I d and caper for su rq i ca I ' d ress i nqs, boxes. cartridqe wrappers, buildinq papers, pasteboards, qasmask filters, printinq, and propaqanda distribution; synthetic wood fibers, such as in rayon, artificial wool and cotton, for clothinq, parachutes, and other textiles; wood cellulose for ex- plosives; wood charcoal for qas masks and steel production; rosin for shrapnel and varnishes, turpentine for flame throwers, paint, and varnishes; cellulose acetate for photoqraphic film, shatterproof qlass, airplane dopes, lacquer, cement, and molded articles; wood flour for dynamite; wood bark for insulation, tannin, and dyestuffs; and alcohol from wood for rubber Only recently the Government has ordered that all Army truck bodies be built of wood to conserve steel — a use that is currently requirinq approximately a million feet of hardwood a day. The amount of lumber used for containers is almost unbelievable. The number of boxes required for the shipment of ammunit'on alone runs into the scores of thou- sands per dav. It is estimated that more than seven billion board feet of lumber will be required for containers in 1942 and a substantially qreater amount in 1943. Al I told our wood needs this year (accordina to the War Production Board).-, exceed 39 billion board feet Actually we are estimated to be cuttinq only 33 bill ion feet A stock pi ie of some five bi I I ion feet in the hands of manufactur- ers is rapidly van i sh i nq in the face of this qap between production and consumption A Critical Materi al The bumper qrain crop this year called for additional storaqe capacity which re- ed release of lumber frozen for military purposes. In the ii»r cultural im- plement field there is uroent need to replace war-commandeered steel with wood if we are to continue to meet aqriculturai production qoals. Lumber, therefore, has become one more critical material of which we do not have enouqh. Eiqht months aqo our war aqencies were beqinninq to seek ways and means of sub- stituting wood for steel wherever practicable, but today they are also frantical- ly searchinq to find substitutes for wood (often in uses where wood oriqinally replaced steel). Avai I ab I e materi at s for I umber subst i tutes i nc I ude paper and "Published in Southern Lumberman, December 15, 1942 DI426 fiber products, glass, brick, masonry, and cement. It seems a safe prediction that before long the manufacture of additional hundreds of wooden articles in common use today will be sharply restricted or denied altogether The Forest Products Laboratory has been deluged by requests for information about wood, the most urgent of which have come from the Army, Navy, War Production Board, and other war agencies. The Laboratory's big job today is to help soh'e the manifold wood use problems of these same agencies and of the war industries having the job of winning this war in the factories, in the arsenals, and on the distant fighting fronts. Six months before Pearl Harbor the research program irato ry argely swung over has been on a 100 >e rcent had been to war objectives and since that day the Laboratory has been on a I uu pe war footing. Personnel has been increased from 170 to nearly 500 and the needs of the Army and Navy for additional services and information may require further expansion to perhaps 600 or 700 before the end of the year Extra shifts have already been added Obvious'y, some of the specific things that the Forest Products Laboratory is do- ing to help win the war cannot be freely disclosed These are activities car- ried on in ciose co-operation with the Army and Navy. Other important develop- ments wh ch can be discussed are described in the following paragraphs. Timber Connectors connectors for timber construction are increasingly coming into their own ■ of war-time construction. These relatively simple fittings ates inserted between surfaces in contact in timber over a much wider area of wood than does the ordinary Mode rn under the urgency in the form of rings or p io nts • d ■ st • bute stresses bo ted jo nt The bo 'ted connection result is a joint four or five times as strong as the simple The det the For its gen us i n t factor i and m i I read wood to actua I used wi and a q war use erm est nat i Prod era 1 ace his war es, a i rp itary st to shop serve e f i g ht i ng th conne uarter o s where on of ucts eptan How I ane ructu fabr ffect i mp I ctors f a m on ly eng i nee Laborato ce by ar ever, it hangars, res thro i c at i o n i ve ly in ement s to d at e i I I i on t stee I wi ring ry d ch i t did mo I ugho and the A b -mo ons I I s dat u r i n ects ar r d Io ut t qu i c b re i I II re t of s erve a on 9 th and i ve fts, he n k em ach on a han teel the mod e early eng i nee in time, warehou at i on ergency 'eft by nd a hal half of has con ern con 1930 s, rs arri and it ses, an The con const ru steel t f board this am sequent nectors w and it c ved none has been d other I nectors I ct i on and hat has b feet of ount i n t ly been s as car r i ed out by an be said that too soon to serve i nsta I I ed in new arge i ndust rial end themselves t hey are helping een d i ve rted to t i mbe r has been he last year — aved f or d i rect Glued Laminated Arch Another timber construction principle that became available just in time to help fight this war is the glued laminated wood arch. The Laboratory worked out the basic design principles that have enabled architects and engineers to design arches of greatly varied size and shape to support ■- with no obstruction to floor and overhead space -many vital structures, such as hangars, drill halls, and garages, a transport airplane hangar with laminated arches having a span of 152 feet, will house the largest transport planes now being designed Place one type of glued laminated arch on its back and you have sorneth'ng with the appearance of a boat keel That is the precise naval use in which the tech- nique of shaping thin laminations and giuing them into strong curved shapes may DI426 serve to harass Hitler and his undersea minions. The lamination principle is also being applied to airplane wing beams. The development of the new synthetic resip glu th their high resistance to moisture — is helping in this develop- ment. These glues require heat to set them, however, and the Forest Products Laboratory has built and is testing electrostatic heating equipment for setting glue in laminated structural members and for seasoning of critical lumber items. New Designs for Boxes and Crating Co operating with the War Department, the Laboratory is extensively engaged the development of designs and specifications for boxes and crates and for load- ing and packaging of ordnance equipment and munitions, including tanks, guns, and other combat equipment for the expeditionary forces. Items must be so pack- ed as to arrive whole free from moisture, rust, and decay, plainly marked, read- y and quickly accessible, protected against pilferage, and packaged so as to conserve weight, lumber, and vital cargo space. Simitar services are being given to Lend-lease and other Government war agencies as required. Hundreds of thou- sands of items are involved, and in practically all cases better packages are developed, with savings of vital shipping space of from 5 to 30 percent Radio commentator Raymond Gram Swing recently made this observation, "We are living in a time when the ton of cargo space is the most important unit of power in the United Nations' war." Seasoning Problems In a great many products ranging from gunstocks to airplanes, seasoning is be- coming a critical bottleneck in lumber production despite the fact we are un- fortunately compelled to use lumber practically green from the saw in much con- st ruct i on work Chemical seasoning as developed at the Laboratory is at least a partial answer to the seasoning problem, making possible faster drying schedules and cutting losses through checking and degrade to a minimum. For example, early in this war three-inch Douglas-fir planks needed for pontoons required 28 days to season in a dry ki In, and even then about a fourth of the stock dried had to be thrown out because of degrade The high loss made seasoning of such stock uneconomic. With Laboratory methods of chemical seasoning, however, the drying time was cut to less than a week and degrade losses cut to I or 2 percent. The success with pontoon stock has since led to application of the chemical seasoning process to other types of thick lumber Here is another example -in a shoe last block, an item in our Lend-lease program Under ordinary methods of seasoning, involving air drying followed by kiln dry- ing, six months or more may be needed to dry maple shoe lasts to the proper moisture content With good kilns and effective kiln schedules, the Laboratory has dried such stock experimentally in about 45 days. Chemical seasoning materials have been adapted to extend the supply of wood for shuttles needed by the textile industry, which is. working under the burden of large orders for uniform cloth and other war goods Dogwood has a combination of hardness, fine texture toughness, and smooth wearing qualities long recog- nized and demanded by the industry Demand has pushed the price up to $1 a board foot, and still the demand cannot be met The Laboratory has treated other species, notably birch and persimmon, with chemicals, thereby increasing their hardness by as much as 45 percent Textile mills are now trying Labor a tory-treated shuttles experimentally With similar chemical treatment, maple DI426 bobbins have also been produced more rapidly and with a degree of hardness that promises to give them longer life in service and to eliminate the need for the metal ferrules now applied to the ends. The modern sem i automat i c- ri f I e and the carbines with which our growing armies are being equipped require wooden nunstocks. 8lack walnut is the preferred species. Here again, seasoning is a bottleneck in production that can be materially widen- ed. Stepped up kiln schedules and techniques developed at the Laboratory to re- duce the drying time of these walnut gunstock blanks from 70 to about 50 days have been suggested to the industry. At the same time, research has shown that black cherry is an excellent substitute species for black walnut. Cherry has a specific gravity about the same as that of walnut, and can be kiln-dried in about two-thirds the time. It has very simi- lar machining qualities, according to tests made in an eastern gunstock plant. Plywood for Airplanes Owing to the scarcity of metals, increasing quantities of plywood are going into training and combat planes, gliders, and cargo planes. Plywood has been manu- factured and used in airplanes, in the United States for years. But before ply- wood goes into modern military craft in which the lives of American airmen are at stake, the Army and Navy must be assured that plywood can, as an engineering material, take the terrific punishment to which such planes are subjected. This calls for the immediate development and testing of mathematical formulae by which the specific properties of plywood, such as resistance to fatigue, buck- ling, and torsion, can be more accurately calculated for design purposes. To obtain these formulas the Laboratory's engineering staff has been greatly expand- ed and, in order to expedite the testing required, a force of women is operating test equipment in two shifts from 6 o'clock in the morning until II p.m. New Glues The recent development of highly water-resistant synthetic resin glues for ply- wood necessitates that these glues, as they come on the market in ever increas- ing numbers, be careful ly checked to assure that they measure up to certain standards. The Laboratory is constantly making tests of new glue formulations in order to inform the public, and particularly the armed services regarding new products which may or may not have been adequately tested by their producers. Along with the new glues and the use of flat plywood there has been developed by various manufacturers the process of molding plywood by means of fluid pres- sure applied through flexible bags or blankets of rubber or other impermeable_ material. This development frequently termed "bag-molding" is of particular im- portance at the moment in the making of aircraft parts of various degrees of curvature. In size these parts may vary from a fairing for a tail wheel to a half fuselage complete with bulkhead rings. They include all combinations of single and double curvatures, cylinders, paraboloids, portions of a sphere — in short, any curved piece for which a mold can be made and later separated from the finished product. The Laboratory is conducting experiments to extend the scope of the process and to produce specimens such as test cylinders with which to study buckling and other plywood design criteria. DI426 iTipreg and Compreg The search for chemical treatment that would make wood a substance less affected by mo i stu re-- p rotect it, that is, from shrinking and swelling and consequent warping, cupping, twisting, and the like — has led to two distinct, yet closely related, products: impreg and compreg. Strips of ordinary veneer are the raw material from which impreg and compreg are usually made, although the process is applicable to thicker wood. The problem was to protect the wood cells aaainst the comings and goings of moisture which cause swelling and shrinking. various materials were tried over a period of years; the most successful have proven to be modern synthetic substances called phenolic resi ns. It was found that when these resins were dissolved in water, a solution was ob- tained which penetrated not only the cell cavities, but also the wery cell walls of wood, displacing the moisture within the cell structure. Upon heating, this solution became permanently fixed within the wood, and a material of ^ery high water resistance was the result.. Thus was born impreg. With this treated veneer the next step logically was to make an improved ply- wood In the course of these experiments a number of more or less unexpected de- velopments came about. Most outstanding was the fact that when the resin treated veneers were placed in a press before they had been heated to "set" the resins, *s, or laminations, had a decided tendency to become plastic as pressure were applied simultaneously. In fact, it was found that, in hot press- ods. the sheet and heat we Subsequent tests disclosed the fact that compreg can be molded to single or double curvature. For the period of the war emergency, it will doubtless remain a material solely for milita ry uses. It is now being tested in various mi I i tary applications, notably propellers, aircraft landing wheels, torpedo boat electric- al control housings, and other parts requiring high strength and waterproof qua I i t i es Propellers demonstrate the adaptability of compreg to a nicety. Where great strength is needed, as at the hub, high pressure can produce this strength. The rest of the blade may be compressed only to mold it to the correct aerodynamic curvatures and proportions in order to produce an efficient, yet relatively light member. Similarly, compreg faces and impreg cores can be assembled into a product that is light in weight, yet possessing high moisture resistance. PI ast i cs The Forest Products Laboratory has under development three distinct types of plastics. These are IN plastic wood, which is a product little changed in ap- pearance from ordinary wood; <2) a molding tender and a molcinf sheet — both of which are wood plastics as distinguished from plastic wood and produced from sawdust or other wood wastes and contain a relatively high content of lignin; and (3) a Laminated pater plastic of great tensile strength and having other pro- perties which give it much promise as a substitute for aluminum and other metals. DI426 -5- The plastic wood process was discovered in the course of exper'ments in chemical seasoning Searching for a chemical that would draw water to the surface of green lumber so that fast drying would not set up stresses within the wood which would check and degrade it, wood was treated with urea. Upon heating the wood the usual procedure, it was noted that it had suffered a striking change it had actually become plastic and could be twisted, bent to extreme curvatures, or shaped over forms. On further experimentation, it was found that when wood was treated w'th urea-aldehyde this chemicai combined with the lignin In the wood to form a thermosetting plastic When cooied this time, the wood became hard and he id its shape permanently This product certainly challenges the imagination, but it is so new that there has been little opportunity to test its properties; and, while some applications of the process are being examined, such developments must be devoted exclusively to war work The piastic moid ng compound and the laminated sheet a i ready ment.oned are out. growths of Laboratory research on the innate plastic and bond^ng qualities of . gr n Both are made from hardwood wastes, and their commercial development therefore promises an outlet for much wood that is today necessar; y d scarded .n the woods and at the sawmill. For more than a decade the molding compound has been under development at the Laboratory Shortly after Peari Harbor, representatives of a leading storage battery manufac turer visited the Laboratory in a desperate search for a materia! to replace hard rubber used >n their battery boxes and covers By th.s time, the molding com pound had been developed to a fair state of utility and was technically known as hyd . o zed wood It was dec.ded to try it for battery cases because of its known acid resistance, and the product resu ; ttng gave clear i nd cat i on of being an ade quate substitute not oniy from tfvs standpoint, but because it proved lighter in weight by a third, and possessed better strength As a plastic, moreover^, it re- quires on y about haif as much resin as the genera! purpose piast:cs on the mar ket today An offshoot of the hydrolized wood moiding compound is the hydroiized wood i am inating sheet Though still in the development stage. t appears to have the same resin economy, moldab.lity, and resistance to acids and water that have already been exh.b ted by the molding compound A strong paper base piastic is the Laboratory's newest material Its develop ment to its present promising stage has been I iteral iy a matter of months It is made of a new type of paper developed at the Laboratory and impregnated with synthetic res ns after which th.n sheets are compressed together into sheets or shapes Th.s plastic is more than twice as strong in tension as the convention- a i paper p , ast i cs its translucent amber color is characterist c as is the smooth finish Most im portant however, is its strength The tens; e strength is n fact, equal on a we'ght bas . s to that of a urn num. It can be moided to desired shapes at tempera- tures and pressures and on equ pment now used for making plywood It is highly res.stant to moisture and remains extreme ; y stable at both h;gh and I ow temper- atures Tests i nd cate that it is more resistent to scratching and denting than a i urn num and does not splinter tear or flower out when pierced by bullets A :ead ng manufacturer has begun experimental product on of structural aircraft parts and the Army and Navy are givng the paper p ast c cons'derat on as a subst tute to a eviate grow ng shortages of other materia s its propert es, D 426 ~6- UNIVERSITY OF FLORIDA 1262 08924 5541 which can be varied in manufacture to meet special needs, also give promise for its use in water craft ranging from small boats to large cargo vessels, and in f ly i ng boats Chem i ca I s Lignin, the material that once was thought to have been put in wood largely to plague the paper mi I I chemists, has been demonstrated to offer a source of a number of chemicals vital to the war effort A year or two ago the Laboratory first used hydrogen under pressure to break lignin down into a number of const i tuents that were in some cases brand new to the chemist Frankly the stuff was being torn apart to find out how it was put together-— an exercise in pure chem i st ry . The experiments have been repeated on a pilot plant scale and the origin al results verified and extended In the light of the events of the last nine months those results no longer are of purely academic interest Here are some of the chemicals obta i ned - -st r i pped of their technical nomenclature a chemical for doctoring motor fuel to produce . other materials are resins that appear to be possible lacquer bases and others appear to have possibilities asxicizers- but the list suffices to indicate that wood, before long, may be Luax§d to yield a group of products comparable to those obtained from coal tar and "by s'mi lar processing n connection with the process of lignin hyd rogenat i on , it is interesting to note that when wood itself, not just i:gnin. is hydrogenated the lignin breaks down into s mi lar