Wood goes to war

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Title:
Wood goes to war
Physical Description:
Mixed Material
Creator:
Winslow, Carlile P
United States -- Forest Service
University of Wisconsin
Publisher:
Dept. of Agriculture, Forest Service, Forest Products Laboratory ( Madison, Wis )
Publication Date:

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All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 29301095
oclc - 225106796
System ID:
AA00020551:00001

Full Text

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,! L 24


WOOUD CIES TO WAIR


Dececcmber 1942
















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No. ID142(5


UNITED STATES DEPARTMENT OF AGRICULTURE
FOREST SERVICE
FOREST PRODUCTS LABORATORY
Madison, Wisconsin
In Cooperation with the University of Wisconsin











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C'. LiLE P WINSLOW, DI ECTOP

In the popular mind this is a war of dive bombers and hi -h-sreed armored divisions
--vet this war of machines re.,iires a larger quantity and variety of forest prod-
ucts than has been used in any previous war. As a matter of fact, this has been
rec_''nized by the .-rmans for a I r,, time; they ut wood secod S n on the list of
essential materials--second only to steel--in planning this war.

Lumbermen are aware of the vast quantities of lumber qoing into the co instruction
of military building s. However, it is likely that few comprehend fully the list
of wood items demanded by wars insatiable a cetite--wood for han-ars, scaffold-
i r boats, wharves, bridges, pontoons, rai lway ties, telephone poles, mine crcrs,
anti-tank barriers, shoring, shippin' containers, and air-raid shelters; plywood.
for airp anes, blackout shutters, prefabricated housing, concrete forms, ship cat-
terns, assault boats, ship interiors, truck bodies, and arm,' lockers; fuel for
qaso:enes, for trucks a-,i tractors; pulp and paper for surgical dressingn .s, boves,
cartrid, e wrappers, bu dinq prs, b s, :-,.teboards, qasmask fil ters, printing and
pro.-,.'anda distribution; synthetic wood fibers, such as in ra :n, artificial wcol
and cotton, for clothing, 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 phot-t graphic film, shatterproof qlass, airplane dopes, lacquer, cement,
and molded articles; wood flour for d.ramite; 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 requirinr-. approximately a million feet of hardwood a day.

The amount of lumber used for containers is almost unbelievable The number of
boxes re.pui red for the shipment of ammunit on alone runs into the scores of thou-
sands :er day It is estimated that more than seven billion board feet of lumber
wi ll be required for containers in l 42 and a substantially greater amount In 1943.

All told our wood needs this year (according to the War Production 2card)will
exceed "? bil lion board feet Actually we are estimated to be cutting only 53
billion feet A stock pi le of some five billion feet in the hands of man'ufactur-
ers is rapidly vanishir'n in the face of this qap between proJuction and consunction

A Critical Material

The bujr:--r rain cr:- this year called for additional storage c racity which re-
qu red release of lumber frozen for mi itarv purposes In the Doricultural im-
plement filed there is urgent need to replace war-commandeered steel with :ood
if we are to continue to meet -ricultural production ,calst Lumber, therefore,
has become one more crit 'cal material of which we do not have pncu-h.

Eiqht months 1-,; o our war agencies were beqinninq to seek ways and rens of sub-
stitut r; wood for steel wherever practicable, but todIay they are also frantical-
Iy searchir to find substitutes for wood (often in uses where wood originaft 'y
replaced steel ). Available materials for lumber substitutes include :-acer and


Ib ished in Southern Lumberman, 'ember 15 1-2
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fiber products, gl si 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 A-,ny, Navy, 'War Production
Board, and other war agencies. The Laboratory's big job today is to help sol -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 had been largely swung over
to war objectives and since that day the Laboratory has been on a I- ) --rcent
war footing. Personnel has been increased from 170 to nearly 500 and tne 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 c ose co-operation with the Army and Navy. Other important develop-
ments wh ch can be discussed are described in the fol lowing paragraphs.

Timber Connectors


Modern connectors for timber construction are increasingly coming into their own
under the urgency of war-time construction. These relatively simple fittings
in the form of rings or plates inserted between surfaces in contact in timber
o!nts distr bute stresses over a much wider area of wood than does the ordinary
toied jo nt The result is a joint four or five times as strong as the simple
bo ted connect ion.
The determ nation of engineering data on the modern connectors was carried out by
the Forest Products Laboratory during the early 1930 s, and it can be said that
its general acceptance by architects and engineers arrived none too soon to serve
us in this war However, it did arrive in time,, and it has been installed in new
factories, airplane hangars, mold lofts, warehouses, and other large industrial
and mi litary structures throughout the nation., The connectors lend themselves
readily to shop fabrication and quick emergency construction and they are helping
wood to serve effectively in the breach left by steel that has been diverted to
actual fighting implements A billion and a half board feet of timber has been
used with connectors to date more than half of this amount in the last year
and a quarter of a mi lion tons of steel has consequently been saved for direct
war uses where only steel will serve

Glued Laminated Arch

Another timber construction principle that became avai lab e just in time to help
fight this war is the glued laminated wood arch. The Laboratory worked out the
basic design prince ples 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, dri I I hal Is, and
garages; a transport ai rplane hangar with laminated arches having a span of 152
feet, wil l house the largest transport planes now being designed

Place one type of glued laminated arch on its back and you have something 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 sl-h)es may


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serve to harass Htiler ad his undersea minions. The lamination principle is
lso bein app ed to airplane wing beams. r deve cLrent of the new synthetic
resin ....I ith thei r high resistance to moisture--is helping in this leI'.'elop-
en. Tese es r "uire heat to set them, however, and the + forest Products
Labor ry as b ilt and is testirg electrostatic heatirj ejipment cr setting
Sle n minted structural members and for seasoning of critical lumber items.

Ne signs for ".xes and Crating

Co o. rat i' with the r irtment the Laboratory is extens lively r .... d in
the deve opment of designs aj specifications for bc'es and crates ar. f-r load-
n .ck ,ing of ordnance e i-:. i i v nt and munitions, inc I udir.-_ tanks ^.ns,
an other combat ::iri,-rrt for the expeditionary forces. Items must be so pack-
ed as to arrive whole free from moisture, rust, and decay, plainly mar'-Ie, read-
i y and .ickly accessible, protected against pi I fer.)e, and pic.:ed' so as to
conserve we ght, lumber, and vital cario space. Similar services are being given
to Lend ease and other Goverrnment war agencies as required Hundreds of thou-
sands of items are involved, and in practically al l cases better : r .es are
developed, with savings of vital shipping space of from 5 to :-rcent

Radio commentator -z,-nd ram Swinr recently made this observation, ',c are
I yvir in a t ime when the ton of cargo space is the most important unit of pover
in the United Nations war "


Seasoning Problems

n a great many products ranging from gunstocks to ai-clanes, season is be-
comn a crit cal bottleneck in lumber production despite the fact we are un-
fortunately cmpel led to use lumber practically green from the saw in much con-
st ruct ion work

Chem ca seasonir: as developed at the Laboratory s at least a partial answer
to the seasonir, problem, making possible faster dryir: schedules and cutting
osses thro -'.h checking and degrade to a minimum. For ex z: le, early in this
war three-inch Dou ilas-fir planks needed for pontoons -e'-uired :- days to season
in a dry ki n, and even then about a fourth of the stock dried had to be thrown
ut because of d -rade. The high loss made seasoning of such stock uneconomic.
.'.ith Laboratory methods of chemical seasoning, however, the dryi' time was cut
to less than a week and degrade losses cut to I or 2 -ercent. T-' success with
pontoon stock has since led to application of the chemical seasoning process to
other ty--s of thick lumber
Here m s another example in a shoe last block, an item in our Lend-lease program
Under ord nary methods of seasoning, involving air drytir followed by kiln Jdry-
ng, sx months or more may be needed to dry m.,rle shoe iasts to the pr:er
mosture content .' ith good kilns and effective kiln schedules, the Laboratory
has dr.ed such stock experimental ly in about 45 days.

Chemca season" materials have been adz3ted to extend the supply of wood for
shutt es needed by the textile industry, which is.working under the burden of
irge orders for uniform cloth and other war goods 7-wood has a combination
f hardness) fine texture to. hness and smooth wearir u .lities -': rec:.3-
n ized and demanded by the industry .nd has rushed the price up to $1 a
board foot, and sti the demand cannot be met. ne Laborator, has treated
other s es, notab y b ch and :-rsimmon, with chemicals, thereby increase i.
their hardness by as much as 46 recentt textile mi l ls are now ,' r: Labora-
tory treated shutt es expermental ly *'. th similar chemical tre .t-Pr" 7 rle











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 semiautomatic-rifle and the carbines with which our growing armies are
being equipped require wooden "unstocks. lack walnut is the preferred species.
Here aqain, seasoning is a bottleneck in production that can be materially widen-
ed. Stepped up ki ln 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 -herry is an excel lent 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 I I 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.


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lnrr-i and Compreq

The search for chemical treatment that would make wood a substance less affected
by noistur-- protect it, that is, from shrinking and swelling and consequent
warping, cupping, twisting, and the like--has led to two distinct, yet closely
related, products mpr.-" and c :,mc r,:-q
Strips of ordinary veneer are the raw material from which imcreq and compare are
usual l made, altho..h the process is ai)uplIicablie to thicker wood. The problem
wa to protect the wood celts lainst the comings and loinqs of moisture which
cause wel I ing and shrinking. Various materials were triel 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-
ta ned which penetrated not only the cell cavities, but also the very cell walls
of wood, displacing the moisture within the cell structure. Ucon heating, this
solution became rmanently fixed within the wood, and a material of very high
water resistance was the result Thus was born impre:.

*'th this treated veneer the next step logically Aas 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,
the sheets, or laminations, had a decided tendency to become plastic as pressure
and heat were ,.:plied simultaneously. In fact, it was found that, in hot press-
ing, the laminations could be c:.-..ressed into a product one-half or one-third
their original combined thickness. And when taken from the press, this product
retained 'ts compressed dimensions even when soaked in water for prolonged periods.
Moreover, it was found that no glue was needed to bind the resin-treated veneer
sheets to each other, enough of the resin within each sheet was squeezed out to
form a strong bond between adjacent sheets. Here, then was a product (now known
as "c,-. r,---i" wood) extremely resistant to moisture, with hardly any detectable
shrinking or swelling; with a glossy finish and surface hardness approaching that
of glass Its properties, too, were remarkable.

Subs-luent tests disclosed the fact that comprei can be molded to single or
double curvature. For the period of the war emergency, it will doubtless remain
a material solely for military uses It is now being tested in varilous military
applications, notably propel lers, aircraft landing wheels, torpedo boat electric-
al control housings, and other c.3rts requiring high strength and waterproof
J ia cities

Propel lers demonstrate the ad ptab ility of comprea 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 c'-rressed only to mold it to the correct aerodynamic
curvatures and proportions in order to produce an efficient, yet relatively
i ght member
S5mi early, compr,-,- faces and i-creg cores can be assembled into a product that
is ght n we ght, yet possessin- high moisture resistance.

Past i cs

The Forest Products Laborator, has under development three distinct types of
ast cs. These are (!) plastic wood, which is a product little chan,ced in ap-
earance from ordinal, wood; (2? a m'lIdzi, lowder and a mo sl):n c s 'ee--both of
which are wood plastics as distinguished from plastic wood anJ produced from
sawdust or other wood wastes and contain a relatively high content of liinin;
and 5} a laminated ier plastic of great tensi le strength and having, other pro-
eries which give it much promise as a substitute for aluminum and other metals.
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The Placstic wood process was discovered in the course of experiments 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 with n 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 6ad actual ly 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 with urea-aldehyde this chemical combined with
the lignin in the wood to form a thermosetting plastic, When cooled th s time,
the wood became hard and held 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 app cai ons
of the process are being examined, such developments must be devoted exclusively
to war work

The plastic mo d.ng compound and the laminated sheet already mentioned are out.
growths of Laboratory research on the innate plastic and bonding qua ties of
igni n. Both are made from hardwood wastes and their commercial development
therefore promises an outlet for much wood that is today necessary, y d scared n
the woods and at the sawmi Il.,

For more than a decade the molding compound has been under development at the
Laboratory
Shortly after Peart Harbor, representatives of a leading storage battery manufac
turer visited the Laboratory in a desperate search for a material to replace hard
rubber used in their battery boxes and covers,. By th s time, the molding corn
pound had been developed to a fair state of utility and was technical iy known as
,hyd.ol zed wood It was decided to try it for battery cases because of its known
acid resistance, and the product resulting gave clear ind cation of be ng an ade
quate substitute not only from this 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 half as much resin as the genera; purpose plastics on t6e mar
ket today
An offshoot of the hydrolized wood molding compound is the hydroiized wood iam
inating sheet. Though stiI in the development stage, t appears to have the same
resin economy, moidabiHty, and resistance to acids and water that have a ready
been exhibited by the molding compound

A strong paper base plastic is the Laboratory's newest material Its develop-
ment to its present promising stage has been iitera iiy 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 thn sheets are compressed together into sheets or
shapes This plastic is more than twice as strong in tension as the convention-
al paper plastics

Its translucent amber color is characterist c, as :s the smooth finish Most lm
portant however, is its strength The tens e strength is,, n fact equate on a
weight basis to that of aluminum. It can be molded to desired shapes at tempera
tures and pressures and on equ pment now used for making plywood It is highly
resistant to moisture, and remains extreme y stable at both h gh and ow temper
atures Tests ind cate that it is more resistent to scratching and denting than
alum num. and does not splinter, tear. or flower out when ,pierced by bul lets
A leading manufacturer has begun experimental production of structural aircraft
parts, and the Army and Navy are giv "ng the paper p ast c cons iderat on as a
substitute to a eviate grow ng shortages of other mater a s its property es,


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which can be varied in manufacture to meet special needs, also give promise for
its use water craft ranlirn.q from smaHl boats to large cargo vessels, and in
fly ri boats

Chemicals I.

Lignin, the material that once was thought to have been put in wood largely to
plague the :'iper mil l chemists, has been demonstrated to offer a source of a
number of chem cais vital to the war effort A year or two ago the Laboratory
first used hyd-'ien under pressure to break lignin down into a number of consti-
tuents that were in some cases brand new to the chemist Frankly the stuff was
beiri torn apart to find out how it was put together--an exercise in pure chem
istry 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 obtained---stripped
of their technical nomenclature: a chemical for doctoring motor fuel to produce
high antiknock qualities; glycols (for possible use as anti freeze agents';
glycer ne, the ingredient of explosives that the Government is trying to recap-
ture from the housewife s skillet; phenols, for making an infinte variety of
plastics to serve where only plastics can serve and to replace metals, industry
al alcohol used in making formaldehyde, constituent of important plastics for
bonding p ,.'.-.>ds and for producing plastics of the bakelite type This is not
the c-r',iete roster of lignin constituents--some of the'other materials are resins
that ap.'ar to be possible lacquer bases and others appear to have possibilities
a I. ast cizers -but the list suffices to indicate that wood, before long, may
be coax I to yield a group of products comparable to those obtained from coal
tar and "by s mi iar processing
in connection with the process of lignin hydrogenation, it is interesting to
note that when wood itself, not just i ignin, is hydrogenated the i gnin breaks
down nto ( m Iar intriguing fractions and the ce i,ulose comes off in the form
of pu l Some day something should come of this process which converts all of
the wood into tractable chemical products














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