The Log of the lab;


Material Information

The Log of the lab; items of current research
Physical Description:
v. : ; 20 cm.
Forest Products Laboratory (U.S.)
USDA Forest Service, Forest Products Laboratory
Place of Publication:
Madison, Wis
Publication Date:


Subjects / Keywords:
Forest products -- Periodicals -- United States   ( lcsh )


Dates or Sequential Designation:
Jan. 1916-
General Note:
Title from caption.

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 004891875
oclc - 47028071
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Items of Current Research



Madison, Wisconsin V 0 Release June 1, 1936

BETTIER JINTS FOR0 allowances for bolts in the wood.
TIM IEIR With these data it is now a simple
matter to design a joint with no
jfLTHOUGH billions of board feet of more and no fewer bolts than are
wood are used every year in America necessary to carry safely the load
for building purposes, rarely if ever required. The joint becomes a de-
has wood had a chance to demon- pendable link in a chain 6f security.
state its full capacity for structural Of even greater interest to the
service. Its true merits will be real- modern structural engineer is the
ized through more perfect knowledge use of inserted metal rings, shear
of its properties and better engineer- plates, and tooth fastenings for join-
ing means and methods of utilizing ing timbers together. The split ring
them. One favorable development in and the shear plate fit into precut
this direction is the recent improve- grooves, while the toothed ring is
ment of the structural timber joint, applied by merely being pressed into
Investigations at the Forest Prod- the wood as the two members are
ucts Laboratory have largely elimi- drawn together by a special bolt
nated the "factor of uncertainty" af- and wrench. The advantage of such
fecting use of bolts in timber fram- connectors is that they distribute the
ing. The joint is the critical point of load on the wood over a broad area,
any structure, and' the value of the with fewer bolts and bolt holes than
Laboratory's work lies in showing, would otherwise be necessary. The
from the results of hundreds of tests, net result is that smaller timbers can
just what bearing strength is to be be used to obtain a given joint
expected of a given species and thick- strength, and there is a more equal
ness of wood under the pressure of balance of strength in the different
a bolt of a given size, when the pres- parts of the structure.
sure comes either lengthwise, side- These jointing devices, referred to
wise, or at an oblique angle to the collectively as "modern connectors,"
grain. Supplementing this informa- had their origin in Europe. With
tion were many tests to determine their advantages widely recognized
the proper spacing and marginal there, even more successful use of
SMaintained at Madison, Wis., in cooperation with the University of Wisconsin.

them can be expected in the United
States, because of the many struc-
tural species of timber available here.
In cooperation with the National
Committee on Wood Utilization,
through whom the aid of foreign man-
ufacturers was obtained, several thou-
sand samples of eight important
types of plates, rings, and other con-
nectors were obtained and tested at
the Forest Products Laboratory.
Data were obtained on the strength
of these connectors with two impor-
tant structural woods, southern pine
and Douglas fir. Tests with other
species were later included. Design
values for split rings have been ob-
tained for joints at different angles
with the grain, with various end and
edge margins, and with various
thicknesses of timber. Similar data
are being obtained for other con-
To say that wood has entered a
new structural era as a result of this
development is no exaggeration.
Structures are going up that would
never before have been thought of
in connection with wood. About 200
million feet of timber from the West
Coast region alone has already been
used in construction employing mod.
ern metal connectors, with new adap-
tations occurring almost daily.
For instance, the radio broadcast-
ing tower of the Edgeworth Tobacco
Co. station, WRVA, at Richmond,
Va., is an all-wood structure, 326
feet high, or 39 feet higher than the
Capitol at Washington. It is built of

southern yellow pine and framed
with split rings. Recently station
WEBC, at Superior, Wis., decided
to increase the height of its steel
tower from 240 to 360 feet. A
wooden base section 120 feet high
was built with the aid of modern
connectors, and the steel tower was
mounted on top. Wood supplies the
need, long felt, for a nonconducting
material for broadcasting towers;
only since the introduction of modern
connectors has the necessary height
for powerful stations been reached
with timber.
A number of forest lookout towers
have been constructed of wood, with
modern connectors, by the U. S. For-
est Service. Last year at Dolan
Creek, Calif., a 180-foot arched tim-
ber highway bridge was built of red-
wood, with split rings for the joints
and splices. Long timber approaches
were built, also framed with the new
Among numerous structures re-
cently built in the United States with
plate or ring connectors are rock
and gravel bins at Berkeley, Calif.,
roof trusses for a large riding hall
in Virginia, tank towers, theatres,
school auditoriums, and a building
for club use. As proved by Euro-
pean experience, the way is open for
the use of timber in many other large
structures, such as warehouses, rail-
way sheds, and aircraft hangars.
The record of Forest Products
Laboratory research on bolted joints
is found in U.S.D.A. Technical Bul-

letin No. 332, and on modern con-
nectors in the Laboratory's "Wood
Handbook." Both these publica-
tions are for sale by the Superintend-
ent of Documents, Government
Printing Office, Washington, D. C.


ONE of the first problems encoun-
tered by the Forest Products Labor-
atory in its current investigation of
the design of fiber shipping con-
tainers was the lack of a satisfactory
means of counting the plies in a box
board built up of consolidated layers.
In the past an alcoholic solution of
phenolphthalein has been used as
an indicator; applied to the edge of
a board, this detector reveals the
lines of junction by turning pink in
contact with the alkaline adhesive
used usually sodium silicate.
Unfortunately, this test does not
always give the reaction desired; for
various reasons the alkalinity of the
adhesive may be too low to cause
the necessary color change in phen-
In the search for a more sensitive
chemical, many of the common in-
dicators were tried, among which
methyl red, phenol red, chlorphenol
red, bromphenol blue, and bromthy-
mol blue all proved more satisfactory
than phenolphthalein. Methyl red
was found to be the best for sharp-
ness of line and permanence of color.
A one-tenth percent solution of
methyl red in distilled water is now

used, and the best results are ob-
tained where the board has been cut
with a sharp knife. Adhesives of
even the slightest alkalinity, includ-
ing practically any preparation of
casein glue or sodium silicate, are
shown as yellow lines on a red field,
so distinctly that measurements of
the film thickness can be made with
either a micrometer microscope or
micrometer slide.
This method is simple, accurate,
and suited to commercial as well as
research use.

the purpose of aiding farmers and
home owners in the efficient selec-
tion of lumber for all common types
of construction, a descriptive pam-
phlet of 45 pages has been pub-
lished under the authorship of C. V.
Sweet and R. P. A. Johnson, Forest
Products Laboratory engineers. It
classifies all species of lumber com-
mercially available under 28 main
types of wood use about the home
and farmstead, including exterior
siding and trim, flooring for kitchen,
living quarters, and porch, interior
trim, sash, shelving, roofing, joists
and framing, sills, stanchions, man-
gers, silos, concrete forms, fence posts
and gates. Qualities of the different
woods are explained in direct rela-
tion to the service required.
Designated as Farmers' Bulletin
No. 1756, Selection of Lumber for
Farm and Home Building," copies of
the new publication can be obtained


from the up ]Nf THE 1 3 1262 08740 0221
ments, Go er neit Printing Offic4 THE NATION
Washingto i, C,,at i price of
cents each 2. Land Use

.. Forestry is responsible to the Amer-
QUESTIONS THE LABORATORY ican people for the productive use
IS ASKED of hundreds of millions of acres of
land use which will return positive
Q. What is applewood, and values in employment, human well-
what is it used for? being, and community revenue.
A. Applewood is what its name It is the crop and utilization value
implies, wood from trees of the apple of trees that makes it possible to
orchard. It is distinctive among think of withdrawing vast acreages
commercial species for the exceed- of submarginal land from agriculture
ing fineness of its pores and the and putting them into forest; we are
"closeness" of its grain. These char- thinking about productive land use,
acteristics combined with hardness about people's livings, and the money
give it unusual finishing and wearing they can make by cutting fuel and
qualities. Handles for carpenters' timber and railway ties, selling pulp-
tools, especially handsaws, probably wood, and supplying the Nation with
consume the bulk of applewood. building materials and manufactured
Some apple is used in high-quality commodities of wood such as it has
plane blocks, tobacco pipes, circular had in abundance in the past.
shuttle tops in the textile industry, The purpose of the Forest Prod-
and other specialties. ucts Laboratory is to aid our great
Q. What woods are used for forestry program on the practical,
baseball bats? dollars-and-cents side by improving
A. The properties required in a the utilization of wood, making it
good bat are lightness, hardness, and a more adaptable and satisfactory
toughness. White ash is generally material for the requirements of mod-
considered the best wood for this ern life. Such utilization is needed
purpose and is by far the most com- to liquidate the billions invested in
only used. Northern hackberry is forest lands by both public and pri-
being used to some extent; if the vate ownership.
wood is properly selected, it makes Our effort is to help in establishing
a serviceable bat. Low-priced bats not only forests but a permanent for-
for juvenile use are of many species, est economy in the United States of
but probably of the lower grades of America.
ash for the most part. (To be continued)

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