Technical Description of Flr Plywood Grades

By John T. No*hom, Manaser Harbor Plywood Corporation of Southern California

Fir Plywood is now a major material in the building industry, and is manufactured in several grades. There are four commercially standard face veneer grades from which all grades are developed.

"A" is called sound, and although permitting patches of various types and sizes. is intended for natural, paint or stain finishes.

"B" is described as solid, and the identifying patch is tlre round plug patch about 23f" in diameter. It is unmatched for color or figure, and the direction r.rf the grain in the pat,ch does not necessarily parallel the grain of the face veneer. This grade is intended for use where open de{ects are objectionable, and is considered :;uitable for painted surfaces. Sound. tight knots up to 1" in diameter are permitted, but seldom found, in this grade.

"C" and "D" are really reject veneers due to the fact that both u,'i11 permit open defects, such as knotholes. The main difference is the maximum size knotl-role permitted. The "C" adnrits one up to l" in least dimension. The "D" admits knotholes no larger than 2f" largest dimension. There are some other technical differences. but these are the two most readily observed.

The "C" is used as the back on "one-side" Exterior ftlyu,ood i as the face on Plyscord Sheathing, and as inner plies in Exterior.

"D" is used as the back on "one-side" Interior Plywood and Interior Sheathing. There are three basic types of Douglas Fir Ply'it'ood manufactured at the present time. These are properlf identified as "Interior," "Exterior," and "Boat Hull."

Interior Fir Plyrvood is manufactured in several grades, and for many uses, but all grades use a l0-cycle glue which is only water resistant and should not be used in any place subjected to extreme moisture conditions.

(The term lO-cycle is derived from the testirig method used. This test requires that a sample 6 inches square be placed in water at room temperature and allou'ecl to "soak" for four hours, after whi'ch it is removed and allowed to dry for 20 hours at a temperature no higher than 100 degrees Fahrenheit. This is a "cycle." After this cycle has been completed ten times the panel must not show delamination longer than 2f" along the 6" edge, nor deeper th.an f" into the glue-line of the panel. If this delamination is no more than that the panel is then qualified as a lGcycle glue panei.)

Exterior Fir Plywood is manufactured in ;rany "face grades" also, but all grades use as the bonding agent, a fullv n'aterproof adhesive, and is intended for use in places subjected to u,ater or extreme moisture conditions.

The test used to determine the degree of ivater-proofness of the glue-bond is rather extensive and complicated, but a general explanation of some of the steps may be of some interest.

Small samples of the panel are prepared and boiled in water for four houqs, after which they are dried at a temperature of approximately 140 degrees Fahreni-reit, for 16 hours. They are then boiled again for the same period of four hours. While still wet the samples are placed between two steel "jaws" and literally pulled apart-at the glueline.

After this "shearing" or "pulling apart" of the plywood a careful examination is made to determine how much of the "glue-line area" shovi's exposed glue or adhesive, and how much of the same area is still covered n'ith wood fibers. If the wood fibers completely cover the area it indicates complete u'ood failure and no glue failure. If 75% of tlre area is covered with 'ivood fibers, and 25/o shows the adhesive, it indicates 75/o wood failure and 25/o glue failure.

A glue or adhesive, to be approved for use in Exterior Fir Pl1'rvood, must sholv a "wood-failure" factor ol %/o or rnore. and plywood carrying the EXT. DFPA stamp, (Continued on Page 58)

Buitding

PER,ITITS FOR SEPTEMBER CITY

Fir Plywood Grodes

(Continued from Page 54) under testing, must shon' an average of 85/, u'ood-failure to clualify as an Exterior Fir Plywood.

Nlarine Fir Plyu-ood is no longer an official type accordin to the industry, Comtrrercial Standards o:: Nlilitary Spccifications, (MIL-P-66A. Amdt. 1). This has been replaced by "BOAT-HULL" and the name ::Nlfarine"orr longer designates a definite type.

BOAT-HULL Fir Ph-u'ood (bonded rvith a Full-Waterproof Exterior Adhesir.e), according to the Nfilitarl' Specifications, is suppliecl in AA. Some AB hls been accepted. llou'ever, as a COI\{N{ERCIAL item Boat-Hull CONSTRUCTION Fir Plyu'ood is manufactured in all of the same grades as other Exterior Type panels. The most important feature of the Boat-Hull panel is the COI{E. or INNER-PLY CONSTRUCTION. All of the InnerPlies. or \reneer. MUST BE SOLID, rvith all Knothoies or Voids prroperll' patched before gluing into plvn'ood. This resultt it, u plyn'ood free of all concealecl r'oids-and is consiclered by leading Boat Builders as the best panel for boat construction.

"Boat-Hull' typ" Fir Plyu'ood is also verv it-nportallt in many Industrial uses. not only because of the lvater-proof boncl. but also the SOLID CONSTRUCTION.

Do YOU knou' the differences between "INTERIOR", "EXTE,RIOR", "N'IARINE". and "BOAT-HULL" Fir Plvr.r'ood ?

Here is a chart that mav helP:

INTERIOR

FIR Sapwood & Heartrvood

EXTERIOR l(notholes dr Other Open Def ects Perrnitted

BOAT-HULL SOLID No Open Def ect

Los Angeles Hoo-Hoo Concqt Hociendq Country Club November 20

Plans have been completecl for a full clay, Novernber 20, for members of Los Angeles Hoo-Hoo Club, according to John Lipani, president of the Black Cat organization.

Startine at 10:00 a.m. the golfers will tee off for the all-day tournament, under the supervision of Chariman Harvey Koll' At approxin.rately 5 :39 p.m. a large class of "Kittens" will irc inducted into the light of day by "Rutch" Harringer and his initiation comrnittee. And at 6:59 p.m. members and their friends will be served dinner at this fine club where the cuisine is considered the frnest in Southern California' Following dinner "Big Time" entertainment straight frorn the Las Vegas and eastern night club circuit will be enjoyed along with color motiou pictures of past Concats fihned by Larrv Weiland.

"The policy of giving the membership good entertainntetrt has been established and we have gone all out to obtain topnotch talent for each and every meeting. \A-e ask that reservations be rnade early-by calling DUnkirk 2-7912-because we anticipate a big turn-out for the Noven.rber 20th event," said Snark Lipani. Hacienda Country Club is one mile east of the Orange County line just north of La Habra and can easilv be reached by following the direction rnarkers rvhich are posted for this purpose on Whittier Rouievard.

Poper ond Pulp Mon likes Outlook

10-Cycle Water RESISTANT orrly

WATER. PROOF (Marine)

Stated cluite simpll'-the difference bett'een INTFIRIOR and EXTERIOR is the GLUE, and the differeirce bet'uveen

E\TERIOR and BOAT-HULL is the C(,INSTRUCTION.

R. B. Robertson, Jr., president of the great Champion Paper & Fibre C<rmpany, u'hich manufactures huge quantities of fine paper from wood pulp, writing from his office in Harnilton, Ohio, expresses high optimism regarding the business outlook. He stated that there had been no summer slump in 1953 as there was in 1952, and that a 6"u1'y demand for all their products makes him very optimistic cnncerning the immediate future.

"NIARINE" is just an Adjective, and does NOT designate. an official type of Douglas Fir Plyrvoocl. As used by manr', it rnerely indicates that the GLt.f E used is Water-Proof.

CONSTRUCTION as well as GLUE-BOND must be considered in selecting a plyrvood, if satisfactorl' performance is expected.

Mr. Carl Kreig, owner-manager of Carl Kreig X,Iillwork Shop, Route 3, Hood River, Oregon, operates a small planing rrill and dry kiln for the purpose of producing dry finish lum_ ber. This lumber is utilized in the manufacture of doors. win_ dow sash, cabinets and interior trim. Mr. Kreig, rvho does construction work in the Hood River area, also kiln dries dimension lumber for use in floor joists and studding.

His Moore Cross-Circulation Kiln is possibly the srnallest and most modern that has been installed on the pacific Coast in the last few years. The kiln building and boiler house are housed within one building with a r2'i tire wall betr,veen the