Door Installations for Blimp Hangars

When Navy designers planned the giant flameproofed wooden hangars for the coastal patrol of blimps, they had few structural precedents to guide them. Never before had such huge structures" of timber framing been built. Horvever, nearly a score of the giant hangars already have been completed under Bureau of Yards and Docks plan. Essentially, the hangars consist of an oval-arched roof, stifiened by a series of arch ribs, and two end doors. Hangar dimensions run like this: 1000 feet long, 170 feet high at the crown, nearly 300 feet wide at ground level.

Doors for the huge openings at either end of the hangars were unusual engineering problems in themselves. It was necessary to construct them' to be independent of the main building so that they would not weigh upon the hangar framing. This framing could not be birilt to resist either the weight of doors generally used for steel hangars of similar shape, or the wind pressure which would be transmitted from the doors of such immense area. Meeting these design problems, two types of doors were finally selected: (l) a flat sliding door with separate support, and' (2) a semi-dome door which would be self-supporting in any position from open to closed.

Twin reinforced-concrete pylons support an enormous, sguare built-up timber girder to guide the flat, sliding door type. Most of these door installations were made by Byrne Doors, Inc., whose multi-leaf electric operators will close and open the six sections of the doors at the touch of a button. The leaves are tZO feet high and are supportett laterally by guide rails at the top. They roll on flanged steel wheels over railroad type tracks. The operating mechanism is so engineered as to rnove the several segments, or leaves, at differential rates of speed-the second travelling twice as fast as the first, and the third three times as fast-causing all three leaves to arrive at oPen or closed positions simultaneously. Maximum speed of the flat door is 75 feet a minute, making it possible to open or close these doors in less than two minutes.

The basic requirements of rigidity, light weight, and large size posed a design problem which was met at three different bases by three different combinations of materials, including one new product, which has an extremely important future-flameproofed plywood. One solution to the problem of door construc.tion uses steel frames (actually box trusses on end) faced with pressure-flameproofed 1x6 tongue-and-groove pine sheathing, nailed to purlins on the truss face. Another design incorporates steel longitudinal members stifrened with wood braces which furnish the base to which asbestos-cement boards are fastened. At one West Coast base, the door retains the all-steel truss frame, but is sheathed with Minalith-flameproofed fir plywood, mounted on steel angles which are bolted to the truss frame.

Because of its light weight, and the large size of the panels, the treated plywood sheathing permitted faster,

PBospect simpler erection than either of the two other types. No scaffold was required in mounting the plywood sheets on the door panel trusses; the sheets were handled by a Motocrane with an extended boom, two or three men placing and bolting up the panels. Materials used throughout the hangars were fabricated, and after fabrication timber used in the structures was shipped to wood-preserving plants to be pressure-treated for fire resistance.

In addition to providing support to the door leaves, the boxbeam girder at the top of each door construction carries the enclosure framing for the remainder of the end opening of the hangars. Continuity of the box girder (which measures 21 f.eet 9l inches square in cross section) with the towers and the cantilevers is provided by means of chord splices and shear connection anchored into the t,ower walls.

At one locality, where poor foundation conditions exist, flat doors were found impracticable because of the heavy .concentrated loads on the tower bent piers. The semi-dome door, distributing weight over a larger area, was the solution here. With the exception of a center assembly piece of steel at the crovr'n, the semi-dom,e door is made entirely of flameproofed timber. fn fact, 600 tons of structural steel per hangar is saved by the semi-dome method of construction. The door is 159 feet high at the crown, and is shaped like an half circle with a t"diu. of 120 feet.

The door opens at a 90 degree angle, taking a position parallel to the hangar and 400 feet away from the structure when open. On a set of ll concentrically curved tracks, lZ Byrne operating trucks carry the huge door. The trucks are complete with their own diesel power units, special gear reduction units, brakes and control devices.

The semi-dome door can be operated at three speeds, ranging from 10 feet per minute to 62.5 feet per minute, and requires approximately 1O minutes to move from closed position to a fully open position parallel to the hangar.

Bqy.s Scntcr Moniccr Ycnd

The Golden State Lumber Company, Santa Monica, has purchased the Alley Brothers plant in that city. Frank G. Kranz is proprietor of the Golden State Lumber Company.

Alley Brothers operated the yard in Santa Monica for a number of years, and Hadley J. (Jack) Alley, who organized the company with his brother, Frank, passed away last November. The firm operates a sawmill and planing mill at Medford, Oregon.

Up And Down The State

W. R. Chamberlin, W. R. Charnberlin & Co., San Francisco, and Mrs. Chamberlin, spent the holidays in Los Angeles.

Ralph Zinn, Baskett Lumber Company, is now with the Wilshire Oil Co. He was associated with the yard for 24 years, and until several years ago it was operated under the name of Whittier Lumber Company.

'Pete Toste, Southern California manager for Kilpatrick & Co., Wilmington, is back on the job again and reports that he is feeling fine. Pete was confined to the Seaside Hospital, Long Beach, for a month.

E. H. Clarke of E. H. Clarke Lumber Co., Sweet Home, Ore., visited San Francisco in the latter part of November.

Jim Jansen, owner, Jansen Lumber Co., Ashland, Ore., Herbert Fischborn, manager of the mill, and their wives, were San Francis,co visitors over the Christmas and New Year holidays.

R. L. (Dick) Ustick, well known retail lumberman, who was for many years with Stanislaus Lumber Co., Modesto, and for the past three years with Stanislaus Implement & Hardware Co. is back in the lumber business. He is now associated with the Ross Lumber Co., Modesto.

Seth L. Butler, Northern California representative of Dant & Russell, fnc., left January 8 to visit the firm's head office in Portland. He was accompanied by Mrs. Butler and will be gone about two weeks.

Mace Tobin, sales manager, Willamette Valley Lumber Co., Dallas, Ore., recently visited San Francisco and Los Angeles on business.

Coos Bcry Lumber Co. lg43 Cut

Coos Bay Lumber Company,s mill at Marshfield, Ore., cut a total of 102,600,000 feet in 1943. while this is no_ where near the big mill's all-time record it is a substantiar contribution to the war effort.