Wood hangars 1,000 feet long and 170 feet high were spotted around the East and West Coasts during World War II. Their engineering is a testament to U.S. ingenuity,and the story forms a vital part of U.S. wood industry lore.
Created to house blimps hunting German U-boats, the soaring Naval Air Stations were built of wood, saving precious steel for production of tanks and planes. A total 17 of the giant structures were built during the war. So well made were these buildings that eight survive to this day.
Some are open for visitors, such as the NAS Tillamook in Tillamook, Oregon, operated today as an airplane museum.
Construction of the Tillamook hangars - a pair was built, one later was lost in a fire - was quite an undertaking in 1942 and 1943. After land was cleared, a railroad line was built to the construction site, to deliver the timbers and hardware. Construction continued through the fall, with the first hangar dedicated 51 weeks after Japan's attack on Pearl Harbor.
The shortage of steel brought the engineers of the Tillamook hangar to opt for wood: strong, easily shaped, and plentiful in the Pacific Northwest. But the use of wood beams required new construction methods; no one had ever built a clearspan wooden structure of such immense size.
Hangars uses 2 million board feet of lumber, saving 2,050 tons of steel. Lumber, mostly sourced in Oregon but also including California Redwood and Southern Pine, was fabricated by Timber Structures, Inc., Portland OR. Wood was fireproofed with Minalith and Protixal salts, a job of such epic proportions that 51 firms were involved.
The construction employed a cleverly engineered arched truss that, when joined, formed a rigid frame. A history of the hangars relates, "Each of the 51 double-arched frames, 20 feet on center, would be comprised of a series of smaller timbers ranging from 3 inches by 8 feet to 6 inches by 14 feet."
A huge timber box beam, 304 feet long, resting on concrete, To further conserve metal, gutters and downspouts were built of wood. Since wood lamination was new in 1942, timbers were held together with bolts, shear plates and split rings.
"Huge jigs were assembled on the ground," notes the history. "Trusses were assembled while on these jigs." The first hangar took nine months to construct; the second took 27 working days, as the engineers and construction crews gained in proficiency.
The blimps flew along the Northwest and Northeast U.S. coasts. But they were not really on the look-out for enemy submarines. Rather, convoys escorted by blimps were safer, since subs usually submerged after spying the lighter-than-air craft. One below the surface, submarines could sail at just four knots, less than one-fourth their top speed on the surface, and U.S. and British supply convoys easily outran them.
Interestingly, after retiring from war service, the Tillamook hangars housed wood planing mills for Rosenberg and for Angel Lumber Company. Rosenberg was later acquired by Diamond Lumber which converted the operation to a plywood mill, sold finally to Louisiana Pacific in 1972.
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