In 1992, Peter McMillan and his team organized a worldwide effort to build an authentic Vimy replica to relive the pioneering adventures of 1919-1920. Construction of the Vimy replica was led by John LaNoue. The project required thousands of pages of new drawings and more than 25,000 hours of labor. Completion took 17 months from start to FAA certification in August 1994—a remarkable testament to the team's dedication and resourcefulness. |
Raw Materials Used:
- 4,130 steel tubes
- 330 feet (100 meters) of box spars
- 3,000 board feet (914 meters) of Douglas fir
- 500 yards (457 meters) of aircraft-quality (90/inch thread count) Grade A cotton
- 10,000 knots
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In January 1993, the Vimy team obtained a set of original drawings for the British Vimy Vickers World War I bomber from Bill Whitney of Aeronautical Designs Australia. Whitney was commissioned to design the required stress analysis for a replica using modern materials and power plants.
The Vimy replica was to be the world's largest homebuilt airplane. The fuselage would be crafted from 4,130 steel tubes instead of a wire-braced wood truss, and powered by a pair of geared-down Chevrolet big block V8s in 454cu (7.4 liters) apiece. The wings and tail would be designed much like the Vimy flown during World War I, and the shape of the plane would be painstakingly crafted to be as authentic as possible to the original plane.
By March 1993 the basic design was finalized and construction began in Australia on the tail and the propeller speed reduction units (PRSUs). By May the wing design was complete and a 15,000 square foot (1,400 square meter) building was found in Sonoma, California, to be the site of the Vimy's construction.
John LaNoue was brought on board as the Vimy's chief engineer and contracted to build the wings and complete the airplane's construction. LaNoue's first task was to find materials to build the wings: 330 feet (100 meters) of box spars would need to be built, as well as 100 complex ribs, many measuring over 10 feet (3 meters) long apiece. The design called for Sitka spruce and aircraft-quality birch ply. The birch ply could be readily obtained from Finland, but little aircraft-grade Sitka spruce is available in such large sizes today—many parts would need to be 22 feet (7 meters) long. To address this shortage, Douglas fir would be used—a heavier, but stronger wood that was more plentiful than the spruce. Nearly 3,000 board feet (900 meters) of fir was hand selected from commercial sources to build the Vimy, subject to rigorous inspection based on a 330-page U.S. Army/Navy publication issued in 1944.
In addition to building the plane, the Vimy construction crew would need to build all the tooling, fixtures, fittings, and jigs, as well as reinvent long-forgotten skills or dream up modern solutions to challenges. Time and finances dictated construction methods and both were limited. John LaNoue later would say the team "developed a Zen-like approach to our work. Do it once, do it right, no wasted motion, no going backwards."
"We developed a Zen-like approach to our work. Do it once, do it right, no wasted motion, no going backwards."
—John LaNoue, Vimy Builder
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The spar caps (horizontal elements of the box spars), for instance, required eight pieces of fir measuring 4 inches (10 centimeters) by 24 feet (7 meters) to be laminated. To apply even pressure during gluing, a fixture was made that allowed eight sections to be done at once (in fact, 16 sections—after cure they were sawed into 2-inch (5-centimeter) wide blanks for milling). It was essentially a long, very strong U-channel; four glued spar cap sections were placed in each side of the fitting, and a fire hose run between them. Inflated by compressed air, it applied an even 100 pounds per square inch while the glue cured.
A similar but inverted scheme was used for the spar webs, the vertical elements of the box spars. Made of ply faces sandwiching a ladderwork of compression blocks, these were glued on a vacuum table. The glued components were laid on a perforated table and covered with a thick vinyl sheet taped to the table edges. All the perforations were connected to a powerful vacuum pump and, when switched on, it acted like an 11-ton (10-metric ton) press using atmospheric pressure.
There was nothing complicated about the design or unusual in the construction methods. It was just the sheer scale of the airplane that was daunting. With a wingspan nearly twice that of a light single, the wing area is eight-and-a-half times that of a Cessna 152. The empty weight—a good measure of materials that went into the project—totals just under 8,000 pounds (3,600 kilograms).
The empty weight—a good measure of materials that went into the project—totals just under 8,000 pounds (3,600 kilograms).
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The target deadline for the Vimy's construction was 12 months. McMillan was determined to recreate one of the great Vimy record-setting flights—England to Australia—on the 75th anniversary of that flight. Romantics have a thing about anniversaries...
By June 1993, the forward fuselage and PSRUs were completed in Australia. Sponsorship and assistance came into the project from diverse sources—museums, universities, and individuals. Components came together fairly rapidly. All spars were completed by July 1993, and the lower wings at the end of August. The center section was complete one month later, and by the time the rear fuselage was completed and shipped from Australia in October 1993, the wings were complete. In November the tail's construction had been completed and testing began on the engines and PSRU gearboxes. By then, National Geographic had joined the team as a major sponsor for the Australian flight.
In the interest of accuracy, the Vimy was covered exactly as it had been 74 years earlier, using grade A cotton with a thread count of about 90/inch instead of 50-odd/inch—the difference being instantly recognizable to those with an eye for historical accuracy. It was also decided to apply the dope by brush, which leaves a characteristic signature to the finish and was the method of application in 1919. In December 1993, the master fabric team from AJD Engineering in England came over for ten days to instruct the American fabric crew in the use of natural fabrics. (There is little experience these days in the United States with using cotton and linen for covering aircraft.)
The tally of covering materials left the crew amazed: 500 yards (460 meters) of aircraft-quality grade A cotton that arrived in 5-foot (1.5-meter), 100-yard (91-meter) bolts was sewn into blankets for various components. The fabric was draped over each piece, trimmed, and glued at the edges before being shrunk with distilled water. Final tautening was accomplished using nitrocellulose dope, just as it was for the original Vimy Vickers.
Rib stitching was the last great task. More than 10,000 knots had to be tied. The wing panel took several days to tie, requiring about 1,000 knots. With practice, time was reduced to twelve hours per panel tied by three or four people, at the rate of three hours per rib of 84 knots.
The surface tapes, covering the rib stitching and reinforcing critical areas, had to be right. Modern surface tapes usually have a pinked (zigzag) edge, whereas in 1919 they used frayed tapes. These are made by ripping cotton into strips, and stripping a couple of the warp threads from the edges, leaving the characteristic frayed edge. In effect, they work exactly like pinked edges. Nearly a mile of tapes were ripped, frayed, ironed, and hung over several weeks, before being doped on, followed by a further three coats of nitrocellulose.
In the interests of safety, the silver (ultraviolet barrier) and green finishing coats of dope were butyrate. The color of the finish coats was matched to a piece of the original fabric from G-EAOU-the entire left aft fuselage cover. The covering job took four months alone.
Rigging the wings for the first time proved to be a case of making it up as they went along. Rather than assemble it as Vickers did 75 years before—by starting with the lower center section and working up—they completed the lower panels and then fitted the top wing, including ailerons, in one go. This presents something of a problem when you are dealing with a flimsy 68-foot (21-meter) structure weighing 1,000 pounds (450 kilograms) needing to be accurately positioned 16 feet (5 meters) up. The strength is developed once it has been tied into a rigid box structure with the rigging wires.
The components were moved to a large hangar at Hamilton Army Airfield in Novato, California, and a giant truss was built to support the top wing while it was hoisted into position. Bracing wires were provided by Bruntons Aero Products of Musselburgh, Scotland, the company that had provided the wires for the original Vimy. In the interests of better safety margins, the flying wires (those that go up and outboard) were doubled up. No one had any experience of such a large biplane, and a fair amount of trial and error was required to complete the job.
