Research

To date, the largest and longest restoration project undertaken by the Museum is that of the Curtiss HS–2L The magnitude of the job resulted partly from the large size of the machine and partly from the need to reconstruct a complete hull. While a portion of the original hull had been salvaged, as related elsewhere in this book, the condition of the wood was not suitable for restoration. In addition, the Museum wished to retain this portion in its salvaged condition as a historical exhibit.

The project began in September 1975 with construction of the hull. It is not practical to give a detailed account of this complicated operation here, but an abbreviated description with the accompanying illustrations provides a good idea of the hull's construction.

The Curtiss HS-2L hull on November 25, 1975, about two months after construction started.

By November 1976, the hull planking had also been started.

This construction was typical of the early Curtiss flying boats, and the HS–2L was the last one to use it before it went out of production in 1918. First, the contour of the keel was cut in a series of plywood sheets which were set vertically on the floor; this formed the support or `jig' during the assembly operation. Then the steamed green ash keel pieces, one forward and one aft, were clamped in place. Next the fabricated floor frames, or floors, were placed at the prescribed intervals along the length of the keel and then the chine stringers were fitted along the outer ends of the floor frames. The six assembled mould frames, or bulkheads, had to be placed in position on the hull. Next the green ash frames had to be formed to the varying hull cross sections and set in place at intervals varying from about 6 to 8 inches (15.2 to 20.3 cm) along the hull. Temporary battens were set in place from bow to stern and the frames all brought into alignment with one another to produce smooth hull lines. These battens were then removed and the seam battens fastened in position from bow to stern, and pitched from one another to suit the width of the hull planking. Then filler strips were fitted to each frame between the battens to bring them level with the seam battens.

To double plank the hull bottom, it had to be inverted. Two plywood forms cut to circular shape were secured around the hull and the hull rolled over.

The upper portion of the hull was planked with pine planks 5/16inch (7.9 mm) thick. The structure of the fins (or sponsons) was added to each side of the hull from the bow to the step, and following this the whole hull was inverted to permit planking the bottom. The bottom planking was of 5/32 inch (3.9 mm) mahogany and was installed in two layers. The first layer was at 45° to the keel and a coatof marine glue was applied and fabric laid over it. This was followed byanother coat of marine glue and the second layer of planking wasapplied parallel with the keel. The hull was then placed upright, theupper surfaces of the fins were planked, and the cockpit coamings,already formed to shape, were fitted into the hull. The hull was then complete.

The tail surfaces were from the Pacific Marine Airways I HS–2L and while they were complete, their age and previous service made considerable work inevitable. They required disassembly, cleaning, rib repairs, one or two new ribs and new trailing edges: some of the metal parts of the rudder were corroded and required repairs. All were put ingood shape in quite short order.

The wings, also from the Pacific Marine Airways machine, were another matter mainly because of their sire. The upper wing spanned 74 feet (22.6 m) and was made in five pieces, while the lower wing was 64 feet (19.5 m) in span and made in six pieces. All of these wing sections required disassembly, rib repairs, and often some rib replacements; one section required a new piece spliced into its solid spruce spar. All trailing edges required replacement and all four ailerons required repairs. All struts required only cleaning and refinishing, but all-new bracing cables had to be made up and fitted. Needless to say, the restoration of the wings, struts and cables was a time-consuming job.

An interior view of the HS-2L cockpit. The lever at upper right is the throttle. The two control wheels are mounted on a wood yoke which bridges the legs of both pilots, a typical control arrangement for larger flying boats. At the bottom of the pilot's panel is the manual fuel pump which is used until sufficient speed is attained for the air driven pump to take over. The numeral A-1876 is the USN serial of G-CAAC.

In this view, taken on May 14, 1979, the hull is structurally complete, and cockpit openings have been cut and fitted with their coamings. A trial installation of the tail surfaces is also being carried out.

In addition to the airframe components, the 12-cylinder Liberty engine had to be disassembled, refinished and reassembled, and its plumbing, oil tank and radiator shutters made and installed. The new oil tank and radiator shutters were based on some skimpy and much-corroded remains and, of course, photographs. The radiator itself, salvaged from the Ontario Provincial Air Service aircraft G-CADS, had to be repaired and restored to display condition. Many other parts were made from drawings and/or badly corroded parts that had been salvaged, including the three main fuel tanks, the fuel gauges and the air-driven fuel pump and other fuel system components, all of which were completed to working condition.

The main structure was completed in the fall of 1984 and a trial assembly was made of all main components. The covering and doping which came next was a major job), not because of any unusual difficulty but because of the large area of the components and large number of hand stitches required. The final operations were the fitting of the flight controls, the engine and radiator controls, and the cockpit instruments and other details. Everything was completed by June 1986. It is now on public display in the new building.

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