Choroszy Modelbud 1/72 Savoia-Marchetti SM.78
Reconnaissance Flying Boat
by Richard Mendes


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The Savoia-Marchetti S.78 bomber and reconnaissance biplane flying boat developed from the S.62bis was the last wood and fabric biplane flying boat used in numbers by Italy, the prototype MM.222 making its first flight late in 1932, 49 were built, 32 by Piaggio and 17 by Savoia-Marchetti with production ending in 1935.

The S.78 retained near the same wings, tail and fuselage of the S.62bis but with different of Handley Page wing slats. Fuselage frames and longerons were made from poplar and ash respectively; the plywood-skinned double-layered bottom hull had an external layer of orthogonally arranged cedar laminate flanks. The fabric-covered wings had spruce longerons and poplar ribs painted to render them water impermeable, twin stabilizing floats were mounted mid-wing.

The S.78 was powered by a single Isotta Fraschini Asso 750 W-18 engine nested in a suspended steel gondola mounted between the two wings driving a four-bladed variable pitch propeller manually set before takeoff; a remotely operated CO² fire extinguisher was mounted next to the engine. A total of 2,200 liters (580 US gallons) of fuel was carried in six unarmored duralumin fuselage tanks arranged two aft, two central and two forward.

The pilot and co-pilot were seated side-by-side in an enclosed cockpit for the S.78 prototype but was replaced by open cockpits in production aircraft. A 7.7 mm (0.303 in) Lewis machine gun station manned by the co-pilot was in the nose that also contained two cameras. An enclosed rear dorsal turret station with a Lewis gun was manned by the radio operator who also operated a R.A.350 transmitter and a A.R.4 receiver sets. The aircraft was not fitted with an electric intercom system so the pilot and radio operator communicated by written messages and via a pneumatic messaging system.

The forward Lewis gun had 564 rounds of ammunition in 12 magazines, the aft gun had 470 in 10 magazines, up to 700 kg (1,540 lbs) of bombs were carried in bomb bays within lower wings next to the fuselage. Typical payload combinations included: 2 × 250 kg (550 lbs) and 2 × 100 kg (220 lbs) bombs, 6 × 100 kg (220 lbs) bombs, 4 × 70 kg (150 lbs) depth charges or 6 × 12 kg (26 lbs) of training bombs. Smoke generators also could be mounted on inner hard points; a Jozza bombsight was located in the right cockpit behind a glazed window.

The SM.78 flew with the 141a Sq. based at La Spezia, 144a Sq. at Livorno, 182a Sq. at Nisida, 189a Sq. at Syracuse till 1938 when they were replaced by the far superior CANT Z.501. Some planes remained in service as air-sea rescue aircraft early into World War II. Spain operating SM.62s and tried unsuccessfully to acquire a license to build the SM.78 leaving Italy as sole operator of the SM.78.







Construction

The resin + clear styrene parts of the 1/72 Scale Choroszny Modelbud Savoia-Marchetti S.78 model kit released in 2008 is the only one available of this lesser-known Italian flying boat. Well molded and detail rich the kit includes four cylindrical fuel tanks though placing them within the fuselage proved quite difficult. Kit decals depict red 4 of 144 Squadriglia based at La Spezia c.1934-35; anti-camouflage stripe decals were included but painted them instead on the top wings.

Biplane model construction always is challenging even with experienced modelers the S.78 being no exception, remarkably the construction process went well, including placement of the Isotta Fraschini gondola I'd fully expected to have been a nightmare. The four-blade propeller in five resin parts was a challenge to construct, i.e. the spindle being undersized relative to the blades and attachment hubs, not wanting to risk breaking ANY parts in remedying this problem chose instead to pair align "short" and "long" blades and attachment hubs perpendicular from each other on the spindle mounting the whole assembly on the Isotti Fraschini engine with the "short" blades aligned vertically so as to clear the fuselage – prop sizes appear tad off, better that than breaking them though fiddling!

Brace Wire Rigging for wings & floats was simulated with EZ Line elastic threads of different sizes. Thanks to generous spacing between wings this was done with some ease though due to a paucity of S.78 reference photographs on the Internet bit of guesswork was involved in placing some of the rigging. The kit included a ground transport dolly and tail A-Frame support, these were painted black as seen on some period photos of similar Marine ground equipment employed by the Regia Aeronautica Italia.

The late 1990s "IPMS-Italy Regia Aeronautica Color Chart" based on Umberto Postiglioni & Andrea Degl' Innocenti's "Colori e Schemi Mimetici della Regia Aeronautica" (Trento, 1994) was employed in painting the S.78 along with instructions provided in the Choroszy Modelbud S.78 kit.

Testors Flat Aluminum enamel replicating Alluminio was chiefly employed painting the aircraft along with Testors Flat Red replicating Rosso Bandiera 8 for the Anti-Camouflage top wing stripes and fuselage tops; Testors "utility" enamels flat black and white, olive green, bronze et. al. colors also were employed along with Testors Model Master 2105 Dark Blue Grey painting the Isotta Fraschini engine. All spray work was accomplished with Testors Aztek A320 single and A470 double action airbrushes, 9304CX 0.30mm, 9305CX 0.40mm, 9306CX 0.50mm spray nozzles. Large-area spraying was accomplished with 0.50mm and 0.40mm nozzles.

The whole model was over-sprayed with Testors Model Master Semi-Gloss Clear Lacquer Finish thinned 50% with Klean Strip Lacquer Thinner (WAY cheaper than Model Master thinner and just as good), prefer semi-gloss finish over flat, detail "pops out" better plus aesthetically more pleasing in appearance.

Technical Data

Aircraft: Savoia-Marchetti SM.78
Manufacturer: SIAI-Marchetti
Type: Reconnaissance/Bomber
Year: 1932
Engine: One Isotta-Fraschini Asso 750R 18 cylinder W configuration, 850 hp (634 kW)
Wingspan: 54 ft 8 in (16.66 m)
Length: 40 ft 2 1/2 in (12.26 m)
Height: 14 ft 2 7/8 in (4.34 m)
Weight: 11,354 lb (5,150 kg) (Loaded)
Maximum Speed: 152 mph (245 km/h)
Ceiling: 13,100 ft (4,000 m)
Range: 1,490 miles (2,400 km)
Armament: 2 machine guns; 1,540 lb (700 kg) of bombs
Crew: 3

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July, 2018
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