1:72 Cunliffe-Owen “Marlin” SR.2; aircraft “235-R (s/n WB266)” of the Fleet Air Arm 812 Squadron, HMS Glory during the Korea War, 1951 (Whif/converted Fujimi Aichi B7A)
+++ DISCLAIMER +++
Nothing you see here is real, even though the conversion or the presented background story might be based on historical facts. BEWARE!
Cunliffe-Owen Aircraft was a British aircraft manufacturer of the World War II era. They were primarily a repair and overhaul shop, but also a construction shop for other companies' designs, notably the Supermarine Seafire. But the company also undertook contract work for the Air Ministry, Lord Rootes, Shorts and Armstrong Siddeley worth £1.5 million, and undertook design and development work.
The Marlin torpedo bomber was designed by Cunliffe-Owen Aircraft to Admiralty Specification O.5/43 as a replacement for the carrier-based Fairey Barracuda in the torpedo/dive bomber role for the new Malta Class ships. Cunliffe-Owen’s engineers had been convinced that a state-of-the-art torpedo bomber would have to be a fast and agile aircraft, so the airframe’s dimensions remained as compact as possible – and in fact the resulting aircraft was not bigger than the Barracuda, even though it was more massive in order to make room for an internal bomb bay. Much attention was given to aerodynamic and weight refinements, so that the aircraft – despite its considerable size – would still perform well with a single engine.
The primary choice fell on the Bristol Centaurus and the aircraft was expected to achieve 370 mph (600 km/h) top speed. Other engines with a similar output, e .g. the R-2800 and R-3350 from the USA as well as the British, air-cooled Exe 45 24 cylinder inline engine, were considered, too. However, the American export engines had been reserved for domestic use and the Exe was, at the time of the aircraft’s design, still far from being a reliable engine in the 3.000 hp class.
The Cunliffe-Owen Marlin was a conservative two-seat, mid monoplane aircraft design. As the Marlin was intended for carrier service, it came complete with hinged wing sections to allow for folding, as well as an arrester hook and a sturdy landing gear. The wings had a pronounced inverted gull wing design, so that the wings’ main spars could be positioned between the bomb bay and the cockpit floor and the landing gear struts could be kept as short as possible.
Even though the new Malta Class ships would allow bigger aircraft to be stored and deployed, the Cunliffe-Owen design team was cautious and tried to keep the aircraft as compact as possible – also with hindsight to the aircraft’s overall performance. In order to achieve this goal and set the Marlin apart from its Fairey and Supermarine contenders, the designers decided at a very early stage to limit the biggest size driver: the internal bomb bay. On the Marlin, it was not to be long enough to carry an 18” torpedo internally. The effects were dramatic: the Spearfish, for instance, had a wingspan of more than 60 ft (18m) and had a MTOW of more than 10 tons, while the Marlin had only a wing span of less than 50 ft and weighed only 25% less.
Instead of carrying the torpedo internally, a ventral arrangement, offset to port, allowed for the external carrying of a single 18” torpedo under the fuselage or of up to two 1.000 lb bombs in tandem. Alternatively, a single 1.000 lb bomb could be carried internally on a swing arm that would clear the bomb in a dive from the propeller arc. When dropped in free fall, up to four 500 lb. bombs or four 450 lb (205 kg) depth charges could be carried internally. Other options included a photo camera pallet for reconnaissance duties and/or auxiliary fuel tanks.
Hardpoints under the outer wings allowed the carriage of more iron bombs, mines or depth charges of up to 500 lb caliber, 90 gal drop tanks, or up to sixteen unguided 3” missiles for attack purposes. The Marlin’s total ordnance load was 3,000 lb (1,361 kg).
Additionally, two forward-firing, fixed 20mm cannons were mounted in the leading wing edges while a defensive, remote-controlled Frazer-Nash FN95 dorsal barbette with two 0.5” (12.7 mm) machine guns was mounted behind the rear cockpit position for defense, being operated by the navigator.
In August 1943, Cunliffe-Owen received an order for two Marlin T.1 prototypes. The first prototype, serial number RA359, was constructed at Cunliffe-Owen's Southampton Airport factory and first flew on 5 July 1945. The second prototype did not fly until late 1946 and was earmarked for the integration of a surface-search radar.
Test pilot and naval aviator Captain Eric Brown evaluated the first prototype at the Royal Navy Carrier Trials Unit at RNAS Ford, Sussex, and found "the controls in cruising flight were relatively heavy, but the aircraft responded well to stick input, and it is fast – despite its ponderous looks.” The Marlin also lacked any sort of stall warning, which would have been a problem in operational use as the stall and approach speeds were fairly close. For the landing, the aircraft proved quite docile, though.
The later prototype had, as an interim measure, ailerons boosted by hydraulic power and artificial feel to the stick from a spring. But during tests Brown found that "the second prototype was much less the pleasant aircraft to fly as the stick continually hunted either side of neutral and there was no build-up of stick force with increase in speed." Several improvements had to be made to the airframe, but no major flaws were discovered. In addition, the flaps were to be enlarged and lateral control was to be provided by spoilers with small "feeler" ailerons.
In the meantime, the strategic developments in the Pacific theatre of operations had changed. In 1945 the original order of four Malta Class ships from 1943 for the Royal Navy had been cancelled, even before they were laid down, and with this cancellation the Fleet Air Arm no longer had a requirement for new torpedo bombers. The whole program was cancelled, including the Marlin’s main competitor, the Fairey Spearfish, which was only built as a prototype.
However, the Marlin’s good performance so far and its relatively compact dimensions and high performance saved it from complete cancellation. The type was now regarded rather as an attack aircraft that would complement the Hawker Sea Fury fighter, another late WWII design. Some refinements like a new exhaust system and a fully retractable tail wheel were integrated into the serial production and the updated type’s designation was changed into SR.2 in order to reflect its changed role. The torpedo bomber capability was kept, even though only as a secondary role.
Originally, production orders for 150 aircraft were placed to be built at Southhampton, starting in late 1944. The first ten aircraft were still finished to the T.1 specification and used a Bristol Centaurus IX 18-cylinder radial engine, 2,520 hp (1,880 kW) radial engine. Then production switched to the TR.2, but instead of fulfilling the complete order, just a scant 114 TR.2 production aircraft, all outfitted with a 2,825 hp (2,107 kW) Centaurus 57 engine, followed. Some were outfitted with an ASV Mk.XV surface-search radar, mounted in a pod under the outer starboard wing, but all of them came too late to see any action in the Pacific.
After the Second World War, the Marlin remained in front line service with the Fleet Air Arm until the mid-1950s, but soon after World War II, anti-aircraft defenses were sufficiently improved to render aerial torpedo attacks suicidal. Lightweight aerial torpedoes were disposed or adapted to small attack boat usage, and the only significant employment of aerial torpedoes was in anti-submarine warfare.
Nevertheless, British Marlins got actively involved in several battles. For instance, the type carried out anti-shipping patrols and ground strikes off various aircraft carriers in the Korean War, and the Royal Navy successfully disabled the Hwacheon Dam in May 1951 with aerial torpedoes launched from Marlin fighter bombers - this raid constituted the last time globally that an aerial torpedo was used against a surface target, and was the only time torpedoes were used in the Korean War. The Marlin also served in the ground-attack role during the Malayan Emergency between 1951 and 1953.
The Marlin’s FAA front line career ended in late 1954 with the introduction of the Fairey Gannet. By that time, Cunliffe-Owen had already been, due to huge losses in the Post-War civil aviation market, dissolved since 1947.
Length: 39 ft 7 1/2 in (12.10 m)
Wingspan: 47 ft 3 in (14.40 m)
Height: 13 ft 4.5 in (4.07 m)
Wing area: 35.40 m² (381.041 ft²)
Empty weight: 10,547 lb (4,794 kg)
Max. takeoff weight: 16,616 lb (7,553 kg)
Fuel capacity: 409 imperial gallons (1,860 l; 491 US gal)
1× Bristol Centaurus 57 18-cylinder radial engine, 2,825 hp (2,107 kW)
driving a 5-bladed Rotol VH 65, 14 ft (4.3 m) diameter propeller
Maximum speed: 540 km/h (293 kn, 335 mph)
Maximum range: 900 mi (783 nmi, 1,450 km)
Combat radius: 349 mi (303 nmi; 562 km)
Service ceiling: 31,600 ft (9,630 m)
Rate of climb: 2,600 ft/min (13 m/s)
Time to altitude: 7.75 minutes to 10,000 feet (3,048 m)
Wing loading: 158.9 kg/m² (32.5 lb/ft²)
Power/mass: 240 W/kg (0.147 hp/lb)
2× 20 mm (0.79 in) Hispano autocannon in the outer wings
2× 0.50 in (12.7 mm) M2 Browning machine guns in a dorsal, remote-controlled
Frazer-Nash FN95 barbette
1× 1,850 lb (840 kg) 18” Mk. VXII torpedo or 2 × 2,000 lb (910 kg) bombs under the fuselage,
or up to 2.000 lb of bombs in an internal bomb bay
Alternatively, up to 16× RP-3 rocket projectiles, bombs or 2× 90 gal (408 l) drop tanks
on underwing hardpoints; total ordnance load of up to 3,000 lb (1,361 kg)
The kit and its assembly:
This converted Aichi B7A2 was inspired by a whiffy Royal Navy skin for this type for a flight simulator, found at warthunder.com and created/posted by a user called byacki. The aircraft was otherwise unchanged, but the result looked so convincing that I earmarked the idea for a hardware build.
This time has come now: the 2018 “RAF Centenary” Group Build at whatifmodelers.com was a neat occasion to tackle the project, since I already had stashed away a Fujimi kit for this build.
In fact, Cunliffe-Owen submitted a competitive proposal for the Spearfish’s requirement, but details concerning the respective aircraft remain obscure, so that the B7A2 fills this gap well. The Fujimi kit itself is VERY nice, well detailed and goes together like a charm. In order to stay true to the original inspiration I did not change much, but the Fairey Spearfish of the late WWII era had some influence.
First of all, the engine was changed into a Bristol Centaurus – a very simple rhinoplasty, since the B7A2’s front fuselage diameter turned out to be ideal for this swap! The original nose was cut off just in front of the exhaust stubs, and a Centaurus from a PM Model Sea Fury was mounted in its place – even though it had to be “squashed” a little in order to fit properly (achieved through the use of a screw clamp and 2C putty inside to stabilize the new shape). Inside of the new cowling, a styrene tube was added for the new five blade propeller, also form a Sea Fury, which received a metal axis.
Another addition is the gun barbette, a common feature among Admiralty Specification O.5/43 designs (the Fairey Spearfish carried one, too). I was lucky to find a leftover chin turret from an Airfix B-17G in the pile, which fitted well in shape and size. The casing ejector openings were faired over and then the turret was mounted upside down in a round opening at the end of the cockpit section. Cockpit floor and canopy were modified accordingly and the result does not look bad at all! Inside of the cockpit the OOB bucket seats were replaced by bigger alternatives – the Fujimi parts look like 1:100 scale!
The OOB torpedo was retained and I added some unguided 3” rockets under the aircraft’s wings, left over from my recent Sea Hawk trainer build. Another addition is a radar pod under the port side wing (a modified cardboard drop tank from a WWII P-51D), and the main wheels were changed – from a Matchbox Me 262, because they feature more details than the OOB parts. The tail wheel was modified, too: instead of the B7A2’s fixed wheel, I implanted the front wheel from a PZL Iskra and added covers, for a retractable arrangement.
Painting and markings:
Well, a conservative choice, and since I wanted to stay true to the original CG design, I stuck to classic RN colors in the form of Extra Dark Sea Grey (Humbrol 123) for the upper surfaces and Sky (Tamiya XF-76 IJN Green Grey, which is a very similar, yet slightly darker tone) for the undersides, with a high waterline. A personal twist came through Korean War era “invasion stripes”, which were carried for easy identification esp. by propeller-driven aircraft in order to avoid friendly AA fire from the ground. The stripes were created after basic painting with white and black generic decal sheet material (TL Modellbau): large white bands (32 mm wide) as foundation, with single black bands (each 6.4 mm wide) added on top. Application around the radar pod and on the slightly tapered fuselage was a bit tricky, but IMHO still easier than trying to mask and paint the stripes.
Other markings were puzzled together from a PrintScale Fairey Firefly sheet, from different Korean War era aircraft.
As per usual, the kit received a light black ink wash in order to emphasize the engraved surface details, and then the panels were highlighted through dry-brushing. Lightly chipped paint was simulated with dry-brushed silver and light grey, and gun and exhaust soot were created with grinded graphite.
Finally, everything was sealed under a mix of Italeri’s matt and semi-gloss acrylic varnishes, for a sheen finish.
I am astonished how natural the Japanese B7A2 from late WWII looks in Royal Navy colors – even without my minor modifications the aircraft would look very convincing, even as a post-war design. It’s really an elegant machine, despite its bulk and size!
The Centaurus with its five blade propeller, the missiles under the wings and the gun barbette just add some more muscle and post-war credibility. I could also imagine this elegant aircraft in WWII Luftwaffe markings, maybe with an engine swap (BMW 801 or Jumo 213 power egg), too?