1:72 North American F1J “Sea Mustang”; VF-82, USS Bennington (CV-20), April 1945 (Whif/Heller kit conversion) - Beauty pic

DISCLAIMER

Nothing you see here is real, even though the conversion or the presented background story might be based historical facts. BEWARE!

 

Some background:

The P-51 was a relative latecomer to the Pacific Theatre. This was due largely to the need for the aircraft in Europe, although the P-38's twin-engine design was considered a safety advantage for long over-water flights. The first P-51s were deployed in the Far East later in 1944, operating in close-support and escort missions, as well as tactical photo reconnaissance. As the war in Europe wound down, the P-51 became more common: eventually, with the capture of Iwo Jima, it was able to be used as a bomber escort during B-29 missions against the Japanese homeland.

 

Anyway, impressed by the type’s performance, the U. S. Navy requested a navalized version of the able fighter – despite the preference for radial engines. Work on the so-called Sea Mustang began in early 1944 with the intention to provide the U.S. Navy with a long range, high performance successor for the Grumman F6F Hellcat. The specifications called for an aircraft able to operate from the smallest carrier, primarily in the interceptor role.

North American’s F1J idea to modify the proven Mustang to marine needs took a long way – longer and more twisted than expected. A first attempt to navalize the Mustang was done under the “Project Seahorse”: An early-series P-51D-5-NA, serial number 44-14017, was re-designated ETF-51D and sent to Mustin Field, near Philadelphia, for initial carrier utility testing in September 1944. One of the runways at Mustin Field was specially modified in order to test the naval Mustang. Markings simulating the size of an aircraft carrier's deck were realized and arrester cables were installed, as well as a launch catapult.

During the months of September and October 1944, test pilot Lt. Bob Elder made nearly 150 simulated launches and landings with the ETF-51D. Sufficient data concerning the Mustang's low speed handling had to be gathered before carrier trials could begin.

The Mustang's laminar-flow wing made for little drag and high speed but was relatively inefficient at low speed, resulting in a high stall speed. As the arrester cables could not be engaged at more than 90 mph, Elder reported that “from the start, it was obvious to everyone that the margin between the stall speed of the aircraft (82 mph) and the speed imposed by the arrester gear (90 mph) was very limited.”

Rudder control at low speeds and high angles of attack was inadequate. In addition, landing attitude had to be carefully controlled to avoid damaging the airframe upon landing. One of the handling quirks of the Mustang was also potentially dangerous: during a missed approach or a wave-off, power had to be re-applied gently, due to torque. If not, the aircraft could roll rapidly, or even snap-roll. At such low speed and altitude, the result could only be fatal.

Later, the tests went on with live action on board of a carrier, the USS Shangri-La (CV-38). Bob Elder “made all carrier landings at the speed of 85 mph. Luckily, the Mustang reacted well, even in the most delicate situations. One just had to use the throttle wisely.” Elder reported that speed control on the ETF-51D was excellent. He also stated that “the forward visibility was good and never gave me any problems. In fact, fighters with radial engines such as the F4U or F6F were worse than the P-51 in that respect.” The aircraft also behaved well during catapult launches.

The carrier suitability trials were rather short, though: only 25 landings and launches were made. Elder wrote “Although I had ‘premiered’ many US Navy aircraft carrier landings, no such experience had been as interesting as with the Mustang”.

However, North American Aviation did not forget about the ETF-51D experiments. Building on this experience, the company later presented another navalized Mustang project to the Navy: NAA-133. This machine was technically based on the P-51H, the last Mustang model to see production. The airframe of the NAA-133 was strengthened, though, as the P-51H airframe was lighter but not as sturdy as the P-51D’s.

 

While the basic Mustang airframe was retained for the NAA-133, a lot of detail work was done. Most obvious difference was the cockpit, which was slightly moved forward, for a better field of view, with the oil tank moved aft. Additionally, the radiator bath was moved forward in order to keep the area in front of the arrester hook, which was part of a strengthened landing gear, free from potential obstacles.

The wings were modified, too, featuring wing tip tanks for extended range as well as folding joints just outboard of the landing gear wells. All tail surfaces were slightly enlarged in order to improve slow speed agility. A six-bladed contraprop was fitted, too, in order to decrease the propeller’s diameter for easier landing as well as to improve acceleration and handling at low speed, due to the torque problems associated with the original four-bladed propeller. The internal armament was also enhanced, comprising now four 20mm M3 cannons instead of the former 0.5” machine guns.

Structurally the fuselage used flush riveting as well as spot welding, with a heavy gauge 302W aluminum alloy skin. However, the USN’s requested target loaded weight of 8,750 lb/3,969 kg was essentially impossible to achieve as the structure of the new fighter had to be made strong enough for aircraft carrier landings and resilient to high salt and humidity levels – in fact, the reinforced lightweight basic airframe of the P-51H became as heavy as the former P-51D, and performance was only as good as the D’s, despite the stronger engine.

The F1J “Sea Mustang” prototypes, how the type was officially designated, were ordered in August 1944 and first flew on 15 January 1945. By early 1945, though, the islands of Okinawa and Iwo Jima were conquered, and their airfields were immediately taken over by US forces, providing fighter units with bases from which they could escort bombers to mainland Japan. The Navy’s P-51 was no longer needed and the program was cancelled after about a dozen airframes had been completed. These were operational by 21 May, but World War II was over before the aircraft saw serious combat service.

The completed Sea Mustangs were later used as instructional airframes. In service the F1J was superseded by Grumman’s F8F Bearcat and Vought’s F4U Corsair, which had a significant development advance and became the USN’s major piston-engined fighters in the late 40ies.

 

 

General characteristics

Crew: 1

Length: 32 ft 3 in (9.83 m)

Wingspan: 37 ft 0 in (11.28 m) w. wing tip tanks

Height: 13 ft 4½ in (4.08 m w. tail wheel on ground, vertical propeller blade.)

Wing area: 235 ft² (21.83 m²)

Empty weight: 7,635 lb (3,465 kg)

Loaded weight: 9,200 lb (4,175 kg)

Max. takeoff weight: 12,100 lb (5,490 kg)

Aspect ratio: 5.83

 

Powerplant:

1× Packard V-1650-9 liquid-cooled supercharged V-12, 1,490 hp (1,111 kW) at 3,000 rpm, 2,220 hp (1,655 kW) at WEP

 

Performance:

Maximum speed: 437 mph (703 km/h) at 25,000 ft (7,600 m)

Cruise speed: 362 mph (580 km/h)

Range: 1,650 mi (2,755 km) with external tanks

Service ceiling: 41,900 ft (12,800 m)

Rate of climb: 3,200 ft/min (16.3 m/s)

Wing loading: 39 lb/ft² (192 kg/m²)

Power/mass: 0.18 hp/lb (300 W/kg)

Lift-to-drag ratio: 14.6

Recommended Mach limit 0.8

 

Armament:

4 × 20 mm (.79 in) M3 cannon, 190 rounds per gun

2× hardpoints for up to 2,000 lb (907 kg) of bombs or drop tanks, plus 6× 5” (127 mm) unguided rockets

 

 

The kit and its assembly

The idea of a navalized Mustang is IMHO a nice and rich whif theme. When I delved into history I was surprised that the idea as such had actually been taken to hardware status – the ETF-51D mentioned above is/was real, as well as the later NAA-133 proposal to the USN. But the latter never got as far as described, and that’s where whifery came to play. Anyway, what sounds like a simple plan became a major surgery, since I wanted more than just a blue P-51 with a hook glued to it.

 

My original plan was to convert a Hobby Boss kit, but when I tried to move both cockpit and radiator bath forward, that kit’s massive (!) fuselage piece prevented any decent modification. Hence, I fell back to an “old school” P-51D kit with two fuselage halves: a Heller Mustang which I still had in my stack. Not a bad kit, but with its raised panel lines it certainly is sub-optimal, esp. when you change many things on the hull.

 

Both cockpit and radiator intake were moved about 5mm forward, a major surgery. The cockpit was taken OOB, just some ribs inside and a pilot figure were added (an old Matchbox figure), and radio equipment simulated behind the seat. The canopy was cut open.

 

The contraprop is new, too, a scratch-built piece, made from, AFAIK an F4U drop tank. It gives the Sea Mustang a sleek, beefy look, but also makes sense from an operational point of view.

 

The landing gear received new/better wheels and extra struts, also for a sturdier look. The new tail wheel was taken from an Airfix A-1 Skyraider, with an added arrester hook and an accordingly modified well with new/longer covers.

 

The tail was completely modified: the horizontal stabilizers were replaced by bigger ones, taken from an F4U, and the original vertical rudder was replaced by a taller construction created from a Ju-87G rudder (!) and a stabilizer from a Bell AH-1, both ancient Matchbox kits.

The Heller kit provides a separate fin fillet piece, but I left it away, in order to pronounce the taller fin and longer back of the F1J.

 

The wings received wing tip tanks (taken from a Grumman F9F Panther) as well as a changed armament with four cannons with longer barrels (from the Airfix A-1) instead of the classic six 0.5” machine guns. New panel lines, where the wing folding joints would be, were engraved. In order to add some realism for display, flaps were opened/lowered - an easy task with the Heller kit.

 

The 250 lbs. bombs were taken straight from the Heller kit, the 5” HVARs come from a Matchbox Grumman F9F Panther, with scratch-built launch rails made from polystyrene profiles (Evergreen).

 

 

Painting

The old adage that a subtle whif works best with a simple livery is true: the dark blue (FS15042/AN607) suits the slender lines of the Mustang very well, even if it is my hunchback modification! Unfortunately, my favourite paint choice, Humbrol 181, is out of production (Shame on you, Airfix!), so I had to hunt down Testors’ 1718 as a replacement.

All interior surfaces were painted with Humbrol 226 (Interior Green), then dry-brushed with Zinc Chromate (Testors 1734) and Humbrol 80 (Grass Green).

 

Markings were taken from 1:72 a Hobby Boss F4U (leftover from my FAS conversion) and a vintage F6F from Monogram in 1:48. The squadron markings depict a machine from VF-82 "Fighting Fools", based on the carrier USS Bennington (CV-20) in the Pacific theatre in 1945. National insignia had to be puzzled together and improvised with white stars and separate all-white bars. The yellow band behind the propeller rather belongs to machines from VF-84 on board of USS Bunker Hill (CV-17), though, but since this is a whif, the marking is a nice contrast to the all-blue livery. That the machine sports the bort number "82" is a weird conincidence!

 

Some weathering was done with dry-brushing (e. g. Humbrol 77 & 189), rubbed graphite dust and soot stains around cannons and exhausts, and light colour chipping on leading edges and around the cockpit was done. Finally, the kit received a coat with semi-gloss varnish – I did not dare using a 100% gloss coat, because that would IMHO have made the machine look too new and out of scale.

 

 

In the end, a nice little model/project, realized in less tha a week - despite the major surgeries, but the single colour paint job was simple. A fighter with a twist, and with a really subtle whif factor, even though my interpretation of a Sea Mustang differs in many aspects from the real NAA-133 proposal. But this model is not intended to be a representation of North American’s project, rather a personal and dramatized idea of what might have been. :D

Done