1:72 Great Lakes Aircraft Company SBG-3 “Prion”; aircraft “6-S-4” (BuNo. 01850), lead aircraft of Section 2, U.S. Navy Scouting Six Squadron (VS-6); U.S.S. Enterprise (CV-6), Caribbean Sea, late 1938 (Whif/Modified Heller kit)

+++ DISCLAIMER +++

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

 

 

Some background:

During the interwar period, the U.S. Navy Command had placed considerable emphasis upon the role of armed aerial reconnaissance aircraft. To meet this interest, during 1931, the young Great Lakes Aircraft Company (founded in 1929 in Cleveland, Ohio) decided to embark on the development of a new naval combat aircraft to meet this role. The new aircraft, which was designated as the SBG, was a relatively modern all-metal design, even though some conservative traits like a fixed landing gear were kept.

 

The SBG was a low-wing cantilever monoplane, featuring all-metal, metal-covered construction. The crew of three consisted of a pilot, a bombardier and a rear gunner. The bombardier's combat station was situated in a gondola underneath the hull. The pilot was positioned well forward in the fuselage with an excellent field of view, within a fully enclosed, air-conditioned and heated cockpit, while the observer was seated directly behind him and could descend into the ventral gondola during applicable parts of a given mission, where he had an unobstructed field of view underneath the aircraft. A lookout station at the gondola’s front end could be outfitted with a bombsight.

 

The fixed undercarriage was covered with spats and comprised a pair of cantilever struts and single tail wheel, all of which were outfitted with pneumatic shock absorbers. One of the more unusual features of the SBG was the design of its three-piece low-mounted wing: In order to produce a wing that was both light and strong, the wing construction combined a revolutionary heavy-gauge corrugated duralumin center box and a multi-cellular trailing edge, along with a partially stressed exterior skin composed of duralumin. It was one of the earliest implementations of a metal sandwich structure in the field of aviation. Furthermore, the wings could, for storage on carriers, be manually folded back, just outside of the landing gear.

 

The fuselage of the SBG had an oval-section structure, composed of a mixture of duralumin frames and stringers, which were strengthened via several struts on the middle section. The fuselage exterior was covered with smooth duralumin sheet, which was internally reinforced in some areas by corrugated sheeting. The rear fuselage featured a semi-monocoque structure. A cantilever structure composed of ribs and spars was used for the tail unit; fin and tail plane were covered by duralumin sheeting, while the rudder and elevators had finely corrugated exterior surfaces.

 

The SBG’s original powerplant was a Pratt & Whitney R-1830-64 Twin Wasp radial engine of 850 hp (630 kW). The aircraft's offensive payload consisted of bombs. These were carried externally underneath the fuselage and the wings, using racks; the maximum load was a single 1,935 lb. (878 kg) Bliss-Leavitt Mark 13 aerial torpedo or 1,500 lb. (700 kg) of bombs, including a single 1,000 lb. (450 kg) bomb under the fuselage and up to 200 lb. under the outer wings.

The SBG was also armed with several machine guns, including rearward-facing defensive ventral and dorsal positions, each outfitted with a manual .30 in (7.62 mm) Browning machine gun. Another fixed machine gun fired, synchronized with the engine, forward through the propeller arc.

 

The first XSBG-1 prototype, which was christened “Prion” by Great Lakes, was ready in early 1934 and made its maiden flight on 2nd of April. While the aircraft handled well, esp. at low speed, thanks to generously dimensioned flaps, it soon became clear that it was seriously underpowered. Therefore, Great Lakes tried to incorporate a more powerful engine. The choice fell on the new Pratt & Whitney R-2180-A Twin Hornet. However, the bigger and heavier engine called for considerable changes to the engine mount and the cowling. The R-2180 also precluded the fixed machine gun, so it was, together with the synchronization gearbox, deleted. Instead, a pair of .30 in machine guns were added to the spats, which were deepened in order to take the weapons and the magazines.

 

Furthermore, the heavier engine shifted the aircraft’s center of gravity forward, so that the tail section had to be lengthened by roughly 1’ and the tail surfaces were enlarged, too. Various other alterations were made to the wings, including the adoption of more effective slotted ailerons, improved flaps and center-section slots. The latter feature served to smooth the airflow over the tail when flown at high angles of incidence. However, despite these changes, the SBG’s good handling did not suffer, and the modified XSBG-2 took to the air for the first time in late 1935, with a much better performance.

 

Satisfied with the changes, the US Navy's Bureau of Aeronautics (BuAer) placed an initial order for 54 SBG-2s in 1936 with the aircraft entering service during 1938, serving on USS Yorktown and Enterprise. However, faults were discovered with the Mark XIII torpedo at this point. Many were seen to hit the target yet failed to explode; there was also a tendency to run deeper than the set depth. It took over a year for the defects to be corrected. Another problem of the SBG when carrying the torpedo was the aimer’s position, which was located directly behind the weapon and obstructed the bomb aimer’s field of view forward. When deploying bombs from higher altitudes, this was not a problem at all, but as a consequence the SBG rarely carried torpedoes. Therefore, a second order of 48 aircraft (designated SBG-3) were pure bombers. These lacked any torpedo equipment, but they received a ventral displacement yoke that allowed to deploy bombs in a shallow dive and release them outside of the propeller arc. Furthermore, the bomb aimer/observer station received a more generous glazing, improving the field of view and offering the prone crewman in this position more space and comfort. Another modification was the reinforcement of the underwing hardpoints, so that these could now carry stores of up to 325 lb each or, alternatively, drop tanks. While the total payload was not changed, the SBG-3 could carry and deploy up to three depth charges against submarines, and the extended range was a welcome asset for reconnaissance missions.

 

In prewar use, SBG units were engaged in training and other operational activities and were gradually approaching the end of their useful service life with at least one aircraft being converted to target tug duty. By 1940, the US Navy was aware that the SBG had become outclassed by the fighters and bombers of other nations and a replacement was in the works, but it was not yet in service when the US entered World War II. By then, attrition had reduced their numbers to just over 60 aircraft, and with the arrival of the Curtiss SB2C “Helldiver” in December 1942, the obsolete SBGs were retired.

 

 

General characteristics:

Crew: 3

Length: 31 ft 9 in (9.682 m)

Wingspan: 45 ft 9 in (13.95 m)

Height: 10 ft 10 in (3.3 m)

Wing area: 288 sq ft (26.8 m²)

Empty weight: 4,251 lb. (1,928 kg)

Gross weight: 6,378 - 6,918 lb. (2,893 - 3,138 kg) for reconnaissance missions

7,705 - 7,773 lb (3,495 - 3,526 kg) for bombing missions

Fuel capacity: 200 US gal (740 l; 160 imp gal) in six wing tanks plus

7.9 US gal (30 l; 6.6 imp gal) in a gravity feed collector tank in the fuselage

18 US gal (70 l; 15 imp gal) of engine oil was also carried in a forward fuselage tank

 

Powerplant:

1 × Pratt & Whitney R-2180-A Twin Hornet 14 cylinder radial engine with 1,200 hp (865 kW),

driving a 3-bladed Hamilton-Standard Hydromatic, 11 ft 3 in (3.43 m) diameter constant-speed

fully-feathering propeller

 

Performance:

Maximum speed: 245 mph (395 km/h, 213 kn) at 3,650 m (11,980 ft)

210 mph (338 km/h, 183 kn) at sea level

Stall speed: 110 km/h (68 mph, 59 kn)

Range: 1,260 km (780 mi, 680 nmi)

Service ceiling: 7,300 m (24,000 ft)

Time to altitude: 2,000 m (6,600 ft) in 4 minutes

4,000 m (13,000 ft) in 11 minutes 10 seconds

Wing loading: 116 kg/m² (24 lb/sq ft) to 130 kg/m2 (27 lb/sq ft)

Power/mass: 6.3–6.8 kg/kW (10.4–11.2 lb/hp)

 

Armament:

2x fixed forward firing 0.30 “ (7.62 mm) Browning machine guns in the spats, firing forward,

plus 2x flexibly mounted 0.30 “ (7.62 mm) Browning machine guns in ventral and dorsal positions

A total of up to 1,500 lb (700 kg) of bombs on hardpoints under the fuselage (max. 1.000 lb; the SCG-2

could carry a single Mk. XIII torpedo) and under the wings (max. 325 lb per hardpoint, SCG-2 only 200 lb)

 

 

The kit and its assembly:

I had the idea to convert a PZL.23 into a carrier-borne light bomber on the agenda for a long time and also already a Heller kit stashed away – but it took the “In the Navy” group build at whatifmodelers.com in early 2020 to dig everything out from the stash and start the hardware phase.

 

Originally, this was inspired by a picture of a Ju 87D with USN “Yellow wings” markings which I came across while doing online research. This looked really good, but since the USN would never have accepted a liquid-cooled engine on one of its pre-WWII aircraft, the concept had IMHO some flaws. When I came across the PZL.23 in another context, I found that the aircraft, with its cockpit placed well forward and the generous window area, could also be a good carrier-based recce/light bomber/torpedo aircraft? This was the conceptual birth of the SBG.

 

The basis is the vintage, original Heller kit of the PZL.23: a VERY nice kit. It has been crisply molded, fit is very good, and even the interior detail is decent, e.g. with a nice fuselage structure and dashboard. Surface details are raised but very fine, and the styrene is also easy to handle.

 

Basically the PZL.23 was built OOB. The only changes I made are a crew of three figures (all Matchbox WWII pilots, two of them with their heads in different directions), a tail wheel instead of the original skid, an opening for an arrester hook under the fin (there’s even plausible space available!) and a new engine: the PZL.23’s bulky 9 cylinder Jupiter radial engine with its generous cowling and the two-blade propeller was completely replaced. The engine dummy is actually a matching R-2600 and comes from a Matchbox SB2C, even though its rear bulkhead was trimmed away so that it would fit into the new cowling. The latter came from an Italeri La-5FN, cut off long time ago from another conversion project, and I added a carburetor/oil cooler fairing underneath. Inside of the new engine I implanted a styrene tube which attaches the engine to the fuselage and also takes the metal axis of the new propeller, a (rather clumsy) donor from a Matchbox Douglas A-20G. The whole package works well, though, and gives the PZL.23 a more modern and different look.

 

A late modification is the glasshouse for the rear gunner. Since the PZL.23 offered considerable comfort for its crew, at least for pilot and observer, I thought that a closed rear position would make sense. I found an old rear gunner station glaizing from a vintage Airfix B-17G in the stash, and with some tailoring (including an opening for the OOB manual machine gun) the piece could be inserted into the fuselage opening. Small gaps were left, but these were simply filled with white glue. I think this was a good move, since it changes the PZL.23’s profile a little.

 

Other small cosmetic changes include the machine guns instead of the original large landing lights on the spats, an additional antenna mast and a cranked pitot, made from brass wire. Furthermore, I added small underwing bomb pylons and a ventral hardpoint with a scratched swing arm and a 500 lb iron bomb from an Academy kit.

 

 

Painting and markings:

For proper anachronism and some color in the shelf, I wanted the SBG to be a pre-WWII aircraft in the USN’s bright “Yellow Wings” markings, just like the Ju 87 mentioned above. As a slight twist, the fuselage was finished in all-over Light Gull Grey (FS 36440, Humbrol 40) instead of a NMF – some aircraft like F4Bs were finished this way, even though some fabric-covered parts were still painted with alu dope. In 1940, however, the bright colors would be replaced by a uniform light grey livery with subdued markings, anyway.

 

The aircraft’s individual markings were a bit tricky, because the USN has a very complicated color code system to identify not only the carrier to which an aircraft would belong, color markings would also identify the individual aircraft within a full squadron of 18 aircraft and its six sections. I won’t go into details, but I chose to depict the lead aircraft of section two of the scout bomber squadron on board of USS Enterprise.

 

For this carrier, the tail surfaces became blue (I used Modelmaster French Blue for the authentic “True Blue”), while the 2nd section had white aircraft markings on fuselage and wings. The lead aircraft (connected with the individual aircraft code “4”) had a full ring marking around the cowling. The fuselage band seems to be rather optional on bomber aircraft (more frequent on fighters?), but I eventually decided to add it - pictures suggest that probably only lead aircraft of a Section in the scout or torpedo squadrons carried this marking?

Like the cowling ring, it was painted with white and then black borders were added with decal strips. The wings were painted with Revell 310 (Lufthansa Yellow, RAL 1028), which is a pretty rich tone, and the section markings on top of them were fully created with decal material, a white 5mm stripe over a black 6mm stripe on each wing.

The aircraft’s tactical code was created from single US 45° numbers; the “S” had to be scratched from an “8”, since the decal sheet did not contain letters… Other decals were gathered from the scrap box and improvised.

 

After the free-standing exhaust pipes had been fixed, the kit received a light weathering treatment and was finally sealed with a coat of semi-matt acrylic varnish (Italeri semi-gloss with some matt varnish added).

 

 

A colorful aircraft model, and the transformation from a Polish light bomber into an American armed scout aircraft worked well – for an interesting result with that anachronistic touch that many interwar designs carried. However, even though the conversion has been conceptually successful, I am not happy with the finish. The glossy Humbrol paints I used refused to cure properly, and the decals were also not without problems (e.g. when you realize that the roundels you wanted to use had a poor opacity, so that the yellow underneath shines blatantly through). But despite a lot of improvisation, the outcome is quite O.K.

 

Done