LWF H Owl nose 1923

LWF Model H Owl Mail Plane / Bomber

By William Pearce

In 1915, the Lowe, Willard & Fowler Engineering Company was formed in College Point, Long Island, New Work. Of the founders, Edward Lowe, provided the financing; Charles Willard was the engineer and designer; and Robert Fowler served as the shop foreman, head pilot, and salesman. Willard was previously employed by the Curtiss Aeroplane and Motor Company and had developed a technique for molding laminated wood to form a monocoque fuselage. Willard was eventually granted U.S. patent 1,394,459 for his fuselage construction process. Previously in 1912, Fowler became the first person to fly west-to-east across the United States.

LWF H Owl nose

The LWF Model H Owl in its original configuration with six main wheels. The engine on the central nacelle has a spinner, a single service platform, and a separate radiator. Note the numerous drag inducing struts and braces for the wings, nacelle, and booms.

The business partnership was short-lived. In 1916, Fowler and Willard left the company, and Lowe assumed control, renaming the company LWF Engineering. By this time, LWF had become well-known for its molded wood construction process. However, management changed again as other financiers forced Lowe out. In 1917, the firm was reorganized as the LWF Engineering Company, with “Laminated Wood Fuselage” taking over the LWF initials.

By 1919, LWF began design work on a large trimotor aircraft intended for overnight mail service between New York City and Chicago, Illinois. Other uses for the aircraft were as a transport or bomber. Designated the Model H (some sources say H-1), construction began before an interested party came forward to finance the project. Because of its intended use for overnight mail service, the aircraft was given the nickname “Owl.” As construction continued, the United States Post Office Department declined to support the Model H. However, LWF was able to interest the United States Army Air Service, which purchased the aircraft on 16 April 1920. The Model H was assigned the serial number A.S.64012.

LWF H Owl rear

In the original configuration, the Owl’s cockpit was just behind the trailing edge of the wing, and visibility was rather poor. Note the aircraft’s two horizontal stabilizers and three rudders. The smooth surface finish of the booms is well illustrated.

The LWF Model H Owl was designed by Raoul Hoffman and Joseph Cato. Although the Owl’s design bore some resemblance to contemporary large aircraft from Caproni, there is nothing that suggests the similarities were anything more than superficial. The Model H had a central nacelle pod that was 27 ft (8.23 m) long and contained a 400 hp (298 kW) Liberty V-12 positioned in the nose of the pod. The cockpit was positioned in the rear half of the pod, just behind the wing’s trailing edge. The cockpit’s location did not result in very good forward visibility. Accommodations were provided for two pilots, a radio operator, and a mechanic. Mounted 10 ft (3.05 m) to the left and right of the central pod were booms measuring approximately 51 ft (15.54 m) long. The booms were staggered 24 in (.61 m) behind and 16 in (.41 m) below the central pod and extended back to support the tail of the aircraft. At the front of each boom was a 400 hp (298 kW) Liberty V-12 engine. Each boom housed fuel tanks and small compartments for cargo. The main load was carried in the central nacelle.

The monocoque central nacelle and booms were made using LWF’s laminated wood process. The construction method consisted of a mold covered with muslin cloth. Strips of thin spruce were then laid down and spiral wrapped with tape. Another layer of spruce was laid in the opposite direction and spiral wrapped with tape. The final, outer layer of spruce was laid straight. The assembly was then soaked in hot glue and covered with fabric and doped. The resulting structure was about .25 in (6.4 mm) thick, was very strong, and had a smooth exterior. Where reinforcement was needed, formers were attached to the inside of the structure.

LWF H Owl in flight

The Owl was a somewhat sluggish flier and reportedly underpowered. However, its flight characteristics were manageable. It was the largest aircraft in the United States at the time.

The nacelle and booms were mounted on struts and suspended in the 11 ft (3.35 m) gap between the Model H’s biplane wings. The wings were made of a birch and spruce frame that was then covered in fabric, except for the leading edge, which was covered with plywood. The upper and lower wing were the same length and were installed with no stagger. The wings were braced by numerous struts and wires. Large ailerons were positioned at the trailing edge of each wing. The wings were 100 ft 8 in (30.68 m) long with an additional 26 in (.66 m) of the 17 ft 8 in (5.38 m) ailerons extending out on each side. The incidence of the upper and lower wings was 4.5 and 3.5 degrees respectively. A bomb of up to 2,000 lb (907 kg) could be carried under the center of the lower wing.

A horizontal stabilizer spanned the gap between the rear of the booms. A large, 24 ft (7.32 m) long elevator was mounted to the trailing edge of the stabilizer. Mounted at the rear of each boom was a vertical stabilizer with a large 6 ft 9.75 in (2.08 m) tall rudder. A second horizontal stabilizer 28 ft (8.53 m) long was mounted atop the two vertical stabilizers. A third (middle) rudder was positioned at the midpoint of the upper horizontal stabilizer. Attached to the upper horizontal stabilizer and mounted between the rudders were two elevators directly connected to the single, lower elevator. The lower stabilizer had an incidence of 1.5 degrees, while the upper stabilizer had an incidence of 4 degrees.

LWF H Owl crash 1920

The Model H was heavily damaged following the loss of aileron control and subsequent hard landing on 30 May 1920. However, the booms, central nacelle, and tail suffered little damage.

The Owl’s ailerons and rudders were interchangeable. Each engine was installed in an interchangeable power egg and turned a 9 ft 6 in (2.90 m) propeller. Engine service platforms were located on the inner sides of the booms and the left side of the central nacelle. The Owl was equipped with a pyrene fire suppression system. The aircraft was supported by a pair of main wheels under each boom and two main wheels under the central nacelle. At the rear of each boom were tailskids.

The LWF Owl had a wingspan of 105 ft (32 m), a length of 53 ft 9 in (16.38 m), and a height of 17 ft 6 in (5.33 m). The aircraft had a top speed of 110 mph (117 km/h) and a landing speed of 55 mph (89 km/h). The Model H had an empty weight of 13,386 lb (6,072 kg) and a maximum weight of 21,186 lb (9,610 kg). The aircraft had a 750 fpm (3.81 m/s) initial rate of climb and a ceiling of 17,500 ft (5,334 m). The Owl had a range of approximately 1,100 miles (1,770 km).

LWF H Owl crash 1921

The Owl on its nose in the marshlands just short of the runway at Langley Field on 3 June 1921. The nose-over kept the tail out of the water and probably prevented more damage than if the tail had been submerged.

Although not complete, the Model H was displayed at the New York Aero Show in December 1919. On 15 May 1920, the completed Owl was trucked from the LWF factory to Mitchel Field. Second Lt Ernest Harmon made the aircraft’s first flight on 22 May. The aircraft controls were found to be a bit sluggish, but everything was manageable. An altitude of 1,300 ft (396 m) was attained, but one engine began to overheat, and the aircraft returned for landing. The second and third flights occurred on 24 May, with a maximum altitude of 2,600 ft (792 m) reached. The fourth flight was conducted on 25 May. Water in the fuel system caused the center engine to lose power, and an uneventful, unplanned landing was made at Roosevelt Field. Modifications were made, and flight testing continued.

On the aircraft’s sixth flight, it had a gross weight of 16,400 lb (7,439 kg). The Owl took off and climbed to 6,000 ft (1,829 m) in 15 minutes. The engines were allowed to cool before another climb was initiated, and 11,000 ft (3,353 m) was reached in seven minutes. No issues were encountered, and the aircraft returned to base after the successful flight.

LWF H Owl nose 1923

The Owl in its final configuration with four main wheels. On the central nacelle, note the new radiator, lack of a spinner, service platforms on both sides of the engine, and the opening for the bombsight under the nacelle. A bomb shackle is installed under the wing on the aircraft’s centerline.

On 30 May, a turnbuckle failed and resulted in loss of aileron control while the Owl was on a short flight. A good semblance of control was maintained until touchdown, when the right wing caught the ground and caused the aircraft to pivot sideways. The right wheels soon collapsed, followed by the left. The owl then smashed down on the right engine, rotated, and then settled down on the left engine, tearing it free from its mounts. The cockpit located near the center of the isolated central nacelle kept the crew safe, allowing them to escape unharmed.

The Model H was repaired, and flight testing resumed on 11 October 1920. Tests continued until 3 June 1921, when Lt Charles Cummings encountered engine cooling issues followed by engine failure. The Owl crashed into marshland just short of the runway at Langley Field, Virginia. The aircraft ended up on its nose, but the crew was uninjured. The Owl was recovered and returned to the LWF factory for repairs.

LWF H Owl rear 1923

The new cockpit position just behind the engine can be seen in this rear view of the updated Owl. In addition, the gunner’s position is visible at the rear of the central nacelle.

While being repaired, various modifications were undertaken to better suit the aircraft’s use in a bomber role. The cockpit was revised and moved forward to directly behind the center Liberty engine. The middle engine had a new radiator incorporated into the nose of the central pod. An engine service platform was added to the right side of the central pod so that both sides had platforms. A gunner’s position, including a Scraff ring for twin machine guns, was added to the rear of the nacelle pod. A bombing sight opening was added in the central nacelle. The ailerons were each extended 10 in (.25 m), increasing their total length to 18 ft 6 in and increasing the wingspan to 106 ft 8 in (32.51 m). The landing gear was modified, and a single wheel replaced the double wheels for the outer main gear. A bomb shackle was added between the center main wheels.

The Owl flew in this configuration in 1922. To improve the aircraft’s performance, some consideration was given to installing 500 hp (373 kW) Packard 1A-1500 engines in place of the Libertys, but this proposal was not implemented. In September 1923, the Owl was displayed at Bolling Air Field in Washington, DC. The aircraft had been expensive, and it was not exactly a success. Quietly, in 1924, the LWF Model H Owl was burned as scrap along with other discarded Air Service aircraft.

LWF H Owl Bolling 1923

The Owl on display at Bolling Field in September 1923. Note the windscreen protruding in front of the cockpit. The large aircraft dwarfed all others at the display.

Sources:
“The Great Owl” by Walt Boyne, Airpower (November 1997)
“The 1,200 H.P. L.W.F. Owl” Flight (14 April 1921)
“The L.W.F. Owl Freight Plane” Aviation (1 March 1920)
Aircraft Year Book 1920 by Manufacturers Aircraft Association (1920)
Aircraft Year Book 1921 by Manufacturers Aircraft Association (1921)
American Combat Planes of the 20th Century by Ray Wagner (2004)

arsenal vg 33 rear

Arsenal VG 30-Series (VG 33) Fighter Aircraft

By William Pearce

In the early 1930s, some in France felt that French aviation was falling behind the rest of the world. French aircraft manufacturers were not experimenting much on their own, and government-funded conventional aircraft projects were not pushing the technical boundaries of aeronautics. On 2 July 1934, Pierre Renaudel proposed creating a state research institution to study and develop modern aircraft for the French military. The Arsenal du matériel aérien (Arsenal aerial equipment) was formed later that year with engineer Michel Vernisse as its director. When the French aviation industry was nationalized in 1936, the organization was renamed Arsenal de l’aéronautique (Arsenal aeronautics) and took over the Bréguet works at Villacoublay, near Paris, France.

arsenal vg 30

The mockup of the Arsenal VG 30 as displayed at the 1936 Salon d’Aviation in Paris. Note the location of the radiator housing. Otherwise, the aircraft was very similar to subsequent VG 30-series fighters.

One of Arsenal’s first designs was the tandem-engine VG 10 fighter. Designed by Michel Vernisse and Jean Galtier, the initials of their last names formed the ‘VG’ of the aircraft’s designation. The VG 10 was never built and was redesigned and redesignated as the VG 20, which was also never built. However, the design was reworked again and eventually emerged as the Arsenal VB 10, first flown in 1945.

In 1936, the Ministère de l’Air (French Air Ministry) was interested in the concept of a light-fighter built from non-strategic materials. As a result, Arsenal designed the VG 30, a single-seat fighter constructed mostly of wood. The aircraft had a conventional taildragger layout with a low wing and featured retractable main undercarriage. At the rear of the aircraft was a non-retractable tailskid. Originally, the VG 30 was to be powered by the Potez 12 Dc: a 610 hp (455 kW), air-cooled, horizontal, 12-cylinder engine. However, delays with the 12 Dc resulted in a switch to the Hispano-Suiza 12Xcrs: a 690hp (515 kW), liquid-cooled, V-12 engine.

The wood used in the VG 30’s construction was primarily spruce, and the aircraft’s wooden frame was covered with molded sprue plywood to form the aircraft’s stressed-skin. The skin was then covered with canvas and varnished. The wings consisted of two spars and incorporated hydraulically operated flaps. The fuselage was mounted atop the wings, which were made as a single structure. The cockpit was positioned above the wing’s trailing edge and featured a rearward-sliding canopy. The engine’s cowling was made of aluminum, and to cool the engine, a radiator was housed in a duct positioned under the fuselage between the wings. Proposed armament consisted of a 20 mm cannon firing through the hub of the three-blade propeller and four 7.5 mm machine guns, with two housed in each wing. The cannon had 60 rounds of ammunition, and the wing guns each had 500 rounds.

arsenal vg 33 two

The VG 33 prototype sits complete with main gear doors on a muddy airfield. Many of the completed VG 33s, like the second aircraft in the image, were finished without gear doors.

A mockup of the VG 30 was displayed in November 1936 at the Salon d’Aviation in Paris. The Air Ministry found the mockup sufficiently impressive to issue specification A.23, requesting proposals for a light-fighter. A prototype of the Arsenal VG 30 was ordered in early 1937, and construction of the aircraft commenced in June. Some delays were encountered, and the VG 30 was first flown on 6 October (some sources state 1 October) 1938. The pilot for the flight was Modeste Vonner, and the aircraft took off from Villacoublay. Official tests were carried out from 24 March to 17 July 1939, during which the VG 30 reportedly reached 500 mph (805 km/h) in a dive. Overall, the tests revealed that the VG 30 had very good performance and was faster than the more-powerful Morane-Saulnier MS 406, France’s premier fighter just entering service.

The VG 30 had a wingspan of 35 ft 5 in (10.80 m), a length of 27 ft 7 in (8.40 m), and a height of 10 ft 10 in (3.31 m). The aircraft’s wing area was 150.69 sq ft (14.00 sq m). It had a top speed of 301 mph (485 km/h) at 16,240 (4,950 m) and climbed to 16,404 ft (5,000 m) in 7 minutes and 15 seconds. Despite the aircraft’s performance, VG 30 production was passed up in favor of more advanced models, and only the prototype was built.

The Arsenal VG 31 was a development of the VG 30 intended to enhance the aircraft’s speed. An 860 hp (641 kW) Hispano-Suiza 12Y-31 replaced the 690 hp (515 kW) engine; the radiator was relocated further back; two of the wing guns were removed; and a smaller wing was designed, resulting in 19.9–21.2 sq ft (1.85–2.0 sq m) less wing area. Wind tunnel tests indicated the aircraft would have reduced stability, reduced maneuverability, and an increased landing speed. The small gain in top speed was not worth all of the drawbacks. The VG 31 was never completed. The wings were used for static testing, and the fuselage was used on the third VG 33 aircraft, which became the VG 34.

arsenal vg 33 rear

A completed VG 33 without gear doors seen at Toulouse-Blagnac airport in June 1940. Note the radiator housing under the fuselage.

The Arsenal VG 32 was an attempt to secure a second source of power for the VG 30 aircraft. A 1,040 hp (776 kW) Allison V-1710-C15 (-33) replaced the Hispano-Suiza engine, requiring the fuselage to be lengthened by 16.5 in (.42 m) to 28 ft 11 in (8.82 m). The wings were modified to accommodate one 20 mm cannon and one 7.5 mm machine gun. Because of delays with acquiring the V-1710 engine, the VG 32 project followed after the VG 33. The fifth VG 33 airframe formed the basis for the VG 32, and a desperate France ordered 400 copies of the aircraft in 1940. However, the Germans arrived before the V-1710 engine, and the VG 32 was never completed. The aircraft was captured at Villacoublay in June 1940.

The Arsenal VG 33 was an enhancement to the basic VG 30 aircraft. The VG 33 used the 860 hp (641 kW) Hispano-Suiza 12Y-31 from the VG 31 but retained the larger wing of the VG 30. The engine turned a 12 ft 4 in (3.75 m) diameter three-blade, adjustable-pitch, metal propeller. An oil cooler was incorporated into the engine cowling just below the spinner, and a scoop for engine induction was located on the bottom of the cowling. The aircraft’s fuselage was lengthened slightly to 28 ft .5 in (8.55 m), and its height was 11 ft (3.35 m). The VG 33 prototype made its first flight on 25 April 1939 from Villacoublay. Official trials spanned from August 1939 to March 1940. The VG 33 was stable, maneuverable, easy to fly, and possessed good control harmony. The aircraft’s maneuverability and speed were superior to that of the more-powerful, all-metal Dewoitine D.520, France’s newest fighter.

arsenal vg 33 front captured

A VG 33 aircraft captured by the Germans and being tested at Rechlin, Germany. The captured aircraft carried the designation 3+5. The inlets for the oil cooler can bee seen just under the spinner. Under the cowling is the engine’s intake. Note the machine guns mounted in the wings.

The VG 33 had a maximum speed of 347 mph (558 km/h) at 17,060 ft (5,200 m) and a ceiling of 36,089 ft (11,000 m). The aircraft weighed 4,519 lb (2,050 kg) empty and 6,063 lb (2,750 kg) fully loaded. Its range was 746 miles (1,200 km) with 106 gallons (400 L) of internal fuel. Two fixed 26-gallon (100 L) external tanks could be attached under the wings to extend the aircraft’s range to 1,118 miles (1,800 km).

Before the flight trials were over, the Air Ministry ordered at least 200 VG 33s in September 1939. Another purchase request was submitted a short time later placing a total of approximately 720 VG 33 aircraft on order. The first deliveries were scheduled for January 1940, and the first fighter group equipped with VG 33 aircraft was to be operational in April 1940. The bulk of the orders went to SNCAN (Société nationale des constructions aéronautiques du Nord or National Society of Aeronautical Constructions North) at Sartrouville, with Michelin at Clermont-Ferrand expected to start production later.

Ironically, delays with acquiring enough non-strategic spruce resulted in the first production VG 33 aircraft not making its first flight until 21 April 1940. Production numbers for the VG 33 vary by source. By the time France surrendered to Germany on 22 June 1940, only about seven aircraft had been delivered to the Armée de l’Air (French Air Force) out of a total of 19 VG 33s that had been flown. Approximately 160 airframes were in various stages of completion at SNCAN, and at least 20, which were basically complete, were destroyed by the French before German forces could capture them. The French managed to fly out 12 VG 33 aircraft to Châteauroux, where they were placed into storage. By November 1942, the Germans had managed to seize around 5 VG 33 aircraft, and at least one underwent testing at Rechlin, Germany. All VG 33s were eventually scrapped.

arsenal vg 34

The engineless VG 34 prototype sits derelict at what is most likely Toulouse-Blagnac airport. Note the additional supports on the canopy.

The Arsenal VG 34 was the second VG 33 re-engined with the more powerful Hispano-Suiza 12Y-45 that used a Szdlowski-Planiol supercharger and produced 910 hp (679 kW). First flown on 20 January 1940, the VG 34 achieved 357 mph (575 km/h) at 20,341 ft (6,200 m). Only one example was built. The VG 34 was flown to Toulouse-Blagnac airport on 18 June 1940 and was presumably captured there by the Germans.

The Arsenal VG 35 was the fourth (some sources say third) VG 33 airframe but with a 1,100 hp (820 kW) Hispano-Suiza 12Y-51 engine installed. The aircraft was first flown on 25 February 1940 and eventually reached 367 mph (590 km/h). However, flight testing was never completed, and the sole prototype was seized by the Germans.

The Arsenal VG 36 was a more developed and refined VG 35. The aircraft had a modified rear fuselage and used a shallower and more streamlined radiator duct. The VG 36 was first flown on 14 May 1940 and was later destroyed at La Roche-sur-Yon in eastern France.

arsenal vg 36 front

On first glance, the VG 36 was very similar to the VG 33. The most notable difference was the redesigned radiator housing, which was shallower than the housing used on earlier VG 30-series aircraft and required a redesign of the rear fuselage.

The VG 37 was a proposal for a long-range VG 36, and the VG 38 was a VG 35 with a more powerful Hispano-Suiza 12Y engine that incorporated two Brown-Boveri turbosuperchargers. Neither of these aircraft projects were built.

The Arsenal VG 39 was based on the VG 33. The wing had a new internal structure that accommodated three 7.5 mm machine guns in each wing. The fuselage was slightly modified and lengthened to 28 ft 8 in (8.75 m) to accommodate a 1,200 hp (895 kW) Hispano-Suiza 12Zter engine. The inlets and position of the oil cooler at the front of the engine cowling were revised, and the radiator housing under the aircraft was also slightly smaller. The 20 mm engine cannon was omitted. First flown on 3 May 1940, the VG 39 achieved 388 mph (625 km/h) at 18,865 ft (5,750 m) during initial tests. Only one VG 39 was built. It made its last flight on 15 June 1940 and was destroyed by the French at Toulouse-Blagnac airport before the Germans captured the field. The planned production version was designated VG 39bis, used the fuselage of the VG 36 with its shallow radiator, was powered by a 1,300 hp (969 kW) Hispano-Suiza 12Z-17 engine, and included a 20 mm engine cannon. No VG 39bis aircraft were built.

The VG 40 was a study to power the VG 33 with a Rolls Royce Merlin III engine. Compared to the VG 33, the VG 40 had a larger wing. The aircraft did not progress beyond the design stage.

The VG 50 design incorporated the fuselage of the VG 36 with the six-gun wings of the VG 39. This package would be powered by a 1,200 hp (895 kW) Allison V-1710 engine. The VG 50 was never built.

Of the series, only the Arsenal VG 33 entered production. On paper, it was one of the best French fighters of World War II and on par with the frontline fighters of other nations. However, the aircraft never had the opportunity to be tested in combat. The VG 33’s slightly protracted development and production delays resulted in none of the type being available at the start of hostilities and too few being delivered during the Battle of France to have any impact on the conflict.

arsenal vg 39

The VG 39 prototype probably at the Toulouse-Blagnac airport. Note the exhaust stains on the engine cowling. The cowling was revised to accommodate the new oil cooler and the evenly-spaced exhaust stacks of the 12Z engine.

Sources:
French Fighters of World War II in Action by Alan Pelletier (2002)
French Aircraft 1939–1942 Volume I: From Amoit to Curtiss by Dominique Breffort and André Jouineau (2004)
The Complete Book of Fighters by William Green and Gordon Swanborough (1994)
War Planes of the Second World War: Fighters – Volume I by William Green (1960)
Hispano Suiza in Aeronautics by Manuel Lage (2004)
https://fr.wikipedia.org/wiki/Arsenal_VG_33

daimler-mercedes d vi back

Daimler-Mercedes D VI W-18 Aircraft Engine

By William Pearce

By 1915, the Germans had begun to experiment with very large aircraft known as Riesenflugzeug (giant aircraft). These aircraft had been developed from the G-class bombers and are often referred to as R-planes. In 1916, the potential of such an aircraft to carry heavy bombloads into enemy territory was recognized, and the deficiencies of airships that had been developed to serve in that same role was apparent. Efforts were undertaken to increase R-plane production and withdraw airships from long-range bomber missions.

mercedes d.vi (2)

The preserved Daimler-Mercedes D VI W-18 engine. The individual cylinders on each bank were linked by a common overhead camshaft housing. Note the water-jacketed copper intake manifolds. (Evžen Všetečka image via www.aircraftengine.cz)

To promote the development of larger and more capable R-planes, larger and more powerful aircraft engines were needed. As early as 1915, the Idflieg (Inspektion der Fliegertruppen or Inspectorate of Flying Troops) had encouraged various German engine manufacturers to develop large aircraft engines capable of 500 hp (375 kW). These engines were known as Class VI engines and would be used to power R-planes. Daimler Motoren Gesellschaft (Daimler) was one of the companies that worked to build a large Class VI aircraft engine.

Daimler’s design was known as the D VI, but it is also referred to as the Mercedes D VI or Daimler-Mercedes D VI. Daimler often used the Mercedes name for many of its products. The D VI engine utilized the basic cylinder from the 180 hp (134 kW) Daimler-Mercedes D IIIa engine and incorporated features from the 260 hp (194 kW) D IVa engine. Both of those engines were six-cylinder inlines. However, the D VI had three rows of six-cylinders, creating a W-18 engine. The center cylinder row was vertical, and the left and right rows were angled 40 degrees from the center row.

mercedes d.vi (3)

Front view of the D VI illustrates the water pump mounted directly in front of the center cylinder bank. Note the direct drive crankshaft. (Evžen Všetečka image via www.aircraftengine.cz)

The D VI engine used individual steel cylinders with one intake and one exhaust valve. The valves of each cylinder row were actuated by a single overhead camshaft driven from the rear of the engine via a vertical shaft. The camshaft acted upon rocker arms that protruded from the camshaft housing above each cylinder to the exposed cylinder valves. A water jacket made of pressed steel was welded to the cylinder. Each piston was made of a forged-steel head screwed and welded onto a cast iron skirt. The cylinder’s compression ratio was 4.7 to 1.

Each cylinder was attached to the two-piece steel crankcase via four studs. Most likely, the studs for the center cylinder row extended into the bottom half of the crankcase and helped secure the two crankcase halves. The crankshaft was supported by seven main bearings and was connected directly to the propeller. A water pump was driven by the crankshaft at the front of the engine. At the rear of the engine, a vertical shaft extending from the crankshaft drove a magneto for each cylinder bank and an oil pump. Each of the cylinders had two spark plugs.

Induction air was drawn into an air chamber inside the crankcase where it was warmed. The air then passed through two water-jacketed pipes cast integral with the lower crankcase half at the rear of the engine. The two pipes split into three inline carburetors, each feeding one cylinder bank via an intake manifold. The intake manifold was made of copper and was water-jacketed. The left cylinder bank had its intake manifold positioned on the right side. The center and right cylinder banks had their intake manifolds positioned on the left side. The exhaust was expelled from each cylinder via an individual stack on the side opposite the intake.

daimler-mercedes d vi back

Rear view of the D VI shows the engine’s induction stemming from the lower crankcase housing and feeding into the three carburetors.

The D VI had a 5.51 in (140 mm) bore and a 6.30 in (160 mm) stroke. The engine’s total displacement was 2,705 cu in (44.3 L). The D VI produced 513 hp (382 kW) at 1,440 rpm for takeoff and had a maximum continuous output of 493 hp (368 kW) at 1,400 rpm. Specific fuel consumption was .477 lb/hp/hr (290 g/kW/h). The engine weighed 1,636 lb (742 kg).

The Daimler D VI engine was first run in 1916. However, development of the D IIIa and D IVa engines took priority, causing the D VI to lag behind. The D VI passed a certification test in December 1918, but World War I was over by that time, and such and engine was no longer needed. Military restrictions imposed on Germany by the Treaty of Versailles most likely influenced the abandonment of the D VI engine, and no further work was undertaken.

The sole surviving D VI engine has been preserved and is on display at the Flugausstellung L.+ P. Junior museum in Hermeskeil, Germany.

mercedes d.vi (1)

The D VI engine had mounts cast integral with the upper crankcase, but the engine was never installed in any aircraft. Note the pedestal pads onto which the cylinders were mounted. (Evžen Všetečka image via www.aircraftengine.cz)

Sources:
Flugmotoren und Strahltriebwerke by Kyrill von Gersdorff, et. al. (2007)
Report on the 180 H.P. Mercedes Aero Engine by the Ministry of Munitions Technical Department—Aircraft Production (March 1918)
Report on the 260-H.P. Mercedes Aero Engine by the Technical Information Section of the Air Board (July 1917)
http://www.aircraftengine.cz/Hermeskeil/

timossi-verga laura 3 front

Timossi-Verga Laura 3 Hydroplane

By William Pearce

Mario Verga was a successful silk merchant born in Milan, Italy in 1910. In the late 1940s, he became a well-known Italian speedboat racer, competing in the 450 kg (992 lb) class. He left boat racing in 1950 when he married Liliana Burlazzi, but the pull of the sport was too strong for Verga to stay away.

abbate-verga laura i

The Abbate-built Laura I was a sleek design. Aluminum bodywork covered the Alfa Romeo Typo 159 engine. Note the step between the sponson and the hull.

In 1952, Verga returned to the speedboat world with his 450 kg (992 lb) class Laura I racer. Named after Verga’s young daughter, the boat was built by Guido Abbate at Lake Como and was 17 ft 3 in (5.25 m) long and 7 ft 6 in (2.28 m) wide. The Laura I was powered by an Alfa Romeo Typo (Type) 159 engine, the same type of engine that propelled auto racing legends Nino Farina and Juan Manuel Fangio to respective Formula 1 World Championships in 1950 and 1951. The “a” after the number in the boat’s name designated the Alfa Romeo engine. Verga and the Laura I captured the 450 kg (992 lb) class championship in 1952.

On 7 July 1952, and half the world away on Lake Washington’s East Channel near Mercer Island in the Pacific Northwest, Stanley Sayres and Elmer Leninschmidt set a new world absolute water speed record at 178.497 mph (287.263 km/h) in the three-point hydroplane Slo-mo-shun IV. Sayres, Ted Jones, and Slo-mo-shun IV had set the previous record at 160.323 mph (258.015 km/h) on 26 June 1950, the first post-World War II water speed record. For both records, Slo-mo-shun IV was powered by an Allison V-1710 engine.

timossi-verga laura ii

The Laura II used the same bodywork as the Laura I. However, the sponsons had no step between them and the hull, and the hull had larger fuel tanks. Note the engine’s eight exhaust stacks.

Modifications to Laura I had increased the boat’s weight, and it fell within the 800 kg (1,764 lb) class. On 29 January 1953, Verga set an 800 kg (1,764 lb) class speed record of 125.670 mph (202.247 km/h) in Laura I. He increased the record to 140.737 mph (226.495 km/h) on 15 February 1953. Both records were set on Lake Lugano.

Verga had a new 800 kg (1,764 lb) class boat built by Carlo Timossi at Lake Como. The new boat was named Laura II, and it was 17.5 ft (5.33 m) long and powered by the same Typo 159 engine that powered Laura I. Images indicate that the aluminum bodywork of Laura I was used on Laura II. Verga and the Laura II won the 800 kg (1,764 lb) class championship in Europe on October 1953 and then traveled to the United States. The Laura II won the Orange Bowl International Regatta Grand Prix held at Miami Beach, Florida in December 1953, and also set a speed record for the 151 cu in (2.47 L) hydroplane class, averaging 131.680 mph (211.919 km/h).

Verga’s speed records and the records of other Italian speedboat racers (Achille Castoldi averaged 150.188 mph / 241.704 km/h in the 800 kg class, Ferrari-powered Arno XI on 15 October 1953 at Lake Iseo) inspired the Italian Motornautical Federation to offer a £5,000,000 prize to the sportsman that surpassed Slo-mo-shun’s 178.497 mph (287.263 km/h) record. Stipulations for the prize were that the boat had to be made in Italy, powered by an Italian engine using Italian fuel, and driven by an Italian driver. Verga and a couple of other Italian racers accepted the challenge. However, the other contenders soon dropped out as complications were encountered.

timossi-verga laura 3 engines

The two Typo 159 engines mounted in their frame, as the frame is installed in the Timossi-built Laura 3. The two-stage Roots-type supercharger can be seen on the front engine. Note the propeller shaft extending below the rear engine.

For the water speed record challenge, Vega turned to Timossi for a specially-built boat, named Laura 3. Verga continued with the Typo 159 power plant but decided to use two of the engines. The Typo 159 design stemmed from the Alfa Romeo Typo 158, originally designed in 1937. Commonly called an Alfetta, for Little Alfa, the engine was a straight-eight that used a one-piece aluminum cylinder head and block mounted to a magnesium alloy crankcase. The cylinders had a 2.28 in (58 mm) bore and a 2.76 in (70 mm) stroke, making the engine’s total displacement 90 cu in (1.48 L). The Typo 159 employed a two-stage Roots-type supercharger that enabled the engine to produce an impressive 420 hp (313 kW) at 9,300 rpm.

The two Typo 159 engines were positioned back-to-back, with a 2-into-1 gearbox positioned between the engines. Combined, the engines produced over 800 hp (597 kW). The gearbox increased input speed so that the propeller shaft turned at 1.133 times engine rpm. The engines and gearbox were mounted in a special, tubular-steel frame built by Alfa Romeo. The wooden Laura 3 was a three-point hydroplane built around the steel power train frame, which was installed in the front of the boat. Aluminum body panels covered the engines and cockpit. Extending behind the cockpit was an aluminum tail that had a ground adjustable rudder for stability. The Laura 3 was 23 ft 7.5 in (7.20 m) long and 8 ft .5 in (2.45 m) wide. The boat weighed 2,028 lb (920 kg).

timossi-verga laura 3 hoist

The completed Laura 3 was an elegant hydroplane. Note the tail extending behind the cockpit. The rudder on the tail was ground-adjustable, and its angle could not be changed while the boat was in motion.

In July 1954, Verga and the Laura 3 made a series of test runs up to 100 mph (160 km/h) on Lake Pusiano. The boat was then moved to the larger Lake Iseo. The testing continued in August, and 165 mph (265 km/h) was reached. Verga made a record attempt on 28 August, hitting 170 mph (274 km/h), but a cooling issue was encountered that resulted in damage to one of the engines. Repairs were made, and testing resumed in September. At higher speeds, Verga fought against the boat’s tendency to pull to the left, but was unable to keep the Laura 3 traveling in a straight line. Efforts to correct the issue had been unsuccessful, and it was decided that modifications to the hull were needed before a record attempt could be made safely. Changes to both sponsons were made, and the boat was completed on 8 October.

timossi-verga laura 3 top

Top view of the Laura 3 illustrates the long bodywork needed to enclose the two Typo 159 engines. Note the eight exhaust stack on both sides of the cowling. The writing behind the cockpit reads Bi Motore Alfa Romeo 159 Scarfo Timossi, with “scafo” meaning “hull.”

Although full testing of the modifications had not been conducted, Verga was confident that Laura 3 could break Slo-mo-shun IV’s record. On 9 October 1954, Verga had waited until midday for the Il Trvano wind to die down over Lake Iseo and settle its waters, but the wind persisted. Verga decided to make a run anyway. As Verga and the Laura 3 sped over Lake Iseo at a speed of approximately 190 mph (305 km/h), the boat hit a couple of small waves that raised its bow. At speed, the aerodynamic forces caught the bow and lifted the Laura 3 out of the water. The boat flipped and rolled before smashing back down into Lake Iseo and sinking. Verga was instantly killed in the crash, and the Laura 3 was destroyed. Verga’s run in the Laura 3 was the last time an Italian tried to set an absolute world water speed record.

timossi-verga laura 3 front

The beautiful Laura 3 sits ready for a test run. Note the individual induction scoops for the Typo 159 engines.

In 2015, the Laura I was restored by Tullio Abbate, Guido’s son, with a non-original (2.5 L Alfa Romeo V-6) engine installed. The boat is on display at the Museo della Barca Lariana on Lake Como. The fate of the Laura II is not known. The tail of Laura 3 was salvaged and preserved.

Note: As previously mentioned, the Laura I and Laura II used the same aluminum bodywork. The boats were very similar but had different sponsons. Some sources state that Laura II set the 800 kg record in 1953. However, newsreel footage and the museum housing the preserved Laura I credit the Laura I with the record.

timossi-verga laura 3 front 2

Mario Verga prepares to make a run in Laura 3. Note the “Mario Verga” text on the front of the boat.

Sources:
Risk Takers and Record Breakers by Doug Ford (2012)
Classic Racing Engines by Karl Ludvigsen (2001)
“The Glorious Obsession of Mario Verga” by David Tremayne, Veloce via www.lesliefield.com
“Aqua Romeo!” by Doug Nye, MotorSport (February 2013)
“Southward Ho!” by Solly Hall, Motor Boating (December 1953)
http://www.vintagehydroplanes.com/boats/laura_3/laura3.html
https://www.threepointhydroplanes.it/abbate-guido-1953-62_c140_en.htm
https://www.threepointhydroplanes.it/timossi-1953-1_c229_en.htm
https://www.threepointhydroplanes.it/timossi-1954-1_c230_en.htm

America’s Round-Engine Airliners

By Craig Kodera
and William Pearce

Some of the most significant engineering and technological breakthroughs of the 20th century centered on the development of piston aero engines from 1920 to 1957. America’s Round-Engine Airliners explains in detailed, well-illustrated, and easy-to-understand terms how these piston-powered radial-engine airliners advanced rapidly. The aircraft originated with fabric-covered fuselages with wooden wings and morphed into all-metal Ford Trimotors as the world’s first true “modern airliner,” the Douglas DC-3, long-range four-engine transoceanic flying boats. Finally, the ultimate “Queens of the skies” Lockheed Constellations, Douglas DC-7s, and Boeing Stratocruisers flew at the zenith of the piston age in the mid-to-late 1950s.

Many magnificent aircraft bridged the gap from small single-engine airliners carrying six passengers in the 1920s to large long-range, four-engine landplanes carrying 60-to-80 passengers and linking all the world’s continents by air in the 1950s. This book not only traces the technical evolution of every radial-engine powerplant used over that time span but also includes interesting and fact-filled sidebars that detail what it was like flying aboard each generation of these aircraft. In 1948, the largest radial piston engine ever produced entered airline service, the mighty 3,500-hp 28-cylinder Pratt & Whitney R-4360; it is one of 12 different radial engines covered in-depth by the authors of this book.

Contents:

Forward by Jon Proctor
Introduction
1. From Inline to Round
2. One Wing, Two Engines, All Metal
3. Presenting the Ship as an Airplane
4. Landplanes Become Viable Contenders
5. Expanding the Envelope
6. Some Serious Air Transports
7. Shrinking the Envelope
8. The Big Time
9. Twilight of the Goddesses
Epilogue: From Best of the Radials to the First Jets
Bibliography
Index

Specialty Press
$46.95 USD
Hardcover
10 in x 10 in
216 pages
500 illustrations
ISBN 978-1580072571
Sample pages (2 MB pdf)

America’s Round-Engine Airliners: Air Frames and Powerplants in the Golden Age of Aviation is available for pre-order through Specialty Press and at Amazon.com or other retailers.