wuzak
Captain
Could it have been done?
de Havilland Vampire FB6 (from Wiki)
General characteristics
Crew: 1
Length: 30 ft 9 in (9.37 m)
Wingspan: 38 ft (11.58 m)
Height: 8 ft 10 in (2.69 m)
Wing area: 262 ft² (24.34 m²)
Empty weight: 7,283 lb (3,304 kg)
Max. takeoff weight: 12,390 lb [44] (5,620 kg)
Powerplant: 1 × de Havilland Goblin 3 centrifugal turbojet, 3,350 lbf (14.90 kN)
Performance
Maximum speed: 548 mph (882 km/h)
Range: 1,220 mi (1,960 km)
Service ceiling: 42,800 ft (13,045 m)
Rate of climb: 4,800 ft/min[44] (24.4 m/s)
Armament
Guns: 4 × 20 mm (0.79 in) Hispano Mk.V cannon
Rockets: 8 × 3-inch "60 lb" rockets
Bombs: or 2 × 500 lb (225 kg) bombs or two drop-tanks
Now, with my basic calcs the speed and thrust equate to a power of around 1900hp.
Using a prop efficiency of 75% means a prop version would need of the order of 2500hp to get the same performance.
The de Havilland Goblin was 50" in diameter and 107" long. Rear part of the nacelle would need some re-profiling.
A Napier Sabre should fit in the hole vacated by the Goblin. The tail pipe would be replaced by an extension shaft, gearbox and pusher prop. The radiators would go in the inner wing in place of the jet intake. An adjustable outlet above or below the centre wing could be made for the radiator ducts. Maybe an exhaust pipe could be routed to assist in extracting the cooling air from the radiators.
The installed weight of the Sabre is going to be about twice that of the Goblin - which will reduce performance. Altitude performance would also suffer with the Sabre as it is only a single stage engine.
Alternatively a pari of B-series turbos could have been mounted in the inner wing - not sure how big they are compared to the wing section. This adds another 400-500lbs, at least, to the installation, further degrading performance.
Late 1943 a Sabre should be good for 2400hp?
The biggest issue I see is that the landing gear on the Vampire was incredibly short. To get a decent sized prop would require lengthening the landing gear, or having a much higher thrust line.
Other issues would be the interference of the airflow around the prop and the booms, and how the airflow across the wings and nacelle effect he operation of the prop. The XB-35 and B-36 both experienced vibrations in the props due to the airflow off the wings, the former more so becuase the thrust line was further away (height wise) from the trailing edge. The XP-56 was predicted to do above 460mph but tests showed top speeds below 400mph - one of the reasosn thought to be the shape of the fuselage causing turbulence ahead of the prop and causing a drop in prop efficiency.
So, what say you? Possible?
de Havilland Vampire FB6 (from Wiki)
General characteristics
Crew: 1
Length: 30 ft 9 in (9.37 m)
Wingspan: 38 ft (11.58 m)
Height: 8 ft 10 in (2.69 m)
Wing area: 262 ft² (24.34 m²)
Empty weight: 7,283 lb (3,304 kg)
Max. takeoff weight: 12,390 lb [44] (5,620 kg)
Powerplant: 1 × de Havilland Goblin 3 centrifugal turbojet, 3,350 lbf (14.90 kN)
Performance
Maximum speed: 548 mph (882 km/h)
Range: 1,220 mi (1,960 km)
Service ceiling: 42,800 ft (13,045 m)
Rate of climb: 4,800 ft/min[44] (24.4 m/s)
Armament
Guns: 4 × 20 mm (0.79 in) Hispano Mk.V cannon
Rockets: 8 × 3-inch "60 lb" rockets
Bombs: or 2 × 500 lb (225 kg) bombs or two drop-tanks
Now, with my basic calcs the speed and thrust equate to a power of around 1900hp.
Using a prop efficiency of 75% means a prop version would need of the order of 2500hp to get the same performance.
The de Havilland Goblin was 50" in diameter and 107" long. Rear part of the nacelle would need some re-profiling.
A Napier Sabre should fit in the hole vacated by the Goblin. The tail pipe would be replaced by an extension shaft, gearbox and pusher prop. The radiators would go in the inner wing in place of the jet intake. An adjustable outlet above or below the centre wing could be made for the radiator ducts. Maybe an exhaust pipe could be routed to assist in extracting the cooling air from the radiators.
The installed weight of the Sabre is going to be about twice that of the Goblin - which will reduce performance. Altitude performance would also suffer with the Sabre as it is only a single stage engine.
Alternatively a pari of B-series turbos could have been mounted in the inner wing - not sure how big they are compared to the wing section. This adds another 400-500lbs, at least, to the installation, further degrading performance.
Late 1943 a Sabre should be good for 2400hp?
The biggest issue I see is that the landing gear on the Vampire was incredibly short. To get a decent sized prop would require lengthening the landing gear, or having a much higher thrust line.
Other issues would be the interference of the airflow around the prop and the booms, and how the airflow across the wings and nacelle effect he operation of the prop. The XB-35 and B-36 both experienced vibrations in the props due to the airflow off the wings, the former more so becuase the thrust line was further away (height wise) from the trailing edge. The XP-56 was predicted to do above 460mph but tests showed top speeds below 400mph - one of the reasosn thought to be the shape of the fuselage causing turbulence ahead of the prop and causing a drop in prop efficiency.
So, what say you? Possible?
