W.Green, G.Swanborough The Complete Book of Fighters

SABLATNIG SF 4

   A Marineflieger demand for a single-seat waterborne fighter for offensive patrol and seaplane station defence resulted in the design of the SF 4, one of five such types ordered for prototype evaluation in June 1916. The SF 4, of which two examples were ordered, was powered by a 150 hp Benz Bz III six-cylinder inline water-cooled engine. The first prototype, delivered on 17 February 1917, was an unequal-span staggered single-bay biplane with twin floats. The X-type interplane struts and the small inverted V-type struts (the latter providing anchorage points above the upper wing for bracing) were faired by fabric. The first prototype proved to possess poor manoeuvrability and the Sablatnig-Flugzeugbau elected to undertake major redesign and to complete the second SF 4 as a triplane (which see). The SF 4 had an armament of one synchronised 7,9-mm LMG 08/15 machine gun.

Max speed, 98 mph (158 km/h) at sea level.
Time to 3,280 ft (1,000 m), 5.5 min.
Empty weight, 1,742 lb (790 kg).
Loaded weight, 2,359 lb (1 070 kg).
Span, 39 ft 4 3/8 in (12,00 m).
Length, 27 ft 4 in (8,33 m).
Height, 12 ft 2 7/8 in (3,73 m).
Wing area, 304.2 sq ft (28,26 m2).


SABLATNIG SF 4DR Germany

   The poor manoeuvrability demonstrated by the first prototype of the SF 4 biplane led to major redesign, the second prototype being completed as an equi-span triplane. This, the SF 4Dr, retained the Bz III engine and single-gun armament of the first prototype, together with the fuselage structure and floats. The interplane and cabane struts were of broad-chord I-type and the tail surfaces were entirely redesigned. No details of the results achieved during flight testing of the SF 4Dr have survived and no further examples were built.

Span, 30 ft 4 1/8 in (9,25 m).
Length, 27 ft 4 in (8,33 m).
Wing area, 305.49 sq ft (28,38 m2).

J.Herris German Seaplane Fighters of WWI (A Centennial Perspective on Great War Airplanes 2)

Sablatnig SF4 Biplane & Triplane

   Designed as a single-seat floatplane fighter, the SF4 was unique in that it was built in both biplane and triplane versions. Both were powered by a 150 hp Benz Bz.III and carried one fixed, forward-firing Spandau machine gun. The biplane, Marine #900, was tested first, and while speed was competitive, it had the lowest climb rate of all the singleseat floatplane fighter competitors. Worse, its maneuverability was poor due to its large wingspan and, despite its multitude of bracing wires, its structure was insufficiently robust; wing vibration was excessive in even a shallow dive. To improve the climb rate a triplane version, Marine #901, was built; like the biplane it was not competitive.
   Company founder Josef Sablatnig was a trained mechanical engineer and a well-known pioneer pilot, so it is especially disappointing that he was unable to design an airframe that was at once light, strong, and streamlined. Although nose entry was streamlined, the wing structure created a lot of drag due to extensive bracing wires, and despite that the wing structure was weak.

J.Herris German Seaplanes of WWI (A Centennial Perspective on Great War Airplanes 15)

Sablatnig SF4 Biplane & Triplane

  Designed as a single-seat floatplane fighter, the SF4 was unique in that it was built in both biplane and triplane versions. Both were powered by a 150 hp Benz Bz.III and carried one fixed, forward-firing Spandau machine gun. The biplane, Marine #900, was tested first, and while speed was competitive, it had the lowest climb rate of all the single-seat floatplane fighter competitors. Worse, its maneuverability was poor due to its large wingspan and, despite its multitude of bracing wires, its structure was insufficiently robust; wing vibration was excessive in even a shallow dive. To improve the climb rate a triplane version, Marine #901, was built; like the biplane it was not competitive.
  Company founder Josef Sablatnig was a trained mechanical engineer and a well-known pioneer pilot, so it is especially disappointing that he was unable to design an airframe that was at once light, strong, and streamlined. Although nose entry was streamlined, the wing structure created a lot of drag due to extensive bracing wires, and despite that the wing structure was weak.


Sablatnig SF-Series Specifications
SF1 SF2 (#609-618) SF4 (#900)
Engine 160 hp Mercedes D.III 160 hp Mercedes D.III 150 hp Benz Bz.III
Span 19.1 m 18.53 m 12.0 m
Length - 9.525 m 8.33 m
Wing Area - 56 m2 28.26 m2
Wt. Empty 1,105 kg 1,078 kg 798 kg
Wt. Loaded 1,650 kg 1,697 kg 1,078 kg
Speed 125 km/h 130 km/h 158 km/h
Climb:
1,000 m 10 minutes - 5.5 minutes
1,500 m - 18 minutes -
2,000 m - - 14 minutes
Armament None None 1 Spandau
Notes:
1: SF3 was powered by a 220 hp Benz Bz.IV; no other data available.
2: SF4 #901 (triplane) spanned 9.25 m, was 8.33 m long, and had a wing area of 28.38 m2.