Junkers EF 140 (oz16216)

About this Plan

Junkers EF 140. Free flight scale model for rubber power.

Direct submission to Outerzone.

Quote: "JUNKERS/OKB-01 (EF-140) 27” TWIN RUBBER/SINGLE PUSHER. CONSTRUCTION ARTICLE.

HISTORY: The EF 140 jet bomber was built in the USSR under the auspices of the design bureau OKB-1 (comprised mainly of former Junkers engineers), so at first glance it would not qualify for inclusion in this website. However, I have opted to include the EF 140 because it was derived from the Junkers Ju 287 and EF 131 forward-swept wing jet bombers.

In late 1947, Brunolf Baade and other veteran Junkers engineers at design bureau OKB-1 began work on a twin-engine derivative of the EF 131, designated EF 140. The appearance of the EF 140 was similar to that of the EF 125 twin-engine variant of the Ju 287, but the EF 140 differed from the EF 125 in having two Mikulin AM-TKRD-01 turbojets in place of the Junkers Jumo 012 or BMW 018 turbojets. Unlike the EF 131, the EF 140 lacked a tail-mounted gun turret and the cockpit was fitted with Soviet and American flight instrumentation and electronics, including a Norden bomb sight, a Honeywell C 1 autopilot, and an SCR-269 radio-compass (built under license in the Soviet Union as the ARK-5). Defensive armament comprised a pair of turrets with 20 mm cannons, one slightly aft of the cockpit and one underneath the forward fuselage. The cockpit also accommodated four crewmen (pilot, dorsal turret gunner, radio operator/ventral turret gunner, and navigator), and it was provided with armor for protection against enemy aircraft.

A full-scale mock-up of the EF 140 was built and inspected on March 20, 1948, and the airframe of the third EF 131 prototype (EF 131 V3) was used in construction of the EF 140. The EF 140 V1 was completed on July 22 (by which time development of the EF 131 was halted), and in August it was disassembled and transported to an airfield in Tyoplyy Stan, where it was reassembled on September 3. On September 30 the EF 140 V1 made its first flight, and 17 flights were made until May 24, 1949. – Blog at Wordpress

CONSTRUCTION:

WING: The wing is built using the Dave Rees’ Sliced Rib Construction Technique. This builds a very strong and light wing. Mike Stuart has a great tutorial on this construction technique on his site ffscale.co.uk here’s a link to the tutorial: https://www.ffscale.co.uk/rees.htm All the dimensions are found on the plans. The wing can be built in one piece if building the twin rubber powered model. That way the whole wing can pass through the fuselage and the jet/rubber prop nacelles added after the wing is attached to the fuselage. If building the single pusher rubber power, build the wing in two panels and mount them to the fuselage separately using a jig to hold the fuselage and wing panels in alignment. Maxfliart shows this type jig in his video build of the Beech Twin Staggerwing, episode #7: https://www.youtube.com/watch?v=oHvJr5voVUw

HORIZONTAL STAB: The stab is built as one piece from 3/32” sq balsa for the twin rubber powered model. If building the single pusher, the horizontal stab is built in two panels attached to the outside of the fuselage to 1/16” sheet fill in place of the hz stab slot for the one piece hz stab.

FUSELAGE: The fuselage is built using the box style technique. This is where the side of the fuselage is built using 3/32” sq longerons and uprights. When the side is finished, build the second side over the first so you will have two identical sides. These sides are then joined over the top view of the fuselage using the 3/32” sq cross members. I recommend joining to start at the wing area first, adding the top and bottom crossmembers. I recommend using right triangles or equivalent to hold the fuselage sides vertical. Once this is dry begin adding the crossmember towards the tail. Then moisten, with hot water, the longerons from the wing leading edge towards the nose of the aircraft to allow the longerons to bend easier. Use the right triangles to hold the sides in position as the crossmembers are added to the fuselage sides. Once the fuselage sides are completed add the top 1/16” formers to round out the top of the fuselage and add the 1/16” stringers to finish off the top of the fuselage. Fiddly Bits: turrets, ventral radar bump are made of foam, balsa block etc. If using balsa block I recommend hollowing out the balsa to lighten the pieces.

NACELLES: The nacelles are built using a ladder jig as used when building fuselages, where the formers are mounted on the jig and then the stringers are added. Add your favorite prop block and anchor blocks for the motors. I recommend making your own props from clear plastic from the clear plastic cheese puff or pretzel containers found at the market. Clear 2 liter soda bottles will work as well. Maxfliart shows this technique in a video tutorial in his Free Flight Basics #11: https://www.youtube.com/watch?v=lV7z8MGE460 Remember you’re making two (2) nacelles! Once the body of the nacelle is made add the mounting fin to the top rear of the finished nacelles from 3/32” sheet balsa and sand to airfoil shape tapering to 1/16” at the exhaust end of the nacelle. Note the nacelle notches to the wing so the nacelle needs to have a top former aligned with the wing leading edge.

Many thanks to Steve and Mary for this great site!"

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