My “Build of the Month” (BOTM) Series was created to help those who are trying to get started in building their own Radio Controlled (RC) Model Aircraft.

  "Aerofred.com" and "Outerzone.co.uk" are two of my favorite web sites to obtain free RC model airplane plans for my new builds. Additionally, they like to post images of Builder's models, and both sites have posted my RC model images and build descriptions under the heading of the associated aircraft model. Other good sources for free plans are: "Hip Pocket Aeronautics Builders' Plan Gallery", "Vintage & Old-Timer RCM Free Plans", "James Hatton Blog Free Plans and Articles", "Hlsat Blog RCModeler Free Plans and Articles", and "Don Dewey Memorial RCM Plans Collection."

  If you are currently not an active builder, and you would like to be, my BOTM Series is a great place to start. If you have an RC model aircraft that you would like to see featured in this section or feel others may find interesting, please let me know and I will make every attempt to find scratch build plans, photos, and maybe even a published build article, which I will then post in one of my future BOTM editions. Just send me an email @: Build of the Month.

Build of the Month Series - May 2026 Edition

  I hope you enjoyed last months BOTM Edition on the DG-600 Jetpower. If you have an RC model that you would like to see featured in this section or feel others may find interesting, please let me know and I will make every attempt to find scratch build plans, images, and maybe even a published build article, which I will then post in a future edition. Just send me an email @: Build of the Month.

  Ok, now lets see what I have for the month of May 2026. During my search for my March 2026 BOTM Edition, there was another aircraft that met the criteria of a military aircraft from the “post WW-II” period, had to have twin engines, or more, and something that had several RC model scratch build plans to select from. Given these same requirements, this month features the Douglas A-26 Invader, an American twin-engined light bomber and ground attack aircraft.

Images Source: Douglas A-26 Invader Webpage.

  First, a little history on the actual Douglas A-26 Invader. The Douglas A-26 Invader (designated B-26 between 1948 and 1965) is an American twin-engined light bomber and ground attack aircraft. Built by Douglas Aircraft Company during World War II, the Invader also saw service during several major Cold War conflicts. A limited number of highly modified United States Air Force aircraft served in Southeast Asia until 1969. Not only was it a fast aircraft capable of carrying a large bomb load, but it could also be fitted to produce a formidable ground-attack aircraft.

  The Counter Invader was a highly modified version of the Douglas A-26 Invader, a World War II attack bomber. Redesignated B-26 in 1948, the Invader served again during the Korean War (1950-1953), mainly as a night intruder against North Korean supply lines. It was removed from service in 1958, but in 1961 the USAF recalled many Invaders for use as tactical bombers in Southeast Asia. Combat duty and two decades of wear took their toll, and in 1964 the B-26s again were removed from service.

  In 1966 the old bomber was resurrected once more when the improved B-26K Counter Invader returned to Southeast Asia for ground-attack missions along the Ho Chi Minh Trail. Modified by On Mark Engineering, the B-26K had a rebuilt fuselage and tail, strengthened wings, improved engines, reversible propellers, wing-tip fuel tanks and other refinements. Redesignated A-26As, Counter Invaders remained in Southeast Asia until 1969 and retired from USAF service.

• Actual Douglas A-26 Invader Specifications:
• Crew: 3
• Wingspan: 70 ft (21 m)
• Length: 50 ft (15 m)
• Height: 18 ft 6 in (5.64 m)
• Wing area: 540 sq ft (50 m2)
• Airfoil: NACA 65-215
• Empty weight: 22,370 lb (10,147 kg)
• Gross weight: 27,600 lb (12,519 kg)
• Max takeoff weight: 35,000 lb (15,876 kg)
• Fuel capacity: 925 US gal (770 imp gal; 3,500 L) normal + optional 675 US gal (562 imp gal; 2,560 L) ferry tank in the bomb bay; Oil capacity 60 US gal (50 imp gal; 230 L) in two nacelle tanks
• Powerplant: 2 × Pratt & Whitney R-2800-27, -71, or -79 Double Wasp 18-cylinder air-cooled two-row radial piston engines, 2,000 hp (1,500 kW) each for take-off
• Propellers: 3-bladed Hamilton Standard Hydromatic, 12 ft 7 in (3.84 m) diameter constant-speed fully-feathering propellers
• Maximum speed: 359 mph (578 km/h, 312 kn) at 16,700 ft (5,100 m) (normal rated power)
• Cruise speed: 266 mph (428 km/h, 231 kn) at 5,000 ft (1,500 m) (62.5% rated power)
• Range: 1,600 mi (2,600 km, 1,400 nmi) without ferry tank at 5,000 ft (1,500 m) at 206 mph (179 kn; 332 km/h)
• Combat range: 700 mi (1,100 km, 610 nmi)
• Ferry range: 3,000 mi (4,800 km, 2,600 nmi) with ferry tank at 5,000 ft (1,500 m) at 210 mph (180 kn; 340 km/h)
• Service ceiling: 28,500 ft (8,700 m) ; 14,400 ft (4,400 m) on one engine
• Armament
• Guns: 6 or 8 0.50 in (12.7 mm) M2 Browning machine guns in solid, "all purpose" nose: or 2 × 0.50 in (12.7 mm) M2 machine guns in glass "bombardier" nose
• Up to 8 × 0.50 in (12.7 mm) M2 machine guns paired in four optional under wing pods: or 3 × 0.50 in (12.7 mm) M2 machine guns in each outer wing panel
• 2 × 0.50 in (12.7 mm) M2 machine guns in remote-controlled dorsal turret
• 2 × 0.50 in (12.7 mm) M2 machine guns in remote-controlled ventral turret
• Rockets: Up to 10 × 5-inch (12.7 cm) HVAR rockets on "zero length" launch pylons, five under each outer wing panel
• Bombs: Up to 6,000 lb (2,700 kg) capacity - 4,000 lb (1,800 kg) in the bomb bay plus 2,000 lb (910 kg) carried externally on underwing hardpoints

Images Source: Outerzone A-26 Invader (oz10379) webpage.

  RC MODEL CONSTRUCTION: The RC 1/15th Scale A-26 Invader model featured this month was designed by Dick Sarpolus and featured in Flying Models Magazine, August 1985. The plan drawing is clean and has a complete set of fuselage formers. As quoted from Dick Sarpolus in his article: “This A-26 model is stand-pretty-far-off scale; my primary aim was to get an easy flying twin engine model, easy to build, with a reasonably scale appearance. As a scale reference source, I used the Squadron/Signal publication, A-26 Invader in Action. This book provided a good 3-view drawing along with many, many photographs of all the A-26 details and design variations.

  In laying out the model design, the biggest intentional deviation from scale was an increase in the wing chord, to get more wing area while still trying to keep the overall appearance close to scale. I was concerned about the power available from two tired old OS .19s, so wanted to keep the model to a reasonable size for the engines. The result was a wingspan of 54 inches and a fuselage length of 42 inches. The wing area is 480 square inches, and a semi-symmetrical airfoil is used for good lift and flight characteristics. The root airfoil is 17% thick, and the tip is 18% thick; the result is that this wing doesn't want to stall. Horizontal stabilizer area is 19% of the wing area, maybe a little small but okay. The vertical fin area is about 11% of the wing area, more than enough for stability. I wanted plenty of vertical fin area for safe single engine flight operation.

  Construction is conventional and straight-forward. The fuselage is a basic box, with tri-angle stock in the corners to permit rounding to shape. Tail surfaces are sheet balsa. Engine nacelle's are box construction with shaped blocks where needed. Engine cowlings are made from the plastic bottoms on large soda bottles; their diameters were reduced by cutting and overlapping to get the right size. The paint used, butyrate dope, didn't stick too well to the plastic cowls but they're sure low cost and easy to use. Rather than try to vacuum form a clear plastic canopy, the canopy area was shaped from balsa blocks and airbrushed to simulate the window areas.

  The wings are conventional with top and bottom spars and are completely sheeted with 1/16 inch balsa. A built-up wing was used rather than foam as we felt it would be easier to install the aileron bellcranks and throttle linkages in the built-up structure. The completed wing, with two engines, seems heavy, but the fuselage seems light. The total weight of the prototype is 5.75 pounds.

  The plane handles pretty much like a sport pattern model; rolls, loops, and inverted flight are easy although we don't plan to get too wild with it. Flaps are not needed as it will slow up enough for easy landings. Bomb bay doors would be a fun addition and maybe we'll try that.”

• A-26 Invader RC Model Specifications:
• Aircraft Type: Stand-Off Scale Warbird
• Flight Performance Category: General Sport Scale
• Scale: 1/15th
• Wing Span: 54″
• Wing Chord: 10.8″ (centerline) - 6.7″ (wing tip)
• Total Wing Area: 480 sq. in. (approx.)
• Wing Location: Mid-Fuselage Wing
• Airfoil: Semi-Symmetrical 1.88″ (centerline) - 1″ (wingtip)
• Wing Platform: Double Tapered
• Fuselage Length: 42″
• Fuselage Width: 3″
• Horizontal Stabilizer Span: 18″
• Horizontal Stabilizer Chord: 6″ (centerline) - 4.4″ (stab tip) (w/elevator)
• Horizontal Stabilizer Area: 90 sq. in.
• Stabilizers Airfoil Sections: Both 1/4″ Flat
• Vertical Stabilizer Height: 8″
• Vertical Stabilizer Chord: 7.3″ (base) - 5″ (tip) (including rudder)
• Center of Gravity Location: 2-2.65″ back from wing root leading edge
• Required No. of Channels: 4 - Throttle, Rudder, Elevator, and Ailerons
• Landing Gear: Tri-cycle Gear
• Ready to Fly Weight: 92 oz. depending on power system selection
• Glow Fuel Engines: Twin .19 cu. in. two-stroke
• Fuel Tank Size: 4 - 6 oz.
• Electric Powered: Output of 400 watts each, 40 Amp ESCs, 3-cell LiPo pack sized up to 3,500 mah.

  The A-26 Invader RC model in this months BOTM Edition can be built from a set of plans and article that are available @: Outerzone A-26 Invader (oz10379) webpage.

  Should you like a larger A-26 Invader RC model, you can build a 100″ wing span, twin .45-.60 two-stroke engines version designed by Gary Fuller from a set of plans and RCM article that are available @: Aerofred, or Outerzone.

  I hope you have enjoyed this months selection, and just maybe, I have spurred some interest in trying your hand at building an RC model airplane.

Until next month - Keep the Balsa Dust Flying!!!

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