AMA Plans Service Showcase-2013/04
NBP-60: An electric model with power in the back
Al Masters built the NBP-60 with the Astro 60 motor drive installed at the rear—out of harm’s way—hence the name NBP-60 (Never Break a Prop). He designed it as a challenge for modelers entering electric flying who wanted the feel of a fuel-powered aircraft.
Overview / Specifications
- Type: Rear‑drive electric model (pusher)
- Builder/designer: Al Masters
- Empty weight: 9 pounds, 10 ounces
- Wingspan: 65 inches
- Battery: Up to 34 sub‑C cells (mounted forward to offset motor/prop weight)
- Motor: Astro 60
- Propeller: Zinger 14 x 8 pusher, cut to 13 inches and balanced
- Typical flight times:
- Reduced‑throttle: ~10 minutes
- Throttle‑up aerobatic: 4–5 minutes
Construction
Al designed the fuselage to hold a maximum of 34 sub‑C cells in the nose to offset the 23‑ounce motor and propeller weight. The NBP-60 was not difficult to build, but Al paid careful attention to weight control by selecting light materials wherever possible. Except where specified on the plans, he used light balsa with a 4- to 6‑pound density.
The fuselage nose section used plywood for strength. Fuselage bulkheads and formers were made from balsa, Lite Ply, and birch plywood. The motor‑mount tube was made from 12 inches of 1/64‑inch plywood wrapped around the motor.
The tail was kept lightweight: the upper fin and stabilizer were built together, and 1/16‑inch plywood was added after the stabilizer was removed from the building board. Hinges were installed, the complete tail assembly was covered, and then attached to the fuselage.
Electrical
- Motor wiring: 12‑gauge stranded silicone wire to fit into Sermos connectors
- Cell interconnects: Copper braid for the NiCd pack
- Arming switch: Radio Shack MS‑169
- Protection: 30‑amp inline fuse
Al noted that the Astro 60 with 34 cells produced plenty of power. He said, “Getting into the electric side of the hobby has been easier than I anticipated.”
Landing Gear
The model was designed to use Spring‑Air heavy‑duty landing gear retracts. To save weight, Al bushed the main struts with K&S brass tubing so they would fit the retract unit with 5/32‑inch struts. The nose wheel strut was a standard 3/16‑inch unit.
Covering and Finish
The NBP-60 was covered with MonoKote iron‑on film. Al used clear MonoKote for the canopy. Final trim included the Zinger propeller (cut and balanced as noted).
Availability
The NBP-60 was featured in the September 1997 Model Aviation (MA) as AMA Plans Service listing 838. Plans are available for $24 plus shipping and handling. AMA members can access the MA Digital Library on the AMA website for more information (see page 151), or visit www.modelaircraft.org/plans.aspx for ordering details.
Transcribed from original scans by AI. Minor OCR errors may remain.
