Electric P-51 Mustang

Model Airplane News, Aug 2003 by Ziroli, Nick Sr

Easy-to-build backyard fighter

You may look at this model and think, "Oh, no, not another P-51!" Well, it is difficult to find fault with its beautiful lines; the North American P-51 Mustang is without a doubt the most popular WW II fighter ever built. Flying models of the Mustang are available in every size from small rubber-powered versions to giant 1/4-scale gas burners, warbirds, Reno racers and civilian-owned P-51s, and you can choose from many great color schemes, too. And most important, P-51s translate well aerodynamically into flying models. The few changes I made to this model improve its flight performance but are not so drastic as to change the unmistakable Mustang lines. This P-51 is intended for electric power, but a .15- to .25-size engine would also give it good performance, if you prefer glow power. Some reinforcing of the nose would be required for glow engines.

Several electric motors can be used to power this model, from a geared Speed 480 on up to a direct-drive Mega ACM16/15/7 brushless motor. I have powered it with the Astro 801G geared 010 and Astro 803G geared 020 brushless motors using 10, 800mAh Ni-Cd cells. These motors are interchangeable, but the 010 gives very mild performance; the 020 motor turning a 9x6 or 10x5 APC E prop provides the performance one would desire from a P-51.

CONSTRUCTION

* Fuselage. Cut out all fuselage pieces, then glue the two FF-1 pieces together to form the fuselage floor. Assemble formers F-2, 3, 5 and 7, making sure that they are square to the floor. Glue the fuselage sides to the formers and floor assembly, then add formers F-4, F-6 and the cockpit floor CF-1. Pull the tail ends together, and add the remaining rear formers and the top 1/8x 1/4inch stringers. Check that the fuselage is straight, then pull the front ends together, and glue formers F-1 and MM-1 in place. If you plan to use a railmounted motor, omit former MM-1 and install the MM-2 supports and MM-3 rails. Trim the top of the MM-2 supports so that the rails position the motor in such a way that the 2-inch Du-Bro spinner lines up properly with the front of former F-1. Add the bottom nose stringers, and for additional strength, if desired, fill in the space between the nose stringers with 3/16-inch balsa and sand to shape. Cover the cockpit side areas with 1/16-inch CS-1 pieces. Dampen the outside surfaces to aid in bending.

Set the servos in place, and install the small plastic pushrod guides; these can be the inner tube of a plastic pushrod set. Use the 1/32-inch pushrod wires to ensure that the guide tubes line up with the servo-output arms. I used Airtronics 94091Z Super Microlite servos on all control surfaces. The output-arm pushrod holes on most servos are 1/16-inch diameter and must be "bushed" to fit the 1/32-inch wire. Insert a short length of 1/16-inch o.d. aluminum tube in the servo-arm hole, and flare the ends to hold it in place. Small 1/16-inch-o.d. eyelets also work well.

Install the bottom cross-brace FB-1. This prevents the sides from collapsing when hand-launching. Add the FS-1 radiator sides, then cover the fuselage bottom with 1/16inch balsa lengthwise at the rear and cross-grain on the curved radiator. Round the bottom corners. Glue the WS-1 and WS-2 wing-saddle doublers to the inside of the wing opening. Glue the wing mount plate pieces WM-1 and WM-2 together, install the 6-32 blind nut, then glue the assembly securely into place.

Very lightly tack-glue the hatch-edge pieces FH-1 to the top of the fuselage formers so they are even with the inside edges of the sides. Add the hatch formers and the top stringer FH-2. Place a thin cardboard spacer and a piece of plastic wrap between FH-5 and F-4, so you don't glue them together. Plank the hatch partially with 1/16x 1/4-inch balsa strips. So the hatch isn't glued to the edges of the fuselage, start to plank 1/4 inch up from the fuselage sides. The hatch is held in place with two dowels that slide into holes drilled into the lower portion of former F-1. The top of F-1 forms the front former of the hatch after it is cut away from the bottom part of the former. Once the planking glue has dried, remove the hatch by finishing the partial cuts through F-1 (see plan), add the remaining planks and sand them smooth with a hard sanding block. Glue two 1/4-inch lengths of 1/8-inch-diameter dowel into the holes in the U-shape hatch-mount former FH-6. Tack-glue FH-6 to the top rear part of former F-1 with a dab of thick Zap CA, then install the hatch so the dowels fit into the holes in F1. After the glue has dried, remove the hatch and finish gluing FH-6 to the top of F-1 with thin Zap. The aft part of the hatch is held in place with a latch made from a small plastic tube and a bent piece of wire. It's detailed on the plan.

Build the tail surfaces from 3/16-inch-thick balsa strips over the plan. The trailing edges are 1/8x 1/4 inch and must be blocked up 1/32 inch to center them properly on the ribs. Block-sand the ribs to blend into the trailing edges. If desired, you can cut the tail surfaces out of light 3/16-inch sheet balsa with lightening holes cut as indicated on the plan. If you plan to use landing gear, bend the tailwheel strut to shape and attach it to the rudder.