Micro Mustang (oz2271)

About this Plan

Micro Mustang. Radio control scale WWII fighter model, for micro RC and electric power with brushed can motor.

Update 31/10/2019: Replaced this plan with a clearer copy, thanks to theshadow.

Quote: "In all my years of modeling, I had never built a scale P-51 Mustang. This was kind of odd, as it is one of my all-time favorite machines. I decided to develop this model from the late Fred Reese’s 1/2A P-51D model design, with a variety of subtle changes: some simplify the construction, and others enhance the model’s flight qualities. The resulting model flies great and looks acceptably enough like its full-scale counterpart. Many construction articles start by giving some historical background on the full-scale prototype but, in this case, I’ll assume that almost everyone is familiar with the venerable P-51 and get on with it.

For the record, if you are considering building this model, you should probably have micro experience. To get results similar to mine, you’ll also need the very lightest equipment available. My model is powered by a DC5-2.4 motor that’s geared 4.2:1 and spins a 5.2 x 5.2 homemade propeller. You can make an alternative prop by trimming a Peck-Polymers plastic 6-inch prop to this diameter (some minor re-pitching may be required). The drive battery is a 5-cell pack of 50mAh Ni-Cds that provide at least 4-minute flights.

My RC equipment consists of a Sky Hooks & Rigging Pro receiver along with two very early WES-Technik kit servos and an FMA Mini 5 ESC that I rewired to reduce weight. I fly this package with a Hitec Prism 7X transmitter with a Spectra model, which offers me superb setup capabilities, along with the flexibility of quick frequency changes on the field.

The Micro Mustang is set up to be controlled with ailerons and elevator; this is a very smooth way to fly a low-dihedral, low-wing model. Of course, it has throttle control as well. The actual flight qualities are really sweet. The rate of climb is about 200 feet per minute, and it handles like a much larger model. Smooth rolls and loops are a piece of cake, and when I make a firing run on the weed patch with the 'Merlin' howling, I can almost see the muzzle flashes from the .50s! Power off, the glide is very flat with a smooth flare. The cruising speed is about 20mph, with a top of maybe 25 to 27mph and a landing speed of between 12 and 15mph. Moderate breezes are no problem - especially in an open area away from tricky turbulence. Want to build one? Let’s go.

BASIC CONSTRUCTION:

The most important thing to remember is that the weight is critical! No part of the Micro Mustang needs heavy or hard balsa. I am very satisfied with the wood that I received from Superior Wood Products. The density of the balsa used should be no more than 5 to 7 pounds per cubic foot. The fuselage sides and wing ribs should be cut from the stiffer C-grain stock. The rest of the wood can be very light, clear-grain stock.

The trick to getting a light fuselage is to be sure to remove all of the unnecessary material from the inside of the blocks and nose. My Dremel tool with a large grinder point was my best friend in this process. The goal is to end up with a wall thickness of between 1/32 and 1/16 inch. A very handy way to estimate the remaining material is to hold the part up to a light. None of this is very difficult, but a patient touch is required.

The basic wing is really quite simple: just ribs and sticks with a little sheeting. The aileron linkage will require a light touch to fit the torque-rod bearings without getting glue in the wrong places. I made my bearings from old veterinarian hypodermic needles that were slip-fit onto the 0.020-inch wire. Of course, the tail is just sheet balsa cut to shape and sanded to a streamlined airfoil. Canopy? Well, it would sure look naked without one! I carved a balsa mold and heat-formed mine out of an old plastic blister pack. The spinner is balsa spun in a drill and covered with thin fiberglass and thin CA and then hollowed with a Dremel tool.

Let’s run through the process and touch on some of the fun stuff. You really need to build the wing first, because you’ll need to fit it to the fuselage later. I used medium CA for all of the construction and was stingy with that. The leading and trailing edges (LEs and TEs) are stripped of 1/8-inch-thick balsa. Note the taper in the LE and that the TE is cut to include the ailerons at this stage. Carve and sand the taper into the TE first. When you cut the ribs, it will go faster if you use a glue stick to laminate two sheets of wood and the pattern for each rib station. Pop them apart shortly after cutting and before the glue has a chance to set hard. Strip the spars out of stiff but light 1/16-inch-thick balsa. Put a layer of wax paper over the plan and start sticking things down with pins. I like to clamp the LEs and TEs first, then the bottom sheeting, then the ribs. All dry? Great; go ahead and glue the spar in along with the top sheeting. Remember, the little wedge on the LE makes the Mustang wing distinctive. After everything has dried, pick up the panels and sand things smooth, shaping the LE and cleaning up the 'bumps' around the ribs. The panels are joined with a simple butt joint. Sand them to fit, and glue them without any braces or cloth. Cut the tip blocks out of very soft balsa and glue them into place, except where they touch the ailerons.

Depending on your servo choice, the center-section 'hole' may vary a little in size. Cut away the top sheeting and center ribs where shown. Carefully use a straightedge and a sharp knife to slice off the ailerons and center TE together in one piece. Cut the ailerons free, and trim a little from the ends for clearance. The torque rods are made of 0.020-inch music wire. The bearing tubes are several lengths of hypodermic needle tubing that are slip-fit over the wire. Bend one end of the rod, slip on the tubes and bend the other end as shown on the plan. For a linkage connection, I folded the wire into a tight loop, shrank some narrow heat-shrink tubing over it... "

Update 7/11/2022: Added article (from Backyard Flyer, Winter 2002), thanks to theshadow.

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