3D Mustang (oz14237)

About this Plan

3D Mustang (aka Not Another Mustang). Sport/3D profile foamie model, for electric power. Wingspan 34 in, wing area 400 sq in.

Quote: "Even if it is probably the most recognized and favorite airplane of all time, does modeling really need another P-51 Mustang project? It has been done in about every conceivable format, from rubber-powered, tissue-covered, free-flight models, to profile control liners, to big scale remote-control (R/C) unlimited racers.

Yet, here it is again. This version of the P-51 is a compact, electric-powered R/C profile foamy. It is equipped with the latest in motor and battery technology for a great power-to-weight ratio, so it has the aerodynamics to do 3-D maneuvering. Ever see a Mustang hanging on its propeller and doing torque rolls, or flying the Harrier maneuver? This P-51 model will - provided, of course, that the pilot has the skills for that kind of flying. Yes, it has control surface proportions unlike those of any full-scale Mustang, but if you can accept the scale design compromises made, this aircraft is still recognizable as a Mustang and you can have some wild fun flying it.

3D Design: To morph a P-51 Mustang into a 3D-capable airframe, certain design characteristics are needed: plenty of fuselage side area, very large control surfaces (elevator, rudder, and ailerons), a fairly long tail moment, and a generous amount of wing area. A little surfing on the Internet shows that there have been plenty of profile foam 3D-capable designs posted: I looked at the 3DX, the Trident, the Tempest, the Tribute, the Hovering Cobra, the Vortex, and the Foamtana, among others. All of them helped me to lay out this Mustang. Consequently, my Mustang came out with a 34 in wingspan, 400 sq in of wing area, and a length of 34 in. With a 1200-mAh battery pack, this model has a ready-to-fly weight of 13 oz, so its wing loading works out to be 4.7 oz/sq ft. A 1500-mAh battery pack would add about another ounce, and would not hurt the performance.

Fan-fold foam and Depron foam are becoming pretty common and are accepted by many modelers as an electric-model construction material. Both cost little and make for quick and easy building of this model. These materials accept water-based craft paints, so you can paint and detail your model if you want, too. Bear in mind, however, that sheet-foam models are still pretty fragile. I wouldn't regard one as a long-lived airplane. Fly it with abandon, and try anything - you can either repair it quickly or build another one. That is the beauty of sheet-foam, flat-plate profile construction.

Power to Go: Also very important for wild flying is plenty of power. Along with many other modelers, I like using the GWS gearbox setup because of its simplicity, choices of gear ratios, easy availability of replacement parts, and easy mounting to the airframe. For plenty of power, brushless motors are the way to go. I've used the Razor 350 and HiMaxx 2015-4100 brushless motors in the GWS gearbox with their D 6.6:1 ratio and an 11 x 8 or 12 x 6 propeller, along with the Castle Creations Phoenix 25 electronic speed control (ESC) and 3-cell Lithium Polymer (Li-Poly) battery packs. I've found these to be reliable setups with plenty of thrust for this size and type of aircraft. However, I'm sure there are many other brushless motor setups that could be used. I'm no expert on this stuff, so I appreciate the fact that many modelers share their experiences to the benefit of us all.

Slice Away! Building from sheet foam isn't difficult. I cut up my plans, or a copy of them, and use the paper patterns to cut out the foam parts. A very sharp modeling knife or a single edge razor blade works fine. Carbon-fiber tubing is good for reinforcing the foam and is available in different sizes from a number of modeling sources. Carbon-fiber tubing with a diameter equal to or smaller than the thickness of the foam is fine for reinforcing. I glue the tube spar to the wing panels with 5-minute epoxy, laying the parts out over waxed paper on my building bench. After beveling the leading edges of the ailerons, I hinge them to the wing with clear packing tape. Thinner tape is better for hinging. I put the tape on the top surface first, then bend the aileron back and put the tape on the bottom side. Be sure the tape is stuck firmly to the foam. I epoxy the carbon fiber tube to the top portion of the fuselage only, and then epoxy that part of the fuselage to the top of the wing. The lower portion of the fuselage is then epoxied in place, and the horizontal stab, already hinged, is added to the fuselage.

I use small pieces of 1/16 plywood to retain the servos, mounting them with small screws. To save weight, some modelers just push the servos into tight-fitting holes cut in the foam surfaces and retain them with some hot glue or silicone. The aileron servo is installed in the bottom surface of the wing, close to the fuselage. A hole is cut through the fuselage to clear the servo arm and aileron linkage. I make the control horns from 1/16 plywood and epoxy them into the control surfaces. The elevator and rudder servos are installed in the fuselage, above the wing. I use 0.047 music-wire pushrods for the elevator and rudder horns, with Z-bends at each end of the pushrods. The wire pushrods are supported by a plywood brace glued into the fuselage between the servo and the tail surfaces.

To mount the HiMaxx 2015-4100 motor in the GWS 300-series gearbox, I used the machined aluminum adapter plate available from www.allerc.com to make the job easy. I'm using the 6.6:1 gear ratio and either an 11x8 or 12x6 GWS prop. For the battery pack installation below the wing, I epoxied two pieces of 3/8 square balsa, each with two short 1/8 dowel pieces, to the lower wing surface. Rubber bands hold the battery pack in place. There's space for different types of battery packs, and the battery can be shifted fore or aft for balance adjustment. The speed controller and receiver can be held in place on the fuselage sides with Velcro. I also wrapped the controller and receiver with some thin foam and plastic tape for a bit of protection against crash damage..."

Mustang, Quiet Flyer, June 2004.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ.

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