Construction: Fun-Scale Zero

An easy to build, profile WW II warbird

An easy to build, profile WW II warbird

To those who still like to build their own models rather than purchase an ARF, a sheet foam profile model offers a lot of flying fun for a relatively small investment in materials, cost and construction time. The sheet foam profile A6M Mitsubishi Zero is a little different in that it utilizes a hot-wire-cut foam wing rather than a flat-sheet foam wing. I first tried a foam wing on a light profile model as a way to get better flying capability in windy conditions. I liked the way it flew, so I used this construction technique to develop some “fun” warbirds. They fly well, had plenty of aerobatic performance and I like the way they looked. Also, the cut foam wing cores are available at a low cost. I’ve built an F6F Hellcat and some modelers who have built it said they needed a Japanese Zero to fly combat with. They were right, the Hellcat and the Zero were a frequent WW II matchup. Therefore, with the help of my friend and CAD draftsman Bob Kruger, here is the Zero, ready for some combat flying!

WING CORES

There are a number of different sheet foam materials available that can be used for this model. The plans show the top view of the wing and the root and tip templates if you want to cut your own wing cores. If you are looking to save some time and effort, foam wing cores can be purchased from The Core House. The Too Windy Wing cores are hot wire cut and work great with the Zero. The cores are cut to a standard length of 24 inches, and you trim them for the proper length, planform, and tip shape. For more information contact Phil Cartier at (717) 566-3810.

CONSTRUCTION

I cut the sheet foam parts out with a metal straightedge and a sharp no. 11 hobby blade. The 1⁄32-inch plywood doublers on the nose section really strengthen the fuselage against those rough landings. A carbon-fiber tube epoxied in the fuselage adds sufficient strength for the profile construction to work. If you have trouble finding carbon fiber tubes, a strip of basswood or spruce will work almost as well. If the sheet foam you use is less than 1⁄4inch thick, I have used 1⁄4 x 1⁄2 inch basswood for the fuselage stiffener, and sanded and planed it to a 5mm thickness so it’s flush with the fuselage thickness. I’m always anxious to get the model done in a hurry so I use 5- and 15-minute epoxy for the assembly work. Epoxy works well for most of the sheet foams, but the types with thin plastic covering on both sides will need a bunch of pinholes poked through the plastic skins where the epoxy will be applied. I use 1⁄8 x 3⁄8-inch basswood for the wing spars, although hard balsa should also work fine.

To assemble the wing panels to the fuselage, a 1⁄8-inch vertical plywood joiner passing through a slot in the fuselage goes into slots in the foam cores between the upper and lower spars. An opening for the wing to pass through is not cut through the fuselage, only the vertical slot for the wing joiner; the wing panels butt up against the profile fuselage. Easy to do and plenty strong!

The foam cores can be covered with any low-temperature iron-on material. I use the SLC material sold by The Core House—it’s very thin, light weight, irons on easily and accepts just about any type of paint. Hinging all the control surfaces is done with clear packaging tape

in the usual foamy flyer manner. The leading edges of the ailerons, elevator, and rudder are cut and sanded to a 45-degree angle, and the tape applied to the upper surfaces first. Then, with the control surfaces folded upward, tape is applied to the bottom, pushing it up into the hinge gap and sealing it to both edges. This provides free movement and a strong, completely sealed hinge gap.

HARDWARE

The servos are installed by cutting holes into the foam so the servos are a tight push fi t, and then secured in place with a few dabs from a hot glue gun. Hot glue guns are inexpensive and handy for this type of airplane. Slots are cut into the control surfaces and 1⁄16-inch plywood control horns are then epoxied into place. For all the pushrods I use 0.047inch wire, with Z-bends or the Du-Bro Mini-EZ connectors on the ends. Short pieces of plastic tubing glued to the fuselage sides keep the pushrods from flexing. The speed control, receiver and LiPo battery are attached to the fuselage with Velcro tape, and for the battery, I cut slots through the fuselage for a Velcro strap to pass through and hold it securely in place.

I spray paint my foam planes with low cost, water-based acrylic craft paint available in many colors at most arts

The author/designer Dick Sarpolus holds his model for the camera. A local park or soccer field is fine for this profile warbird.

The brushless outrunner motor is screwed to the plywood firewall. Plywood nose section doublers add strength and stiffness to the fuselage.

Here are all the basic parts for the Zero. The foam wing cores are available commercially, the sheet foam fuselage, tail surfaces, and ailerons are all made from your choice of sheet foam. I use Depron but insulation foam also can be used.

Here you see the basic airframe assembled and ready for paint.

Bottom view of completed airplane and aileron servo installation. The receiver and speed control are held in place with Velcro, the LiPo battery pack is mounted with Velcro plus a strap going through slots in the fuselage, for security.

The completed Zero ready for its first flight.

Canopy area, light blue paint and marker pen outlining adds to scale appearance.