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>>My local club has become eclectic during the past few years, with interests ranging from giant scale, to large and small glow-engine models, EDF (electric ducted-fan) jets, electric-powered airplanes in all sizes, and indoor airplanes flown once a month.
Recently, flat-foam models have made a resurgence with our members in the form of some easy-to-build, great-flying, and imaginative aircraft developed by Joe Gross, an indoor flyer and former FAI aerobatics competitor.
Joe has a range of designs constructed from Dollar Tree (dollartree.com) foam board, and he specializes in providing completely built planes at reasonable prices. Consequently, nearly all of our club’s indoor and park flyers have at least one “JoePlane.”
Joe’s flat foamies tend to have generous, squared-off surfaces and are not intended to be scalelike. I began wondering what could be done with an airplane by using his parameters and giving it sort of a “cartoon scale” flavor. As I thought about a full-scale airplane with a stubby-chubby profile and planform, the Granville Brothers’ Gee Bee came to mind.
I began sketching and cutting foam and in roughly a week, I had something different enough to take to a club meeting for show-and-tell. When several of our members saw it, they said, “Oh, a Gee Bee!” I responded, “Well I wouldn’t go that far. It’s more like a May Bee since it hasn’t flown yet.” Odd how names come about, isn’t it?
The May Bee has been tweaked, modified slightly, and flown extensively, so I’m confident it can provide a quickly built, flat foamie for your hangar that can be flown outdoors or indoors, with only small trim adjustments.
The airplane parts are few in number and are primarily cut from Dollar Tree foam that is guided by full-size templates.
The two major pieces need to fit snugly as they are epoxied together. Note the waxed paper under the joint. Excess epoxy should be cleaned off using a dry paper towel.
The two major parts are the front wing piece and the rear stabilizer piece, epoxied together at the V-shaped notch that is shown.
A 3-inch section of a bamboo barbecue skewer provides the connecting joint between the two elevator halves. The pieces should be dry-fitted together before the epoxy is applied to the skewer and the two foam elevator pieces.
Construction sequence: The May Bee, similar to my other two recent flat-foamie designs, the Avro Vulcan and the Lippisch P.13B, is constructed from two sheets of Dollar Tree foam board. Try to purchase sheets that are as warp-free as possible, and then round up a 2206 1,500 Kv brushless motor or equivalent; a 10-amp ESC; three 9-gram servos; a hot-glue gun, some 5-minute and 15-minute epoxy; and a 7 x 5 propeller. Additional parts and pieces are called out in the following sequenced instructions.
Using them sequentially, in sort of a cookbook fashion, will serve as a checklist of your progress as you move toward completion of your airplane. The few pieces that comprise the model can be cut out quickly by using the full-size templates that are available as a free download (TheParkPilot.com).
I have found it useful to back each template with light poster board. Any type of rubber cement, spray adhesive such as 3M 77 Spray Adhesive (3m.com), or Elmer’s spray adhesive (elmers.com) can be used to attach the templates to the poster board. Scissors or a hobby knife can be used to cut out the patterns.
Notice that two of the larger pieces are half patterns and should be positioned carefully on the foam board with the straight edge of the pattern used as a centerline for flipping the pattern over and tracing the opposite side. Tracing around each pattern should be done with a soft lead pencil so that any stray marks can be carefully erased. A ball-point pen doesn’t offer that latitude.
A #11 hobby knife blade works well for cutting out the pieces. Try to hold the knife as vertically as possible. If you happen to cut an edge that ends up slightly slanted, it can be squared up with a T-bar sander faced with medium-grade sandpaper. Foam board tends to dull cutting edges quickly, so rather than tearing the backing paper, change the #11 blade as needed.
After the parts are cut, it is easier to paint the scallops on the top and bottom of the wing and the color separations of the fuselage pieces before assembly. Because the airplane is constructed with the paper backing of the foam sheets intact, choose a painting method that will not lift or curl the paper by getting it too wet.
Alternately, a coat of oil-based Minwax (minwax.com) can also be brushed on and wiped off with a lint-free rag to seal the paper backing before painting. Be careful to keep it away from the joint lines because hot glue will not stick to a surface coated with Minwax.
I used low-tack artist’s frisket film as a mask for the scallops and color separation lines, and airbrushed the red color using multiple light coats of thinned acrylic enamel. When properly applied, airbrushed paint goes on essentially dry. Patience is the only thing you will need as you alternate between the fuselage and the wing to get the paint to the point of opacity and not dampen the paper backing on the foam board.
Wing scallop lines and color separation lines are marked on the templates for your convenience. Be sure you totally mask out all areas that shouldn’t be painted to eliminate accidental overspray. The painted portions can also be done with rattle can paints such as Testors (testors.com) or another commercial, foam-safe paint, if airbrushing is not your thing. Just be sure to apply several light coats to avoid lifting the foam board’s paper backing, unless you’ve used Minwax to seal it against any moisture.
After the paint has dried, use 5-minute epoxy to join the front wing piece and the rear stabilizer piece, carefully wiping off any excess epoxy that seeps out. Keep the two pieces flat until the epoxy cures. When it has cured, draw a centerline on the top and bottom of the joined pieces to guide you in hot gluing the top and bottom fuselage parts in place. You will need to work quickly before the hot glue sets up.
Experiment with scraps of foam to make a right-angle joint so that you can arrive at a comfort level before the real gluing process begins.
Using the centerline referenced in the previous step, run a bead of hot glue down the line and put the bottom of the fuselage in place, holding it at 90° until the glue cures. Run a bead of glue down each side of the joint to add strength. Flip the wing/stabilizer over and raise it up enough so that it rests flat with the bottom of the fuselage hanging down and not touching anything.
I used piles of books under each wing to give the appropriate clearance. Repeat the gluing operation for the fuselage top, running a bead of hot glue down the marked centerline then along each side of the joint after the base glue cures. Be careful to hold the piece at 90° to the wing/stabilizer platform until it is locked in place.
The addition of the 1/32 round motor mount will complete the basic structure. Run glue down and across the cruciform shape of the front and carefully position the motor mount, holding it firmly in place until the glue cures. For additional strength, add generous glue fillets to all of the surfaces at the back of the motor mount/fuselage joint.
The subassemblies are next. Because they are all control surfaces, sand a 45° chisel shape with the angle facing down on each LE (leading edge) surface of the elevators and ailerons. Be sure and make a right and left side for both! Sand an equivalent chisel-shaped angle to the rudder’s LE using whichever side you choose. A T-bar sander works well for this operation and keeps all LE surfaces straight while cutting the required angle for movement.
The elevators can now be notched as shown on the elevator template to accept the 3-inch bamboo barbecue skewer that will provide a secure connection between the two pieces. Poke a few small shallow holes in the foam in the notch to provide an additional gluing surface. Test-fit the assembly against the stabilizer’s TE (trailing edge) to make sure everything fits and trim it, if necessary, to ensure that the length matches the stabilizer length.
Epoxy the pieces together on top of waxed paper using 15-minute epoxy. Keep everything flat and square to the stabilizer’s TE as the epoxy sets up. After the joints have cured, take a small amount of epoxy and go over them again to make sure glue has reached all of the surfaces.
Hinging the surfaces comes next. Several hinging methods can be used on flat-foam airplanes using various kinds of tape. The one that I like is the quickest and simplest, involving two steps and 1-inch Du-Bro (dubro.com) Electric Flyer Hinge Tape.
Place the two surfaces to be joined butted together, top side up. The chisel shape of the moveable surface should be pointing down. Cut a length of the hinge tape approximately 1 inch shorter than the length of the surfaces to be joined. Lightly and carefully place it lengthwise over the two surfaces, keeping them touching along their seam. Press the tape down firmly after it’s positioned to your satisfaction.
Now cut two 21/2-inch pieces of tape and set them off to the side. Fold the two surfaces you just joined back over each other, keeping the edges even then apply the short pieces of tape perpendicular to the joint. Space them out so that they support the surfaces equally and rub them into place, particularly over the bare foam of the edges.
Flatten out the surfaces and flex them a few times to make sure that the joint moves easily. The rudder uses the same technique as the elevators and ailerons, but the tape should be placed in two locations—one above and the other below the elevator notch on the rudder.
Radio and power installation: Placing the electronics on this model—in particular the three servos—was of great concern in order to meet the projected CG (center of gravity) of 33% of the wing chord, located 61/2 inches back from the front of the motor mount. Although there was some wiggle room to adjust the 2S 500 mAh LiPo battery fore or aft, the CG location marked on the upper fuselage template was the target in order to avoid needing to add any additional weight to the nose.
As you arrive at the locations for your electronics, you might want to experiment with several placement arrangements before committing to any of them. Simply lay the components out on the horizontal surface area and test-balance the airplane each time.
I used three 9-gram Tower Pro (towerpro.com) MG90S metal gear servos. As the photos show, two servos were located in front of the CG and one was directly on the mark. The 10-amp ESC and the Tactic TR624 receiver (towerhobbies.com) were crowded as far forward as possible and held in place with double-sided tape and hook-and-loop material, respectively. A strip of hook-and-loop material for the battery was mounted on the opposite side of the fuselage, as close to the back of the motor mount as the glue fillets would allow.
I screwed the TH 2006-17T 1,500 Kv motor and 7 x 5 propeller assembly onto the motor mount with screws long enough to penetrate the foam. Small holes were cut as required to allow the wire from the ESC to reach the battery and the servo lead wires to connect to the receiver.
The finished airplane shows off its generous surface and control areas, as well as its unusual planform.
Small, easily applied graphics dress up the model in a faux Gee Bee fashion. They can easily be found online, printed on plain paper, carefully cut out, and adhered to the aircraft with a glue stick.
The left underside of the fuselage shows the battery mount, the elevator servo, and the aileron servo that is center-mounted in a hole cut in the lower fuselage. The aileron servo arms extend on both sides of the fuselage.
Control surfaces: Because of the position of the servos, some rather long pushrod runs were necessary. I used .047 music wire for all of the pushrods with Du-Bro Micro 2 Control Horns mounted on the control surfaces using foam-safe CA adhesive. In order to keep the elevator and rudder pushrods from flexing, I used two Flyzone (horizonhobby.com/flyzone) Micro Set A control horns as standoffs for each pushrod and threaded the pushrods through them before connecting everything, as the photos show.
The best technique for connecting the servos, pushrods, and the control horns is to mark the location of the horns and drill holes to mount them, but don’t glue them in place until each pushrod is formed to length with a built-in adjustment kink for minor tweaking.
I recommend a dry run. Because the aileron servo is embedded in a cutout in the lower fuselage with a control arm located on both sides of the fuselage, the servo control arm must be centered before the servo is hot glued in place.
After the aileron servo is firmly mounted, the prefitted pushrods will need to be connected to each side of the servo arm and their respective control horns before the horns are glued in place. Z-bends are used to connect both ends of each pushrod, which imposes some limitations on how and when all connections must be made.
The pushrod locations cross over each other but have plenty of clearance. All of the electronics and controls are located on the bottom side of the fuselage for a cleaner look in the air and on the ground.
This shows one of four Flyzone micro control horns that are used as standoffs for the rudder and elevator pushrods. The standoffs must be threaded onto the pushrods before the rods are attached to the servos and control horns. The micro control horns can be sunk into the foam board at any location and glued in place using foam-safe CA.
Finishing the May Bee: After the electronics and controls are mounted and complete, all that is lacking is to give the airplane some character with Gee Bee markings gleaned from the internet and printed on bond paper. Everything on the airplane was simply cut out with a sharp #11 blade and attached to the surfaces using a glue stick.
The May Bee lettering on the rudder was printed from the stock font styles in Microsoft Word. The canopy was cut from MonoKote trim sheet (both left and right sides are required) and stuck to the fuselage sides.
Because the model is a belly-lander, I added some clear packing tape to the front of the fuselage using a 1-inch strip laid along the bottom of the fuselage. I then notched and wrapped it to protect it against damage.
The May Bee in flight: At this point the work was complete and the fun began. Using the CG location shown, I moved the battery slightly forward to achieve the required balance.
I set my transmitter for low rates and reduced all throws to 70% with 25% exponential. High rates were left at 100% with 25% exponential to soften the controls.
The first test flight was done right at sundown one calm evening in my front yard. With an underhand launch at roughly 50% power and about four clicks of up-elevator, the airplane skimmed along at a 4-foot altitude and made a complete circle, landing just in front of me. I knew it was good to go!
The full maiden flight that followed the next day proved that the model was both aerobatic and stable. Maintaining four clicks of up-elevator for launch (which can be trimmed out after the airplane reaches altitude), it is easy to fly in all modes. It can perform nearly any maneuver you can think of and slows to a hover for landing.
It is unusual and sort of funky looking in the air. Although it’s not scalelike in any way, it has a certain charisma about it that attracts attention.
I would be remiss if I didn’t thank my fellow club member, Harold Anderson, for flying the airplane so that I could get the necessary flight photos, and Joe for his formulaic approach to the flat foamie design that inspired the May Bee. >>