Paul Gentile's Split Stik
Kids often devise the simplest solutions to the most complex problems. One day, I watched as my five-year-old son taped a flat piece of cardboard to a stick and made an airplane. He ran around the house flying his new airplane, and his pride of accomplishment showed me how a simple solution can often be the best way to go.
My eldest son and I headed down to the workshop, and in something like an hour we had the first Split Stik design built. No plans and no fancy equations, just a 2-foot length of spruce, some 3mm Midwest Cellfoam 88, and the power and RC components I had left over from the RaEza design (Park Pilot, Fall 2008).
The very next day, we all took a trip to the park to try the new design, and with just a few tweaks, it really flew well. The Split Stik has been in my hangar for a year now. We’ve taken it on numerous family trips and taught several dozen people to fly with it. It flies indoors and outdoors, and is a real joy to just tool around.
I’ve made some revisions since that original Split Stik. The wing is now a bit larger, and I’ve moved a few components around to balance the model a bit better.
Prepare for the project with a 3mm sheet of Midwest Products Cellfoam 88, a 24-inch piece of 3/8-inch by 3/16-inch Midwest spruce, and a 24-inch length of 3mm carbon-fiber rod. You’re in luck if you built the RaEza, because all of its equipment can be used here.
My Split Stik power train is an E-flite Park 180 brushless motor, a GWS 3030 propeller, an E-flite 10 Amp ESC and a 350mAh Thunder Power LiPo pack. Split Stik onboard RC components are a Spektrum AR6100 receiver and two E-flite S60 sub-micro servos.
Other supplies and tools you will need are a sharp hobby knife, a small hobby saw, a hot glue gun, small pliers, a straight edge, Du-Bro Electric Flyer Hinge Tape, 1/16-inch-diameter music wire, fishing line, and two carbon-fiber or wire rods for the controls. The Split Stik is not a very technical airplane, so If you have built airplanes before or have leftovers from events with other park flyers, you may already have usable components.
Split Stik parts, cut from Midwest 3mm Cellfoam 88 and ready for assembly.
Close-up shot of the fuselage and carbon-fiber spar. Use fishing line as a backup to hold the spar in position.
With the tail feathers, spar and landing gear attached, the project is starting to look like an airplane. The landing gear can be recycled from another plane or you can bend your own from music wire.
The control linkage can be fashioned from lightweight carbon-fiber rod.
Building the Split Stik starts with the wing and tail feathers. Make a copy of the plan and tape it to the Cellfoam 88 sheet. Trace and cut out the wing, elevator and rudder. Before liberating the parts from the foam, use a straight edge and a light marker to transfer the center lines and any markings to the foam. This will make it easier to keep everything square when you attach the parts to the fuselage.
The hinge-side edge of the rudder and elevator need to be beveled at a 45-degree angle so the hinge can operate properly. You can do this with a knife or a bit of sandpaper on a block. Go easy and keep it straight. Use Du-Bro Electric Flyer Hinge Tape to join the stabilizer and elevator, and the vertical fin and rudder. You only need to tape the top side. I have never had an issue with the tape coming off, and lighter is always better for the Split Stik.
Cut the spruce stick to length for the fuselage and make the motor mount from the excess. The mount is bit overkill, but serves the additional purpose of adding some needed weight up front. Think of the Split Stik as a seesaw, and since the model has a short nose, more weight is needed in front to make it balance. Shifting the battery position can also help balance the model.
The motor mount is made from four pieces of leftover spruce with their tail ends cut at a 45-degree angle. Not being concerned about weight up front, I use 5-minute epoxy to glue these parts on the model. You only need a little epoxy, so don’t overdo it.
After the epoxy has cured, sand the front of the mount flat. The Split Stik will fly fine with a perpendicular motor mount, but if you have the skill and want to be fancy, sand the mount for 2 degrees of down thrust and right thrust. Doing this will aim the motor slightly down and to the right, and will prevent the airplane from pulling upward when power is applied. Another way to overcome this is with a bit more trim in your radio setup.
The wing spar is a 3mm carbon rod that you will bend like an archery bow to add dihedral to the wing. Using a hobby knife to make a small notch in the fuselage stick for the spar. Measure carefully to ensure that the rod is square to the fuselage, then use a drop or two of CA to hold it in place. When the CA is set, use fishing line to lash the carbon rod to the fuselage. If you remember your Boy Scout lashings, use a square or a diagonal lashing. If you don’t remember, just make a few wraps in each direction and tie them off with a simple knot. Use CA to set the wrappings.
Attach the tail surfaces before adding the power and RC components. Make sure you’ve hinged the rudder and elevator with Du-Bro tape before you mount them.
The stabilizer and fin are installed with hot glue. Hot glue is easy to work with and makes a nice strong bond. It also makes for an easy repair if you have to replace a component. Measure carefully to make sure that the tail feathers are square to each other and to the fuselage. Since the profile of the Split Stik fuselage is essentially a rectangle, keeping all its components square should be easy.
Bend a length of 1/16-inch music wire for the landing gear. Get the wire at a hobby shop if you don’t already have it in the workshop. Add a pair of 1-inch-diameter lightweight plastic wheels. Du-Bro offers a variety of micro wheels or you can make some wheels out of a couple of foam discs if you are only going to fly your Split Stik indoors. Attach the landing gear to the fuselage stick with a couple of small tie wraps, trim the excess and use hot glue to keep the gear from moving around. Wow! This thing is really beginning to look like an airplane.
Now is a good time to mount the motor, receiver, ESC and servos. Use hot glue to attach the servos, then run a small nylon zip-tie around them for added security. I never use CA to mount a servo because CA can wick into the gear box and ruin the servo. Hot glue can also be used to hold the receiver.
Do your best to keep everything neat, running the wires along the fuselage stick and secure them with small nylon zip-ties or dabs of hot glue.
You’ve already transferred all the center lines, CG and other markings to the foam, haven’t you? Sure you did, so now make the holes in the wing. Lay out the wing with all the markings on the bottom side. With the bottom side up, position the fuselage over its mark. The carbon spar should line up. Once you are confident that the wing aligns and will mount correctly, prepare the tension line to bow the wing spar.
Use a 2-foot piece of fishing line to make a hitch on the tip of one side of the carbon spar. Secure the hitch with CA. Securing one side will make it easier for you to tension the line without the need for two hands too many.
Glue the center of the wing to the fuselage with hot glue, but do not glue the carbon spar to the wing. Hot glue on the carbon spar can weaken it, and you need the wing to be free of the spar so you can bow the spar. Make absolutely certain that the wing is square to the fuselage stick.
Begin bowing the spar by threading the fishing line through the hole in the wing, the goal being to create wing dihedral by bowing the carbon spar. Thread the fishing line on top of the wing and back down through the second hole on the other side of the wing. Tie it off and glue it. When you release the tension, you should have a wing with a slight bow on each end.
I found that If I hold the untied end of the spar close to me and used the workbench to press the tied end, I could hold the bow in myself and tie the knot. Do not get over zealous with pressing on the spar or you can snap it. An inch of bow is all you really need.
Here’s a helpful tip. If your bend made the dihedral too shallow, you can increase it by wrapping the fishing line around the spar one more. If you’ve initially made the bow too large, you’ll have to live with it because you can’t undo it.
I like to adjust the dihedral before I fly, based on the wind and the style I feel like flying that day. Dihedral will give the airplane stability because the model will want to suspend itself from the lowest point of the dihedral curve. Dihedral can also make an airplane slower to respond and more susceptible to crosswinds.
After you’ve set the angle of dihedral, do not glue the spar to the wing. Use clear tape instead, and make sure that the wing and spar are secure so the wing doesn’t flap around when you try a fast maneuver. Since the Split Stik is not really a bird, it will not fly well with a flapping wing.
Mount the power and RC components before attaching the wing. Here, the fuselage is almost ready for the wing, and the equipment has all been tested.
Use shims to make sure the wing is flat before installing it on the fuselage. Do not glue the wing to the spar; use Du-Bro Hinge Tape.
Here’s a close-up of the spar with the fishing line attached. The idea is to make a bow out of the spar.
Paul Martin, the author’s son, has the honors of taking the Split Stik on her maiden flight. He finds the Split Stik easy to fly and responsive when you hit the throttle.
Flying around the baseball infield was easy and fun. The Split Stik easily takes off from the ground and can slow down for a graceful landing.
Finish your Split Stik by adding the control linkage from the servos to the rudder and elevator. I keep the pushrods real simple by making them from 1mm carbon rod with some stiff copper wire at each end to connect them to control horns and the servo arms. Another pushrod option is 1/16-inch music wire, and a wide selection of micro model linkages and other hardware is available from Du-Bro Products. The Split stik is low-tech fun, so whatever you feel comfortable with is fine.
Balance the airplane with the battery mounted. Depending on the pack you choose, you may have to move it forward of the wing so it will butt up against the motor mount. I usually do a quick balance check with the battery mounted before each flight. The CG is forward of the carbon spar, so check your markings and don’t rely on feeling for the spar. With the balance set, your model is ready to fly.
Hand-launching is okay, but I have always been fond of watching model airplanes take off from the ground (ROG: Rise Off Ground). Many of our park flyers are hand-launched so I am happy that the Split Stik is easily capable of a rolling takeoff. I often fly it in a baseball field, taking off from the infield or from a little walkway in the area. The Split Stik can lift off gracefully at only half throttle, and the climb to altitude is steady and sure.
The Split Stik is predictable and relaxing to fly. I flew it inside the famous Lakehurst Hangar One during the Scouts to the Skies Camporee, and without any wind, the Split Stik was more docile than ever. Just put it into a slow, climbing turn and watch the model soar. Several Scouts took the controls that day and had their first experience on the Split Stik.
Add a set of lightweight LED lamps to the wings and the Split Stick can have you carving graceful circles in the night sky. Day or night, indoors or out, I rarely fly the Split Stik at more than half power. It’s a simple design with classic lines that is easy to build and fly.