If you are like most RC enthusiasts you have spare spare motors, servos & batteries. This instructable shows you how to make a flat foam airframe in a couple hours. I've modified free plans from http://www.foamyfactory.com/ for a faster build that is also stronger.This requires just 1 foam core board that can be purchased from a craft store.I used the 1/2" thick board instead of the more common 3/16" version I've used in the past.
Step 1: Airframe Layout
Print out the full scale design available free from http://www.foamyfactory.com/Put the design on poster board so you can easily trace out the design for future builds.I've found that making just the vertical profile of the fuselage, the whole wing and the tail is all you need.Trace out the designs on the foam board.
Step 2: Cut it outCut out the design using a jig saw. You could also use an Exacto knife but the jig saw is much faster and easier. Cut out the slots where the wing fits and the tail fits as well. We'll cut the servo mounts out later.
Step 3: Making the wing control surfaces
I do limited stunt flying so all I use are ailerons and the elevator. You can make a rudder for more advanced flying but I left it out of this instructable but you can apply the same techniques. The simplest control hinge is made from packing tape.
Using the jig saw cut both ailerons at a 30-45 degree angle where the control surface meets the wing. To make the hinge, mate the control surface to the main wing body at the cut angle and apply the tape along the length. Then fold the control surface the other direction and tape under side of the wing and aileron.
Next, slide the wing through the slot in the airframe. Apply glue to the center of the wing and slide in place. Allow the glue to dry then repeat the taping procedure on the other side of the wing.
Step 4: Making the elevator
Cut out the slots to fit the elevator in the airframe. See photo for locations.
Instead of angle cutting the elevator (#2), cut the stationary piece labeled #1 in the photo at the 30-45 degree angle just as in step 3.
Slide and glue piece 1 into place. Slide part #2 into place and tape the elevator hinge just as described in step 3.
Step 5: Install Servos
Find your servos and control linkages. The length of the control linkages dictate where the servos should be mounted.
Simulate the locations of the control horns then make an outline of the servo on the airframe. Repeat this for the elevator. Cut out the servo locations.
Use a hot glue gun to fix the servos to the airframe. Screw down the control horns or hot glue them in place.
Step 6: Mounting the motor
Use a table saw to cut out a slot in a block of wood to mount your motor on. Pre-drill the mounting holes in the block. Glue the block to the airframe. Mount the motor to the block.
I recommend using a folding prop so you can belly land the plane and you won't need landing gear.
Step 7: Mounting the rest of the electronics
You now need to mount the ESC, Radio, and Battery.
I just use tape to mount the electronics.
Use the battery to balance the plane. Make sure the plane balances about 1/3 to 1/2 the wing cord length back from the leading edge of the wing. The further back the more unstable the plane becomes. Its also easier to do 3D aerobatics.