When you change a model airplane you must keep one thing in mind, namely, the center of gravity. This is the balance point and any deviation from this point will have a negative effect on the flight characteristics. Adding radio control equipment to a foam "chuck" glider is fairly simple as long as the center of gravity remains the same after conversion as before.
Find the center of gravity. Assemble the glider, place your fingertips under the wing and along the fuselage, move your fingers toward the tail until the glider sits flat. Now move your fingers slightly back so that the nose of the glider drops a little below level. This is the center of gravity. Mark the position of your fingers on the fuselage.
Create the movable section of the rudder. If the rudder is removable then take it off the plane. Using a sharp knife cut the rudder in half vertically. Clean up the cut with sandpaper. Create a beveled edge on the rear section of the rudder so that it will move smoothly when reattached. You now have a vertical stabilizer and a rudder.
Cut slots in the vertical stabilizer and the rudder. The slots in the stab and rudder must align perfectly, this is where you mount the hinges. Test fit the hinges and, when you think the rudder is aligned with the stab and moves well, epoxy the hinges into place.
Repeat the steps for the rudder for the horizontal stabilizer and elevator. Some elevators will be split in the middle to allow the rudder to move. Join the stabilizer halves by cutting a groove in the leading edge of the elevator pieces and epoxy in a length of bamboo skewer. Make sure the elevator remains the same width as the stabilizer and that the two halves are level. Install hinges as you did for the rudder.
Attach control horns to the rudder and elevator. The hole that connects the pushrod to the horn should be directly over the hinge line. Horns can be epoxied or hot glued in place.
Mount the servos for the rudder and elevator. Cut a hole in the side of the glider to accept a servo, make one hole on each side of the fuselage and stagger the holes to avoid weakening the fuselage too much. Hot glue the servos in place.
Use piano wire to make push rods. One end attaches to the servo arm, the other to the control horn. Make the rods adjustable by creating a V-bend in the middle of the rod. Connect pushrods to both servos.
Check the balance of the glider again, it should be tail heavy (nose points up). To counteract the tail heavy condition you place the receiver and battery pack toward the nose of the glider until you achieve the proper balance at the center of gravity. If you cannot balance the plane with the RC equipment alone then you will need to add lead weight to the nose of the glider. Try to add as little weight as possible to the glider, weight will affect the flight characteristics.
Reinforce the wings. Run lengths of fiberglass tape along the bottom of the wing, one piece along the leading edge, one along the trailing edge and one down the center of the wing. The tape should run from the wing tip to the center cord. Epoxy the wing halves to the fuselage. When dry you should be ready to fly your RC glider.