Loops and rolls are easy to do with any paper airplane. Since delta wings are the most common paper aircraft, let’s begin with these types of airplanes. Improving aerobatics usually involves no more than adjusting the stabilizer trim tabs. You need a lot of room to get really good loops and rolls, so you will probably have more success with this outdoors.
Most of the typical delta wing style planes require only the movement of two trim tabs located at the trailing edge of the wing, as shown in Sketch 6-1. Bending these tabs up equally will enable the airplane to loop if it is launched with enough energy. Bending the tabs in different directions will result in rolls. Any combination of the two will result in a spectacular rolling loop.
Sketch 6-2 shows a conventionally configured airplane (Design 3 in The Paper Ace). The trim tabs located on the horizontal stabilizer are for looping, while the trim tabs located on the trailing edge of the wings (ailerons) are for rolling. Care must be exercised not to make the ailerons too large when cutting them into the wing, as you might obtain an opposite roll, caused by adverse yaw.
Adverse yaw occurs because the downward aileron on the wing is experiencing more drag due to the higher pressure airflow that exists under the wing. So it will tend to roll in the opposite direction that what you would think. Should this happen to you, simply reduce the amount of downward deflection and double up on the up deflection on the opposite wing.
The design illustrated in Sketch 6-2 uses four control surfaces to do the same amount of maneuvering as the classic delta design. You can also offset any adverse yaw you may experience, with a little rudder trim. You will need to add a trim tab to the rudder (in this case an inverted V or central rudder). If you want to roll the airplane left, you may need to cut and bend the trailing edge of the vertical fin to the left. On some designs, only a rudder trim tab is required to produce barrel rolls. Please note that rudder trim tabs are extremely effective, and a little goes a long way. Don’t be afraid to act as a test pilot and experiment and thus increasing your aeronautical knowledge and skill level.