Archive of the Yahoo! Groups mailing list for the Bug hand-launch glider 2002-2018

From: "John" <gldrgidr@...>
Date: Tuesday, January 13, 2004 11:06 PM
Subject: Two Different SAL techniques
With the talk of presets, it might be good to define what I consider the two methods of Side-Arm-Launching. The original method: There used to be a animated gif on the old Thermal-Gromit Works website (originator of the Red Herring). It showed the original SAL method. The first step was standing with your arm at your side, holding the glider by the wingtip. You raise your arm towards your back until it's almost vertical and then bring the glider back down and continue the arc until you release the glider when it's facing upward. The path of the glider is mostly in a vertical plane. Viewed from the side, the glider makes a U shaped path through the air. During this launch the wings do not develop lift and so there is no need for a rudder preset to counteract yaw. The method I use (half-discus SAL launch): Holding the glider by the wingtip, you twist your body (and the glider) backwards. You then unwind your body with your arm trailing behind and then use your arm for a final power sweep to release. The path of the glider is mostly in a horizontal plane. From above, the glider would appear to make a partial circle (about 120 degrees). This is actually the last part of a discus launch without the footsteps. During this launch the wings do develop lift, so there is a probability that there would be uneven lift developed by the right and left sides of the wing with a resulting possible need for a rudder preset. The original method is limited by the span of the glider and the height of pilot. Most people who use this method actually raise the angle of the arm at the bottom of the U-path, so that the outer wingtip clears the ground. Using this modified method, the wing may or may not produce enough lift to require a rudder preset. If your X-tail is well designed and the boom is rigid enough and long enough, the X-tail will counteract the yaw force and reduce or eliminate the need for a rudder preset. I guess you might wonder why I use the half discus method of SAL since it has a greater need for a rudder preset. First, I also discus launch 1.5 meter dlg's. Which means that the same muscles that are used for the half-discus SAL method are also used in the full discus launch method. Physical strength that is developed in the half discus launch, helps launch height for both half and full discus methods. Second, I believe that you can develop more speed in the launch. The original SAL method uses mostly only arm and shoulder strength with an assist from gravity during the initail downward part of the launch. The half-discus SAL launch uses your waist, torso, shoulder and arm muscles. John