Elastic Launched Glider
|Elastic Launched Glider|
Elastic Launched Glider was a Division B event for the 2015 and 2016 seasons. It was a Division C trial event at the 2012 National Tournament and became a full-fledged Division C event in 2013 and 2014.
- 1 Terms to Know
- 2 Construction
- 3 The Launch
- 4 The Flight
- 5 Troubleshooting
- 6 Resources
Terms to Know
- Aileron: In short, the back edge of a wing of a glider (The edge closest to the tail). They can bend up or down to alter the glider's flight. The most distinct example of what it is is on the Time Machine model from the AMA site.
- Roll: The rotation of the glider upon the main axis of the wings that runs through the glider's center of gravity.
- Pitch: The rotation of the glider about the main axis of the fuse.
- Yaw: The rotation of the glider about the axis perpendicular to both the axis of roll and the axis of pitch.
- Fuse: Short for fuselage; the main body of the glider.
- A-Grain: A type of balsa used in gliders (see below). Its properties include it being softer are more malleable than other balsa.
- B-Grain: A type of balsa used in gliders (see below).B-grain balsa has a wide range of properties, as it is cut randomly from balsa stock, but in general it has properties which fall in the middle of whatever range they are in. Usually, B-grain is not used when A-grain or C-grain would do a better job.
- C-Grain: A type of balsa used in gliders (see below). Its properties include it being harder and more stiff than other balsa.
- Rudder: See vertical stab.
- Elevator: See horizontal stab.
- Stab: This is short for "stabilizer". It can refer to different parts of the glider, depending on who says it. In general, it refers to the whole of the tail of the glider; however, sometimes when someone says it they may only be referring to the horizontal stab or the vertical stab.
- Horizontal Stab: the horizontal part of the tail of the glider, is also called the elevator.
- Vertical Stab: the vertical part of the tail of the glider, also called the rudder.
- Incidence: The angle between the main axis of the wings of the glider and the horizontal stab. When talked about, the incidence is generally given as positive, with the wings tilted upwards when the horizontal stab is parallel with the ground, negative, with the wings tilted downwards when the horizontal stab is parallel with the ground, or 0-0, with the wings and the horizontal stab parallel with the ground at the same time.
Because of the fact that the Elastic Launch Glider must be able to withstand traveling at a very high velocity, but also must be aerodynamic, different types of balsa may need to be used so that the glider can transition from these two elements of its flight, depending on the design being used. One such type of design is the Time Machine, the plans for which can be found at the AMA glider website linked to below. The three types of balsa used are commonly called A-grain, B-grain, and C-grain. the definitions of these types of balsa are given above.
Gripping the Glider
Angling the Glider and Launch Handle
As stated in other parts of this article, the launching of the glider into the air is ballistic, not aerodynamic; i.e. the glider is not flying to the ceiling, it is being thrown there. However, it is very important to note that aerodynamics are involved in the ascent. If the glider were to be simply launched into the air without any thought, it would likely stall and fall back to the ground. Instead, the desired approach is to launch it in such a way that it aerodynamically corkscrews to the ceiling without stalling. The spiral will only contain a small number of rotations; maybe 1 to 1.5 turns (this is why it might be hard to observe in videos). Now, as each glider is different, the exact angle of launch will be different for success, but in general it goes like this:
- Hold the launcher in one hand and glider attached to the elastic loop in the other.
- Stretch the elastic the desired amount, and hold the system vertically. The elastic loop should be in a vertical line.
- Move the glider a small distance horizontally away from the launch handle. This way, the glider is less likely to hit the handle during launch.
- Tilt the system so that it is not vertical but 70 to 80 degrees in respect to the ground. This is so the the glider does not go straight up and thus can transition into its glide.
- Roll the glider (rotate it about the axis of the fuselage) about 45 degrees. Make sure to roll the launch handle (i.e. rotate your wrist of the hand with the launch handle) the same amount! This is what gives the corkscrew ascent.
- Launch and pray.
Controlling the Launch Height
There is a wonderful, much-more-in-depth article about this on the AMA website linked to below; please go and check it out. However, here is a decent summary of freeflight trimming:
- The nose starts dipping up and down (Stall): Simply add some weight to the nose, or if this is not desired, bend the the elevators down. The latter is risky because it creates negative incidence, which is bad for the design.
- Nosedives immediately after its transition: This is probably an issue with incidence. Try bending the trailing edge of the elevator upwards a little (be careful, though... too much bend and the glider will loop backwards instead). Try this.
- Flips backward it its transition and loops backward before going into a glide (or doesn't make it into a glide at all): This is most likely an incidence problem. Try bending the trailing edge of the elevator downwards a little (be careful, though...too much bend and the glider will nosedive instead, which is generally more likely to cause damage to the glider). Another thing that might help is simply launching the glider at less steep an angle.
- Is not turning properly (it flies straight in its glide instead of gliding in circles): To fix this, the easiest thing to do is probably going to be to carefully remove the glider's rudder, and reglue it at more of an angle. To get it to turn in a left-hand circle, glue it so that the front end of the rudder is further to the left than the back end. Reverse this if a right-hand circle is desired but do not add weight to one wing, as this messes up the center of gravity, and isn't very effective.
One incredibly helpful website which covers almost all aspects of this event can be found here (this is the aforementioned AMA glider website). The 2012 Forum thread which can be found here lays down much groundwork for the event. Also, when searching for videos for this type of glider, be sure to try searching "Catapult Launch Glider", which is another name for this project.
Two kits which are relatively easy to build, fit the 2012-2013 specifications, and will produce decent to very good gliders (depending on the build itself) are:
- Freedom Flight Model: This is just the Freedom Flight website; obviously, it is the glider that you want.
- Science Olympiad Little Sweep: This is a genreral order form. The Science Olympiad Little Seep is the kit you want for this event.
- Guru Engineering Tech (Non-Profit): This is the Kit page but they also have other flying resources available.