Balloon Launch Glider

Balloon Launch Glider (BLG) was a B division event in the years of 2007 and 2008.

Overview
Balloon Launch Glider is most similar to the event Elastic Launched Glider. They both require building a free flight glider, the difference being the type of launch. As such, the tips for constructing the glider itself are very similar.

Balloon Launch Gliders included some similar parts to Wright Stuff planes. For example, these gliders required a wing, a stabilizer, and a rudder (vertical stabilizer). All of these would rest on a fuselage. However, unlike Wright Stuff, there were no motors on BLG's.

Construction
Participants in this event were able to test up to two gliders that could be constructed from wood, foam, paper, plastic film, and glue. Other materials, such as music wire, malleable wire, paper/plastic tubes, and/or rubber bands could be used to attach components. The total mass of the glider must be at least 2.0 grams throughout the flight.

Maximum dimensions were as follows:
 * Horizontally projected wingspan: 48.0 cm
 * Wing chord: 10.0 cm
 * Horizontally projected stabilizer span: 28.0 cm
 * Stabilizer chord: 9.0 cm

A crucial part of the event is the launch. Building a rack to rest on top of the balloon is a good way to make sure the glider doesn't slip off prematurely. It is also good to avoid a glider launching from an angle with the nose down, or at a different angle than from hand test launches. Something made from paper would work. Place the glider on the rack, and carefully raise the balloon towards the ceiling. To launch, just quickly lower the balloon down about two feet, with a tug on the string.

Testing and Adjusting
Once your glider is constructed, a bulk of the event is testing and adjusting, also known as trimming in the free flight world, so that your glider flies smoothly. The goal is to have a glider turn in left circles while gently descending to the ground, devoid of rapid dives or stalls. It is best to make these adjustments from observations made with a simple hand toss. If the glider doesn't fly smoothly from a hand toss, it won't when launched from the balloon. Remember to record everything after each adjustment! It's important to know what change caused the glider to do better or worse for future reference.

Stalling
Stalling can easily be mistaken for diving. A stall is when the nose of the glider flies, nose up, but then suddenly the nose sinks and dives rapidly lower. There are a couple of things you can do to fix this:
 * Add ballast to the front of the glider (the nose). Clay or sticky tack works.
 * Bend the elevator down a tad. It is simpler and better for the design to just add ballast, however.

Diving
Diving is when the nose is pointed downwards, and the glider rapidly descends towards the ground. There are a couple of things you can do to fix this:
 * There may be a problem with incidence, in this case, carefully bend the trailing edge of the elevator upward a bit. Too much, however, and you'll experience stalling.
 * If the glider started diving after adding ballast to the front to fix stalling, remove some of the ballast from the nose.

Turning
You need the glider to turn in circles to avoid hitting walls. If it doesn't turn you can:
 * Have the rudder offset to the left by making the front end of the rudder further to the left than the back end.
 * Stabilizer tilt will make a plane turn. So, to turn left, tilt the stab so the left side is higher than the right, compared to the wings when held level.
 * Add weight to one wing, to turn left add weight to the left wing (with clay or sticky tack, etc.) This may mess up the center of gravity; try the above methods first.

Competition
Teams needed to bring a large helium balloon to the competition. This balloon would be attached to fishing wire, (or the equivalent) and it would be raised to near the ceiling of a gym. The glider would then be released from the balloon, usually by competitors pulling the balloon out from under the glider. At the regional level, the event supervisor was required to provide one balloon for teams; however, this balloon was not outfitted with a platform, so teams were better served by constructing their own balloon launchers to bring to the competition. This option was unavailable for states or nationals; teams were required to bring their own mechanisms. Helium for balloons was not provided at any level.

Teams were also required to bring a log with a minimum of ten flights recorded to the competition. Each flight needed to measure four different variables, three of which were required to be height of balloon at launch, glider mass at launch, and flight time.

Scoring
The winning team was the team with the longest time aloft for two flights, out of the three official flights that were available to teams. The time for the third flight was used as a tiebreaker. Penalties were assessed as follows:
 * Incomplete flight logs: 10% reduction from each flight time
 * Missing flight logs: 30% reduction from each flight time
 * Construction or competition violation: ranked after all teams that did not have any violations

Resources
An extremely helpful site, where much of the information on this page was obtained from, is this site dedicated to gliders. It mostly has information regarding elastic launched gliders, but under the Science Olympiad section, there is a couple of detailed pages about this event.

Plans

 * Kurt Krempetz's documents
 * Glider plan
 * Detailed guide on construction