TOWERS B/C EVENT PRESENTATION Robert Monetza

Description and Event Parameters Design and build the most efficient Tower as specified in the rules. In this context, “most efficient” means the tower which scores the highest. Enter only one tower, built prior to the tournament MUST WEAR #2 EYE PROTECTION – YOU WILL NOT BE ALLOWED TO COMPETE WITHOUT IT! Event Supervisor will provide ALL testing apparatus and assessment devices.

Construction Parameters Dimensional requirements mostly the same as 2011 rules: Span 20 sq. cm. test base opening, on any combination of sides. May not be braced against edges of opening, 8.0 cm diameter restriction in width above test base at 30.0 cm in B, 15.0 cm in C. Must support 5.0 cm sq. test block. Must be a single structure, constructed of wood and glue. No limits on cross section dimensions or lamination by students.

New this year: 3.c: Minimum tower height is 40.0 cm. Towers shorter than this, within the tolerance of measurement, will be second tier with a construction violation. 3.c: Tower heights between 40.0 cm and 70.0 cm inclusive will be scored based on a modified height multiplier, (h-n), where n =5 at Regionals, n=15 at States, and n=25 at Nationals. 3.c: Tower heights greater than 70.0 cm will count as 70.0 cm. No additional height will be recorded or scored. 3.f: “Only the loading block supports the chain and bucket.” That is, the chain must not gain any useful support or restraint from direct contact with the tower.

Testing Apparatus: Basic testing devices and assessment devices are unchanged from last year, and are provided by the Event Supervisor. 4.c: Eyebolt may be either ¼” dia or 5/16” dia. Be sure there is room inside the tower for either size. 4.c.i and 4.c.ii: These dimensions are given to provide the teams with information about the clearance they should provide within the tower, and to instruct the Event Supervisor to provide appropriate testing devices.

Competition: 5.a: Once the team checks in and presents their tower at the event, they may not change it in any way. 5.e: There is nothing wrong with letting the team disassemble the block, eyebolt, chain, etc. if they need to do so to set up their tower. 5.g: Teams must be allowed to stabilize the load as the sand flows into the bucket. The Event Supervisor may determine the safest way to do this, but some provision must be made. Usually, the bucket self-stabilizes before half of the sand is loaded. 5.j: Definition of failure includes lateral support from test base, and bucket touching the floor or anything else.

Scoring: 6.a: Maximum load counted for score is Kg. Minimum is the loading block: if the tower can’t carry the loading block, then it was unable to be loaded. 6.b: Heights greater than 70.0 cm are counted as 70.0 cm. Extra height is a waste of mass! 6.c: Efficiency for towers includes a multiplier derived from the tower height, and varies with the level of competition. 6.d: Tiers, based on rules compliance. Note that a new tier 3 is defined as not meeting competition parameters. Tier four is for towers which cannot be loaded. 6.e: Tie breakers are (first) lower tower mass and (second) taller tower height.

One Clarification so far: Towers B/C (10/17/11): Add one line, "6.c.iv. The tower height is measured to the highest tower point on which the bottom of the loading block rests." Therefore, tower height is the load bearing height of the tower, regardless of any extra vertical extensions which may be attached to the Tower.

What about that new scoring? The height multiplier was introduced to provide more opportunities for student innovation. Instead of a single fixed minimum height, towers will earn varying scores over the range of heights. The height of the tower is modified by deducting an arbitrary constant which increases for higher levels of competition. This creates a non-linear scoring function and increases the bias for taller towers as the constant increases. The scoring formula is: (h-n)L/m. n= 5 at Regional tournaments, 15 at State tournaments, and 25 at Nationals.

What were we thinking? For a given design, short towers are easier to build and more stable than tall towers. For a given design, as towers get taller, they get heavier. It isn’t a strict proportion, but it is generally true. Tall, slender, light weight towers have more tendency to buckle and bend. Teams which successfully build taller towers generally will be more experienced and more skilled. However, at a Regional level, relatively less value is given to the extra height score. This tends to level the playing field. As “n” increases in the formula, shorter towers will earn relatively less height score and taller towers will be favored. Teams may need to redesign their towers to take advantage of the change in formula. The ideal tower at one tournament may not be the ideal tower at another, so teams should take a flexible approach to design and construction. Teams will take a risk in their approach to tower height design. That’s a new piece of strategy.

Scoring Examples: These examples show how some plausible combinations of tower masses, heights, and capacities will score at each level of competition. Tower 1: mass = g, height = 42.5 cm, load supported = Kg Regional Score = State Score = National Score = Tower 2: mass = g, height = 68.2 cm, load supported = Kg Regional Score = State Score = National Score = Tower 3: mass = g, height = 68.2 cm, load supported = Kg Regional Score = State Score = National Score =

Scoresheet/ Checklist: This Scoresheet/Checklist form may be found at and

Graphic Summary of Rules is posted on and

General Principles about Structure Building: Three key components: Competent design, good material selection, and quality workmanship. All of these are acquired through practice and refinement. Don’t be afraid to ask for help from knowledgeable parents and professionals. The kids will learn from them. Provide a clean, organized workplace. Keep food and other distractions to a minimum. Kids should wash their hands. Testing is destructive. Students will understand much more about their structures by observing and analyzing structural failures than they ever will from seeing unbroken structures. Plan on building a lot of towers.

What happens at Competition? Check in, weigh in. As soon as the team presents their tower to the judges, they may not alter or replace it or receive outside assistance. Judging. The judges will measure and assess the tower for compliance with construction parameters. Set up. The team sets up their tower on the test stand. When they are ready the judges will let them begin loading sand. Once the sand loading starts, they may not adjust the set up any more. Loading. The team may load as fast or as slowly as they wish, and they may steady the bucket as allowed by the Event Supervisor to prevent dynamic loading of the tower. If the tower holds all of the sand without breaking, the team may immediately remove the bucket. If the tower breaks during loading, the team must immediately stop adding sand, and the Event Supervisor may remove any sand which is judged to have been unfairly added after breaking. Breaking the tower has no effect on the scoring tier of the tower, provided it holds the loading block initially. The judges will inform the team how much mass their tower held Teams may take their tower with them unless there is a pending arbitration.