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Build

Step 1: Bungee Safety Certification

Before anyone on your team touches a bungee cord, watch your instructor's demonstration and confirm you understand all five protocols:

• Never stand in the release path
• Inspect every cord for fraying or wear before each use
• Check anchor points before every pull, not just the first
• Eye protection any time a cord is under tension
• Release under control — never just let go at full stretch

This is a hard gate: no team begins Build (Sessions 16–19) without every member certified.

Step 2: Read the Client Brief

Your instructor will hand you a brief from Marcus Oyelaran, a youth program coach at Ridgeline Racquet Club. Every team is working from the same one.

He cannot deliver a ball to the same spot twice, so his players end up practicing chasing bad throws instead of practicing the return. He wants a machine that puts a ball where he tells it to — within about three yards of the distance he calls, at three different distances in a session, worked by one person while he watches eleven kids.

Pull the brief apart using the four-part framework from Session 2 and fill in the table on your Design Packet: User, Need, Constraints, and Success Criteria. Everything in it has to come from the brief — don't add a requirement he never asked for, and don't drop one because it's inconvenient.

One line is worth reading twice: “I don't care how far the thing can throw. I care that when I say twenty yards, it goes twenty yards.” That is why this project grades a calibration model rather than a throwing distance — and the ±3 yards is his tolerance, not a rule we made up.

Step 3: Research Existing Launch Mechanisms

Before you design anything, look at what already works. Pick 3 different real launching machines— trebuchet, torsion catapult, ballista, slingshot, air cannon, spring launcher, or another your instructor approves. They do not have to be bungee-powered; the point is to see a range of approaches.

For each one, record three things:

• How it stores energy — counterweight, twisted rope, compressed air, stretched elastic, etc.
• What controls how far it throws— the single most important column. Every one of these machines has something you turn up or down to change where the projectile lands.
• One thing worth stealing — a feature, a proportion, a release method you could actually use.

Then answer one question in writing: which of these is your launcher most like, and why?

Step 4: Choose Your Independent Variable

Pull distance or launch angle — confirm with your instructor whether this is your team's free choice this year. Whichever you pick, everything downstream (your test protocol, your calibration model, your field-day strategy) is built around it.

Your justification must reference your Step 3 research. "We picked pull distance because the slingshot and the ballista both control range by draw length, and our mechanism works the same way" is a real reason. "We picked pull distance because it seemed easier" is not.

Step 5: Generate 3 Concepts + Decision Matrix

Using the exact technique from Session 3: sketch 3 genuinely different launcher concepts, then build the matrix from the evidence you have. Every column must trace to Marcus's success criteria, one of his constraints, or your mechanism research.

Your three concepts should be genuinely informed by Step 3 — if all three look like the same machine you'd have drawn before doing any research, the research didn't do its job.

Include at least one criterion about controllably varying your IV and one about hitting Marcus's ±3-yard success target. Use the Session 3 scoring anchors: 3 clearly meets, 2 is uncertain or needs testing, and 1 conflicts or fails. Defend one helpful score and one harmful score before choosing provisionally.

Step 6: Write Your Test Protocol

State, in writing, all three of these:

• What you're varying (your IV) and across what range
• How many trials you'll run per setting
• How that data becomes a calibration model

You don't need the model yet — just a real plan for building one. A vague protocol will be sent back before Build begins.

Checkpoint

Before Session 15 ends, confirm all of the following:

• Every team member is certified on bungee cord safety
• Three existing mechanisms researched, each with its energy-storage method and — critically — what controls its range
• Three genuinely different concepts were sketched — not 3 variations on one idea
• Your decision matrix has real scores and reasoning, not a pre-decided winner
• Your IV is chosen and justified in writing, referencing your research
• Your test protocol names what's varied, trial count, and how data becomes a model

Reflection

Answer these on your own. Reflections are individual, even when the rest of the session was team work.

1. Marcus says he doesn't care how far the launcher can throw. Name one design decision your team would have made differently if he had wanted maximum distance — and say which of his requirements would have suffered for it.
2. Why does this project require a written test protocol before anyone builds anything, instead of letting teams build first and figure out testing later?
3. Sessions 16–19 are the build. Looking at your chosen concept, which single part of it are you least sure you can actually make with the tools you're certified on?

Submit

Submit your team's Design Packet (mechanism research notes, concept sketch, decision matrix, IV justification, test protocol) and your individual reflection.

Milestone Complete