🛠️ Engineering projects: design, build, test, improve

Science entry or engineering entry?

In a science entry you change one thing and measure what happens, and your hypothesis says what you think will happen. In an engineering entry you have a job for your design to do, and your design goal says how well it must do it. Then you build designs, test each one, and improve.

Some fairs have a separate engineering category or a different sheet for it, and some don't. Read your school's rules first: they win. If yours doesn't say, either kind is usually welcome, and the board's six places are the same with new names:

• ❓ Question becomes "The problem".
• 💭 Hypothesis becomes "Design goal".
• 🧺 Materials becomes "Materials and limits".
• 🪜 Steps becomes "Designs I tried".
• 📊 Results becomes "Test results".
• ✅ Conclusion becomes "Best design and why".

The design process, step by step

Engineers go round the same steps again and again, 6 of them. The engineering design sheet prints them as a table to fill in:

• Ask: What problem am I solving? What must my design do, and what are the limits (materials, size, time)?
• Imagine: Sketch three different designs before building any of them.
• Build: Build the first design, using only the materials on the list.
• Test: Test it three times the same way, and write every number down.
• Improve: Change one thing at a time, build the next design and test it again.
• Share: Say which design worked best, show the numbers that prove it, and what you'd change next.

The loop is the point. A judge would rather see three designs that got better, with the numbers that show it, than one perfect design that came out right the first time.

A design goal, not a guess

A hypothesis says "If I change ___, then ___ will happen, because ___". A design goal says what your design must do, how you'll measure it, and the limits. For paper column shapes: "My column must hold at least 10 books, made from one sheet of paper and tape, at the same height as every other design."

A good design goal has a number in it, so you can tell when you've reached it. It also names the limits (the materials, the size, the time) so every design gets a fair start. Write it before you build anything, and don't change it after the tests.

A worked example: three paper columns

Here's Which paper column shape holds the most books? run as an engineering project. Every number below is made up to show how it works; your own test gives your numbers.

• Design 1, a column folded into a triangle, held 3, 4 and 2 books in three tries. Its mean is 3 + 4 + 2 = 9, and 9 ÷ 3 = 3.
• What failed? The flat sides bent in the middle. So design 2 is a square column with the same paper and height. It held 6, 5 and 7: 6 + 5 + 7 = 18, and 18 ÷ 3 = 6.
• Design 3 has no flat sides at all: a round tube. It held 9, 8 and 10: 9 + 8 + 10 = 27, and 27 ÷ 3 = 9.

In this made-up test, design 3 is the only one that reached 10 books, and only on its best try. Its mean, 9, is just short of the goal, which is worth saying on the board. The project page says why a round column often wins: "A paper column gives way by buckling: its walls bend sideways and fold. A flat side bends easily, while a curved side is stiffer, so a round column often holds the most." For the next round of designs it suggests: "Change a second thing: cut your sheets to 10, 15 and 20 cm tall, test the best shape at each height, and graph books held against height."

Change one thing between designs, as you would in any fair test. If design 2 had a new shape and a new paper, you couldn't tell which one made it stronger.

11 projects built to be improved

Each of these tests one design against another, so each can run as an engineering entry. Easiest first; 10 of them reach 6th to 8th grade:

• Which boat shape carries the most pennies?: 1st–5th grade, 1 day of testing, free.
• Does a wider base keep a cup tower from tipping?: 2nd–8th grade, 1 day of testing, free.
• Which paper bridge shape holds the most coins?: 2nd–7th grade, 1 day of testing, free.
• Which paper column shape holds the most books?: 3rd–8th grade, 1 day of testing, free.
• Do longer blades make a spinner fall slower?: 3rd–8th grade, 1 day of testing, free.
• Does a longer arm make a catapult throw farther?: 3rd–8th grade, 1 day of testing, free.
• Does a pointed nose make a straw rocket fly farther?: 3rd–7th grade, 1 day of testing, free.
• Do bigger hoops make a straw glider fly farther?: 3rd–8th grade, 1 day of testing, free.
• Does a bigger parachute fall slower?: 3rd–8th grade, 1 day of testing, free.
• Which padding keeps a dropped egg from cracking?: 3rd–8th grade, 1 day of testing, about $3.
• Which material makes the slowest parachute?: 4th–8th grade, 1 day of testing, free.

Every one tests each design at least three times. On its project page, the steps, the materials and the results table are ready to print.

The board for an engineering entry

The board kit prints your board's cards at true size. For a build-and-improve project you've kept, pick Engineering entry and it swaps the hypothesis for the design goal and the steps for the designs you tried. Its title letter sheet has 13 titles to cut out: Problem, Design Goal, Research, Limits, Materials, Sketches, Designs, Testing, Data, Results, Improvements, Best Design and Next Time.

Put a sketch or a photo of each design on the board, numbered in the order you built them, so a judge can follow how it got better. Make the results card show every design's tries and its mean, side by side.

Building safely

Most of these are paper, cups, straws and string. The notes on their pages stay on, however many designs you build:

• 💧 Water
• 🧽 A bit messy
• 🚧 Stand back when it goes
• 🧍 Drop from standing: never climb
• 🙅 Never at faces
• 🧼 Wash your hands after
• 🚫 Test food is not for eating

Cut with scissors, never a craft knife, and stop when your design goal is met or you run out of time: you don't need a fourth design for a good board. If you want to build something that isn't on the list, ask your teacher first, and try Is my project OK? with a grown-up.