Grade 3 · Design & Engineering · Lesson 144

Straw Raft

Build a paper-straw raft that floats while carrying three large plastic counters.

Time2 × 45 minutesTeamsPairs; alternate builder and testerEquipmentBasic classroom design materials; no powered equipment

Your project in view

What you are making

Build a paper-straw raft that floats while carrying three large plastic counters.

This generated example illustrates one possible finished design—not actual student work. Use the lesson’s sizes, connected parts and safety steps; your colors and creative details can be different.

Generated finished-project example for Straw Raft: Build a paper-straw raft that floats while carrying three large plastic counters.
Straw Raft · Generated project example

Student directions · Grade 3

What will you make and do?

Build a paper-straw raft that floats while carrying three large plastic counters.

Teacher overview: Students will plan the specific object described below, make and test a first version, then use their results to improve it. Read one step together, demonstrate the unfamiliar action, and let students complete that step before moving on.

  1. 1Plan your project

    Draw two straw arrangements. Mark cross braces and where the three counters will sit.

  2. 2Make the first parts

    Line up equal straws and join them with two cross braces using small tape wraps.

  3. 3Put it together

    Place the empty raft on calm water and check for loose straws before adding the centered load.

  4. 4Test it fairly

    Float with three counters for 20 seconds in three trials. Record tipping, sinking or lost parts.

  5. 5Improve one part

    Change one brace position, raft width or counter layout and repeat.

  6. 6Show and turn in

    Submit the finished straw raft, two labeled ideas and before-and-after evidence. Explain which change the results support.

How will you know it works?

  • Floats for 20 seconds
  • Carries all three counters without losing them
  • Record the stated test and explain one revision

Before you move on

Tell a partner what you are making. Point to the part you will work on next. Draw or dictate your test notes if writing slows you down.

Machine cutting, printer setup and electrical power-on require adult approval. A basic-materials model is a valid way to demonstrate the design when equipment is unavailable.

Keep your plan, test notes and before-and-after evidence with the printable design brief below. Use the detailed teacher plan and any coding guide for tool instructions. These steps continue across the lesson’s meetings, not all in one sitting.

For teachers

Engineering standards

This shows how the lesson connects to the national NGSS engineering standards and what student work you can collect.

Assessed

3-5-ETS1-1

Define the need in Build a paper-straw raft that floats while carrying three large plastic counters. Agree on the two success checks and the listed material limits.

What students show: Two labeled ideas with the target and limits stated.
Practiced

3-5-ETS1-2

Compare the ideas using the project checks: Floats for 20 seconds; Carries all three counters without losing them.

What students show: A selected design with a reason connected to a success check.
Assessed

3-5-ETS1-3

Test, change one feature and retest: Float with three counters for 20 seconds in three trials. Record tipping, sinking or lost parts. Change one brace position, raft width or counter layout and repeat.

What students show: Before-and-after results collected under the same conditions.

Materials

  • Paper straws
  • tape
  • cotton string
  • shallow water tray
  • three counters
  • towel
  • Pencil, planning paper and the printable design brief below

Teacher preparation

  1. Gather per-pair materials: Paper straws; tape; cotton string; shallow water tray; three counters; towel.
  2. Make one rough sample and rehearse the exact test: Float with three counters for 20 seconds in three trials. Record tipping, sinking or lost parts.
  3. Set the size, load or distance marks mentioned in the steps before class. Demonstrate an ordinary first attempt, not a perfect model to copy.
  4. Prepare any holes, fasteners or difficult cuts for students. Check the stated safety note and clear the testing space.

Step by step

How to teach it

Meeting 1 · 0–8 min

See the job and plan

  1. Introduce the finished object: Build a paper-straw raft that floats while carrying three large plastic counters.
  2. Draw two straw arrangements. Mark cross braces and where the three counters will sit.
  3. Students say what would count as a successful result.
Meeting 1 · 8–18 min

Model the unfamiliar action

  1. Demonstrate slowly: Line up equal straws and join them with two cross braces using small tape wraps.
  2. Pause so partners can repeat the action; provide prepared parts if cutting or folding blocks progress.
Meeting 1 · 18–35 min

Build the first version

  1. Place the empty raft on calm water and check for loose straws before adding the centered load.
  2. Partners swap builder and checker roles halfway through. Check the working part before decorating.
Meeting 1 · 35–45 min

Try once and save

  1. Run one trial of the stated test to locate an obvious problem. Do not count a changed procedure as a fair comparison.
  2. Label and store the model; sketch its current shape and clear the work area.
Meeting 2 · 0–8 min

Predict and set up

  1. Revisit the two success checks. Agree on identical starting conditions and prepare a before/after results table.
Meeting 2 · 8–23 min

Collect evidence

  1. Float with three counters for 20 seconds in three trials. Record tipping, sinking or lost parts.
  2. One student operates while the other records. Swap for a later trial while noting a change of operator if it affects the result.
Meeting 2 · 23–35 min

Change one thing

  1. Change one brace position, raft width or counter layout and repeat.
  2. Keep the original results rather than replacing them with only the best attempt.
Meeting 2 · 35–45 min

Explain and clean up

  1. Submit the finished straw raft, two labeled ideas and before-and-after evidence. Explain which change the results support.
  2. Collect the brief and results; separate reusable materials and clean the test area.

Assessment

  • Floats for 20 seconds
  • Carries all three counters without losing them
  • Student demonstrates the actual task: Float with three counters for 20 seconds in three trials. Record tipping, sinking or lost parts.
  • Record includes failures as well as successes.
  • Student identifies one changed feature and uses the retest to explain the result.

Supports & extensions

  • Provide fold marks or pre-cut parts; accept drawings or dictated observations.
  • Start with the smallest working version of straw raft before decoration.
  • Extension after success: choose one more value for the same tested feature, predict its effect and repeat float with three counters for 20 seconds in three trials.

Safety & responsible use

  • Teacher checks materials and test conditions before use. Use classroom scissors; adults prepare difficult cuts, holes and fasteners.
  • No powered tools, coding, hot glue or electrical circuits are required. Keep moving objects contained and test loads light.
  • Use shallow trays away from electronics. Wipe spills immediately and do not drink test water.

No-machine alternative

Use prepared paper parts, larger pieces or an adult-assisted version of the same build. Keep the functional task: Build a paper-straw raft that floats while carrying three large plastic counters. If physical testing is not possible, label sketches as predictions rather than measured results.

Printable student design brief

The challenge

Build a paper-straw raft that floats while carrying three large plastic counters.

Success criteria

  • Floats for 20 seconds
  • Carries all three counters without losing them
  • Record the stated test and explain one revision

Constraints

  • Use only the listed teacher-approved materials
  • Stay within the teacher-set size, load and test-space limits
  • Two 45-minute meetings; keep the first version simple

Engineer’s notes

Who uses this object, and what should it do?
Draw two possible designs. Label the working parts and circle your choice.
Which size, fold, gap or position must you measure or mark?
Before testing, predict what will happen: Float with three counters for 20 seconds in three trials. Record tipping, sinking or lost parts.
Record each trial: condition / expected result / actual result.
Draw the ONE change you made. What stayed the same?
Record the retest. Did the change help, not help, or leave the result uncertain?
Show and explain: one result that supports your conclusion.
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