This contest limits outside help to guidance: the students design and build the entry. Design your own bridge. The designs here are worked examples to learn from, not entries to copy. The advisor certifies that only the two team members worked on the entry (the form quoted is the 2025-26 edition); the rules don't mention AI tools.
Help from adults: The advisor certifies that only the two team members worked on the entry.
“I also certify that only the two (2) team members noted have worked on the entry they are submitting for testing and evaluation.”
Your entry must include:
Everything you need to build this bridge by hand: a full-size plan, the cut list, the joints and the glue order.
Build pack · TSA Structural Engineering 2027, Middle School (balsa, 9 in span)
Loads (simulated, not yet checked on real breaks)
Expected to break first: member crushing/buckling, at E2 (end post).
One truss seen from the side, 9.9 in long. Both trusses are built on this same plan. The plan prints full size across the pages outlined below: trim each page along its dashed line, lay it over the page to its left or above, line up the ⊕ marks and tape it. Print at 100% (“Actual size”) and check the scale bar on each page with a ruler.
2 Letter pages, portrait, at the end of this pack.
Every piece, labelled as on the plan. Lengths are the finished long edge, to the nearest 1/16 in. Angles are between the cut and the stick's edge (90° is square), left end first as drawn (bottom end first for verticals); where an end has two cuts, both are given. For the truss pieces, lay the stick on the full-size plan and mark the cuts from it.
| Piece | What | Cut | Stick | Length, in | Ends |
|---|---|---|---|---|---|
| B1 | bottom chord | 2 | 1/8 × 1/8 in | 2 7/16(2.44) | both square |
| B2 | bottom chord | 2 | 1/8 × 1/8 in | 2 7/16(2.43) | both square |
| B3 | bottom chord | 2 | 1/8 × 1/8 in | 2 11/16(2.68) | both square |
| B4 | bottom chord | 2 | 1/8 × 1/8 in | 2 7/16(2.41) | both square |
| D1 | diagonal | 2 | 1/8 × 1/8 in | 6 15/16(6.91) | 69° + 23° / 10° + 42° + 69° |
| D2 | diagonal | 2 | 1/8 × 1/8 in | 6 15/16(6.95) | 69° / 22° + 69° |
| E1 | end post | 2 | 1/8 × 1/8 in | 6 11/16(6.71) | 75° / 17° + 75° |
| E2 | end post | 2 | 1/8 × 1/8 in | 6 3/4(6.74) | 74° + 16° / 74° |
| FB1 | floor beam | 1 | 1/8 × 1/8 in | 1 5/8(1.63) | both square |
| FB2 | floor beam | 1 | 1/8 × 1/8 in | 1 5/8(1.63) | both square |
| FB3 | floor beam | 1 | 1/8 × 1/8 in | 1 5/8(1.63) | both square |
| FB4 | floor beam | 1 | 1/8 × 1/8 in | 1 5/8(1.63) | both square |
| ST1 | strut | 1 | 1/8 × 1/8 in | 1 5/8(1.63) | both square |
| ST2 | strut | 1 | 1/8 × 1/8 in | 1 5/8(1.63) | both square |
| T1 | top chord | 2 | 1/8 × 1/8 in | 2 13/16(2.83) | both square |
| T2 | top chord | 2 | 1/8 × 1/8 in | 2 3/4(2.72) | both square |
| V1 | vertical | 2 | 1/8 × 1/8 in | 6 1/2(6.47) | both square |
| V2 | vertical | 2 | 1/8 × 1/8 in | 6 7/16(6.42) | square / 22° + 10° |
| V3 | vertical | 2 | 1/8 × 1/8 in | 6 7/16(6.47) | both square |
4 sticks, 36 in long, with 1/32 in for each saw cut.
Stick 1 · 1/8 × 1/8 in · 1.4 in left over
Stick 2 · 1/8 × 1/8 in · 0.0 in left over
Every kind of joint on the bridge, once, enlarged. Blue runs through; amber is cut to fit against it. Truss joints are seen from the side, like the plan; joints between the trusses are seen from above.
Pieces that run through a joint go down first, because the others are cut to fit against them: the chords (and the end posts, where they run through the corner). Then the webs between them. Build the second truss the same way on the same plan. The pieces that join the two trusses go in last: the deck members first, then the bracing above them.
First truss: chords
B1, B2, B3, B4, T1, T2
Pin them down on the plan over wax paper or plastic wrap.
First truss: webs
E1, E2, V1, V2, V3, D1, D2
Cut each end to the plan, then glue it against the chords.
Second truss: chords
B1, B2, B3, B4, T1, T2
On the same plan, once the first truss is dry and lifted off.
Second truss: webs
E1, E2, V1, V2, V3, D1, D2
The same pieces again.
Join the trusses: deck
FB1, FB2, FB3, FB4
Stand the trusses up square, the right width apart.
Join the trusses: bracing
ST1, ST2
Check the bridge is square before the glue sets.
Our summary of the TSA Structural Engineering 2027, Middle School (balsa, 9 in span) rules. If anything here disagrees with the rulebook or the organizer, they win.
These print one per page at full size. On screen they show at your display's scale.
Page A1 of 2 · flat howe-4 for TSA Structural Engineering 2027, Middle School (balsa, 9 in span)
Full size. Row A, column 1.
Page A2 of 2 · flat howe-4 for TSA Structural Engineering 2027, Middle School (balsa, 9 in span)
Full size. Row A, column 2. Trim the left edge on the dashed line.
Stick 3 · 1/8 × 1/8 in · 1.6 in left over
Stick 4 · 1/8 × 1/8 in · 5.9 in left over