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 Design and Engineering 2027, High School (balsa, 9 in span)
Loads (simulated, not yet checked on real breaks)
Expected to break first: member crushing/buckling, at E2 (end post).
This contest asks you to say what help and AI tools you used. Here is a paragraph you can adapt; change it to match what your team really did.
We used Balsa Bridge Lab, a free bridge-design tool that uses computer optimization, to generate a design that meets the TSA Structural Design and Engineering 2027, High School (balsa, 9 in span) rules, which we then studied, checked, built and tested ourselves. Any changes we made and what we learned are our own. We describe this in the Resources and AI Reflection (up to four pages, scored, see TSA's 2027 & 2028 Forms Appendix).
One truss seen from the side, 10.2 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.
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 | 3 11/16(3.71) | both square |
| B2 | bottom chord | 2 | 1/8 × 1/8 in | 3 1/8(3.11) | both square |
| B3 | bottom chord | 2 | 1/8 × 1/8 in | 3 3/8(3.36) | both square |
| D1 | diagonal | 2 | 1/8 × 1/8 in | 8 11/16(8.69) |
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, T1, T2
Pin them down on the plan over wax paper or plastic wrap.
First truss: webs
E1, E2, D1, D2, D3, D4
Cut each end to the plan, then glue it against the chords.
Second truss: chords
B1, B2, B3, T1, T2
On the same plan, once the first truss is dry and lifted off.
Second truss: webs
E1, E2, D1, D2, D3, D4
The same pieces again.
Join the trusses: deck
FB1, FB2, FB3, FB4
Stand the trusses up square, the right width apart.
Our summary of the TSA Structural Design and Engineering 2027, High 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 4 · flat warren-3 for TSA Structural Design and Engineering 2027, High School (balsa, 9 in span)
Full size. Row A, column 1.
4 Letter pages, landscape, at the end of this pack.
| 77° / 77° |
| D2 | diagonal | 2 | 1/8 × 1/8 in | 8 9/16(8.54) | 81° + 22° / 21° + 81° |
| D3 | diagonal | 2 | 1/8 × 1/8 in | 8 5/8(8.62) | 78° + 79° / 20° + 79° |
| D4 | diagonal | 2 | 1/8 × 1/8 in | 8 9/16(8.55) | 81° / 81° |
| E1 | end post | 2 | 1/8 × 1/8 in | 8 9/16(8.53) | 82° / 21° + 82° |
| E2 | end post | 2 | 1/8 × 1/8 in | 8 9/16(8.56) | 80° + 18° / 80° |
| FB1 | floor beam | 1 | 1/8 × 1/8 in | 1 11/16(1.69) | both square |
| FB2 | floor beam | 1 | 1/8 × 1/8 in | 1 11/16(1.69) | both square |
| FB3 | floor beam | 1 | 1/8 × 1/8 in | 1 11/16(1.69) | both square |
| FB4 | floor beam | 1 | 1/8 × 1/8 in | 1 11/16(1.69) | both square |
| ST1 | strut | 1 | 1/8 × 1/8 in | 1 11/16(1.69) | both square |
| ST2 | strut | 1 | 1/8 × 1/8 in | 1 11/16(1.69) | both square |
| T1 | top chord | 2 | 1/8 × 1/8 in | 3 7/16(3.45) | both square |
| T2 | top chord | 2 | 1/8 × 1/8 in | 3 3/16(3.18) | both square |
5 sticks, 36 in long, with 1/32 in for each saw cut.
Stick 1 · 1/8 × 1/8 in · 1.2 in left over
Stick 2 · 1/8 × 1/8 in · 1.6 in left over
Stick 3 · 1/8 × 1/8 in · 0.0 in left over
Stick 4 · 1/8 × 1/8 in · 0.4 in left over
Stick 5 · 1/8 × 1/8 in · 29.1 in left over
Join the trusses: bracing
ST1, ST2
Check the bridge is square before the glue sets.
Page A2 of 4 · flat warren-3 for TSA Structural Design and Engineering 2027, High School (balsa, 9 in span)
Full size. Row A, column 2. Trim the left edge on the dashed line.
Page B1 of 4 · flat warren-3 for TSA Structural Design and Engineering 2027, High School (balsa, 9 in span)
Full size. Row B, column 1. Trim the top edge on the dashed line.
Page B2 of 4 · flat warren-3 for TSA Structural Design and Engineering 2027, High School (balsa, 9 in span)
Full size. Row B, column 2. Trim the left edge on the dashed line. Trim the top edge on the dashed line.