A complete recreation of the famous #3DBenchy calibration boat, built entirely from measurements — cross-sections, silhouettes, and feature positions extracted programmatically from the reference STL, combined with the hard dimensions from the official brochure (60.00 × 31.00 × 48.00 mm, 23.00 mm roof at 5.5°, 10.50 × 9.50 mm front window, ø9/ø12 stern window, ø3 × 11 mm chimney bore, 12.00 × 10.81 × 9.00 mm deck box…). No geometry was copied; every vertex was derived, placed, and verified across 51 build iterations driven through the Blender MCP bridge.
Model Used: claude-fable-5 (Claude Code)
To recreate this Benchy in your own Blender instance, ensure the MCP server is running and execute:
python -m src.main play community/benchy/session.jsonOne replay produces the full model and exports a print-ready sh_benchy.stl.
The session is idempotent: it wipes the scene and rebuilds from scratch every run.
Important
Use the current bundled Blender addon (blender_mcp_addon/) — this session relies on
its batch-safe delete *, deterministic cap triangulation, and loud-failure modifier
baking. Older addon builds will fail the cleanup step or produce corrupted geometry.
| Stage | Highlights |
|---|---|
| Hull | 9-ring create_polygon loft from measured stations: 40° spoon bow, upright bulwark band, uniform 2.6 mm gunwale rail (true perpendicular offsets), 69° raked transom, keel + deck spine rings so both caps are clean quads |
| Deck | Flat aft cockpit at Z=8.5, exact 45° companionway ramp, rising foredeck — all measured |
| Details | Hawsepipe "eyes" as true pipes with flange rings, prop-shaft socket, raked fishing-rod holder, deck box with spec 9.00 mm pocket |
| Cabin | Trapezium loft wheelhouse, side arches with raised double frames, front + stern windows aligned at Z=32 with unified 1.2 mm frames, helm console with recessed steering wheel |
| Roof & chimney | Measured trapezoid roof (rear-flush, front-flared visor) at 5.5°, chimney to exactly 48.00 mm with spec bore |
| Print prep | Bake all booleans → level-2 subsurf on the hull → join 18 parts → 0.15 mm voxel remesh (watertight fuse) → Laplacian smoothing → re-drill eyes + prop socket → engrave SH BENCHY 0.25 mm into the flat bottom → check_mesh_for_printing → STL export |
- Big cap n-gons tent. A loft's end cap over a height-varying ring gets triangulated unpredictably — bridging triangles domed our deck and crumpled the hull bottom. Fix: spine rings so caps degrade to thin coplanar slivers, plus deterministic cap triangulation in the addon.
- Small holes don't survive subdivision + voxel remesh. Subsurf pinches a ø4 hole nearly shut and the remesh unions the pinched material into a membrane. Fix: re-drill every bore into the final solid, after smoothing.
- Engrave bottom text, don't raise it — the print bed needs a flat first layer; the original's shallow bottom letters exist precisely to reveal first-layer squashing.
- Boolean holders before cutters when cleaning a scene, or batch-delete both together.
Load sh_benchy.stl into your slicer. Like the original, it is designed to print at
1:1 without supports — hull overhang ≈ 40°, flat bottom with engraved nameplate,
verified watertight before export.
The final printed SH Benchy — photo coming after the first print!
A second, display-oriented build on top of the same hull: a two-sail square rig (mast, yard, boom, lower spar, main + second sail with a sculpted cloth billow), designed and refined through the AI Assistant panel with live viewport screenshots for self-verification. Every fix — from a floating sail to overhanging spar tips — was driven by an actual slicer test, not a guess.
python -m src.main play community/benchy/session.json --branch sail_rig(Or run the sail_rig branch directly from Blender Studio.) This exports a
second STL, sh_benchy_sail.stl — the merged hull + rig, solidified,
voxel-remeshed, decimated, and watertight-checked, same as the classic export.
The two-sail rig — mast planted in the cabin roof, forward of the chimney
- Horizontal round bars always overhang. A cylindrical spar's underside is
a 90° overhang along its whole length — no amount of bracing underneath
fixes it, since the slicer still trees up to fill the gaps between braces.
Fix: build spars with a diamond cross-section (
vertices=4, rotated 90° so a corner points down) — the two 45° facets read as self-supporting. - Bar tips must land inside a supporting sheet. A spar tip protruding even 2–3mm past the sail it's attached to becomes a floating island. Tips are sized flush with (or slightly recessed into) their sail.
- Vertical is always safe. Where a bracing structure kept getting flagged no matter the angle, switching to plain vertical posts (equally spaced, ≤6mm apart to stay within bridging limits) resolved it immediately.
- Thin decorative sheets need real thickness before export — the sails
are zero-thickness cloth shapes until a
SOLIDIFYpass (1.0mm) is applied, then joined into the hull and voxel-remeshed into one watertight body. - Simplify before export. The merged, remeshed body easily exceeds 1M
triangles, which most slicers flag. A
DECIMATEpass (ratio 0.35) brings it back under budget while preserving the engraved bottom text far better than a coarser remesh would.
Final slice — auto-supports found nothing to flag