Eight triangles, with two short rafters between each pair.
The revised roof follows Stewart’s corrected pattern. Short rafters meet the sides of the neighboring main hips, outside the cupola.
The eight former midpoint pieces J0-1 through J7-1 are retired. The surviving timbers retain their IDs and A/B direction. The lower radial ties are now 6 × 10 in. One reusable symbolic green aid and one black temporary central support assembly are separate construction-only components.
R02 removed eight unsupported lower cupola bands and added eight cupola roof rafters and eight ceiling spokes. The current frame also adds the third inward brace at every main post and uses full 2 × 6-inch stock for all 24 main knee braces, bringing the primary timber count to 112. Complementary joints are modeled and checked numerically. The two upper octagonal timber bands and eight cupola roof rafters remain visible, with the well below open. The temporary fixture and optional roof surface remain separate.
R02: fitted cupola and restored inspection
Cupola posts extend down to the bottom of the 6 × 10 ties. Fitted octagonal 4 × 6 bands connect the posts. The main hips have flat rectangular tops, with no backing bevel. The P0 corner close-up, exploded assembly, end views, edge tables, multi-selection and free navigation are retained. Selecting wood automatically shows bright transparent recesses.
The outside and inside diameters imply a 6 in radial post depth and 41 in center radius. Rotated 6 × 6 posts give a 28.132865 in outward-corner gap, which rounds to 2 ft 4⅛ in. This gap is neither the post-center chord (31.380041 in) nor the clear span on the inside edge.
Readable source values and prior user directions govern the dimensions above. The source lower-member callout is 6 × 8; the model retains Stewart’s earlier explicit change to 6 × 10. The readable 4 × 6 bands are preserved. Glazing height 2 ft 8 in has uncertain endpoints. Roof timber depth, pegs, steel thickness and window dimensions cannot be established from this image.
The proposed fit uses centered shoulder tenons and matching sockets, diagonal brace sockets, and shallow bearing seats. Joint sizes are design assumptions, not source dimensions. The main roof height is offset by the actual member depth to bear above the ties; the ring is aligned with the short-rafter underside. These inferred bearing datums preserve plan dimensions and slopes. Structural capacity, timber movement and assembly sequence remain unverified.
Download the current all-pairs solid and contact audit
Dimensions and their datums
| Dimension | R01 value | Basis |
|---|---|---|
| Main post outside diameter | 30 ft 0 in | Confirmed outside radial post faces |
| Main post-center diameter | 29 ft 4 in | Derived using provisional full 8 in posts |
| Main roof-tip diameter | 33 ft 4 in | 20 in radial overhang beyond outside post face |
| Main radial slope | 4:12 · 18.434949° | Working reading of the main-frame section |
| Short-rafter slope | 4.329569:12 · 19.839312° | Derived normal to the eave; compatible with the radial 4:12 slope |
| Main hip / lower tie | 8 × 10 in / 6 × 10 in | Source hip reading / Stewart’s tie direction |
| Short rafters | 4 × 8 in; 42⅜ in clear gap | Provisional actual section and apparent source gap reading |
| Cupola outside / inside diameter | 7 ft 4 in / 6 ft 4 in | Radial post faces; consistent with rotated 6 × 6 in posts |
| Cupola spacer clear gap | 28⅛ in | Adjacent outward-facing post corners; calculated 28.132865 in |
| Cupola roof | 4:12 radial slope; 12 in overhang | Confirmed; roof tips span 9 ft 4 in |
| Ground-to-tie height H | Unresolved | 7 ft 6 in is used only as the viewer’s display datum |
The new rafter-to-hip connection
Each short rafter runs perpendicular to its eave side. It meets the receiving hip at a 22.5° plan angle. Its physical end follows the hip’s side plane; the rafter does not continue to the hip axis or the cupola.
The viewer’s Inspect rafter-to-hip joints button brings together R0, J0-0 and J7-2. Select either rafter, then a recorded contact surface, to see its angles, boundary lengths and vertices. The model repeats this arrangement around all eight bays.
| Reference measurement | Value | What it describes |
|---|---|---|
| Short-rafter plan run to hip axis | 128.796330 in | Setting-out reference only |
| Short-rafter slope length to hip axis | 136.922963 in | Setting-out reference only |
| Short-rafter reference to hip side face | 125.810940 in | Conditional 8 in hip width; individual physical edges have different lengths |
| Main hip reference to outside cupola face | 164.438438 in | Vertical radial face at 44 in from center |
These are geometric references, not timber cutting lengths. Mortises, tenons, housings, bearing seats, fasteners, roof backing and machining allowances are not supplied by the source plan. The viewer distinguishes the measured contact surfaces from those open design decisions.
Metal components and the cupola
The single reusable green aid retains a symbolic shape between the outward corners of neighboring cupola posts. Their 28⅛ in setting-out gap is not a flat-metal blank length. Metal thickness, end returns, holes and fastening remain unspecified.
The black fitting is one temporary welded-support display assembly: eight radial vertical-plane L straps and three holes per outer leg, 24 total. The owner-confirmed opposite-end span is 90 in (7 ft 6 in), distinct from the unchanged 88 in cupola. The reference drawing gives 4 in strap depth and 14 in total outer-leg height. Thickness, hole diameter and centers, constant-width leg interpretation and elevation are explicitly illustrative display assumptions, not cut, drilling, weld, screw or erection specifications. No erection capacity, fastening or removal criterion is assigned.
Eight flat-topped cupola roof rafters now meet above the open well. Their 2 in width follows the readable 2x framing note; their 6 in depth is provisional. The optional roof surface shows the 4:12 slope and 12 in overhang. “Boston Layout” remains the wall-window source note; window dimensions and openings are unresolved.
Read and export the revised model
Orbit, zoom, isolate pieces or use Free / WASD to move around the frame. The selected-piece tables include edge lengths, face angles and contact-plane angles. Parts, materials and model data can be exported from the viewer. Metal components are excluded from timber board-foot totals.
Open the revised frameCurrent joint registerCurrent downloadsEarlier prototype review
Basis: Octagon architectural geometry study R01, 12 sheets, and Stewart Lundy’s corrections. Original drawing credited to Robert Swinburne / Bluetime Collaborative. Earlier fitted-model reports and GLBs document the superseded prototype and do not apply to this geometry. R01 is a geometry study, not a construction or fabrication set.
Joint strength and load-path audit: central withdrawal restraint and receiver proportions require redesign. Simple integral dovetails are a candidate, not a verified strength upgrade. The horizontal half-inch plywood and eight exposed ceiling spokes are now shown separately from the pitched roof; finish-board thickness remains unresolved.