# Case Design

## Form Factor

Briefcase clamshell:

- **Canopy** — Salvaged K501U laptop lid (display, hinge, bezel). Opens upward, hinge at the bow edge.
- **Base** — Wooden enclosure holding keyboard, SBC, power, and peripherals.

User sits at the stern, facing the bow. See [design-decisions.md](design-decisions.md) for full nomenclature (deck/keel/bow/stern/port/starboard).

## Dimensional Constraints

### Canopy (Lid)

| Dimension | Value | Source |
|-----------|-------|--------|
| Width | 39 cm | Measured, rounded up |
| Height | 26 cm | Measured, rounded up |

The lid dimension is the *outer* shell of the K501U display assembly (plastic casing + LCD panel + bezel). The glass panel itself is smaller — these are the hinge-to-edge and side-to-side mounting boundaries.

### Base External

Tentative, with ~5mm per-side margin beyond the lid:

| Dimension | Value | Notes |
|-----------|-------|-------|
| Width | 40 cm | Lid width + margins |
| Depth | 27 cm | Lid depth + margins |
| Height | TBD | Depends on component stacking |

Base height (internal depth of the wooden box) is the critical unknown. It depends on whether all internal components fit in a single Z-slice or require multiple layers.

## Component Footprint Inventory

Measured and estimated dimensions for everything that goes inside the base. These are 2D floorplan sizes (width × depth); height determines minimum internal clearance.

| Component | W × D × H | Notes |
|-----------|----------|-------|
| TrackPoint keyboard | ~32 × 11 cm × ~1 cm | Depends on specific model, typical compact USB TrackPoint KB |
| Orange Pi 3B | 8.5 × 5.6 cm × ~1.5 cm | With heatsink. Mount on standoffs |
| Display controller (eDP→HDMI) | ~7 × 5 cm × ~1.5 cm | Generic board, may vary. Near hinge |
| IP5389 power board | ~5 × 4 cm × ~0.5 cm | Thin PCB, mount near cell pack |
| 18650 cells ×6 (3S2P) | 19.5 × 3.6 cm × 1.85 cm | Each cell 18×65mm. 3 cells end-to-end = 195mm, 2 cells side-by-side = 36mm |
| USB hub PCB (decased, 10-port) | ~12 × 5 cm × ~1.5 cm | Estimate — depends on specific hub |
| HDMI A/B switch (mechanical) | ~5 × 3 × 2 cm | Passive toggle. Near hinge |
| PAM8403 audio amp | ~2.4 × 2.1 × 0.5 cm | Tiny, anywhere |
| Speakers ×2 | ~3.1 × 7 cm × ~1.5 cm | Small drivers |
| Cooling fan(s) | 4–8 cm square × ~1 cm | Size TBD based on thermal needs |
| 5A fuse + holder | ~2 × 2 × 1 cm | Inline on power rail |

## Floorplan Strategy

The deck surface has two fixed-location items:

1. **Keyboard** — centered, user-facing (stern edge). ~32 cm wide leaves ~4 cm per side within a 40 cm base width for misc ports or switches.
2. **Hinge mount** — along the full bow edge, structural.

Everything else floats between them. The major volume items:

- **Battery pack (19.5 × 3.6 cm)** — longest rigid item other than the keyboard. Placement candidates:
  - Behind the keyboard (between keyboard rear and hinge area) — requires ~20 cm of unobstructed depth behind the keyboard
  - Along port or starboard side — uses the 4 cm gutter on one side
  - Under the keyboard — possible if keyboard is a flat membrane type, unlikely for a mechanical

- **OPi 3B + USB hub** — moderate footprint, flexible placement. Could sit in the area behind the keyboard alongside the battery pack.

- **Display controller + HDMI switch** — short HDMI cable runs dictate they live near the hinge.

### Depth Dimensions (Front-to-Back)

```
Bow edge (back)
│
[hinge area — 2-3 cm]
[display controller / HDMI switch]
[battery pack and/or SBC/hub zone]
[keyboard — 11 cm]
[palm rest area — 5-8 cm]
│
Stern edge (front)
```

Total: roughly 18-22 cm front-to-back for keyboard + palm rest, plus 15-20 cm behind keyboard for electronics. That fits within a ~27 cm base depth with room to spare.

### Port-Starboard Layout (Width)

```
Port edge (left)                 Starboard edge (right)
│                                  │
[2 cm gutter] [keyboard ~32 cm] [2 cm gutter]
```

The gutters can hold the vertical battery pack, side-mounted ports, or switch cutouts.

## Z-Stack (Depth/Layer Planning)

**Goal: single-slice layout** — all boards and components mounted on the same plane (the keel), with nothing stacked above or below.

Feasibility check:
- Tallest component: speakers at ~1.5 cm, OPi with heatsink at ~1.5 cm, HDMI switch at ~2 cm
- Battery pack at 1.85 cm
- Leave ~5 mm clearance above tallest item → internal clearance of ~2.5 cm
- Wood base walls at ~1 cm each → total case height ~4.5 cm

This keeps the case within briefcase norms (~8-13 cm is the typical range, but thinner is fine) and avoids the weight and complexity of a second deck layer.

## Open Questions

- [ ] Exact TrackPoint keyboard model — dimensions and mounting method
- [ ] Battery pack placement — behind keyboard vs side gutter
- [ ] Fan size and placement — SBC heatsink fan vs case fan
- [ ] Lid latch mechanism — holds canopy closed in transit
- [ ] Hinge reattachment — how to mount K501U hinge to wooden base
- [ ] Cable routing paths — power, HDMI, USB within the case
- [ ] SD card reader location — stern edge per port layout
- [ ] Kensington lock slot — stern edge
- [ ] Wood thickness and joinery method

## Revision History

| Date | Change |
|------|--------|
| 2026-06-03 | Initial — dimensional constraints and floorplan approach |