# 180 — Design Notes & Engineering Requirements

> Working engineering log for the 180, for the team and engineering partners
> (university teams, naval-architect advisors). Decisions are evolving; figures are targets
> pending a prototype. Companion to the public [boat page](index.qmd).

## Design intent

An **affordable, light, stable two-person training dinghy** to get people sailing — a
deliberate answer to a sport pricing itself out (new boats of the leading single-hand class
now run ~$9k+, ~$1,250 just to race locally, sails $800–1,500). The 180 should be
**give-away-able at ~$1,000 in at-cost materials**, buildable in a garage with hand layup.

## Hull

- **Stable, scow-influenced two-person hull.** Closest reference is a small two-person
  mini-scow (stable, can later carry foiling blades) rather than a Laser-type hull.
- Loosely Laser-derived proportions but with a **wider, flatter transom** for **downwind
  stability** and room for two — flat and forgiving, *not* tippy.
- **Construction: foam core, skinned with thin fiberglass + epoxy** (a few coats of
  penetrating epoxy), with **structural cutouts / lightening pockets** for a high
  stiffness-to-weight ratio. **No exotic carbon for the hull** (keep glass standard/minimal).
  **No wood, no balsa.**
- **Prefab-friendly:** CNC-cut foam, prefab stringers, **3D-printed fittings**, CNC-carved
  parts. Simple hand layup — no autoclave, no aircraft hangar.
- **Light & car-toppable**, liftable by two people (explicit anti-goal: heavy 470/Tech-style
  "bathtubs" that need a whole team to move and soak up water).
- **Stackable** for storage at programs with limited space.
- **Capacity:** design for up to ~**500 lb** crew (e.g., a 225-lb adult + a 150-lb youth);
  buoyancy to support solo or crewed use. Slow at max load is acceptable.

## Rig

- **Keep it simple — no shrouds / no standing rigging** on the base trainer.
- **Single sail (Laser-style sleeve)** is the simplest baseline. **Optionally a small jib** —
  a jib gives the crew a real task and helps teaching. If a jib is used: a simple
  **free-luff / leading-edge jib** with a light integrated headstay, **no spinnaker/chute**,
  no complex rigging.
- **Boom:** strongly consider an **elevated / wishbone boom** (or boomless) so sailors don't
  have to duck a low Laser-style boom — important for two-up teaching and bigger sailors.
- **Spars:** carbon or **light fiberglass tube** (aluminum is heavier), prefab and
  cut-to-length. **Dacron** sail (inexpensive, durable).
- **Heavy air:** drop the jib and sail on the main — reduce sail area simply.

## The mast step — critical engineering

The mast socket/step must be **bulletproof**. Learn directly from the Laser's failure mode
(soft decks and mast-step deformation under heavy wind and hiking loads):

- The step must **carry load all the way down to the bottom of the hull.**
- Use an **engineered radial "starburst"** that distributes load from the step out into the
  hull in all directions. This is a priority engineering problem for partner teams.

## Foils

- CNC/prefab **daggerboard or leeboard + kick-up rudder**; no wood.
- **Optional foiling blades** as a *future* performance add-on — the base boat stays stable
  and non-foiling; add-ons are sold at cost (and must respect the cost/openness rules below).

## Open-source & the engineering challenge

- **Fully open source:** any engineering improvement must be shared back into the free plans.
- **Material limits:** avoid exotics; **no single upgrade may exceed $25** and must be widely
  buildable. (Acknowledged tension: even a short piece of Dyneema isn't free — buy by the
  reel; minimize total load and use cheap, readily available aluminum/fiberglass tube.)
- Frame as a **university engineering challenge:** give programs the basics, let them refine
  and repair, peer-reviewed by engineers; winning ideas fold into the shared plans.

## Cost target

~**$1,000** per finished boat (hull + spars + sail), via **at-cost materials** through
partnerships (notably West System epoxy at cost — resin *and* fillers). Seed funding
covers materials + shipping for the pilot fleets.

## Reference boats — what to copy, what to avoid

| Boat | Lesson |
|------|--------|
| Laser/ILCA | Simple single sail + durable mast = good; soft-deck/mast-step weakness + now over-priced and tippy for teaching = avoid |
| Penguin | Two-person; older sailors can sit *in* it (low physical demand) — good |
| Lightning | Originally an everyman plywood boat; cautionary tale of a class pricing itself out |
| Optimist | Great kid trainer, but single-youth only |
| 420 | Too tippy, too expensive, too small for bigger sailors |
| Tech dinghy | Too heavy, soaks up water — the "bathtub" anti-pattern |
| Annapolis mini-scow | Two-person, foiling-capable blades, not overly long — **closest to our target** |