WEST SYSTEM Epoxy Guide

WEST SYSTEM is a widely used marine and composite epoxy for bonding, coating and laminating — boat building, structural composites, timber construction and fibreglass repair. It's a two-part system: 105 Resin plus a compatible hardener, with optional fillers to modify strength or sanding properties. By combining these, you can tailor a mix for bonding, laminating, coating, structural repair or fairing.

WEST SYSTEM 105 Resin

A low-viscosity, solvent-free epoxy resin that wets out fibreglass and bonds to timber, metals and composites. Mixed with the correct hardener it cures to a high-strength, moisture-resistant solid. It is always used with a WEST SYSTEM hardener, which sets the cure speed and working time.

Hardeners

Hardener Cure speed Typical use Temp range Key feature
205 Fast Fast Small bonding jobs, repairs, cooler conditions 5–21°C Quick cure, strong bond, low-temp capable
206 Slow Medium Laminating, coating, larger surfaces 16–30°C Longer working time, good for sheathing
207 Special Clear Medium Timber coating, bright finishes 16–30°C Clear, UV-resistant, for varnished timber
209 Extra Slow Very slow Large laminating, hot climates 21–35°C Longest working time, prevents premature cure

Mix ratios

  • 105 + 205 or 206 → 5:1 by volume
  • 105 + 207 or 209 → 3:1 by volume
Important — changing the resin-to-hardener ratio does not speed up curing; it prevents proper curing. Cure speed is determined by which hardener you choose, not how much. Always confirm ratios against the current WEST SYSTEM Technical Data Sheet.

Fillers

Filler Type Typical use Sanding Key benefit
410 Microlight Ultra-light fairing Fairing hulls & cosmetic surfaces Very easy Smooth, lightweight fairing compound
411 Microsphere Lightweight Gap filling, light bonding Easy Good shaping and sanding
413 Microfibre High-strength structural Bonding joints, structural fillets Difficult Very strong adhesive mix
417 Low Density Fairing Surface finishing before painting Easy Lightweight, easy to shape

Common mix combinations

Laminating fibreglass — 105 Resin + 206 Slow Hardener
Timber bonding — 105 Resin + 205 Fast Hardener + 413 Microfibre
Fairing surfaces — 105 Resin + 206 Hardener + 410 Microlight
Clear timber coating — 105 Resin + 207 Special Clear Hardener

Why WEST SYSTEM is popular

  • Excellent adhesion to timber and composites
  • Low viscosity for fibreglass wet-out
  • Strong moisture resistance
  • Versatile filler system for structural or cosmetic work

Safety

Epoxy resin and hardener are sensitisers — wear gloves, ensure ventilation, avoid skin contact, and follow the product Safety Data Sheet.