West System 404 High-Density Filler – 30 lb

West System 404 High-Density Filler – 30 lb

A high-strength thickening additive formulated for epoxy-based hardware bonding, filleting, and gap filling where maximum load resistance is required. When blended into mixed epoxy resin, 404 High-Density Filler produces a stiff, non-sagging adhesive paste that cures to an off-white colour and delivers exceptional resistance to cyclic and shear loads.

The 30 lb bulk format is suited for production boatbuilding, boatyard repair operations, and large-scale projects where filler consumption is high and per-unit economy matters.

Key Features

• Engineered for maximum physical properties in hardware bonding under high cyclic loads
• Produces a stiff, gap-filling adhesive paste when blended with mixed epoxy
• Suitable for filleting, fairing, and structural gap filling where strength is the priority
• Cures to an off-white colour for a clean, paintable finish
• Non-sagging consistency holds position on vertical and overhead surfaces
• 30 lb bulk size for high-volume production and boatyard use

Common Applications

• Bonding deck hardware, cleats, and through-deck fittings subject to high cyclic loads
• Structural filleting at bulkhead-to-hull and frame-to-hull joints
• Gap filling in structural joints where maximum bond strength is required
• Bedding hardware where a rigid, load-bearing adhesive is preferred over flexible sealants

Use With

Mix into combined epoxy resin and hardener to achieve desired consistency. Recommended epoxy systems:

• West System C105A Epoxy Resin – 946 ml — Standard laminating resin base
• West System C105B Epoxy Resin – 3.74 L — Mid-volume resin for extended jobs
• West System C105C Epoxy Resin – 16.46 L — Production-scale resin pail
• West System C205 Hardener – 814 ml — Standard cure hardener

Related Fillers

• West System 406 Colloidal Silica Filler – 10 lb — Thixotropic filler for adhesive bonding and fairing on vertical surfaces
• West System 405 Filleting Blend — Smooth, wood-toned filler optimised for interior fillets and cosmetic joints

Parts Desk Insights

Best Use Cases: 404 High-Density Filler is the right choice when the bond needs to carry real structural load — particularly for hardware installations like cleats, winch bases, stanchion bases, and through-deck fittings where cyclic tension and shear forces are ongoing. It outperforms softer fillers in these applications because its high-density composition resists compression and deformation under load. For cosmetic fillets or fairing where strength is secondary to workability and finish, the 405 Filleting Blend or 406 Colloidal Silica are better choices.

Tip: Add filler gradually to the mixed epoxy and stir thoroughly until the paste reaches a peanut-butter consistency that holds its shape without slumping. Over-filling reduces bond strength — use the minimum amount needed to achieve the desired gap-filling or filleting profile.