I've always had a preference for epi-glue over West Systems but wanted some hard information around why... Below is what ChatGPT told me...

Matt

In high power rocketry (HPR), West System epoxy is sometimes regarded as less ideal compared to products like Epi-Glue or RocketPoxy due to a few key performance factors. Here's a comparison:

🔧 1. Strength and Shock Resistance

• West System Epoxy:

  • Designed for boat building and general composites.

  • Excellent for wood bonding and laminating.

  • More brittle when cured — can crack under high dynamic loads (e.g. motor thrust or recovery ejection).

• Epi-Glue (and RocketPoxy):

  • Specifically formulated for high-power rocketry.

  • Tougher and more impact-resistant, better at handling shock loads during flight and landing.

🌡️ 2. Temperature Resistance

• West System:

  • Starts to soften around 70–80°C, which is often insufficient for components near or around the motor mount.

• Epi-Glue:

  • Has a higher heat deflection temperature, which matters during motor burns and in hot climates or storage.

🧪 3. Fillers and Mix Consistency

• West System:

  • Requires additional fillers (like 406 colloidal silica or 404 high-density filler) for gap-filling or structural applications.

  • This adds complexity and the risk of incorrect mix ratios.

• Epi-Glue:

  • Pre-thickened for fillets and structural bonds.

  • Fewer steps, more consistent results, and easier for rocketeers who want predictable performance.

⏱️ 4. Working Time vs. Cure Time

• West System:

  • Offers flexibility with different hardeners (fast, slow), but these aren't always optimal for rocket construction timelines.

• Epi-Glue:

  • Formulated to balance pot life with quick, strong curing, especially suited to high-power builds where tight timelines or multiple layers are involved.

✅ Summary

🧠 Bottom Line

West System epoxy isn't bad, and in fact it's excellent for woodworking and general composite projects. But for HPR, where shock loads, heat, and reliability are critical, Epi-Glue and other rocket-specific adhesives are better suited.

If you're bonding motor mounts, centering rings, fins, or anything load-bearing — using rocket-specific epoxy gives you peace of mind and a margin of safety.