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Research Notes: Foot Pockets for a Short Carbon Training Fin

I want to build a short carbon bifin for pool and training.
Before cutting any carbon, I need to choose the foot pocket. These notes collect what I’ve learned so far.

The main questions:

  1. Which pockets are most commonly used, and why?
  2. Which ones fit DIY blades without heavy mods?
  3. How much do blade angle and rails matter for short fins?
  4. Where can I find solid references?
  • C4 – lightweight, multiple stiffness options
  • Pathos – 33° angle, minimal rubber for direct power transfer
  • CETMA S-WiNG – ultralight, no side rails
  • Leaderfins Classic – integrated rails
  • SEAC – comfort-oriented
  • Mares Razor / Omer Stingray – widely available, classic rubber pockets

2. DIY blade compatibility

These freediving foot pockets are known to accept third-party or home-made blades:

  • Cetma Composites S-WiNG
  • Mares Razor
  • Pathos
  • Capt. Nemo
  • Sporasub
  • OMER Stingray
  • UltraFins

3. Angle considerations

  • Blade angle usually between 20°–33°.
  • Larger angles favor surface swimming and gliding, but reduce blade snap.
  • Smaller angles (or flat pockets) suit continuous kicking, often better for short fins.

4. Rail considerations

  • Rails stiffen the blade and channel water.
  • Long, thick rails can dampen flex and reduce reactivity — especially noticeable on shorter blades.
  • Finding: small rails at the foot pocket let the carbon blade flex and generate thrust more effectively.

5. References

Comments

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