Engineering Superior Strength: How We Build Carbon Fiber Chainplates

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Key Message Paragraph: When a key component requires replacement, the opportunity exists to build something better than the original. We showcase our professional composite expertise by designing and fabricating a set of custom carbon fiber chainplates for our catamaran. From precise templating and controlled wet-preg lamination to vacuum-bagged consolidation, this process demonstrates the high-level engineering and craftsmanship we apply to every project, resulting in a stronger, lighter, and permanently reliable structural solution.

Author: Shaye and Anna 

A moving chainplate is more than an inconvenience; it’s a countdown to a potential rig failure. What began as a minor leak at the base of our chainplates in the Canary Islands evolved into a critical structural issue in the Caribbean tropics. The humid environment accelerated the rot in the plywood core of the bulkhead, making our previous temporary fix insufficient.

This wasn’t a job for more sealant. It required a complete engineering solution: the design and fabrication of custom carbon fiber chainplates to permanently resolve the issue and restore structural integrity to Paikea’s rig.

The Diagnosis: Confirming the Worst

Upon removing the interior liners, the extent of the damage was clear. The plywood core surrounding the chainplate bolts was soft and rotten. The bolts themselves had elongated the holes, a clear sign of significant movement under load. The tropical rain had reactivated the decay that had been dormant in the drier Mediterranean climate, making a proper repair unavoidable.

Catastrophic chainplate failure showing a bolt tearing through a rotten plywood bulkhead core.

The Solution: Engineering a Carbon Fiber Replacement

Rather than attempting to repair the compromised wood, we decided to replace the entire load-bearing section with a monolithic carbon fiber structure. The advantages are significant:

  • No Rot: Carbon fiber and epoxy are impervious to water.
  • High Strength-to-Weight Ratio: It provides immense strength without adding excessive weight.
  • Precision: We could engineer a perfect fit and optimal fiber orientation for the loads.

The Build: A Lesson in Professional Composites

The fabrication process was methodical and precise.

  1. Precise Templating: We created a detailed template to ensure the new carbon fiber chainplate would align perfectly with the existing deck holes and rigging attachments.
  2. Wet-Preg Lamination: We used a technique called “wet-preg,” pre-impregnating the unidirectional carbon fiber with resin before application. This ensures complete saturation and perfect fiber alignment, which is critical for strength.
  3. Managing Exotherm: Due to the laminate’s thickness ( nearly 10mm), we performed the lamination in two stages. This prevented an exothermic reaction—a runaway heat buildup that can destroy the resin’s properties.
  4. Vacuum Bagging: Each stage was vacuum-bagged to remove excess resin and air bubbles, and to consolidate the laminate for maximum strength and a professional finish.
Hand laminating unidirectional carbon fiber using the wet-preg technique for a custom chainplate.

A Critical Step: The Science of Secondary Bonding
After the first laminate cured under peel ply, we sanded the surface before applying the second. This is a non-negotiable step. Peel ply leaves a resin-rich surface with trace release agents; sanding fractures this surface, providing a mechanically keyed, clean surface for a strong secondary bond. Skipping this drastically reduces bond strength.

Installation and Sea Trial

With the new carbon fiber chainplate cured, we removed the failed hardware and carefully installed the new unit. The final step was tuning the rigging and taking Paikea for a sea trial. Under full sail in a solid breeze, the new chainplate performed flawlessly—no movement, no noise, just quiet, confident strength.

The custom carbon fiber chainplate successfully installed and supporting the sidestay on the catamaran Paikea at anchor.

Conclusion

This project underscores a core principle: true seamanship involves addressing the root cause of a problem, not just its symptoms. By applying professional composite engineering, we turned a potential disaster into an opportunity to make Paikea more resilient and reliable for the ocean miles ahead.

Master Marine Composites with Us

This project is a prime example of the advanced practical skills we teach. In the Youngbarnacles Members Hub, we have structured courses and deep-dives on composite engineering, structural analysis, and professional boatbuilding techniques.

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