Major Hull Surgery: Transom Modifications, Fairing, and Sourcing an America’s Cup Rudder

Executing multiple complex hull projects with a focus on structural integrity and performance gains.

Author: Shayne & Anna

Key Message: A systematic, professional approach allows multiple major refit projects to be run in parallel, turning a daunting workload into a series of manageable, high-impact upgrades.

Introduction

Transforming a boat’s hull lines is one of the most ambitious projects an owner can undertake. For us, it was a necessary step to improve both form and function. This project log covers the intense, multi-faceted work period where we executed transom extensions, full hull fairing, and began the journey of creating new high-performance rudders—a journey that took a thrilling turn with the acquisition of an ex-America’s Cup foil.

The Transom Extension: Adding Form and Function

The original transoms offered little practical space for boarding or swimming. Our goal was to create integrated swim platforms without compromising structural integrity.

This modification was done for functionality, as the original step was difficult to access. The transom steps were tiny and did not allow room to stand comfortably on the lower platform. By extending the top of the step to meet the hull line, we were able to create a comfortable lower platform and improve access from the transoms. We did not actually extend the length of the boat in this project.

In terms of engineering, this was a simple build. As we were not extending the transom in the true sense of the word—only squaring up the step to give more room—the job did not require engineering for extra loads.

Materials Used:

• Airex C70 80kg/m³
• E-glass 400g/m² double bias
• E-glass 300g/m² cloth
• Polyester resin
• Fillers: Cabosil and Q-cell
• Peel ply

The Process:

The existing transom was cut away using a 4″ grinder with a 1mm Ultradine cutoff blade. A chisel was then used for cleaning the rough edges.

The entire interior of the transom was then sanded down first with 60-grit and then with 80-grit sandpaper. This was done for two reasons: to prepare the surface for the new join and for additional repairs that were needed in the area, including new shelves for the steering arms in the engine room.

A 150mm section was sanded away on the perimeter of the exterior where the new join was to be made.

The foam was heated to allow it to form to the existing structure. Pieces were glued in place using polyester resin mixed with 20% Cabosil and 80% Q-cells, and then held in place with clamps and tongue depressor sticks that were hot-glued into place.

The inside skin on the sides was laminated at this stage. As the transom and step pieces were flat, the inside skin could be done on a table prior to fitting. A temporary oven was made using plastic and a bathroom heater to speed the curing process.

Once the inside skins were laminated, the transom and step pieces were glued into place using the same filler ratios as before.

The transoms were bogged and faired to finish the project.

The Result:

The transformation is both functional and aesthetic. We now have a beautiful, robust platform that makes entering and exiting the water a pleasure. It’s one of those upgrades that we use every single day

Hull Fairing and Systems Rationalization

With the structure complete, the focus shifted to the hull surface itself.

• The Great Sand-Off: We stripped the hulls down to the epoxy primer, a dusty but critical step to achieve a perfect base for new antifouling. A fair hull is a fast hull, reducing drag and improving sailing performance.
• Removing Redundant Skin Fittings: Every through-hull is a potential point of failure. We systematically identified and glassed over unused seacocks, reducing complexity and enhancing overall safety.

The Rudder Project: A Tale of Discovery and Opportunity

The removal of the old rudders revealed more than we expected and opened the door to a major performance upgrade.

• The Discovery: Upon extraction, we found the old rudders were water-logged, adding significant weight and compromising the core material. This confirmed the necessity of our planned rebuild.
• The Opportunity: Rather than building from scratch, we sourced a rudder from the Spanish Ibedrola America’s Cup campaign. This provided us with a proven, high-performance foil shape to use as a master for creating our new rudders.
• The Method: We created a “splash mold” from the America’s Cup rudder. This process involves taking a precise female mold directly from the existing object, allowing us to reproduce its exact hydrodynamics in our new, custom-built rudders.

Conclusion

This phase of the refit was about laying the groundwork for massive performance and lifestyle gains. By methodically tackling structural modifications, surface preparation, and leveraging high-performance opportunities, we are systematically transforming Paikea into the modern, capable performance cruiser we envision.

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