Care & Feeding: Wood-Cored Foils
Wood-cored foils—once the standard in sailboat design—are now considered specialized components in a composite-dominated world. At Competition Composites Inc., Phil Locker continues to draw on deep knowledge of both traditional and modern materials to create foils that meet demanding performance and class specifications. This guide offers key considerations and maintenance best practices for wood-cored rudders, centreboards, and daggerboards.
Why Use Wood Cores Today?
While most modern foils are constructed with composite skins over foam cores, there are still compelling reasons to use wood in certain applications:
1. Weight Requirements
Many sailboat classes still enforce minimum foil weights based on legacy rules. Using a dense wood such as mahogany or Douglas fir allows builders to meet these requirements while maintaining structural integrity. In such designs, the composite skin primarily serves as a waterproof barrier rather than a load-bearing element.
2. Mechanical Performance
Wood offers unique mechanical properties that continue to outperform alternatives in specific areas:
Stiffness: Ideal for thin foils, where structural stiffness is required but dimensions are restricted. Stiffness increases with the cube of thickness, making wood a strong candidate for high-performance foils.
Flexibility: Wood can withstand repeated flexing without fatigue, making it suitable for demanding sailing environments.
Compressive Strength: Wood is extremely effective at resisting point loads, particularly in areas such as daggerboard housings or transom-mounted rudder fittings. Many of CCI’s highest performance foils feature at least some wood in the core for this reason.
Best Practices for Installation and Maintenance
Proper installation and ongoing care are essential to maximize the lifespan of a wood-cored foil. Neglect or shortcuts can lead to serious damage. Key recommendations include:
Seal Every Penetration
Any hole drilled into the foil—whether for hardware, a pull rope, or a fitting—must be oversized, filled with epoxy, and re-drilled to the correct diameter. The process should include sealing the inside of the oversized hole with unthickened epoxy before filling with thickened epoxy. This critical step prevents water ingress and protects the integrity of the core.
Inspect Regularly
Foils should be checked frequently for nicks, dings, or laminate damage that could compromise the waterproof barrier. Any suspected breach should be repaired immediately. Visual checks during boat maintenance or after a capsize are not sufficient on their own.
Environmental Considerations
Wood is an organic material that reacts to humidity and temperature. Avoid leaving foils in enclosed vehicles, under tarps in the sun, or frozen in a centreboard trunk over winter. If the boat is stored in water, apply a barrier coat before antifouling to protect the laminate.
Understanding Moisture-Related Failures
Even under ideal shop conditions, variations in ambient humidity between construction and use can affect the wood core. If moisture is allowed to enter the core—especially through end grain or unsealed areas—it can result in swelling, causing waves along the foil’s sides and stretching the composite skins. Fibreglass, unlike wood, does not stretch and may crack under pressure, accelerating the damage.
Conversely, in extremely dry environments or excessive heat, the wood can shrink, causing cupping or internal stress on the laminate. While epoxy resins are water-resistant, they are not completely waterproof—moisture vapour transmission can still occur over time.
Repair and Long-Term Expectations
If swelling or cupping does occur, repair involves sanding back to the laminate, allowing the foil to stabilize in a humidity-controlled environment over several months, resealing, and then re-fairing and painting. This process is both time-consuming and costly, especially if outsourced. Preventative care is significantly more effective and economical.
It’s worth noting that minor movement in wood strips is natural over time, even with proper care. Epoxy-coated foils may eventually show slight changes in shape due to moisture migration, but this can often be resolved with a light sanding and repaint. In most cases, once the foil stabilizes, no further changes are expected.
Final Word
Wood-cored foils offer exceptional performance and remain a smart choice in many class-restricted or high-performance applications. However, they demand attention to detail, proper installation, and ongoing maintenance to ensure long-term reliability. When properly built and cared for, a wood-cored foil can deliver years of dependable service and race-ready performance.
For questions about material choices or to request a custom foil, contact the CCI team.