Corecell used in the construction of Antares Cruising Catamarans. Coring is a structural stiffener sandwiched between two layers of fiberglass skin. Coring is particularly important to a catamaran builder because of the need to create stiffness with reduced weight.
Most production catamaran builders choose to build their hulls and decks using balsa coring, which is made of balsa wood cut across the grain in thin slices to expose the end grain fibers. Balsa core is well known for its high resistance to compression.
Antares chooses to use a product called Core-Cell in the hull and deck construction. Core-Cell is a high-density foam core known for its impermeability to water, toughness, light weight and resistance to impact.
Resistance to Water Absorption
Core-Cell foam core is a closed cell structure that will never rot or absorb water. Balsa core, on the other hand, shows its weakness when exposed to water. Balsa will soak up water from any small cracks or weakness in the skins and has no resistance to water permeability. This leads to rot, loss of structural integrity, weight gain, and undermines the longevity and resale value of the boat.
Core-Cell has been used and extensively tested in marine environments and shows no loss in strength after soaking in water.
Toughness and Impact Resistance
The core needs to have enough elasticity to absorb impact and maintain the bond to the skin. The Core-Cell foam core acts as a shock absorber that supports the outside skin from severe impacts and protects the inside skin by dissipating the impact load over a wider area.
While Balsa core may be stiffer, it is also brittle. Brittleness leaves the core vulnerable to crack spread as the sandwich panel continues to flex on impact. Another symptom of impact is de-bonding. Core-Cell foam bounces back to shape after impact, ensuring the bond is not broken. Balsa core, on the other hand, will de-bond from the skin. Due to its compression strength, there is little outward damage visible on the exterior skin. What happens instead is the end grain splits parallel to the grain, causing localized delamination as illustrated below.
Builders wishing to build long-lasting boats choose performance composite foam core throughout the structure.
It is obvious that construction materials chosen by the manufacturer clearly betray the intentions of the builder. At Antares Catamarans it is our expectation that in 30 to 35 years from now, the catamarans we build today will still have the original engineered properties. Perhaps the best evidence of longevity and quality of construction is in the resale value to the boat.
The question remains, why are so many catamaran builders using balsa coring in the construction of their boats? Maybe the answer lies in the simple fact that on a cost basis, balsa coring is the cheapest option of any of the materials available on the market.