The following article first appeared in American Sailor magazine. It has been edited and updated to reflect some of the latest core material technology. Most sailboats racing IMS, PHRF, and one-design are built with at least one kind of core in their hull and deck laminates, and for good reason.
Cores make the hull of the boat stiff and light.
Stiffness means the hull does not flex out of shape, which would increase hydrodynamic drag and slow the boat down. Lightness means less weight to move through the water, so speed is faster. In addition, cores insulate the hull against heat and cold, dampen vibration from slamming seas, and deaden the sound of chugging engines. Thanks to cores, boats have better performance and enhanced creature comforts. Cores are made from a variety of materials which have different strengths and stiffnesses.