pilotjones said:Core size affects the degree to which a string goes sharp on plucking, and the force to pluck to a given deflection. It does not affect the basic string tension. A string with a given unit weight, speaking length, and pitch will be at a given tension, regardless of core size. With a heavier core it should feel stiffer, as it is harder to pluck.
One slight misuse in statements here is use of the word "gauge." The true factor in the equation is Unit Weight, which is the mass per unit of length - as in grams per centimeter of length, or ounces per foot. This is closely related to gauge, but different strings are constructed differently. The gauge is just the outside diameter measurement of the whole string assembly. Depending on the metals used, the wire form, and the construction, there can be higher or lower mass with the same OD. For example, the compression wound strings mentioned previously use a non-circular outer wrap, and may be heavier than standard strings of the same OD - which would explain them coming to a higher tension despite their being the same gauge.
This post is why I love engineers
lowsound