Not trying to lecture here, just providing information to clear up an all too common misuse of terms. Let the lesson begin!:dance:
CENTERBOARD is a lightweight board used to create resistance to leeway and aid steering. Basically the same function (directionally) as a keel on a larger boat, but with little to no effect on stability (other than directional) a centerboard is NOT a KEEL although both serve to reduce leeway and maintain directional control. Traditionally, a centerboard pivots to retract, a daggerboard raises vertically to retract. A daggerboard is a type of CB. Kind of the old every square is a rectangle, but not every rectangle is a square.
Swing-Keel would be a type of centerboard that has all of the ballast contained within the swing-keel (most are either made of cast-iron or contain lead ballast) and the keel will weigh several hundred pounds, much too heavy to pull up with a light line like the centerboards on our O'DAYs, rather a winch is required, often a trailer winch is adapted.
A Swing-Keel is also called a "retractable-keel".
O'Day built centerboard, Keel/Centerboard, and fixed-keel boats (shoal, deep-fin and wing). They never built any swing-keel boats. The Mariner and O'DAY 19 are "ballasted Centerboard" boats. The MARINER has 200# of lead in the bilge and a 165# centerboard (not a swing-keel because more ballast is in hull than CB, according to Robie Pierce, former VP of O'DAY).
"Mariner - Is and, always has been, a CENTERBOARD sailboat. Please don't refer to as a 'swing keel'. It's not a keel. It has a weighted
centerboard with two 100# lead pigs glassed either side of the CB trunk.
-Robie Pierce, former O’DAY V.P. (1972-78)"
O'DAY 19 has 300# of lead inside the bilge and the CB weighs a mere 52#. Obviously, no real effect on stability from the CB weight.
So, "swing-keel" is more or less a type of CB, but a CB is not a swing-keel because it usually has very little ballast. A swing-keel requires a winch to raise/lower, a CB usually can be raised/lowered using a light line and no winch (on a small boat anyway......larger K/CB vessels may need a winch due to the size/weight of the CB). In other words, a "swing-keel" is a KEEL and provides the primary stabilizing force to the boat. A centerboard merely provides directional control and prevents (or at least greatly reduces) leeway. A centerboard boat may have ballast inside the boat or in a stub-keel (like the almost ful-length skeg of the 19), but the CB will usually only have enough weight to make it easy to lower.
Here is what O'DAY says: (see attached scan of brochure pages). Note that O'Day was VERY critical of "swing-keel" designs and clearly refers to the 19 as a CENTERBOARD boat.