Boats grow and shrink depending upon the circumstances. Certainly, many have had had the experience of the large and commodious boat show cruiser that shrinks once it’s fully stocked and fully crewed and put in service out on the water.
Capacity is therefore not the best measure of size.
At the yacht club, cove or sandbar, boaters can be overheard describing the size of their boats in boastful tones. “ And its twenty-SIX-feet with the pulpit.” Of course could we eavesdrop while that same owner talked to his insurance broker, hired a detailer, or contracted for a seasonal slip, we’d hear his 24-foot model described as “twenty-three-feet, ten-inches, el-oh-ay.”
Length, though convenient in charging for services, proves as distrustful a measure of boat size as capacity.
Weight? Advocates of heavier boats claim more comfort in rough water compared to lighter boats of similar form and size, ergo they are “bigger” in that they perform better at sea. Of course the lighter boat of similar size and form will provide more range with similar power and fuel capacity, and range is, of course, a big safety factor, especially if seas get rough.
For our purposes in sizing boats, weight therefore, provides no real resolution.
Weight’s kissing cousin—displacement—begins to address size admirably. Displacement can be defined as the weight of the boat, plus the weight of its normal complement of gear and stores. It is the weight of the boat in a specific condition of loading. In effect, displacement is a measure of volume, and so goes beyond weight’s simpler measure of the force of gravity on a given mass.
Confused? I’ll leave you with the American Boat and Yacht Council’s definition of length overall (LOA).
40.4.13 Length overall (LOA) - The straight line horizontal measurement from the foremost part of the boat to the aftermost part of the boat, measured parallel to the centerline and to the waterline. Attached bow sprits, pulpits, boomkins (bumpkins), rudders, sails, outboard engine brackets, handles, railings and other similar attached extensions are not included in the measurement. Integrally formed, molded, or welded components and appendages, such as bow pulpits, swim platforms, attachment structures for the propulsion systems, and structural rub rails installed by the builder are included in the length.