Design and Construction
The Southerly 100 measures 33 feet 9 inches overall, with a beam of 10 feet 3 inches and a length-to-beam ratio of 3.20. Northshore built the boat in fiberglass, using a solid-fiberglass hull rather than a cored layup.
The iron swing keel provides variable draft. Depending on load, the boat draws roughly 2.26 to 2.56 feet, allowing her to enter shallow marinas that deeper fixed-keel boats can’t reach. Lowering the keel increases draft to 5 feet 10 inches for sailing in deeper water.
Displacement is 9,950 pounds, with a ballast ratio of 47 percent. Wetted surface is about 322 square feet. The immersion rate of 1,115 pounds per inch indicates how much the boat settles as weight is added—a useful figure when considering provisions for extended cruising.
Rig and Handling
The Southerly 100 has a masthead sloop rig carrying 509 square feet of sail. Her sail-area-to-displacement ratio is 17.30, a modest sail-power-to-weight figure consistent with a heavy-displacement cruiser rather than a light-air rocket.
A displacement-to-length ratio above 284 and a comfort ratio near 25 suggest a steady, predictable sea boat rather than a featherweight racer. The capsize screening value is 1.89, a formula-derived index that places her within the range accepted for offshore-capable cruisers of her type.
The variable-draft arrangement lets the owner choose between a 5-foot-10-inch keel-down profile and shallow-draft mode when coast-hopping or gunkholing. Her modest sail plan and heavy displacement are better suited to relaxed coastal and inland-water cruising than spirited upwind sailing.
Accommodations
The Southerly 100 has six berths, providing accommodation for a small cruising crew or a family. The keel trunk and swing-keel machinery occupy space that would be free floor area in a conventional fin-keel 34-footer, but that’s the trade-off for the boat’s draft flexibility.
Verdict
The Southerly 100 is a purpose-built variable-draft cruiser from Northshore’s Carter-era design partnership. Its iron swing keel provides genuine access to shallow water, while the 47 percent ballast ratio supports stable, comfortable motion with the keel down.
The boat’s modest sail plan and heavy displacement favor relaxed coastal and inland-water cruising over lively performance in light air or spirited upwind work. With 96 boats completed, the Southerly 100 is a recognizable, though not ubiquitous, model in the Southerly story.
Pros
- Swing keel draws as little as 2.26 feet when loaded, opening access to shallow marinas
- Solid-fiberglass hull, iron keel, and 47 percent ballast ratio
- Capsize screening value of 1.89
- Steady, heavy-displacement cruising character
Cons
- Sail-area-to-displacement ratio of 17.30 limits light-air performance
- Keel trunk and swing-keel machinery take up interior floor space
- The only documented accommodation figure is the six-berth count
