Her proportions and recorded design ratios place her firmly among moderate racers rather than heavy cruisers. At the same time, a relatively broad beam provides useful space for a 30-footer.
Design and Construction
The Jupiter 30 has a solid-fiberglass hull and deck. She measures 24 feet 7 inches on the waterline, with a beam of 10 feet 4 inches. Displacement is 7,480 pounds, including 2,998 pounds of lead ballast. Underwater, she carries a fin keel and spade rudder.
Her ballast-to-displacement ratio is 40 percent. The displacement-length ratio of 221 classifies her as a moderate racer, and two-thirds of comparable designs are heavier. In other words, she is relatively light for her length.
The boat’s 2.83 length-to-beam ratio makes for a roomy plan by 30-foot standards. By that measure, she is more spacious than 76 percent of similar designs. Her immersion rate is about 895 pounds per inch, which means she loads predictably.
The capsize screening value is 2.13. That figure falls outside the threshold accepted for ocean racing, marking the Jupiter 30 as a coastal and inshore performer rather than a bluewater contender.
Rig and Handling
The masthead rig’s ISO 8666 reference sail area produces a sail-area-to-displacement ratio of 16.4. With a 135 percent genoa, that rises to 19.7, helping to explain why calculations place her ahead of 54 percent of similar boats in light wind.
The theoretical hull speed is 6.7 knots. Under engine power through the shaft-drive transmission, the calculated maximum is about 4.5 knots.
Standing and running rigging follow conventional masthead proportions. The mainsail, jib/genoa, and spinnaker halyards are each about 87.5 feet long and 5/16 inch in diameter. The mainsheet is 73.5 feet of 3/8 inch line, while the jib and genoa sheets are 29.4 feet of 3/8 inch line.
A Motion Comfort Ratio of 19.4 places the boat above 31 percent of similar designs for ride quality. That isn’t plush, but it is credible for a moderate racer of this size.
Accommodations
Below deck, the Jupiter 30 has five berths, a useful number for weekend cruising or a small racing crew. The beamy hull provides usable interior volume, rather than simply more deck spread, and helps the boat feel larger than her 29-foot-4-inch overall length might suggest.
Verdict
The Jupiter 30 is a van de Stadt-designed moderate racer with a relatively light, roomy hull and a masthead rig that performs respectably in light air. Her capsize screening value excludes her from ocean racing, and her comfort ratio is middling. For inshore racing and coastal weekends, however, she offers a well-proportioned, solidly built platform.
Pros
- Roomy for her size, exceeding 76 percent of similar designs by length-to-beam ratio
- Light, moderate-racer displacement with good light-wind speed potential under genoa
- Solid-fiberglass hull and deck from Jupiter Yachts’ early-1980s production
Cons
- Capsize screening value of 2.13 bars her from ocean racing
- Comfort ratio is better than only 31 percent of comparable boats
- Calculated maximum speed under engine power is about 4.5 knots
