The Island Packet 380 Sailboat

The Island Packet 380, a long-keeled cutter, was designed by Bob Johnson and built in the USA by Island Packet Yachts.

'Harmonium Cays', an Island Packet 380 cutter making good progress on passage from Guadeloupe to AntiguaNote the in-boom roller furling mainsail and the Hoyt staysail boom on this Island Packet 380 cutter.

Published Specification for the Island Packet 380

Underwater Profile: Long keel

Hull Material: GRP (Fiberglass)

Length Overall: 39'7" (12.00m)

Waterline Length: 32'0" (9.8m)

Beam: 13'0" (4.0m)

Draft: 4'4" (1.3m)*

Rig Type: Cutter

Displacement: 21,000lb (9,526kg)

Designer: Bob Johnson

Builder: Island Packet Yachts (USA)

Year First Built: 1999

Year Last Built: 2004

Owners Association: Island Packet Yacht Owners Association

* A centreboard version is also available - 3'11" draught with the board up, 7'7" with it down.


Published Design Ratios for the Island Packet 380

1. Sail Area/Displacement Ratio: 18.7

  • Less than 16 would be considered under-powered;
  • 16 to 20 would indicate reasonably good performance;
  • Over 20 suggests relatively high performance.

2. Ballast/Displacement Ratio: 42.9

  • Under 40: less stiff, less powerful
  • Over 40: stiffer, more powerful

3. Displacement/Length Ratio: 286

  • Under 100: Ultralight
  • 100 to 200: Light
  • 200 to 275: Moderate
  • 275 to 350: Heavy
  • Over 350: Ultraheavy

4. Comfort Ratio: 30.6

  • Under 20 indicates a lightweight racing boat
  • 20 to 30 indicates a coastal cruiser
  • 30 to 40 indicates a moderate offshore cruising boat
  • 40 to 50 indicates a heavy offshore boat
  • Over 50 indicates an extremely heavy offshore boat

5. Capsize Screening Formula: 1.9

  • Under 2.0 (the lower the better): Better suited for ocean passages
  • Over 2.0: Less suited for ocean passages

read more about these all-revealing numbers...


Summary Analysis of the Design Ratios for the Island Packet 380

1. A Sail Area/Displacement Ratio of 18.7 suggests that the Island Packet 380 will, in the right conditions, approach her maximum hull speed readily and satisfy the sailing performance expectations of most cruising sailors.

2. A Ballast/Displacement Ratio of 42.9 means that the Island Packet 380 will stand up well to her canvas in a blow, helping her to power through the waves.

3. A Displacement/Length Ratio of 286, tells us the Island Packet 380 is clearly a heavy displacement cruising boat. You can load her down with all your cruising gear and equipment and it will hardly affect her waterline. Not an ideal choice for coastal sailing, but she'll come into her own on an offshore passage in testing conditions.

4. Ted Brewer's Comfort Ratio of 30.6 suggests that crew comfort of an Island Packet 380 in a seaway is similar to what you would associate with the motion of a moderate bluewater cruising boat - a predictable and acceptable motion for most seasoned sailors.

5. The Capsize Screening Formula (CSF) of 1.9 tells us that an Island Packet 380 would be a safer choice of sailboat for an ocean passage than one with a CSF of more than 2.0.


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