Design and Hull Form
The IP31's character flows directly from that first catboat-like 26-footer that launched the company's identity. The hull carries an almost plumb bow and a vertical stern aligned with the trailing edge of the keel-attached rudder, the coachroof runs parallel to the waterline, and a springy sheer gives the profile its traditional warmth. Maximum beam of 11 feet 6 inches is placed forward of amidships, which is unconventional and central to understanding everything that follows — why the boat is so roomy, why it reaches so well, and why it occasionally struggles upwind in a chop.
That beam exists for two inter-related structural reasons. The IP31 was conceived as a shoal-draft cruiser: the fixed keel draws only four feet while the centerboard version — roughly half of production — gets draft down to three feet board up. Shallow draft makes it impossible to concentrate ballast very low, and ballast in the deep-keel model uses iron ingots set in concrete rather than denser lead, so additional stability is recovered through beam. The engineering logic is internally consistent, but it does define the boat's envelope as a coastal and island-hopper rather than a deep-offshore passage maker.
Construction
Island Packet built the 31 with a solid fiberglass hull using triaxial cloth and polyester resin. The deck employs what the company called PolyCore — a mixture of polyester resin and microballoons — rather than the more common end-grain balsa core. The stated benefit is a chemically coupled deck structure without the delamination risk that older balsa-cored boats routinely develop. Owners reviewing the boat reported no deck problems, and there were no reported cases of blistering in the hull.
The interior liner is also PolyCore, tabbed to the hull and incorporating structural stringers bonded in place. Island Packet was thoughtful enough to stop the liner at settee-backrests rather than bringing it to window height, so the eye rests on wood and fabric rather than large expanses of fiberglass. Hardware is largely quality production gear — Edson rack-and-pinion steering, Ronstan blocks, and Isomat spars. The rudderstock is 1.5-inch stainless steel, and a stainless box acts as a lobster strap connecting the keel to the rudder, keeping lines clear of the propeller.
Rig and Sailing Character
Most IP31s left the yard as cutters, though the rig is more precisely a double-headsail sloop since the mast is stepped relatively far forward rather than amidships. The arrangement gives a genoa forward on the headstay and a staysail on the inner forestay, with no running backstays — the company engineered the Isomat spar to carry inner-forestay loads without additional support. Owners praised the cutter setup for practical heavy-weather management: when conditions build, the genoa furls away neatly and the staysail carries the boat comfortably. Some owners noted learning the nuances of proper trim between staysail and genoa, which rewards attention in mixed conditions.
The boat reaches. Owners consistently call a reach its best point of sail, and the wide forward sections that hurt upwind progress contribute to this. Going to weather is a more qualified story — wide beam forward slows the boat in a seaway according to one owner, and in light air the 31 can feel sluggish. Tacking is the other known limitation: full-keel boats don't tack readily, and on the IP31 the wide forward beam exacerbates this. Getting caught in irons is a real risk for the unfamiliar.
What the 31 delivers in return is helm balance and self-steering ability that owners find almost uncanny. She will steer herself for miles with minimal attention, and multiple owners reported that the boat was tracking independently before they realized the autopilot was off. Despite the beamy, shallow form, she is reported as genuinely stiff — one owner could not intentionally wet the rail.
Accommodations
The interior is where the wide hull pays its clearest dividend. Headroom is 6 feet 3 inches throughout the cabin, with a 6-foot 6-inch V-berth forward, a generous head with shower, full settees in the main saloon, a double quarter berth aft to starboard, and a U-shaped galley in the port quarter. The quarter berth doubles as a nav station with a folding door for separation.
One owner singled out the icebox as huge and exceptionally well insulated, whether used as a cold plate system or a conventional icebox. The PolyCore liner, for all its structural virtues, does carry one practical cost: it does not absorb sound as well as wooden soles, and modifying the layout later is considerably more difficult than in a traditionally constructed interior.
Known Issues and Refit Priorities
The engines are generally reliable. Early production used a 22-hp Yanmar that at least one owner found inadequate for punching tidal currents; later boats received the 27-hp Yanmar, which owners found more satisfactory. Performance under power is rated as good, and engine accessibility is praised. The one consistent complaint is control in reverse — a predictable consequence of a full-keel design with the propeller in an aperture. Practice mitigates it, and it is considered a reasonable trade-off for the protected prop position.
Aging sail inventories are the most common refit priority on older examples. UV damage and flogging are the principal enemies of cruising mainsails on these boats, particularly when previous owners were casual about using sail covers. A full-batten main is a strongly recommended upgrade for the IP31 — the battens reduce flogging, improve flaking, and hold shape far longer in the tropical UV environment the boat typically inhabits. Pairing the full battens with a low-friction mast track such as a custom-machined one-piece polyethylene track resolves the additional hoisting effort those battens create. Running rigging on older examples deserves scrutiny; rope technology has changed substantially and old halyards on a 20-plus-year-old boat rob the sails of shape even when the sail cloth itself is still sound.
The Verdict
The Island Packet 31 is a boat designed around a specific vision of the cruising life — shallow-water access, generous accommodation, and a stable, forgiving motion that lets the crew arrive rested. It fulfills that vision with unusual consistency. The owner community is uniformly enthusiastic, construction quality is high, and the company's owner support is well regarded. The limitations are real but honestly telegraphed by the design: this is not the boat for racing upwind, and anyone contemplating serious offshore passages in severe conditions should weigh the stability tradeoffs carefully. Within the island-hopping, coastal-cruising, liveaboard role it was designed to fill, it remains one of the more coherent packages American boatbuilding produced in the 1980s.
Pros
- Exceptional interior volume and headroom for the waterline length
- Stiffer under sail than the beamy, shallow form suggests
- Cutter rig gives practical heavy-weather sail management without running backstays
- Self-steering tendency reduces helm fatigue on passages
- Solid fiberglass hull; PolyCore deck avoids balsa-core delamination risk
- Strong builder reputation and responsive owner support
Cons
- Wide beam forward hurts upwind performance and invites getting caught in irons
- Iron ballast in concrete limits righting moment compared to lead-ballasted alternatives
- Full-keel/aperture propeller arrangement means poor control in reverse
- PolyCore liner reduces sound absorption and complicates interior modifications
- Early 22-hp engine was undersized; verify later 27-hp Yanmar is installed
- Aging sail inventories on older examples almost always require significant investment
