Laurin 31 Information, Review, Specs

Sailing Performance & Handling

The Laurin 31 is defined by its long keel and heavy displacement, which contribute to a Motion Comfort Ratio (MCR) of approximately 32. This figure indicates a vessel that is significantly more stable in a seaway than modern fin-keel coastal cruisers, making it an ideal candidate for heavy-weather passages. With a ballast ratio of 40% to 44%, the boat is notably "stiff," resisting heeling even when pressed under a full press of canvas.

On the water, the fractional sloop rig provides a versatile sail plan. The boat tracks with remarkable precision, a characteristic inherent to its long-keel geometry, which allows the helmsman to leave the tiller for brief periods without immediate course deviation. However, this directional stability comes at the cost of maneuverability in tight quarters; like most long-keelers, the Laurin 31 has a large turning circle and can be challenging to handle in reverse within a crowded marina. According to technical archives at the Laurinkostersällskapet, the hull's "canoe" stern helps split following seas, preventing the boat from being pushed around by the stern in heavy following winds.

Interior Comfort & Variations

Inside, the Laurin 31 maximizes its 9.45-foot beam to provide a traditional and functional living space. The standard layout features a V-berth in the bow, followed by a head and hanging locker. The main salon typically consists of two longitudinal settees with a central folding table, and a compact galley and navigation station flank the companionway. Unlike its smaller sibling, the Laurin 28, the 31-footer offers "above-average" headroom, which accommodates taller sailors who often find the smaller Koster designs cramped.

A critical distinction for buyers is the difference between the Mark I and Mark II variants. The Mark II was updated with a lead keel (replacing the Mark I's iron) and higher freeboards, which increased both the interior volume and the dryness of the cockpit. Prospective owners should also note that many Laurin 31s were sold as "home-completion" kits. This means that while the hull integrity is generally high, the quality of the cabinetry, electrical wiring, and plumbing can vary significantly from one hull to another depending on the skill of the original owner-builder.

Popular Mentions & Media

The Laurin 31 occupies a prestigious niche in Swedish maritime history. Its design DNA is closely linked to the "Koster Rule," a set of design principles intended to produce seaworthy, double-ended boats for the challenging North Sea conditions. The original mahogany inspiration, Casella II, is well-documented in Swedish racing archives as a pioneer of the type. Arvid Laurin himself is a celebrated figure whose work is preserved in the Sjöhistoriska Museet (Swedish Maritime Museum), where original drawings and design philosophy documents highlight the Laurin 31's role in the transition from wood to GRP construction.

Known Issues & Buyer’s Checklist

As a vessel that is now several decades old, the Laurin 31 requires a diligent survey in several key areas:

• Mast Step & Deck Compression: Like many boats of the 1970s, the deck can suffer from compression under the mast step if the internal support or bulkheads have shifted or softened over time. Check for hairline fractures in the gelcoat around the mast base.
• Iron Keel Rust (Mark I): Early models used iron keels that were spray-galvanized. Over time, this coating can fail, leading to rust "bleeding" and expansion. Mark II models with lead keels are generally preferred for their longevity and lower center of gravity.
• Osmosis: While the hulls were built with heavy, over-dimensioned fiberglass, early GRP resins are susceptible to osmotic blistering. A moisture meter test on the hull is essential during any pre-purchase inspection.
• Rudder Gudgeons: The heavy barn-door rudder is extremely strong, but the bushings and mounting hardware should be inspected for play or corrosion, as these are under constant stress during ocean passages.
• Engine Serviceability: Many original units were fitted with Volvo Penta diesels (such as the MD2B). While reliable, parts for these older engines are becoming increasingly scarce and expensive.

Community & Resources

The primary hub for owners and enthusiasts is the Laurinkostersällskapet (The Laurin Society). This organization maintains a technical archive, organizes annual meets in the Stockholm Archipelago, and provides a wealth of knowledge on refitting these classic cruisers. For those researching the boat's design lineage, the Swedish Maritime Museum offers digitized access to Arvid Laurin's original blueprints.

The Verdict

The Laurin 31 is a "sailor's sailboat"—a robust, honest cruiser that prioritizes safety and sea-kindliness over interior gadgetry or light-wind speed.

Pros:

• Exceptional seaworthiness and motion comfort in heavy weather.
• Timeless "Koster" aesthetic that remains highly respected in the cruising community.
• Robust, over-engineered fiberglass hull construction.
• Strong directional stability for long-distance tracking.

Cons:

• Difficult to maneuver in reverse and tight marina spaces.
• Variable interior quality due to the prevalence of home-completed kits.
• Slower in light air compared to modern fin-keel designs.
• Risk of iron keel maintenance issues on Mark I variants.