Magnum 8.5 Information, Review, Specs

Sailing Performance & Handling

The Magnum 8.5 is defined by its membership in the NZ Multihull Yacht Club 8.5m Class, a development class that demands a high power-to-weight ratio. Sailing this model feels more like handling a large beach cat than a heavy cruising multihull. With a displacement typically hovering around 1,500kg to 1,800kg and a standard sail area that can exceed 50 square meters upwind, the boat accelerates instantly in light puffs.

Handling is crisp, aided by high-aspect daggerboards that allow the boat to point significantly higher than fixed-keel catamarans. According to technical discussions within the class association, the Magnum 8.5 is known for its ability to "tack through the breeze" without the sluggishness often associated with multihulls, provided the daggerboards are managed correctly. In heavy air, the boat remains remarkably sea-kindly due to its flared hull sections, which provide reserve buoyancy and prevent nose-diving when pressed hard off the wind. Its performance is often benchmarked against the "Open" version of the same hull, which lacks the bridgedeck cabin but offers even higher top-end speeds due to reduced weight and windage.

Interior Comfort & Variations

While the Magnum 8.5 is performance-oriented, the "Cruising" variant features a bridgedeck cabin that provides a central saloon area—a luxury rare in 28-foot multihulls. The interior layout typically utilizes the hulls for sleeping quarters and the galley, while the bridgedeck serves as the primary social and navigation hub. Headroom in the hulls is generous for a boat of this size, though the bridgedeck cabin is designed with a "sitting headroom" philosophy to maintain a low center of gravity and low windage profile.

Sibling models include the Magnum 8.5 Open, which deletes the bridgedeck cabin in favor of a massive cockpit and a "trampoline-only" bridge, catering to pure racing enthusiasts. Some custom builds on these hulls have also been modified with "pod" cabins, which are smaller, aerodynamic sleeping pods that offer a compromise between the full bridgedeck cruiser and the open racer. Materials generally consist of foam-core composites or marine plywood/epoxy, which keep the vessel light but require owners to be disciplined about the weight of onboard gear to maintain the boat's intended waterline.

Popular Mentions & Media

The Magnum 8.5 is a frequent name in the annals of the Coastal Classic, New Zealand’s premier offshore race from Auckland to Russell. The model has earned a reputation as a giant-killer in this race, often finishing ahead of much larger monohulls. It is frequently featured in regional publications like Boating New Zealand as a prime example of the "8.5m Rule" success story, demonstrating how a trailerable (via tilting trailer) catamaran can effectively serve as both a weekend racer and a coastal explorer.

Known Issues & Buyer’s Checklist

Prospective buyers should focus on the following technical areas:

• Daggerboard Trunks: Given the high loads generated during racing, the trunks and the daggerboards themselves should be inspected for stress fractures or "slop" in the casing, which can lead to water ingress or structural fatigue.
• Core Integrity: Many Magnums were built using foam-core or end-grain balsa. A thorough moisture meter test of the decks and hulls is essential, especially around stanchion bases and chainplates where water can seep into the core.
• Rigging Loads: Because these boats are highly powered, the mast step and the bulkhead attachments for the stays undergo significant tension. Check for any compression signs at the mast base.
• Weight Creep: Owners often add "creature comforts" over time (batteries, larger anchors, extra water tanks). A Magnum 8.5 that has been overloaded will lose its performance edge and may sit too low in the water, leading to bridge-deck slamming in a chop.

Community & Resources

The primary hub for owners and technical data is the New Zealand Multihull Yacht Club (NZMYC), which maintains the 8.5m Class rules and registers. This organization provides a vital network for sourcing spare parts, rigging specifications, and tuning guides specific to the Magnum's hull shape.

The Verdict

The Magnum 8.5 is an uncompromising choice for the sailor who refuses to sacrifice speed for comfort. While it lacks the "floating apartment" feel of modern production cats, it offers a visceral and rewarding sailing experience.

Pros:

• Exceptional speed and agility, capable of exceeding 20 knots in the right conditions.
• The bridgedeck cabin provides legitimate weekend cruising capability for a small crew.
• Strong resale value and community support within the NZ 8.5m racing circuit.

Cons:

• Weight-sensitive; performance suffers significantly if over-laden with cruising gear.
• Interior volume is modest compared to 28-foot monohulls or larger cruising catamarans.
• Requires active management of daggerboards and sail trim to sail safely and effectively.