Tangaroa Mk IV Information, Review, Specs

Sailing Performance & Handling

The Tangaroa Mk IV is characterized by its deep-V hull form, which provides lateral resistance without the need for vulnerable daggerboards or keels. This design choice results in a vessel that is exceptionally stable in heavy weather, as the hulls tend to "slice" through waves rather than slamming over them. However, the lack of a deep keel means that the Tangaroa’s windward performance is modest compared to modern performance catamarans; tacking requires careful momentum management, often necessitating a "back-milling" of the staysail to bring the bows through the eye of the wind.

The sail plan is typically a flexible ketch or schooner rig, which allows for a low center of effort and easy reefing by a short-handed crew. Because the hulls are connected by wooden beams lashed with high-strength synthetic rope, the entire structure flexes in response to sea states. This "controlled movement" reduces the structural stress found in rigid fiberglass boats, leading to a ride that many owners describe as organic and forgiving. While the Tangaroa is not a high-speed racing machine, it is capable of maintaining consistent 7-to-10 knot averages on a reach, benefiting from its relatively low displacement-to-length ratio.

Interior Comfort & Variations

Accommodation on the Tangaroa Mk IV is strictly confined to the hulls, as there is no bridgedeck cabin. This "split-living" arrangement provides a level of privacy rare in a 35-foot boat, with the galley and chart table usually separated into different hulls. The V-shaped hull design creates a unique interior geometry; while there is ample standing headroom in the center of the hulls, the floor space is narrow, tapering toward the bilge.

The Mk IV version improved upon earlier marks by optimizing the use of "flex-space" in the mid-sections of the hulls, allowing for more dedicated sleeping berths and storage for long-range provisioning. Materials are typically functional—marine plywood sheathed in epoxy and glass—emphasizing durability over luxury. It is common to find variations in the deck layout, as many builders opted for the "Mk IV" plans to incorporate a small "pod" or "doghouse" on the deck for protected watch-keeping, though the purist Wharram configuration remains an open deck with a simple fabric bimini.

Popular Mentions & Media

The Tangaroa and its siblings have earned a legendary status in the "budget circumnavigation" community. The design gained significant visibility through the travels of Glenn Tieman, who spent years exploring the Pacific on his Tangaroa, Manu Rere. Tieman’s voyages highlighted the vessel's ability to navigate shallow atolls and survive extreme weather with minimal mechanical systems. The design philosophy of the Tangaroa is also a central theme in James Wharram’s autobiographical works and technical essays, which argue for a return to traditional seafaring values.

Known Issues & Buyer’s Checklist

When inspecting a Tangaroa Mk IV, the primary concern is the integrity of the build, as most were constructed by private individuals rather than professional shipyards.

• Lashing Points and Beams: The beams (crossbeams) must be inspected for rot, particularly where they rest in the hull cradles. The lashings themselves should be treated as a consumable item; if they appear UV-damaged or frayed, they must be replaced entirely.
• Plywood Rot: Using a moisture meter and a percussion hammer, buyers should check the "stems" (bows) and the areas around the rudders for soft spots in the plywood, which can occur if the epoxy encapsulation was breached.
• Rudder Gudgeons: The traditional Wharram rudder is often attached with lashings or simple pintles. Excessive play in the rudders or wear on the trailing edge of the hull is a common maintenance item.
• Deck-to-Hull Seals: Ensure that the hatches and deck joinery are properly bedded. Because the boat flexes, poorly applied sealants can fail, leading to slow leaks into the living quarters.

Community & Resources

The Tangaroa is supported by a robust and passionate global community. The most authoritative resource for technical drawings and refit advice is the James Wharram Designs office, which still provides support for the Classic series. Additionally, the Wharram Builders and Owners Community serves as a technical clearinghouse for modifications and parts sourcing.

The Verdict

The Tangaroa Mk IV is an uncompromising blue-water voyager for those who value simplicity, seaworthiness, and a connection to traditional maritime history over modern marina-side luxuries.

Pros:

• Exceptional Stability: The flexible, lashed construction and V-hull provide a safe, comfortable motion in heavy seas.
• Shallow Draft: Capable of beaching for maintenance or exploring thin-water anchorages.
• Ease of Maintenance: Simple systems and wood-epoxy construction make it easy for owners to perform their own repairs.

Cons:

• Narrow Interior: The V-shaped hulls offer limited floor space and can feel cramped compared to modern catamarans.
• Windward Ability: High leeway and a modest sail-to-weight ratio make for slow progress when beating against the wind.
• Exposed Deck: The lack of a bridgedeck cabin means the crew is more exposed to the elements during transit.