When people evaluate a catamaran, they tend to focus on what they can see and touch — the saloon layout, the cockpit, the finish of the joinery. But the single most important structural element on any multihull is one most owners never lay eyes on: the main bulkhead.
The Structural Role of Bulkheads
A catamaran’s main bulkhead, typically positioned under the mast, is far more than an internal wall. Shaped like an inverted U spanning both hulls, it ties the two hulls, the bridgedeck, and the mast-bearing structure into a single rigid unit. Its job is to resist the immense compression loads of the rig pressing down, and the lateral and twisting forces generated as the hulls work independently in a seaway — one hull rising on a wave while the other falls. Without a properly bonded, full-strength bulkhead, a catamaran’s hulls can flex and rack against each other, a movement that, over time, fatigues everything from window seals to structural joints.
Because so much load funnels through this single component, how it’s built and how it’s attached to the hull matters enormously. A bulkhead that is simply glued or lightly tabbed to the hull shell — rather than properly bonded and glassed over — becomes a weak point precisely where the boat can least afford one.
Recent Industry Issues
This isn’t a theoretical concern. Over the past several years, owners and surveyors of certain high-volume production catamarans have documented cracking, delamination, and deformation of main bulkheads, in some cases on boats with no history of grounding or collision. Investigations by owners and independent surveyors, along with reporting in publications like Practical Sailor, found that in some affected boats the bulkhead had been bonded to the hull with adhesive alone in places, rather than fully tabbed with fiberglass over the joint — construction more typical of light furniture assembly than offshore structural boatbuilding. The builder acknowledged the reports and introduced repair kits for affected owners, while maintaining that no safety incidents had resulted. The episode nonetheless became a cautionary tale across the multihull industry: with production volumes rising to meet demand, structural details that used to get a boatbuilder’s full attention can become the place corners are cut.
How Knysna Builds Differently
Knysna Yacht Company builds every hull with offshore passage-making in mind, not just coastal or charter use, and bulkhead construction reflects that philosophy from the ground up. Rather than relying on adhesive bonding alone, Knysna bonds bulkheads into the hull using Crestomer 1152PA — a two-part urethane acrylate structural adhesive from Scott Bader with Lloyd’s, DNV, and RINA marine approvals, prized in demanding composite applications for its high elongation and exceptional impact and fatigue resistance. Critically, that bonded joint is then tabbed over with high-strength vinyl ester fiberglass, locking the bulkhead permanently into the hull laminate rather than leaving it reliant on adhesion alone.
This belt-and-braces approach — structural adhesive bonding combined with proper glass tabbing — is exactly the kind of construction detail that determines whether a catamaran shrugs off years of offshore passages or develops the kind of hidden structural fatigue that has plagued other production builders. It’s not the part of the boat that sells a walk-through at a boat show, but it’s the part that matters most when you’re 800 miles from the nearest port in a building sea.
For Knysna, that’s the point: a catamaran should be built to the standard of the ocean it’s designed to cross, not just the marina it’s shown in.