Building a Featherweight Roof: Duracell's Composite Bimini Takes Shape

Last week Matt and Janni from The Duracell Project tackled the supports for a new bimini on their Open 60 sailboat, Duracell. This week Matt moves up to the main event: a full composite hard top that will shade the cockpit, carry a solar array, and hide a maze of wiring underneath a clean, curved roof. As Matt continues turning this legendary racing boat into a comfortable cruising home, the bimini build shows off exactly why he reaches for high performance epoxy and Thixo Pro whenever the job calls for strength without extra weight.

Curving and Bonding the Panels

Matt starts with two Adura foam-core panels, each faced with layers of fiberglass cloth. He scores the panels partway through the foam core so they bend into a curved form that matches the roofline of the boat's doghouse. Once the curves settle into shape, he fills each cut with Thixo Pro thickened epoxy and locks the panel into the form. He runs the same thickened epoxy along the mating edges of both panels and clamps them together, closing the seam into one continuous, curved roof section with a generous radius in the corners.

Building a Hollow Grid for Hidden Wiring

With the shape locked in, Matt builds a grid of foam strips underneath the panel to stiffen the roof and route cable runs for solar panels, lights, and a navigation display. He tapes the foam so it releases cleanly later, then fillets every corner of the grid with thickened Thixo Pro before laminating over the top.

He laminates the whole structure with staggered layers of biaxial fiberglass and carbon cloth, wetted out with High Performance Epoxy. The resin's low viscosity lets it saturate the fabric quickly and evenly, which matters on a part this size where Matt is hand-laying rather than vacuum bagging. He finishes each section with peel ply, so the surface comes out textured and ready to fair without heavy sanding. Once the laminate cures, he chisels the foam out of the grid, leaving hollow channels for every wire run the bimini needs.

Reinforcing the Underside

Before he can attach the grid, Matt turns his attention to the bottom of the roof panel, the surface he cut into earlier to curve the boards. He sands it thoroughly, vacuums, and wipes it down, then glasses over the whole underside by hand rather than vacuum bagging, since he doesn't have enough material to bag the full part. That layup reconnects the skins he cut through during the curving process, turning what was two separately curved panels back into one structurally sound roof rather than relying on the glue joint alone. Running low on peel ply partway through, he switches to a flood coat instead, then sweeps on a layer of High Performance Epoxy mixed with a low-density fairing additive once the first coat turns tacky. That fills the weave and cuts down on sanding the next day.

Bonding the Grid in Place

The next morning, once the underside layup has cured, Matt sands the areas where the grid will land, cleans the surface, and glues the grid down with thickened Thixo Pro. Its no-sag hold matters here, since he's bonding a large, flat grid to a curved overhead surface and needs the adhesive to stay put while it sets. With the grid bonded in place, the bimini roof is structurally complete and ready for its drip rail next week, followed by a trip up to the boat for final fitting.

Matt wraps the episode with a quick nod to Duracell's mast fundraiser, which the channel's patrons and viewers fully funded, and a reminder that any extra will go toward sails. It's a good snapshot of what this refit runs on: careful composite work, a lot of patience, and a community following along step by step.

Catch the full build, along with the rest of Duracell's transformation, on The Duracell Project, and check out how Matt used epoxy earlier in the refit in Duracell's Transom Transformation and Duracell's Upgrade: Securing Heavy Systems.

Have questions about High Performance Epoxy, Thixo Pro, or which one fits your next build? Call TotalBoat tech support at (888) 986-6623 and we'll help you pick the right product for the job.