Pioneering a bold approach to wood-composite boat building
by Lyman-Morse Boatbuilding 1 Apr 2019 02:37 AEDT
Hood 57 © Lyman-Morse Boatbuilding
Lyman-Morse Composites Manager Steve Crane believes that the next revolution in composite boat construction will be about building both aspects of a boat's hull – the outside and the inside – at the same time.
Crane and the team of craftsmen in Thomaston, Maine, are mid-way through the construction of a custom, 57-foot wood-composite express cruiser for C.W. Hood Yachts of Marblehead Mass. This Hood 57, designed in a collaboration between C.W. Hood and Stephens Waring Yacht Design of Belfast, Maine, will feature all the latest 21st-century go-fast gadgets and luxuries: Twin 1,000 HP Volvo Pod drives, a circular titanium stairway to the fly-deck, and a distinctive retro sport-cruiser design.
But what Crane is especially excited about is the innovative construction approach developed by Stephens Waring that assembles both the outside of the hull and the inside structural laminates for that hull simultaneously.
"What we are doing is assembling the entire hull, from exterior surface through the planking and into the structural longitudinal laminates, in four separate modules," he says. "Then we will assemble those four prefabbed units into a single structural hull."
Crane says the construction methods conceived by Stephens Waring are truly innovative. "Nobody I know of has made a composite wooden boat this way before."
Built unlike any other boat
"The cutting-edge methods we're developing use everyday materials," explains Crane. "But we use a new process that allows us to assemble these simple materials into innovative and cost-efficient modules."
The bottom module includes the stem of the boat and about 52 feet of the planing surfaces of the hull. Then there's the smaller transom module, roughly 15-by-8-feet, which is the stern and forms the cylindrical camber of the tumblehome. Finally, there are the two port and starboard topside modules, each about 6 feet high and running the full length of the 57-foot boat.
"Because these module structures are unique, everything about this process had to be reinvented. And I mean everything," Crane says. "We were awarded a grant from the Maine Technology Institute just to install the two overhead gantry cranes that traverse the entire length and width of our construction building. That's what we needed to maneuver these modules as we built them."
Rejigging the obvious
At its core, the Hood 57 is engineered to be a fairly standard wood-composite boat. The hull's planking is traditional Douglas Fir. The fibers that reinforce this wooden core are standard eGlass. The entire structure is either infused or impregnated with well-understood epoxy resins. All materials that can be picked up at any marine supply store.
The composite magic happens in how these elements are combined and then assembled.
For starters, the forms of the jig used to shape the hull are precisely cut with Lyman-Morse's Haas GR-712 CNC machine. The machine is controlled by direct digital outputs from the computers used to design the Hood 57's hull.
The CNC-cut jig pieces create a kind of backbone that captures the exact form of the hull. It is this Digital Age skeleton that allows for both the external hull planking and the internal longitudinal stringers to be assembled in carefully choreographed steps.
"That's what is unheard of in composite construction," says Crane.
Designed to save money
Using the bottom module as an example, Crane describes how his crew assembles the fir hull planking over the jig forms. At the same time, his crew lays out the internal longitudinal stringers alongside the building jig. When the bottom hull section is fully planked and the stringers fully assembled, the planked hull is popped off the jig using the new gantry cranes. Then the pre-finished longitudinal internal stringers are lifted and slotted into precise pre-cut notches in the jigs, aligning them in the required exact location.
Crane's crew then lays out a giant vacuum bag around the bottom hull section and infuses it with two-part epoxy resin. Once cured, that infused hull section is re-attached to the jig and carefully matched to the longitudinal stringers now sitting in the jig.
Once both are bonded together with adhesives, the outside hull structure and internal framing are now a single unit. Then the port, starboard, and transom modules can be completed and attached. The result is a hull of incredible structural strength that can save builders – and in turn customers – money.
This process will give Lyman-Morse another construction option for owners looking for a custom boat, as there is no need to build and then dispose of the molds. Similarly, this kind of modular construction should allow for more efficient integration of internal structures.
"We are always looking for new ways to develop a construction system that is faster, cleaner, and saves customers money," Crane says.