BAR HARBOR — For more than the 200 years Maine has been a state, forest products, boatbuilding and wind power have been central to the economy here. That used to mean dimensional lumber for building homes, stores and ships; boatyards building giant schooners; and wind to move the boats.
Now, those same forces are making possible new frontiers in laminated timbers, bio-based polymers derived from wood, 3-D printed boat molds and boats themselves and floating offshore wind turbines, the acclaimed director of a University of Maine research center explained to a rapt Zoom audience of Mount Desert Island residents last Wednesday.
The talk by Habib Dagher, the founding executive director of the University of Maine’s Advanced Structures and Composites Center, was hosted by the Jesup Memorial Library and A Climate to Thrive.
In the 25 years since Dagher and a few colleagues founded the UMaine Composites Center, the work there has led to more than 50 patents and 10 spinoff companies. Of the 2,500 students who have been involved in the center’s research, all have graduated with at least one job offer.
The launch last year of the world’s largest 3D-printed boat, a 25-foot, 5,000-pound patrol vessel, got a fair amount of attention, but Dagher described other projects of interest to the boatbuilding industry.
One is the MAKO, a high-speed interceptor vessel for the U.S. Navy Seals. The all-composite hull, the first in the Navy’s fleet, was designed to address the problem of shock loading in the previous aluminum hull — 10-20 G’s (gravity accelerations) as the boat crashed through waves at speeds of over 50 knots.
The MAKO was designed in partnership with Hodgdon Defense Composites is East Boothbay. Its composite sandwich structure, Dagher said, significantly reduces the shock loading.
“The first thing a boatbuilder has to do before building a boat is build a mold for it,” Dagher told the group. The Composites Center began exploring 3D printing molds for parts of boats with a roof for a “limo tender” by Hodgdon Yachts. “Over the next year we’re looking at printing a mold for a whole boat,” Dagher said.
One usually thinks of 3D printers as extruding plastics since wood in its natural state can’t exactly be convinced to change its shape. But the bio-based polymers the center is experimenting with include melted polymers filled with wood fibers and microcellulose (for comparison, nanocellulose is basically sawdust). In 20 years, they hope to be able to 3D print entirely with materials derived from wood.
The offshore wind energy work also has obvious connections to the maritime sector, as the floating concrete “hulls” that support the turbines are like boats, and they’re moored to the seabed.
Elsewhere in the country, Dagher explained, offshore wind turbines are built on solid structures that rest on the seabed. But the Gulf of Maine is so deep that “you can’t build a turbine all the way down to the seabed; it would be way too expensive.”
The mooring system for the offshore floating wind turbines were tested at this W2 wind-wave basin at the center’s ocean engineering lab. The forces recorded by load cells on the one-eighth scale prototype deployed off Castine were very close to what were predicted by the models in the lab.
And as far as tipping over in high winds and waves goes, the researchers could extrapolate from the one-eighth scale model how the full-size turbines will react to proportionally bigger waves. That is, they measured the size of the waves relative to the size of the tower to see what happened to it. In what would, for a full-size tower, be a 500-year storm kicking up 70-foot waves, Dagher said, the tower moved seven degrees off vertical.