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By Tom Clynes
In 1995 a Clemson University graduate student named Ed Sutt took off for a spur-of-the-moment trip to the Caribbean. But beaches and rum drinks weren’t on the agenda for this civil engineer. Hurricane Marilyn had just torn through St. Thomas, and Sutt was part of a team examining how and why 80 percent of the island’s homes and businesses had collapsed in the storm’s 95mph winds.
“The destruction was so complete in places that it was almost surreal,” Sutt recalls. “There were troops in the streets and military helicopters hovering overhead.” As Sutt moved through the wreckage of roofless and toppled-over houses, he was struck by the sense that much of the destruction could have been avoided. “In house after house,” he says, “I noticed that it wasn’t the wood that had failed—it was the nails that held the wood together.”
At the time, Sutt couldn’t have predicted that this realization would spark a journey through earthquakes, wind tunnels and head-to-head battles with giant wall-wrecking machines. Or that 11 years, dozens of hurricanes and thousands of prototypes later, he would be credited with reinventing the little spike of steel that holds together most of the world’s houses.
The Overlooked Importance of the Nail
For more than two centuries, nails have been the fastener of choice for wood-frame structures. But for all that is riding on nails, they have been the focus of precious little R&D. Nails have evolved into a grab-whatever’s-cheapest commodity, taken for granted by contractors and engineers.
Sutt should know. The man now known to his colleagues as “Dr. Nail” grew up the son of an architect-contractor in suburban Connecticut, where he spent his weekends at job sites, framing houses from the age of 14. As a young adult, he worked as a carpenter, then started his own construction business. “I wasn’t a very successful contractor,” says the 38-year-old Sutt, “mostly because I liked to hand-nail everything. One day I was nailing off a top plate over a door. I looked at my swollen hands, and I couldn’t see my knuckles. So I decided to go back to school.”
To finance his engineering degree, Sutt took a research-assistant position at Clemson’s Wind Load Test Facility, which had received a grant from the Federal Emergency Management Agency to study the relationship between wind velocity and the failure of wood-frame structures. The position turned out to be a good fit, since it allowed Sutt to combine engineering with his practical knowledge.
“We hand-built these mobile weather stations that measure wind speed and barometric pressure,” he says. “Then we would race out in front of hurricanes and drop them in the storm’s path. After it was over, we came back to see if we could make a correlation between real wind speed and when a house starts coming apart.”
When he integrated the results of the fieldwork with his laboratory experiments, Sutt discovered that the most effective way to strengthen a house was to improve its fasteners, especially the nails that hold the roof and wall sheathing to the frame. “I began to see that the engineers and building-code writers had been missing the point. Everyone had always just accepted that a nail is a nail. No one was focusing on what we could do to make the connection better.”
In 2000, with his Ph.D. in hand, Sutt sent his résumé to Stanley Works. His timing couldn’t have been better. The company had recently begun to increase its investment in fastener engineering, and it called Sutt in for an interview, during which the young engineer shared his vision of a new way to think about research. “In the past,” Sutt says, “fastener companies had focused on how to manufacture nails. I wanted to look at how structures perform based on the nails that are used.”
Sutt signed on as a fastener engineer at Stanley’s subsidiary Bostitch and settled into a new lab at the company’s headquarters complex in Rhode Island. Then he began concentrating on the mission that he had seemingly spent his entire life preparing for: designing a better nail.
Reinventing the Steel
During the HurriQuake nail’s six years of development, 14 major hurricanes and tropical storms destroyed hundreds of thousands of houses in the U.S. and inflicted an estimated $166 billion in damages. The U.S. hasn’t had a major earthquake since parts of the Los Angeles area were leveled in the Northridge quake of 1994, but around the world, thousands of people have lost homes and family members as wooden structures collapsed.
Although there are no precise statistics, Sutt’s research indicated that nail failure accounted for a substantial percentage of the destruction in these catastrophes. And when nails fail, it’s for one of three reasons. Either the nail rips its head through the sheathing, its shank pulls out of the frame, or its midsection snaps under the lateral loads that rock a house during high winds and earthquakes. Sutt’s job was to design a nail that resisted all three. “With the first prototypes,” Sutt says, “we proved that a bigger head has substantial advantages in terms of stopping the nail from pulling through the sheathing. But it couldn’t be too big, because it needed to fit into popular nail guns.”
As the Bostitch team tweaked the head-to-shank ratio, Sutt and metallurgist Tom Stall worked on optimizing high-carbon alloys, trying to find the highest-strength trade-off between stiffness and pliability—the key to preventing snapped nails. “Meanwhile,” Sutt says, “we were focusing on how to keep the nail from pulling out.” The team machined a series of barbed rings that extend up the nail’s shaft from its point, experimenting with the size and placement of the barbs. “You want the rings to have maximum holding power,” he says, “but if they go up too high, it creates a more brittle shank that shears more easily.”
The team tested hundreds of designs, looking for the best compromises. The late prototypes held fast, and Bostitch came out with a barbed nail with a larger head in 2005 called the Sheather Plus. But the solutions created problems of their own: As the barbs pierced the sheathing, they generated a hole that was slightly bigger than the shank, resulting in a loose, sloppy joint.
“We needed a way to lock the top of the shank into the sheathing,” says Sutt, who attacked the problem in a series of brainstorming sessions with his engineers. Their solution: a screw-shank, a slight twist at the top of the shaft that locks the nail in place. The combination of the screw-shank, barbed rings, fatter head, and high-strength alloy added up to an elegant solution to the failures that had plagued nails for more than two centuries. Sutt’s team had, in effect, reinvented the nail.
Snapping Walls for Science
Tests conducted by researchers at Florida International University and the International Code Council—the independent building-safety standards organization—confirmed that the HurriQuake has more than twice the “uplift capacity” of standard power-driven nails. Other independent tests showed that the HurriQuake can double a typical home’s resistance to high winds and add up to 50 percent more resistance to earthquakes.
I wanted to see what that resistance looked like on real boards, so I asked Scott Schiff, the coordinator of the civil-engineering and engineering-mechanics graduate programs at Clemson, to run some tests on the HurriQuake. And I asked Sutt to accompany me back to his old stomping grounds.
Schiff, who taught Sutt at Clemson, meets us at the Wind Load Test Facility, which occupies two large sheds a couple miles from the university’s main campus in northwestern South Carolina. Inside the sheds, Schiff has created something of a storm chaser’s fantasy lab. There’s a giant wind tunnel, Styrofoam models of cities and suburbs, even a homemade cannon that fires two-by-fours into walls.
In the rear shed, a 20-foot-tall frame of steel I-beams rears up like a medieval torture device. Schiff’s students have bolted into the device an eight-foot-square section of wall, built with conventional 8d “common nails,” that will soon be methodically torn apart. “Meet the Monster,” Schiff says, motioning toward the rig’s actuator, which will pull the wall up at a 45-degree angle. “We use it to simulate the forces of simultaneous uplift and shear, which is what is exerted against a house in a high-wind event.”
With a capacity of up to 20,000 pounds of force—“We won’t get near that today,” Schiff assures me—the Monster tests how fasteners perform as part of a system. “The first time I used it,” Sutt says, flashing a guilty grin, “I was trying to apply a shear force on nails through rafters, as part of my Ph.D. research. But I had it set up wrong, and when I turned it on, I basically destroyed it.”
“We had to send it out to get rebuilt,” Schiff says, with an expression hinting at second thoughts about his star student’s reappearance.
“What we’re going to do,” he says, as he punches instructions into a computer, “is simulate what happens to a house over a lifetime, which might include a few nor’easters, several gales, and a hurricane or a tornado.” The Monster will try to pull the wall panel apart, ramping the pressure up and back down again 18 times. Each time, it will gradually increase the force until it hits the wall’s failure point.
During the first few cycles, not much happens. But as the force escalates to 5,000 pounds, the wall begins to crackle and pop. At 7,000 pounds, the sheathing begins to separate at the joints. At 9,000 pounds, the popping gets more intense, as nails begin to pull out of the framework.
“It’s crackling like a holiday fire.” Schiff says, as the gauge tops 10,000 pounds. “Time to get out of the house,” Sutt says, watching the panels twist outward. At 13,500 pounds, the structure splits apart, separating with a sickening crack.
We walk over to examine the nails. In some cases, they have pulled out of the framing; in others, the heads have pulled through the sheathing. Many of the spikes are bent into an S-shape, deformed by the combination of loads. “This is typical of how conventional nails fail,” Schiff says.
He and his students recalibrate the machine and swap panels. An hour later, the Monster is ready to go again. This time, the panels are fastened with the HurriQuake 1, which is the same size as an 8d common nail. Schiff fires up the machine, and we wait.
The screen shows that the Monster is pulling at the wall panel with 12,000 pounds of pressure, but the structure shows no sign of stress. There’s not even a creak. The machine ramps to 14,000 pounds, past the failure point of conventional nails. At 16,000 pounds, the registration marks reveal that the wall has shifted less than a quarter of an inch. Finally, at 18,300 pounds, the Monster begins to pull the nails from the mounting, and the panel begins to move.
After a pizza break, another panel is ready to go. This time, the wall is fastened with the HurriQuake 2, a stockier version of Sutt’s nail. The Monster cranks up to 10,000, then 15,000 pounds. There’s no noticeable effect. Schiff watches his computer screen as the pressure-graph line keeps rising, to 17,000 pounds, to 18,000. The wall lets out a little groan.
“I wonder if we can max the Monster out,” Sutt says.
“Leave your credit card,” Schiff says, casting a worried eye at the screen. At 19,000 pounds, parts of the strand board begin to pull apart slightly, but the nails continue to hold. The line on the graph arcs to 19,500, then trembles up toward 20,000. Schiff steps back as the actuator shudders. Suddenly the cables go slack. “Uh-oh,” Sutt says. “I think I may have trashed the machine . . . again.”
Something to Build On
Upon inspection, Schiff determines that the Monster is in fact OK; the actuator gave up before it gave out. The professor kneels down to inspect the bottom of the wall, shaking his head. “The strand board was starting to give, but the nails held in there,” he says. “I’ve never seen anything like this.” As we nibble at the last cold slices of pizza and watch the students unbolt the wall, Sutt wears a broad grin. His former teacher is clearly impressed with his invention.
Sutt’s bosses at Bostitch must be happy too. The company is selling every HurriQuake nail it produces and has been doubling production capacity every month. Although the nail is currently available only in the Gulf region (it adds about $15 to the cost of an average 2,000-square-foot house), the company is adding new production lines to meet nationwide demand. Meanwhile, the nail is getting rave reviews from building-technology experts.
“This is a major innovation,” says Tim Reinhold, director of engineering for the Institute for Business and Home Safety, an insurance-industry research group. “And in places that are affected by high winds and earthquakes, it looks like it’s going to make a big difference.”
Before I leave Clemson, I ask Schiff if he sees any downside to his protege’s invention. “Homeowners and insurance companies are going to love these nails,” he says. “But contractors are going to hate them, because when they make mistakes, it’s not a trivial thing to remove them. Once you nail something together, it’s going to stay together.
“To us, that’s a good thing.”
In the July issue, Tom Clynes presented a plan for ending our fossil-fuel addiction.
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