Metal Shark One of the Dutch Caribbean Coast Guard’s (DCCG) dozen M 38 Defiant model interceptors built by Metal Shark under way in moderate conditions.
Its alluring blue waters appear idyllic in travel brochures and color charts, but the Caribbean is not a gentle sea. Generations of mariners have been challenged by its seasons of unrelenting winds, steep waves, and threat of hurricanes. For those who sail it professionally, the Caribbean is more often testing ground than playground, taxing crew and vessel resiliency and demanding high standards of vessel construction, maintenance, and operation. That was true for the boat crews of the Dutch Caribbean Coast Guard (DCCG) when they took delivery of a dozen new 12m (39′) aluminum interceptors in 2018. “After one week, the guys started getting back and neck pain,” said Steven Valorian, supervisor of maintenance for the DCCG based on the island of Curaçao. When they persisted in using the new boats, many of the operators ended up in pain and some on disability.
Metal Shark The DCCG interceptor fleet is based in Aruba, Curaçao, and Sint Maarten. Crews conduct law enforcement, search-and-rescue operations, and protection of territorial waters of the Netherlands in the Caribbean Sea.
Valorian and the crews took a more critical look at how the boats were handling and observed that operators struggled to keep the bow down even with the drive trimmed at -6°, which caused the boats to slam in those big Caribbean seas. In addition, operators and passengers often weren’t sitting in the motion-damping seats because of inadequate ergonomic design at the helm station and seat installations. Even though they were expensive, new closed-cabin boats, and a considerable upgrade from the center-console models they replaced, these operational challenges couldn’t be ignored. Valorian ran it up the chain of command and waited.
Fast forward to January 2024. The boats are all running as smoothly as a small boat can in the standard 3′-6′ seas they encounter most days. The crews are sitting in 66 new motion-dampening seats mounted on adjustable tracks. A dozen modified helm stations allow drivers to sit upright, square to the controls. Livorsi 1650 trim tabs keep the bow down and help the boat to get on plane quickly. Operators receive focused boat-handling training to limit slamming in high seas, and all crews get instruction in therapeutic exercises that help reduce their susceptibility to injury. In short, most of the problems were solved.
Not every encounter between an unexpected vessel-performance shortfall, the bureaucratic institution that didn’t foresee it, and the tight service budget that must fund a solution ends this well. It’s worth looking closely at what happened in Curaçao when the DCCG called on multiple collaborators from the U.S. and Europe as they optimized their interceptor fleet to better meet the needs of the mission.
The DCCG is responsible for law enforcement, search and rescue, and protection of territorial waters of the Netherlands holdings in the Caribbean operating from bases in Aruba, Curaçao, and Sint Maarten. With 81,000 km2 (31,274 square miles) of mostly open ocean under its jurisdiction, the service—comprising more than 200 personnel and 20 vessels—has a lot on its plate. In 2024, the DCCG was responsible for the seizure of 15,000 kilograms of narcotics, conducting 1,500 routine checks, and saving 420 people in distress through search-and-rescue operations.
Its active fleet is built around three 42m (138′) Damen-built patrol boats or cutters, the 12 previously described MS 38 Defiant model aluminum interceptors from Metal Shark (Jeanerette, Louisiana), five 7m (23′) inshore boats, as well as backup from the Dutch Navy.
Among the interceptor fleet, operators work long hours as the boats must be ready to respond at any hour in any conditions. Many of them spend an entire career at the same Coast Guard station being exposed to the same conditions every day.
The service life of the boats is demanding and diverse. They commonly run with a crew of six patrolling Dutch waters in drug and weapons interdiction, immigration enforcement, fisheries enforcement, and rescue activity—very much a multi-mission platform that must be nimble, seaworthy, reliable, and able to sustain operations through the night when necessary. “We are dealing daily with sea state 4, sea state 5, sea state 6 [waves 4′-20′],” Valorian said. And the boats must be able to run at high speeds in most conditions. Before 2018, those needs were met by a fleet of open center-console RIBS that left personnel exposed to the unrelenting sun, wind, and waves.
Metal Shark The DCCG interceptors underwent a slight redesign from the standard Metal Shark model to lower the cabin profile allowing the boats to pass under a bridge in Sint Martin.
Selecting the MS 38 Defiant
Henry Irizarry, Senior Vice President of International Business Development at Metal Shark, recalled discussing possible new boats with a DCCG delegation of crew from all three island bases who came to the 2013 International WorkBoat Show in New Orleans. They were looking for a closed-cabin model with inboard diesel engines powering sterndrives. It was Irizarry who suggested two years later, after DCCG had been deluged with boat proposals from builders around the world, that they consider buying through the U.S. Foreign Military Sales (FMS) program. Purchasing through FMS would give them access to models like the 38 Defiant model Metal Shark has built more than 200 of for U.S. Navy, Coast Guard, and services in 12 other nations including Bangladesh, which has 50 of them in its Navy, Army, and Coast Guard. While there is some variation among the different service applications, Irizarry said the boats are all designed and built to American Boat and Yacht Council standards for use at speeds exceeding 40 knots, to be operational in sea state 4, and survivable in sea state 5. Most are powered with twin diesel engines run through waterjets, though there are some outboard versions—twins and triples.
An FMS case was established, and multiple design meetings followed with the DCCG visiting Metal Shark in Louisiana. Irizarry said that’s where the requirement for sterndrives over jet propulsion was articulated by the DCCG and included in the final design.
“As a deviation from the original specs, we lowered the cabin to [accommodate] the height of the bridge in Sint Maarten,” Lieutenant Commander Cornelis Tramper, who served as head of material logistics for the DCCG from 2019-2023, told an industry audience at the 2025 High Speed Boat Operations Forum (Gothenburg, Sweden). Irizarry confirmed that Metal Shark was able to accommodate this requirement lowering the profile cabin height but keeping the original interior dimensions by stepping the cabin sole down lower into the hull.
On-Water Operations
The DCCG took delivery of the first four boats in Curaçao in 2017. Valorian recalled, “The first thing they noticed was that the nose was up and not coming down… it was like a dolphin in the water.” In his presentation, Tramper suggested that “because of the heavy engine at the back, we saw that the trim was not optimal.” It’s worth noting that according to Metal Shark records, the Konrad sterndrives are significantly lighter than the standard HamiltonJet drives installed on most of the MS 38 Defiant models in service and powered with the same Cummins diesels, making the DCCG boats comparatively lighter aft.
Metal Shark The perpetually rough sea conditions in their operating area means DCCG boats and crew are subjected to very high slamming-induced vertical and lateral accelerations.
At first, they thought crews just had to learn the new boats and adjust their expectations for these much heavier enclosed models. But operational problems persisted, and the slamming under way led to more personnel injuries and damage to the boats.
In the first year with the new fleet, Tramper said, “We had maintenance costs which exceeded our budget.” Welds on some of the seats had cracked, and most expensively, the gimble bearings in the lower units of the Konrad sterndrives were failing and the U-joints were subjected to excessive wear requiring replacement as frequently as every 200 hours. Tramper pointed to “sailing constantly in -6° [trim angle] to kick the bow down,” as a possible reason for the unanticipated wear.
Whatever the cause, maintenance demands for Konrad drives had been raised during design discussions. Metal Shark had advocated for the standard jet package precisely because they are more durable than the sterndrives, especially in heavy sea conditions which can cause high torque loading on the prop-driven sterndrives. In making the case, they had noted the standard duty cycle of the Konrad, while more than 200 hours, did not meet the DCCG’s operational requirements.
Worried about the health of the boat crews, Valorian noted that the motion-damping seats weren’t protecting them from the violent slamming as they continued to drive the boats at speed through rough seas. He investigated the seats and helm station and found the crew were frequently standing instead of sitting.
“The seats have to be adjusted to the weight of the guys,” Valorian said. But when duty called in a hurried emergency, they often didn’t have time to tweak the air pressure in the motion-damping mechanism before getting under way. Crews reported that the seats sometimes needed to be pumped up while under way—a distraction from mission focus.
It was no surprise that with multiple crew members out on disability and no solution to the operational performance issues in sight, “the guys said they didn’t want to sail anymore in that boat,” Valorian recalled.
When the injuries and elevated maintenance budget for the 38s was shared up the chain of command, it captured Tramper’s attention. “I couldn’t refuse this… we had to do something for our guys,” he said.
As a mechanical engineer, he wanted to have data to quantify the problems and to back up any request to fund corrective changes. He turned to Dutch research group TNO to measure the dynamics causing injuries. In November 2019, TNO staff conducted a battery of underway tests in a boat fitted with accelerometers to measure vertical and longitudinal accelerations at the hull and the seats, as well as displacement gauges to measure the travel of the seats. They pushed the boat as fast as 36 knots in .5m to 2m (1.6′-6.6′) seas (moderate conditions by Curaçao standards), revealing multiple shortcomings—the air-spring seats are vulnerable to a “soft” bottoming in extreme impacts, even with the standard 6″ (162mm) travel extended to 8″ (203mm), the bow-up trim needs to be adjusted down to help moderate impacts, and poor footrest, seat, and helm-station ergonomics leave crews vulnerable to injury.
Ullman Dynamics Proposed changes to helm-station design and ergonomics illustrate the appropriate position and posture for a boat operator.
In his HSBO presentation, Tramper noted that the testing confirmed impacts as high as 20 g and the inadequacy of the original seats to mitigate those forces, which are common in DCCG operating conditions. Results also demonstrated that lowering the bow-up pitch of the boat lowered impact accelerations under way. With those data in hand, he proposed taking the boats back to Metal Shark to make changes that would solve the trim angle, helm ergonomics, seat functionality, and sterndrive maintenance problems.
Working through the FMS program, the DCCG passed on details of their findings to Metal Shark and asked the builder to identify measures that would reduce the injury rate and improve boat performance.
Ullman Dynamics New motion-damping seats from Ullman Dynamics installed on deck rails can be adjusted fore and aft depending on passenger size.
Irizarry remembered getting the extensive test results and noting that the boats were being subjected to conditions outside of their intended use profile, and that crews seemed to be running the bigger boats the same way they had the lighter RIB predecessors. “Whenever you have 20,000 pounds [9,072kg] that’s pounding in the water, you’re going to feel it,” Irizarry said.
The builder saw there wasn’t a single simple fix for the multiple concerns. They asked Swedish seat manufacturer Ullman Dynamics, whose shock mitigating seats they had used in the past, to help with troubleshooting.
Solutions
In April 2022, Ron Carpenter, President of Ullman Dynamics USA and a retired U.S. Navy “SWCC” Chief Warrant Officer, led a team conducting on-water testing off Curaçao. The first thing he noticed was the boat’s bow-up trim, which he said was evident even at the dock. On the water, he observed that, “the boat is actually driven outside the key performance parameters.”
Carpenter is a combat veteran with 28 years of experience leading Special Boat Teams for U.S. Special Operations. In short, he knows how a high-speed boat for agency service should perform.
“I got under way with a lot of accelerometers and inertial measuring units, and we started trying to figure out what was the best way forward,” Carpenter said. “As the boats would come out of the harbor at idle speed or seven knots, they’re riding bow high, which creates a situational awareness issue.” And once they were on step, the slamming started.
“The impact was so severe to their bodies that they would quickly stand up and they would lean against the seat pan,” Carpenter said of the boat crews. And sitting or standing, the driver was forced to adopt a vulnerable curved-spine stance to reach the helm and controls. “This misaligned posture forced their head forward of their shoulders and increased the acceleration rates on their body and head by 2x to 5x the hull impact,” Carpenter said.
Steven Valorian To help lower the bow height and running trim angle, the DCCG added Livorsi trim tbs outboard of the Konrad sterndrives.
A team from Metal Shark worked with Carpenter and the DCCG to reengineer one of the boats to test possible solutions. They started with onboard seating, addressing the TNO concerns that the existing air-spring seats were inadequate for the extreme operating conditions by adopting Ullman Dynamics Atlantic class seats, which rely on dual leaf-spring suspension with twin pneumatic-hydraulic dampers offering a 200mm (7.9″) stroke. Carpenter explained that at anything below 5 g of accelerations, Ullman seats don’t particularly stand out against other shock-mitigating models, although below that threshold, there’s little risk to the human body. For impacts of more than 5 g from vertical and lateral accelerations, tests were favorable to the Ullman seats. “The harder that seat is impacted, the more it attenuates,” Carpenter said, which makes any sort of bottoming out highly unlikely. The Ullman seats’ dual suspension system with a leaf spring assembly and dampers also eliminated the need for regular pumping up and adjusting pressure in the air springs of the original Shockwave seats. DCCG crews subjected the two seat options to side-by-side testing off Curaçao. The data and crew responses informed the final selection.
In another measure, “we placed tracks on the decks to adjust the seats based on the operator,” Irizarry explained. And to correct driver posture, “they extended the console by about 7″ (178mm) to bring the helm and throttle to the human body,” Carpenter said. The cockpit and dashboard were reconfigured according to the principles laid out by Johan Ullman in “Designing Consoles for Speed” (Professional BoatBuilder No. 141, page 62) and widely adopted by boatbuilders internationally.
To adjust the boat trim, Ullman and Metal Shark suggested installation of Humphree interceptors, but Valorian said the boat crews asked for conventional trim tabs. He spec’d Livorsi 1650s as an option and had engineers at Konrad advise where they should be attached to the boat in relation to the sterndrives.
Steven Valorian The redesigned console was extended toward the helm about 7″ (178mm). The aluminum weld on the side of the console reveals what was added.
Tramper said he preferred the interceptors as well, but when on-water testing indicated negligible difference in performance, DCCG went with the preference of their crews testing the boats—the Livorsi trim tabs won out. Carpenter said the improvement in performance keeps the bow down at low and high speeds with only -1° or -2° trim on the sterndrive, reducing the possibility of any extraordinary wear on gimbal bearings and U-joints from the -6° orientation at which they previously operated.
Irizarry said all the changes to the first boat were engineered and performed in Curaçao by a crew of Metal Shark technicians on site, backed up by the company’s design and engineering team. After a month or more of in-service use to verify that the changes worked, the remainder of the DCCG fleet was converted to the same specifications by local crews in the Caribbean.
The combination of changes to seats, trim tabs, and console geometry “reduced impacts on the human body by 66%,” Carpenter said. Plus, the boats get on plane faster, and the sterndrives last longer. But the solutions were not all technological.
Ullman Dynamics As another measure to prevent injuries while working in their challenging service environment, DCCG crew are now trained to stretch prior to getting under way and to roll out impingements following operations.
There’s a quirk in the human pain feedback loop that gets us in trouble in high-speed boats: If we create a protective technology to limit exposure to damaging vertical and lateral accelerations, operators will frequently increase speed and slamming loads until it hurts pain again. Carpenter, who has painful personal experience with injuries from exposure to excessive slamming, advocated for driver training to operate the boats as smoothly as possible in heavy seas and for exercises and stretching routines to keep crew spines aligned and bodies limber and free of muscle impingements from heavy slamming. Valorian said the DCCG has approved four years of training in human performance, and high-speed boat training in hopes of creating a cultural shift in DCCG to improve their performance on the water and their quality of life while on active duty and long after they are retired.
Ullman Dynamics A graph of the 100 highest impacts measured on the hull and navigator during one 12-minute recording of a reengineered interceptor under way. The impacts on the hull range from 3 g to 13.5 g peak acceleration, while the highest peak accelerations on the operator range from 1.3 g to 3 g.
Conclusion
Carpenter praised the DCCG for their response to the personnel complaints. The service sought assistance through the Coast Guard Foreign Military Sales office to identify what was wrong and to determine “why their people are getting injured at a high rate,” he said. A positive outcome was not guaranteed, but Metal Shark stepped up anyway to address the issues on this fleet of boats being operated outside of key performance parameters due to a combination of operational factors. “Metal Shark got involved and stayed involved,” he said. “That company is one of those leading the charge in human factors now.”
Carpenter sees lessons in the DCCG project for other services around the world facing tragic and expensive legacies of injury from exposure to slamming. Last Nov. 12, New York Times reporter Dave Phillips published a sobering article about the chronic brain trauma suffered by the U.S. Navy’s Special Boat Teams after years of exposure to excessive slamming loads. Carpenter is all-too familiar with the risks crews run in pursuit of extreme missions, even when mitigating technologies and practices exist that can protect them. With thousands of similar small boats operating in the U.S. Navy and Coast Guard, the DCCG experience stands as one practical example of how to reduce injury rates through crew training, vessel ride reengineering, and changes to seat and helm ergonomics to meet demands of specific regional operating conditions.
“If you can prevent the injury, you can sustain operational readiness, and then you can drive down the cost of care post career,” Carpenter said. “You’re saving our country a lot of money.” And a lot of pain.
About the Author: Aaron Porter is editor of Professional BoatBuilder magazine.
