An Aluminum Expedition Catamaran

Courtesy Van Gorkom Yacht Design

With 110′ LOA, a 35′ beam, and 45′ (33.5m, 10.6m, and 13.7m) of bridge clearance, the H-2 catamaran seeks to make a case for U.S. custom boatbuilding.

Hauling toys beyond the horizon is the raison d’être for a rugged go-anywhere catamaran designed and built in the U.S., a notable exception in the world of big yacht projects.

Gunboat might have left town, but there’s another big catamaran under construction in its old facility in Wanchese, North Carolina. It’s called H-2, short for Hippocampus 2, a stout 110-footer (33.5m) that liberally and intentionally quotes from the expedition/workboat vernacular. It’s built from aluminum and was conceived to go to the back of the beyond, where adventure beckons and Vessel Assist doesn’t operate. Aside from commodious and cushy accommodations, the boat offers grid autonomy, ocean-crossing range, and cargo capacity to match the mission of hauling a 26 (7.92m) tender, a 17 (5.8m) skiff, a two-person submarine, a four-seat ATV on the main deck, and a small helicopter on the flight deck aft.

The boat was commissioned by Brian Schmitt, 67, a real  estate executive in the Florida Keys, who pilots his own plane to commute to the Bahamas, where he keeps Hippocampus, his current 57 (17.37m) cold-molded wood/epoxy catamaran. I asked him about the jump from 57 to 110. “I never thought I’d have the ability to do that in my own boat until probably the last few years,” he replied, adding that “it would be 120 [36.58m] if I had to do it today.”

George Willis

Its predecessor, Hippocampus, built in wood/epoxy, was launched in 2003. At 57′ (17.37m), it is about half as long as H-2, but with 22,500 miles under its keels, it was a useful starting point for designing the new vessel.

Wearing shorts and a shirt with the new boat’s name and logo to our meeting, Schmitt talked openly about his project, which he manages as attentively as his real estate brokerage with 130 agents. Communication is his thing, responding to e-mail questions in near real time (in ALL CAPS) and talking to contractors directly. No project manager.

A passionate diver who habitually explores remote and exotic locales, Schmitt said he was happy with the first Hippocampus, which has three staterooms and cruises at 15 knots on twin 370-hp Yanmars. “It was the vehicle that got our 17 tender wherever we needed it.” But running the little boat 60 or 70 miles a day lost its charm. “One of the things I wanted was a twin-engine tender that would have more room for dive gear. That ended up being a 26 Calcutta, so I needed a bigger mother ship.”

With accelerating climate change, the carbon footprint of ships and large yachts is under scrutiny, but hydrocarbons still win when speed, range, and payloads are priorities. While H-2 doesn’t break the mold there, Schmitt pointed to the project’s virtues as a U.S. domestic build. “You can’t complain about global warming when you’re flying around in your G500 jet that’s contributing more CO2 emissions than anybody else in the world,” he said. “You can’t complain about all the boats being built in Germany, The Netherlands, and Italy, and then go buy a boat [there].” Schmidt wanted to build locally, keeping jobs and money in the U.S. Besides, he noted, this approach simplified communications and enabled him to personally check on progress during COVID. Perhaps most importantly, he could pick a team of trusted and compatible mates to turn his dream into a boat.

Chris Hannant

The vast build hall left vacant when Gunboat left Wanchese, North Carolina.

He selected John Marples, a fellow pilot, inventor, and multihull specialist for the design and Felix Herrin to build H-2. Both men had worked for him on Hippocampus, and their familiarity helped when meeting today’s challenges, such as damaging trade tariffs that drove up aluminum prices, and a pandemic that killed millions, wreaked havoc on global supply chains, and caused labor shortages in industrial sectors. These factors have conspired to delay H-2’s launching by roughly two years and counting.

Advantage Aluminum

A key decision early on was to build in aluminum, which promised a robust structure but required extra steps to deal with corrosion and noise mitigation. “Construction was reduced to something simple—a V-bottom deadrise model, stretched out,” Marples explained. “There wasn’t any benefit to round bilges on an aluminum boat. You’d have to add internal structure to support the flat panels, and it drives the cost and difficulty of construction way up. We’re talking about a speed-to-length ratio of 2 or less, which is not a big deal. His current boat would do a speed/length of about 3, so the extra length means that you’re never really pushing the boat that hard, so shape was not a huge consideration.”

Marples and Herrin go back at least three decades to their mutual acquaintance with naval architect and boatbuilder Dave Dana, who assisted Marples with the hull design for Admiral Pete, a catamaran passenger ferry still serving Puget Sound. Herrin works with different construction materials, but having built crew boats for Petróleos de Venezuela (PDVSA) at Sea Force in Palmetto, Florida, he has spent considerable time with aluminum.

Dieter Loibner | Professional BoatBuilder Magazine

Taking a break during IBEX 2021 are builder Felix Herrin (left) and owner Brian Schmitt. H-2 is their second
joint project with designer John Marples.

The structural components on H-2 are 5083-H32 alloy aluminum plate and extrusions of 6061-T6 alloy. Scantlings, materials, and weldment comply with the American Bureau of Shipping’s (ABS) 2016 design guidelines for pleasure motoryachts. Hulls and wing structures have transverse frames and bulkheads spaced on 36 (0.91m) centers. Those frames are supported by substantial centerline vertical keels (CVKs) welded atop twin 3 x 8 (76mm x 203mm) solid extruded-aluminum-bar keels. Intermediate subframes in the forward and aftermost hull compartments strengthen the hulls for operating in ice. Schmitt indicated he wants to traverse the Northwest Passage. For the same reason, there’s 3⁄8 (10mm) plate running the length of the boat above and below the waterline.

The topside and underwing plating is primarily ¼ (6mm), with areas of 5⁄16 (8mm) to strengthen slamming zones in the bow. The main deck plating is also 1/4 while the foredeck plate is specified at 5⁄16. The bottom plating is 5⁄16 in the aft two-thirds of the hull and 3⁄8 forward. “We built all the frames and bulkheads first, then scarfed together the keel sections [and] lined those up on the bunks that we built on,” Herrin explained. “We welded the CVK on top of the keel, then started installing frames.”

Courtesy Van Gorkom Yacht Design

Hulls and wing structure have transverse frames and bulkheads on 36″ (0.91m) centers. The hulls are supported
by centerline vertical keels.

Herrin said he changed aluminum suppliers midway through the project, sourcing from Bayou Metal Supply, an ISO 9001:2015–certified distributor in Slidell, Louisiana. “We sourced the material from Greece and from domestic suppliers,” said Taylor Smith, who handles Bayou’s sales. Tariffs, he said, did not slow down business much, but the aluminum cost more. “Felix sent cut files. We had the material in inventory, we cut it, processed it on a router, and shipped it on time. Everything flowed well.”

Naval and structural engineering and detailing was contracted out to Van Gorkom Yacht Design in Portsmouth, Rhode Island. “My first responsibility was looking at structures,” Geoff Van Gorkom said. “Given that this is an aluminum yacht, we can do literally all the structures in 3D and have all the metalwork precut before it came into the yard. All the frames and longitudinals and all the primary structure were precut, which saved huge amounts of time.” Van Gorkom said he uses Rhino 3D and some of the numerous modules such as Orca 3D for hydrostatics and hydrodynamics, and 2D AutoCAD to produce construction details.

Chris Hannant

Helping save time and money, 3D-modeling allowed frames,
longitudinals, and the primary structure to be cut before being
sent to the building site.

Van Gorkom observed that H-2 is not a fussy high-performance vessel that needs minimum weight to achieve maximum speed. Besides ABS guidelines that address torsional loads in catamaran structures, he also consulted A.L. Dinsenbacher’s paper “A Method for Estimating Loads on Catamaran Cross-Structure” (Marine Technology, Vol. 7, No. 4, October 1970) to estimate load conditions in beam and quartering seas. “This is going to be a very stiff boat. It’s going to be a very strong boat simply because it has to be, and that was one of the criteria that Brian put out there right from the very start of the project. The boat is sturdy and stout, a strong expedition yacht.”

Van Gorkom also engineered the setup for a folding deck crane housed under a flush hatch in the helideck on the port side to launch and retrieve the two-man submarine or the ATV. “It’s basically an enclosure that opens up, so the crane extends out,” he explained. “It comes up on a telescoping pipe to swing out and pick up something from the side of the boat.” It required support from beams on each side of the crane and cutting a slot in the helideck for the lifting bridle so the loads can move inboard or outboard. On the starboard side, the 5,500-lb (2,492-kg) Calcutta tender is an even heavier load moved by twin overhead beam cranes. The 17 Twin Vee is launched and retrieved from the foredeck with a 2,500-lb-capacity (1,153-kg) crane.

Catamarans are known to be weight-sensitive, so how will H-2 handle the weight of all the toys and high superstructure? The arch over the flybridge is 33 (10.05m) above waterline, Van Gorkom confirmed. “Add another 10 [3.05m] for the radar, mast, etc., so a comfortable bridge clearance would be around 45 [13.7m].” Marples conferred with Van Gorkom about the effect of the added weight on the center of gravity, which was deemed “almost imperceptible,” Marples remembered. A quick calculation suggests that a 5,500-lb deck load is equal to only 1.57% of a full-load displacement given as 350,000 lbs (158,550 kg).

High Power, Low Noise

Van Gorkom hired engineers at HydroComp to evaluate the design’s hydrodynamics and propulsion systems, including the influence of hull-shape parameters and demi-hull spacing on resistance. HydroComp also offered a speed-power prediction to aid with engine selection and recommended optimum shaft rpm and propeller parameters. Technical director Donald MacPherson, who prepared the report, outlined the process and findings: “Particularly interesting for this project was the use of its novel analytical distributed volume method [ADVM] for the vessel’s resistance modeling. This 2D technique (between parametric methods and CFD) uniquely allows for assessment of the influence of local sectional area curve regions (such as ‘shoulders’ or inflections) in wave-making drag. It also directly evaluates the effects of catamaran hull spacing.” HydroComp helped optimize the hulls by identifying the regions that contribute most to wave-making drag, and securing a 3% reduction in total drag at the design speed by making what MacPherson called “very minor changes to the immersed volume distribution.”

Chris Hannant

Rob Ayers works on the installation of the starboard engine’s Evolution Marine Shaft System that will be fitted with a 36″ (0.91m) five-blade propeller.

That simulation was mapped to benchmark performances of four similar catamarans, and the process was run for two design variants, followed by a propulsion simulation for partial-load conditions. The hull-spacing study concluded that the originally designed 35 (10.7m) beam remained suitable despite the boat being 20 (6.1m) longer than originally drawn. The chosen propulsion system comprises two MTU 10V 2000 M96, 1505-mhp diesels with ZF 3000 flange-mounted marine gears, providing an estimated top-speed range of 20–22 knots, cruising speeds of 12–15 knots, and 10–13 knots for long-range voyaging. Actual performance will be established during sea trials.

The recommended propeller specifications developed by HydroComp were for five-blade models with 36 dia­meters. HydroComp applied Prop­Elements, a wake-adapted propeller-analysis tool, to determine the advisability of installing a nozzle or shroud to restrict transmission of pressure pulses to the hull and to create a more uniform inflow. This would reduce interior noise but would increase appendage drag and power demand. Schmitt said he will wait to see if cavitation or prop noise is an issue before making a final decision.

He invested heavily in noise and vibration mitigation, knowing that an aluminum boat won’t provide the natural sound-dampening of a wood/epoxy structure like that of his first Hippocampus. Consulting with Soundown of Salem, Massachusetts, Schmitt wanted to replicate what worked well on his old boat, starting with the Evolution Marine Shaft System, in which the prop shaft runs in an oil-filled tube and uses roller and needle bearings instead of standard water-lubricated bearings. “You have a lot less shaft noise, but one of the primary benefits of an integral thrust bearing is that it transmits all the thrust directly into the hull, as opposed to pushing on the gearbox or the engine and gearbox combination,” said Sam Smullin, Soundown’s marketing and quality assurance manager. “It allows for a much softer engine mounting, so you reduce the noise from the shaft itself and get a much quieter engine installation, which reduces structure-borne noise.” Because of the relative weight sensitivity of catamarans, Smullin said, “it’s particularly important to do a really good job on the driveline.” His father, Joseph Smullin, president of Soundown and J&A Enterprises Inc., an engineering firm for noise and vibration control, estimated that this could reduce driveline noise levels by 5 dBA to 10 dBA compared to a conventional system.

Chris Hannant

Clemente Perez, one of Herrin’s build crew, works on the interior. The extensive sound and thermal insulation
includes foam sprayed into the cavities.

Soundown also looked at the two 38-kW Northern Lights gensets, which have double-isolation mounts to reduce structure-borne noise. The firm also recommended structural changes to ensure that the mount foundations were as stiff as possible.

Energy from propulsion or generator engines invariably transmits to the boat structure and then resonates through big, flat panels like bulkheads, decks, ceilings, and liners, causing the familiar vibrating rattle. To dampen those vibrations, Herrin said he used Roxul, a lightweight, semi-rigid stone-wool insulation for fire resistance and sound control. His crew also sprayed cavities with Dow Froth-Pak, a quick-cure polyurethane foam for thermal insulation, and installed Sylomer (a microcellular PUR-elastomer) between the structural components and the floors, walls, and panels. “We glued the Sylomer, which is kind of a spongy foam, to the structure of the boat, and then the plywood of the subfloors and walls are glued to that,” Herrin explained, adding that this created a floating interior without any fasteners.

The plywood, called QuietCore, is a composite sandwich panel comprising marine plywood skins and an acoustic damping layer that converts acoustic energy into small amounts of heat that are dissipated. Soundown claims that an 18mm (0.7) QuietCore bulkhead can reduce noise transmission by up to 10 dBA, an audible reduction 50% greater than with regular marine plywood of equal thickness.

Electricity for a Small Town

Going off grid on H-2 does not mean anyone will suffer, as long as the electrical system keeps powering the boat’s myriad house loads—hydraulic Maxwell windlasses and thrusters; a Webasto air-conditioning system; two full-size stand-up freezers, two refrigerator freezers, and two under-counter refrigerators in the galley, all by Vitfrigo; Krüshr compactors for recyclables and garbage; Headhunter sewage-treatment system; Alfa Laval fuel-polishing system; two FCI watermakers; a complete set of Garmin navigation electronics with full redundancy; and a Böning vessel control and monitoring system.

Chris Hannant

Two Northern Lights 38-kW gensets are the heart of H-2’s AC system, which also includes a 37-kW Atlas inverter to connect to shore power in foreign ports.

Much of the AC side was designed and specified by Ward’s Marine Electric in Fort Lauderdale, Florida, in cooperation with OceanPlanet Energy of Woolwich, Maine, and principal Bruce Schwab, who helped design and integrate the DC components. “Today there’s a big trend in the industry to use shore-power converters as inverters and superlarge lithium-ion battery banks to provide power, at least temporary power, for major loads like air-conditioning, chiller plants, and things like that,” said Ward Eshleman, chairman of Ward’s Marine Electric. “So, rather than using only smaller inverters and synchronizing them and stacking to get additional kW, the trend for the larger vessels is to use shore-power converters as inverters. There is an inverter bus in the main switchboard.”

True to its go-anywhere mission, H-2 was fitted with an Atlas 37-kW inverter to connect to shore power in places that do not serve 60 Hz, 240V single-phase power. “We can take anything from 90V to 400V and pretty much anything from below 50 Hz to the 60 Hz and single- or three-phase,” Herrin explained.

Eight GTX24V315A-F24 lithium-ion batteries from Lithionics are split between a house bank that can run all DC loads for at least 24 hours, and an emergency bank to operate critical DC loads—display screens, radios, nav lights—for 24 hours. The boat is equipped with 10 Solara Ultra-S 160W panels paralleled in two groups of five each, connected to two Victron SmartSolar MPPT 100/50 solar controllers to charge the house bank. Given enough sunshine, solar and battery power should be “capable of running lights and refrigeration but not air-conditioning or heating,” Schmitt said. “Since we will likely spend most of our time in the tropics, we did not believe that solar power alone could do the job we needed.”

OceanPlanet Energy specified four Victron Buck-Boost DC-DC converters, two for each engine, to help charge the house bank from the starter batteries without having to modify the engines’ stock alternators, which would have voided the warranty. “The converters activate based on the input voltage from the starting batteries,” Schwab explained. “With lower rpm, the alternators would not produce enough current to feed both converters without the starting-battery voltage dropping, turning the converters off. Then the voltage will rise, the converters turn on again, drop the voltage, turn off…over and over. Staggering the input voltage cut-in, hopefully starting the converters one at a time, will more smoothly supply power to the house bank across the engine/alternator rpm range.”

Dieter Loibner | Professional BoatBuilder Magazine

OceanPlanet Energy specified the DC system including DC/DC converters and hefty battery banks to power house loads and critical electronics.

There are two 4,500-watt 240V split-phase engineroom-ventilation fans connected to two Victron Quattro 5-kW 24V inverter-chargers configured for 240V/120V split-phase AC loads. They can accept AC inputs from two sources (shore power or generators) and automatically connect to the available source. “In the event of a grid failure or power disconnect, they take over the supply to the connected AC loads by inverting from the Lithionics house-battery bank,” Schwab said.

“It’s more complicated than that,” according to Herrin. “Typically, we’re going to be operating with the A-bus and the B-bus tied together, so we can power everything with one generator. The B-bus actually passes current through the Victron inverter-chargers on its way to the load. We have the ability to split the A-bus and the B-bus and run the A-bus on one generator and the B-bus on the other in the few instances we’re exceeding the capacity of one of the generators. If we lose both generators, then the essential loads are still going to be carried,” meaning engine vents or water pumps.

Redundancy and emergency backups also figured largely in the deliberations of John McKay, manager of the Switchgear Systems Division at Ward’s Marine Electric and point man for this project.

One of his challenges was limiting the voltage drop in the estimated 53 (16.2m) cable run between engines, which in an emergency allows the starboard engine to be started from the port battery and vice versa. “For a starter group, you can allow a 20% voltage drop,” McKay said and noted that starting the engines requires 720 amps, while the gensets needed only 200 amps. “I was keeping the 720-amp current between 7% and 11% voltage drop, getting up to some pretty good-sized copper. Some sections of the run were 240mm2 [500MCM] cable.” Knowing that the boat is capable of going to high latitudes, McKay recalled his youth and the frigid winter mornings in Massachusetts, “where you can crank a diesel all day long at a low rpm, and it’ll never start. You just need to turn it over one or two times at a higher rpm, and it’ll be running. So, I was making certain that the starter was going to crank at the highest rpm possible and not lose it all to voltage drop.”

Protecting Assets and Finishing the Job

No matter how fast or how far H-2 will travel, corrosion caused by galvanic current between dissimilar metals, by stray currents or by electric fault, is an enemy that needs to be kept in check. That’s the calling of Ted Schwartz, who runs Electro-Guard (Mount Shasta, California). He’s one of the country’s foremost experts on cathodic protection, and also served on ABYC’s E2 Cathodic Protection Project Technical Committee.

“We designed the system and supplied all the equipment and steered them through the installation,” Schwartz said. It’s a 15-amp impressed-current-cathodic-protection (ICCP) system, model 715 A-2, with three anodes and two reference cells. Regarding the boat’s Evolution shaft system with driveshafts running inside an oil-filled tube, Schwartz said: “It was a real challenge because you can’t actually make contact with the propeller shaft on the inside of the boat.” He consulted with Soundown and found a solution. “At the coupling on the inboard end of the tube, a bit of the shaft stuck out through the seal,” Swartz said. “There’s this coupling that Soundown built that fastens to the shaft, and we asked them to provide a surface on that coupling where we could put our silver slip rings on [to provide an electrical connection] to protect props and shafts.”

Every anode can deliver up to 5 amps of current using its own current controller that receives a signal from the main controller, which determines exactly how much current each anode will put out. The entire system consists of three anodes, three current controllers, the main controller, and a separate monitoring station connected to the controller by signal cable. Later, Schmitt also ordered a backup system employing aluminum sacrificial anodes.

On catamarans, the company installs a reference cell aft near the prop of each hull, and an anode on the aft section of each hull, and one anode amidships on the inboard side on one hull.

Courtesy Brian Schmitt

Chromate, two layers of epoxy, copious amounts of fairing compound, and various primers rendered the surface fair and ready for a yacht-quality paint job.

At the time of this writing, the vessel had been shot with chromate and two layers of epoxy before approximately 500 gal (1,893 l) of fairing compound and 325 gal (1,230 l) of various primers rendered the surface fair and ready for a yacht-quality Alexseal paint job with 35 gal (132.5 l) light ivory, 24 gal (91 gal) stark white, and 2 gal (7.6 l) cordovan gold. Parallel to the exterior, construction was on the home stretch with installation of the crew quarters and the saloon overhead. On the systems side, pressure checks were performed for hydraulics and plumbing.

Since H-2 is a much larger and more complex vessel than the original Hippocampus, with a multitude of systems that need to be managed, monitored, and maintained, I was curious how many crew Schmitt was planning to hire to help run his new boat. He said he consulted with captains and headhunters, and “the consensus is three or possibly four at most. I just completed my 100-Ton Masters and will build time on the new boat as well. We won’t charter and are not accustomed to being cooked for or served or having our beds made and all that. So mostly I’m looking for a qualified captain and engineer to maintain the systems.”

Little surprise that a hands-on operator like Schmitt does not want to cede too much of the game he loves to play. But as big, bold, and broad-shouldered as H-2 will be when she finally emerges from the old Gunboat shed in Wanchese, the proud owner is quick to remind anyone that it’s still “a vehicle to get the toys wherever.”


H-2: The Designer’s View

H-2’s owner, the adventurous Brian Schmitt, has dived into deep caves to see submerged caverns, hand-fed large sharks that would normally view him as food, and spent years in his off-time exploring Caribbean archipelagos in Hippocampus, his current 19-year-old 57 (17.4m) power catamaran. Nearing retirement age, he gave the order for his “ultimate” yacht.

Courtesy Van Gorkom Yacht Design

The foldable hydraulic deck crane to launch and retrieve a two-man electric submarine or an all-terrain vehicle required cutting a slot in the helicopter deck for the lifting bridle.

The first talk about the new design was between the owner, the builder, and me. As we discussed the mission of the boat, it became clear that it would fall into the category of expedition vessel with more guest staterooms, more range, and more room for equipment than his old boat. Brian defined the function of the vessel as a carrier for a 26 (7.92m) twin-outboard catamaran, an outboard skiff, a small car, and a small helicopter, which needed a flight deck. This vessel was to be used with family and guests while also serving as an operations base for outbound travel by air, land, or sea.

Aside from commodious accommodations, a key requirement was comfortable motion on rough seas. This was to be a catamaran, like his current boat, which offers extensive real estate afloat in a seagoing vessel. The only restriction for the new design was a beam no greater than 35 (10.6m) to fit the largest Travelift.

The trade-off for overall beam width involves room versus roll motion. A wider catamaran responds more quickly to roll in seaways but with less amplitude, whereas a narrower beam rolls more slowly with slightly more amplitude. The slower roll is preferable as long as overall roll stability is maintained. Roll in catamarans is unlike roll in single-hulled vessels. Because the vessel is supported by two buoyancy chambers (hulls) with distance between them, motion has little to do with roll inertia, but rather with response of the hulls to the seaway. Each hull responds to a passing wave independently by heaving (up/down) and rolling, which is a circular motion around the center of gravity (CG) that translates to lateral motion when standing above the CG, especially high up on the bridge. Power catamarans, unlike sailing catamarans, do not require wide hull spacing to generate righting moment (to support a sail plan), so they can have closer hull spacing, which still preserves sufficient stability, slows wave-response roll characteristics, and takes up less space in port.

One of the expected routes for this vessel is the Northwest Passage over the top of North America. Boats venturing there can expect floating ice, so we added thicker hull plating at the waterline and an ice-separation chamber on the cooling water intakes. We also designed the hull to give the propeller protection by positioning it behind a deep canoe-stern afterbody with no exposed shaft. A rudder horn, below the propeller extending aft from the hull, adds support for the rudder and protection for the prop. This configuration is useful as a hedge against the possibility of grounding. In fact, this boat can be careened on the beach between tides if necessary for repairs. The hull includes a strong, deep, vertical keel structure that allows for blocking anywhere along its length.

Speed and range became the largest determinates of the design. A maximum range of 4,000 miles at 15 knots (enough to cross the Atlantic Ocean) was proposed. Catamarans are easily driven at modest speeds due to lack of significant wave resistance by narrow hulls. A preliminary speed prediction analysis showed that we would be in the ballpark with about 1,400 hp (1,050 kW) and 5,000 gal (18,925 l) of diesel per hull. The final installed fuel capacity is 12,500 gal (47,313 l).

Courtesy Van Gorkom Yacht Design

The general arrangement plan shows crew quarters in the
hulls, three guest cabins, office, saloon, and galley on the
main deck and owner’s suite on the bridge deck level.

A totally new design normally goes through a lengthy proposal and critique cycle between designer and client, especially if the client is knowledgeable and involved. The vessel’s first iteration started at 90 (27.43m) LOA, but it became evident that it needed more length to relieve a number of ills. After adding 10 (3.05m) we saw improvements, but it wasn’t until the 110 (33.5m) length proposal that we felt all the requirements had been satisfied: more slender hull shape, more open interior space, and better placement of machinery and tankage. The flight deck for the helicopter became larger, and the forward superstructure fairings gave the boat a sleeker look. And at 110 we achieved an efficient length versus waterline beam ratio that reduced wave drag and fuel consumption at the target cruise speed.

While beam remained at 35, lightship displacement increased significantly to 230,000 lbs (104,190 kg). Accommodations now include crew quarters for four persons in the bows; three double guest cabins and a ship’s office forward; a large saloon amidships with adjacent galley, and a dive and a storage locker aft on the main deck. The upper deck is arranged with a full-width-bridge steering station forward, protected by a Portuguese bridge, and a master stateroom with en suite bathroom aft. The flight deck extends aft of the master stateroom. Access to the upper deck is by either a staircase from the foredeck, an interior staircase adjacent to the ship’s office, or by stairs from the starboard side deck.

The largest variable weight on the boat is fuel, so the tankage is located amidships to minimize its influence on trim. Engine and machinery rooms aft of the tankage take up the remaining spaces all the way to the transoms. Other amenities include a utility area aft of the crew quarters port side with storage and washing machines, and a walkway through the tank spaces and enginerooms to the boarding decks at each transom. Another late addition is the flying bridge to aid with shallow-water operation by improving the vantage point to see coral heads and other obstructions. Its protective bimini serves as a mounting platform for lights and antennae.

—John R. Marples