Courtesy Frank Carver Frank Carver’s new 51′ (15.5m) charter boat Loosen Up was designed by DLBA and built by Weaver Boatworks (Deale, Maryland).
Designers DLBA Naval Architects (Chesapeake, Virginia) and builders at Weaver Boatworks (Deale, Maryland) have worked together for more than 20 years. DLBA’s diverse portfolio includes high-speed motor yachts, workboats, patrol vessels, production boats, and top-end custom sportfishing yachts. Jim Weaver and his team are known for building sportfishing yachts that regularly extend the limits of performance with superior fit and finish. The two teams have collaborated on designs ranging between 41′ (12.49m) and 97′ (29.57m). I have been fortunate to work with Jim and his crew for many years on multiple projects.
In addition to conventional sportfishing yachts best suited to running offshore for trophy fish, we’ve collaborated to develop a line of low-profile bay boats that feel right at home in and along the waterways of the Chesapeake Bay. These range from 43′ (13.1m) to 51′ (15.54m) in length and are a departure from the high-performance offshore models Weaver is best known for, but they are equally refined fishing machines for recreational and commercial charter operations.
The largest of the Weaver Bay Boats is a 51-footer built for Frank Carver, owner of Loosen Up Charters, a fishing charter service operating out of Deale, Maryland—the same town Weaver Boatworks calls home. They are literally a stone’s throw down Rockhold Creek from one another. Like any fisherman, Carver had very specific requirements for the new boat he wanted when he brought the Weaver and DLBA teams on board for what would become a not-so-typical build for Weaver. Let’s take a look at the design, build, and splash of the latest addition to the Loosen Up fleet.
The Brief
When Loosen Up Charters needed a new boat to take parties fishing on Chesapeake Bay, Carver’s friend Jim Weaver at Weaver Boatworks was the obvious choice to build a custom vessel to meet his requirements. To start, the look was important—a combination of a classic bay-style craft with some added modern features. Performance had to be superior for what was to be a single-screw design. Finally, and perhaps most challenging, this boat had to meet U.S. Coast Guard (USCG) requirements for a Subchapter T vessel carrying up to 49 passengers. Designing and building a boat to USCG standards requires significantly more effort (and money) than creating a non-certified vessel. Myriad features and parameters must be considered, weighed, and adjusted early in the design discussion to meet all necessary criteria.
For this build, the DLBA office provided naval architecture and engineering design including hullform development, structural design and hull jig frames for production, propulsion arrangement and performance estimates, general arrangements and deck styling, mechanical layout, and general consulting to support the requirements for a Subchapter T vessel.
Knowing the boat needed to accommodate as many as 49 passengers, we settled on 51′ LOA and a 15′ (4.57m) beam to provide ample interior and exterior deck space. The concept design started with the aesthetic goal of replicating the general look of previous Weaver Bay Boats. That meant a hull with a sweeping sheer and a small amount of tumblehome aft transitioning into a nicely balanced flare in the forward sections—a blend of classic sportfisherman and bay-boat styles. The deckhouse would have a long overhang sheltering much of the cockpit and sportfishing-inspired window lines. A raised trunk forward allows for comfortable standing height down below. Those characteristics are clear in an early rendering.
Courtesy DLBA An early rendering illustrates the boat’s low profile and traditional Chesapeake Bay DNA.
While she has somewhat traditional lines from the waterline up, the hull bottom was far more modern. Top speed was important to the client. Knowing this, and consulting the projected equipment lists provided by Carver and Weaver, we developed a preliminary weight estimate early in planning. Weight and center of gravity are critical in the design of planing craft. Dialing them in was somewhat more challenging in this case because the boat would be a charter vessel with passenger totals ranging from a few people to 49. That variation in load impacts performance and drives basic design considerations regarding USCG requirements—more on that later.
Hullform
Performance and efficiency are goals for almost any new hull design, but with this project, they were especially important. The hull had to produce good top speed to reach fishing grounds (like most sportfishing yachts), and as a charter boat, fuel burn would be critical. With high projected operating hours, minimizing fuel consumption at a reasonable cruise speed was a priority.
With initial weight predictions in hand, we made a performance estimate based on Carver’s engine of choice, a single 900-hp Scania DI 16 diesel. At a predicted normal operating weight of approximately 32,000 pounds (14,500kg), the resulting speed prediction at top end was about 33 knots. We built it on a hard-chined planing hullform with a deadrise increasing from a relatively flat 9° near the transom to approximately 20° near midships, transitioning into a fine entry forward. The warp designed into the running surface allows for a controlled running trim and efficient operation across the full speed range. Since the boat is typically operated in the bay, we could get away with a somewhat flatter bottom than sportfishing yachts that operate in open-sea conditions.
The large fluctuations in load due to varying passenger counts and location made it challenging to keep the longitudinal center of gravity (LCG) consistently far enough aft to ensure superior ride quality and predictable handling. On a typical cruiser or sportfishing design, most people tend to collect in the aft areas of the deckhouse or cockpit, but on this charter boat, many could congregate far forward on deck and in the enclosure, shifting overall LCG forward. Our solution was a direct-mount V-drive gear that kept the engine well aft, helping to ensure proper LCG placement. To the same end, the two 225-gallon (851.7l) fuel tanks are located relatively far aft.
A centerline propeller tunnel helps reduce shaft angle, maximizing propeller efficiency, which is important as the large-diameter prop sees somewhat high loading. Another benefit of the propeller tunnel design is decreased draft, though that wasn’t a prime driver for the design.
Structural Design
Structural development of Loosen Up followed Weaver’s established construction methods—cold-molded with epoxy and Okoume marine plywood planking, and internal stringers and stiffening of Douglas fir. All hull planking is skinned on the outside and inside with fiberglass, which also encapsulates the stringers. The deck and deckhouse are built with a stiffener grid and Okoume plywood planking skinned with fiberglass. This true composite build comprises bottom structure of 2.5″ (63mm) laminated Okoume core sheathed between skins of 1208 and 1808 fiberglass on both sides. Hull topside sheathing is 3/4″ (19mm) Okoume sheathed in slightly lighter laminates. And in way of the propeller tunnel and shafts, wood and laminate structures are thicker.
Courtesy Weaver Boatworks Weaver’s conventional wood/epoxy composite construction method includes Douglas-fir stringers and stiffeners, Okoume plywood planking and bulkheads, and fiberglass sheathing inside and out on hull, deck, and cabin structures.
The result is a very solid boat. With the structural wood elements, once the design is made strong enough for service, it is more than stiff enough. Unlike single-skin fiberglass, which can transmit excessive movement and vibration, the wood structure damps noise and softens wave impacts. While this construction method is not new, the materials—especially the fiberglass skins—employ modern technology, and the Weaver team has fine-tuned their process to create a robust structure without excess materials or weight.
Typically, DLBA uses a first-principles approach to the structural design of a Weaver boat. But this one was different, as it needed to be reviewed and approved by the Coast Guard to meet an accepted guideline. We designed the structure to American Bureau of Shipping (ABS) Yacht Rules, which the Marine Safety Center (MSC) approved up front. While it provides a slightly heavier scantlings plan, it is not excessively heavier than a design using a more traditional approach. In short, it didn’t require Weaver’s crew to deviate markedly from their standard scantlings or build method.
Interior and Engine
Interior arrangements on this charter fishing boat are relatively simple but set a high standard for the application. As with many sportfishing boats, our design path started with the cockpit, which we wanted to locate at a specific height relative to the expected waterline. For fishing, optimal height may be 6″ to 9″ (152-229mm), but a USCG requirement sets this dimension at a minimum of 10″ (254mm) in the heaviest full-load condition. On the new Weaver, this had to include the maximum passenger count of 49 people, which can add more than 6,000 pounds (2,722kg)—not an insignificant amount on a hull with lightship displacement just over 27,000 pounds (12,247kg). The requirement drove up the cockpit deck height, which had knock-on impacts on other elements of the boat, such as raising the hull and deckhouse profiles.
Courtesy DLBA The V-drive transmission keeps the engine weight and box aft, allowing charter guests to ride forward under the shelter of the long deckhouse overhang.
Another height-related requirement states that there must be a step up or lip between the exterior (cockpit) deck and the salon (deckhouse interior) deck with a minimum height of 6″ (152mm). This minimizes possible water ingress from the cockpit into the deckhouse. While this detail is not uncommon, its design impact here is worth noting—it, too, drives up the deckhouse deck height. These two requirements combined to create a hull and overall boat height (off the water) somewhat taller than standard for a recreational boat of this style not being chartered.
While the deck-height requirements are not directly consequential to the performance of the boat, they are critical in achieving certification as a T-boat. If she didn’t pass the loading test after construction by meeting stability criteria—including deck height above water—Loosen Up would not be certified. Because deck and topside height are not easily modified features, our design work started with an accurate weight estimate.
We designed the deckhouse interior with good sight lines from the helm and space for passengers to shelter from the elements. Additional seating and a small head are available down below. All interior spaces are climate-controlled. Because this is a fishing vessel, most activity takes place outside in the cockpit, which offers expansive space with seating on the engine and machinery box located on the centerline. The total deck area aft of the deckhouse is approximately 280 square feet (26.01m2). The long roof overhang covering some aft-facing benches just outside the deckhouse provides ample shade for those wanting relief from the sun. With such a long top, there is plenty of space to accommodate all electronics, the life raft, and numerous rocket launcher rod holders.
Courtesy Weaver Boatworks The centerline propeller tunnel reduces shaft angle and draft while accommodating a large-diameter prop.
Engine choice was driven by the client’s preference and validated by our initial design numbers. The Scania is a proven engine with a superior power-to-weight ratio, providing the necessary horsepower to hit desired speeds. The single diesel is quieter than twins, and resilient mounts and insulation in the engine space and box further limit engine noise.
Propeller noise and vibration can be heightened in a poorly designed propeller tunnel, so we ensured appropriate tunnel geometry and tip clearance for the 30″ propeller.
At the helm station, the modern engine instrument display is joined by a standard onboard electronics package: a 96-mile (154.5km) radar, FLIR, GPS, depth finders, and communication systems.
Subchapter T Impacts
There are too many requirements triggered by Subchapter T status to detail here. They include the structural scantlings and general layout of the boat discussed above but also touch almost every onboard system. In some instances, certification requires simple documentation of system components to ensure they meet minimum requirements, but others are more involved and directly impact design and construction. For example, fuel tanks on a certified vessel must be inspectable (an annual requirement), while in a non-certified build, this is not a concern. On Loosen Up we arranged the tanks appropriately, including a fuel shut-off valve within 12″ (305mm) of the fuel compartment access point.
Often, an arrangement or detail that makes sense from a pure design or use standpoint doesn’t meet the requirements. In those cases, we must balance good design with regulatory compliance. For example, on Loosen Up much effort was made by the builder and equipment suppliers to provide drawings and documentation illustrating that the electrical system met standards. In that process, many details had to be considered, including the proper grade of conduit and drawings delineating features of the overall system.
The Weaver team navigated system requirements with the help of the Officer in Charge, Marine Inspection (OCMI), who ultimately must be satisfied that all requirements are met for final certification. For this reason, early communication between the design and build teams and the OCMI is important, and it proved to be beneficial as the build reached later stages. (For more on building for Coast Guard Certification see John Marples’s “Satisfying Subchapter T,” Professional BoatBuilder No. 211, page 40).
Conclusion
Whenever a new design first splashes, excitement and stress levels run high. In the case of a T-boat, the load test is a high-stakes milestone—failure can be a showstopper. Loosen Up was put in the water and tested at full load, including the weight of 49 passengers. The critical detail was that the cockpit deck maintained or exceeded the minimum required height above the waterline, which she did. Because the OCMI had been involved with the project from early on, most of the other arrangement and system requirements were already known to meet criteria.
Courtesy Weaver Boatworks The single 900-hp Scania DI 16 diesel rests on its engine beds as systems and structure are built in around it.
Sea trials followed, and the new model proved to be a superior performer. While coming in just a bit heavier than the design weight, she runs upward of 34 knots at wide open turning the 30″ x 34″ (762 x 864mm) four-bladed propeller through the 1.75:1 V-drive gear. At a cruise of 2,000 RPM, she makes 25 knots while burning only 31 GPH (117.3l/h). Carver reports that over the first year of operation, Loosen Up ran approximately 30% faster and 40% less fuel than his old boat, which was only 46′ (14.02m) long with 2′ (610mm) less beam.
The hull bottom design incorporating the single propeller and tunnel, results in a dry ride and extremely clean wake—a sign of an efficient running surface and a benefit for fishing. Carver said the efficient hull design knocks the water down, resulting in a very dry and soft ride, even when running in head, beam, and following seas. He also appreciates that the shallow draft afforded by the propeller tunnel opens up skinny-water areas on the bay for fishing.
From the paying customer’s perspective, a charter boat should provide comfort, fun, and safety on the bay—something Carver reports Loosen Up does with ease and grace. That’s music to a designer’s ears. Word is she also raises fish with the best of them, though I would have to give credit for that to her captain.
Courtesy Frank Carver The successful fishing charter boat is certified by the Coast Guard to carry up to 49 passengers. She cruises at 25 knots and provides a soft dry ride.
About the Author: Christopher Swanhart is Director of Recreational Boats at DLBA Naval Architects.
