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Design Discussions
When we began the process of creating a fuel-efficient trailerable trawler, there were a number of issues we knew would require serious consideration and calculation. Chief among these was the hull design. For nearly 20 years, we've built full-displacement trawlers that benefited by carrying extra weight at or below the waterline, and we actually looked for ways to add weight in the right places. By contrast, this new design would challenge us to see just how light we could make a 35-foot boat while maintaining the exemplary structural integrity for which our products have always been known.
There is an old adage in the aircraft design field that “the lighter you make it, the lighter you can make it.” The idea is that when you reduce weight in one area it will quite often allow you to save weight in another. As an aircraft's total weight is reduced, horsepower requirements go down. As horsepower is reduced, fuel load can also be reduced. And when you reduce both the horsepower and the fuel load, there is a good chance you will be able to reduce structural weights.
The same principle holds true on the water. The transom of a boat designed for 250 horsepower outboards needs to be substantially heavier than a transom holding a pair of 60 horsepower engines. As we followed this “design spiral” to its logical conclusion, we felt strongly that by utilizing modern materials and fabrication techniques, we would be able to build a boat with the strength we wanted, while keeping to a dry weight under 7,000 pounds.
The 7,000 pound benchmark is important not only for meeting efficiency goals, but also because we needed a trailering weight that fell within the maximum towing capabilities of a modern half-ton pickup. With the target weight established, the next task was to design a hull that actually floated where it was supposed to at that desired weight. This is the area that can be the most challenging. The boat needed a comfortable running shape with adequate stability, while also providing the interior volume required to create a comfortable cruiser. We had decided long ago that an eight-foot beam was insufficient to create the desired living spaces. Too much like camping. From decades of towing over-width boats on highways all across the country, we knew that a ten-foot width was a sweet spot that could be moved without hassle, while allowing for a very livable interior.
From the start we planned for a hull with a very fine entry, as this would compensate for the lighter hull weight when confronting head seas. When working with a 44,000-pound hull like our Great Harbour 37s, which are designed to move at eight knots, the bow can be much fuller. These heavy-displacement boats simply bull through the waves. But at less than one-fourth the weight and twice the speed, the TT would need to slice through the waves. The bow profile we settled on will do exactly that. The plumb stem also helps with all of those expenses like bottom jobs and dockage that marinas and boat yards charge for by the foot, because the extra three or four feet of a raked bow count in the cost estimates.
To meet efficiency goals, the planing surfaces of the TT hull must provide ample flatness for lift, while retaining enough vee in the hull bottom to maintain ride quality. The specific shapes of these running surfaces were dictated by the projected operating speed. The TT35 was designed to cruise at a "sweet spot" around 15 knots, where it will enjoy an optimum combination of speed and efficiency. This mission profile established a range of parameters that included the thickness and type of laminates required, the bow entry, bottom deadrise angle and horsepower requirements—all of which are factors impacted by the speed of the vessel.
Also important was comfort underway and at rest. To enhance stability, we concentrated a significant portion of overall weight low in the hull. We also added pronounced hard chines to increase stability. Waterline surfaces are designed to minimize water slap at anchor or at the dock, and the absence of bow or stern overhangs work to dramatically quiet the boat.
In the end, it took quite a bit of thought, research and lessons learned from decades of boat building to bring together all the elements needed to realize the design goals we set for the TT. This boat could not be built using yesterday's methods. And maybe it was just waiting to be built once the construction technologies, market demographics and maybe even stars finally came into alignment.
Ken Fickett
There is an old adage in the aircraft design field that “the lighter you make it, the lighter you can make it.” The idea is that when you reduce weight in one area it will quite often allow you to save weight in another. As an aircraft's total weight is reduced, horsepower requirements go down. As horsepower is reduced, fuel load can also be reduced. And when you reduce both the horsepower and the fuel load, there is a good chance you will be able to reduce structural weights.
The same principle holds true on the water. The transom of a boat designed for 250 horsepower outboards needs to be substantially heavier than a transom holding a pair of 60 horsepower engines. As we followed this “design spiral” to its logical conclusion, we felt strongly that by utilizing modern materials and fabrication techniques, we would be able to build a boat with the strength we wanted, while keeping to a dry weight under 7,000 pounds.
The 7,000 pound benchmark is important not only for meeting efficiency goals, but also because we needed a trailering weight that fell within the maximum towing capabilities of a modern half-ton pickup. With the target weight established, the next task was to design a hull that actually floated where it was supposed to at that desired weight. This is the area that can be the most challenging. The boat needed a comfortable running shape with adequate stability, while also providing the interior volume required to create a comfortable cruiser. We had decided long ago that an eight-foot beam was insufficient to create the desired living spaces. Too much like camping. From decades of towing over-width boats on highways all across the country, we knew that a ten-foot width was a sweet spot that could be moved without hassle, while allowing for a very livable interior.
From the start we planned for a hull with a very fine entry, as this would compensate for the lighter hull weight when confronting head seas. When working with a 44,000-pound hull like our Great Harbour 37s, which are designed to move at eight knots, the bow can be much fuller. These heavy-displacement boats simply bull through the waves. But at less than one-fourth the weight and twice the speed, the TT would need to slice through the waves. The bow profile we settled on will do exactly that. The plumb stem also helps with all of those expenses like bottom jobs and dockage that marinas and boat yards charge for by the foot, because the extra three or four feet of a raked bow count in the cost estimates.
To meet efficiency goals, the planing surfaces of the TT hull must provide ample flatness for lift, while retaining enough vee in the hull bottom to maintain ride quality. The specific shapes of these running surfaces were dictated by the projected operating speed. The TT35 was designed to cruise at a "sweet spot" around 15 knots, where it will enjoy an optimum combination of speed and efficiency. This mission profile established a range of parameters that included the thickness and type of laminates required, the bow entry, bottom deadrise angle and horsepower requirements—all of which are factors impacted by the speed of the vessel.
Also important was comfort underway and at rest. To enhance stability, we concentrated a significant portion of overall weight low in the hull. We also added pronounced hard chines to increase stability. Waterline surfaces are designed to minimize water slap at anchor or at the dock, and the absence of bow or stern overhangs work to dramatically quiet the boat.
In the end, it took quite a bit of thought, research and lessons learned from decades of boat building to bring together all the elements needed to realize the design goals we set for the TT. This boat could not be built using yesterday's methods. And maybe it was just waiting to be built once the construction technologies, market demographics and maybe even stars finally came into alignment.
Ken Fickett
