Shore Hopper
The Shore Hopper design delivers cargo to small towns, using minimal infrastructure for unloading. A profitable ship that fits a market niche while relieving congestion on freeways.
Introduction
How to relieve congestion on the freeways? Stop carrying cargo on trucks! Instead, use ships designed for shallow water. We call this short sea shipping. It’s a dream that inspired many naval architects to create innovative concepts. And I’m no different! Introducing the DMS Shore Hopper. A vessel designed to travel coastlines and waterways all across the USA, and beyond, including:
- Lower Mississippi River
- Great Lakes
- Gulf Coast
- Atlantic Coast
- Pacific Coast
- Alaskan inland route
- European coastlines
The Problem of Infrastructure
So much cargo travels by intermodal container. TV’s, I-phones, lumber, auto parts, refrigerators, everything. It all loads onto a container ship and travels efficiently to your front door. This is the advantage we seek in short sea shipping. A single ship can carry hundreds of containers, replacing all those trucks.
Except that transit requires more than just a container ship. We rely on a vast network of infrastructure to transport these containers. One of the biggest components is a container terminal. A massive complex filled with expensive cranes to unload the ships, reach stackers to move and stack the containers, rail yards and truck depots to load the containers. And this is the problem with short sea shipping.
If we want a small ship traveling up and down the coast, delivering to small towns along the way, then we need to create all that infrastructure at every delivery point. That’s ridiculous. It costs millions to develop a full container terminal. Even at small sizes, we still need all the equipment. The large cranes, reach stackers, weighing equipment, rail yards, etc. No tiny American town can afford to develop all that infrastructure.
Instead, we need to bring the infrastructure to them. The Shore Hopper was intentionally designed for minimal infrastructure. It brings its own equipment to load and unload containers. We have a reach stacker onboard, ready to stack the containers on nearby trucks. We don’t even need a deep channel to dock the vessel. The vessel easily nestles up against shallow river banks to unload. The only infrastructure required is a riverbank with a slope of 8.0 deg and a concrete pad for the ramp to touch down. Maybe a few mooring bollards to hold the ship in place. And a parking lot for the trucks to pull up.
I just described a boat ramp for launching recreational boats. Nearly every small town in America has one of those, or can afford the minor investment. If you can launch a fishing dinghy, we can use the same spot to unload cargo. That is the only infrastructure we need.
Vessel Features
Table 3‑1 lists the major vessel particulars. And the following sections discuss the key features of this vessel. With a length to beam ratio of L/B = 3.4, the Shore Hopper behaves more like a barge. She has a wide hull with a shallow draft. That allows us to carry plenty of cargo, and it supplies a massive deck area. But unlike a dumb barge, the Shore Hopper includes a pointed bow and curved hull; a true ship. This grants the grace to handle moderate waves and coastal waters. We don’t need to hide in rivers.
But rivers remain an option. At 68.0 m long, the Shore Hopper is slightly longer than a typical Mississippi barge. And that river regularly carries trains of barges, rafted together at nearly 300 m long. Don’t worry about tight turns. With twin propellers, twin rudders, and a stern thruster, the Shore Hopper easily handles rivers.
| Length | L | 68.0 m
(223 ft) |
| Beam | B | 20.0 m
(65.6 ft) |
| Depth | D | 4.1 m
(13.5 ft) |
| Draft | T | 3.1 m
(10.2 ft) |
| Design displacement | Δ | 2138 MT
(2104 LT) |
| Design speed | U | 14 knots |
| Range | R | 3500 NM |
| Propulsion Power | P | 2670 kW
(3580 hp) |
| Cargo Capacity | Container Cargo | 168 TEU
1350 MT (1329 LT) |
| Liquid Cargo | ||
| Tonnage | GRT | 1380 GRT |
| NRT | 118 NRT | |
| Crew | 16 |
Major Vessel Innovations
Stern Ramp
The Shore Hopper started as a landing craft. And all landing craft suffer from a major conflict: the bow ramp. To unload cargo, we want a wide ramp close to the water. But that doesn’t work when fighting through ocean waves. Against waves, we want a narrow pointed bow, with high sides. Try to combine a wide bow ramp with a narrow bow, and you just get disappointment all around. DMS eliminated the conflict. We moved the ramp to the stern. We have a conventional pointed bow, perfectly designed for ocean waves. And the stern ramp stretches the entire width of the ship, allowing easy unloading. The benefits extend below the waterline too. To land against a sloping shore, we need the bottom of the ship to also slope upwards. This lets us get close to shore and minimizes the size of the stern ramp. (We want a short stern ramp, if possible.) By happy coincidence, that gentle upward slope falls close to an ideal hydrodynamic shape for the stern of the ship. Gentle sloping sterns make for lower water resistance and lower fuel consumption. Another conflict eliminated. Most landing craft designs scream with conflict. One requirement fighting against another, with no one happy in the end. The stern ramp eliminates most of those conflicts and allows a harmonized design. We get the best of a coastal ship and a landing craft.
Reversing Into Port
The stern ramp requires us to dock the vessel in reverse. The ship pulls perpendicular to the dock, and then reverses in. Normally a challenging task, but the Shore Hopper employs a few tricks to make this easier. Starting with retractable rudders. The ship uses twin rudders for conventional steering when moving forward. These stick down below the hull, which is great for maneuvering, but a disaster when backing into a shoreline. To avoid any damage, the rudders pivot up into the hull before we start reversing. Sounds complicated? It’s not so bad. We don’t even need to invent new technology to do this. We borrow from a similar industry. Cruise ships use a device called an active stabilizer fin. It sticks out from the hull side horizontally and reduces roll motion. But when the cruise ship comes in to dock, that stabilizer fin pivots back into the hull. Take the same device and turn it sideways: the stabilizer fin now acts like a rudder. We need to adjust some programming to make it behave like a rudder. But the machinery already exists. We already solved this problem and just need to use the solution in a slightly different way. With the rudders retracted, the ship loses some maneuverability. We still rely on twin propellers, which offer a lot of control. And we supplement that with an azimuthing stern thruster. It helps to control the stern while reversing. And this thruster stays flush inside the hull. Just a small grate along the bottom of the hull. Perfect for backing into the river bank. Now you might be worried about those twin propellers. Won’t they hit the river bank? Nope. Because the propellers sit at the bow, not the stern.
Bow Propellers
The propellers always require compromise on most landing craft. Our primary fear revolves around damaging the propellers, bending or breaking them on the river bottom as we approach shore. That fear drives designers to recess the propellers, tucked behind deep tunnels in the hull. A horrible place for propeller efficiency. And no guarantee because the propellers still suck up silt and gravel. DMS solved this problem by moving the propellers to the bow. Even when the stern touches the shoreline, the propellers sit at the other end, safe in open clear water. The hull even protects the propellers in normal transit. They sit halfway protected by tunnels at the bow of the ship. Any large debris in the water will likely get deflected by the ship’s hull before it ever endangers the propellers. Now some of you may think this can’t work. Won’t the wash from the propellers push back against the hull, negating any thrust? Not really, because that’s not how propellers work. Oversimplified, a propeller works in two halves. It creates a region of lower pressure forward of the propeller. This pulls the propeller (and ship) forward. Half of the thrust comes from that suction. The other half comes from a region of high pressure aft of the propeller, pushing forward. Every propeller generates this combination of suction at front and high pressure at the back. A conventional ship, with the propellers in the stern, still deals with interactions between these pressure regions and the hull. In their case, the low pressure at the front pulls back against the hull. And that reduces the effective thrust by around 10% or less. We know about this drawback and adjust for it when designing the hull and propeller. Naval architecture already solved this problem decades ago. It’s the same issue when we put the propeller at the bow. We just interact with the high pressure side. But again, nothing novel. A problem already solved There are only two reasons to put the propellers at the stern. First, they perform slightly more efficiently when operating in the ship wake. Second, the propeller wash runs over the rudders. This high speed water across the rudder helps with maneuvering at low speeds when docking in harbor. With the Shore Hopper, we achieved the same low speed maneuvering through a stern thruster. No propeller wash needed at low speed. No rudders needed for low speed. No problem with bow propellers..
Economics
Want to make some money? Economics matter with any ship. It needs to be profitable. That’s why DMS ran a preliminary economic analysis right from the beginning. We estimate the ship costs about $46M USD to build. And over a 30 year lifetime, it generates $223M in income. (Estimates fluctuate wildly depending on current freight rates.) Combine everything with a discounted cashflow model, and the ship generated a net present value of $35M USD over its lifetime. (Figure 7‑1) Yes, thats 35 million! Pretty good return on investment.
Future Developments
Do you have a list of comments and suggestions for improvements? So do I! Like all concepts, we only start from this idea. Each vessel gets customized and redesigned based on the individual Client needs. And that includes a laundry list of further work on the design. Some of the other major items include:
- Refine the economic model
- Consider variations in interest rates
- Consider variations in cargo freight rates
- Examine benefits of off-design cases.
- Traveling with less cargo. Do we reduce fuel consumption significantly? Is it worth the reduction?
- Examine benefits of reduced speed. Even dropping from 14 to 12 knots will cut engine power in half.
- Further design of stern ramp.
- Detailed design of every single part of the ship.
Conclusion
Most ships require compromise. But the Shore Hopper happily removed many of those design conflicts. It required minimal infrastructure, just a boat ramp to unload cargo. The ship moved equally well on shallow rivers and in coastal waters. And she delivers good return on investment. A profitable ship that fits a market niche while relieving congestion on freeways. Sounds interesting to me.
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