On a cruise ship, the ocean can seem like an endless void of water. The sea is calm most days, but there are still waves and wind. To keep your vessel from tipping over or even capsizing altogether, ships use stabilizers that work much as fins do in airplanes.
The stabilizers on a ship keep it from rolling too much, and with these vast underwater, they help cut through the waves more easily. By reducing fuel consumption for their weight in a chain reaction (as happens when there’s less shaking), ships can travel forward without losing speed because of drag!
You’ve gone through security at the airport and checked your bags. Now it’s time to board the plane. You climb into one of those little seats, buckle up and take off down the runway — only this flight isn’t going anywhere significant. It is bumpy too, which makes sitting even more unpleasant than usual.
If only they’d installed some fin between your seat and the ground! Then when turbulence hit, all you would have had to worry about was whether you could make it back home before dinner without spilling soup everywhere. Imagine if someone did just such a thing for cruises!
How cool would that be? Of course, we don’t live in our private floating city, so things aren’t quite convenient. But with modern technology, we can get pretty close. One way to accomplish this feat is by installing stabilizers on boats. This article will explain how these devices operate and what happens inside them when rough weather hits.
The ocean has been known to play tricks on sailors since ancient times. On August 24, 1492, Christopher Columbus set sail from Genoa, Italy, with three vessels bound for India. However, his flagship, Santa Maria, began to lean dangerously forward by early September due to lousy seamanship.
After several attempts to right the ship, Columbus ordered every crew member to stay below decks until he found out why the boat kept turning turtle. He eventually determined that the hull wasn’t properly ballasted and that too many bodies were packed onto its frame. Luckily, no lives were lost during the ordeal.
Overloading a ship creates weight distribution problems that cause it to tip over, especially if winds pick up or seas become choppy. Without proper ballasting, a tall mast may also collapse under heavy loads. This event led to new regulations regarding the size of ships’ crews, particularly their number of passengers.
But while man-made factors contribute to accidents, Mother Nature herself sometimes plays a part. When Hurricane Katrina slammed into Mississippi in 2005, the storm surge caused damage to 30 percent of New Orleans’ piers.
During another hurricane season later that year, two Carnival Cruise Lines ships collided near San Juan, Puerto Rico. Both suffered severe engine damage and required extensive repairs costing millions of dollars. In 2010, Royal Caribbean’s Independence of the Seas experienced rudder failure after hitting high surf in Hawaii. As a result, the ship had to return to port for $9 million worth of repairs.
In light of these events, it seems clear that something needs to be done. And indeed, engineers and designers have come up with various solutions to combat the problem. For example, ferries now employ flexible “hydrofoils instead of traditional masts.”
These move vertically above the surface of the waves rather than horizontally across them. They allow boats to travel faster and farther distances because the foils create less drag (a force opposing motion) than sails would. Another technique involves placing large weights on a ship’s bow to counterbalance any extra cargo or people onboard.
However, none of these methods eliminate the possibility of a disaster occurring. That brings us to something called a stabilizer system. Read on to find out how to cruise liners utilize these gadgets.
Cruise Ship Stability
A good analogy exists between airliners and cruise ships in terms of stability. Airplane wings provide lift and buoyancy by creating areas where air flows downward along with the wingtips. Similarly, stabilizers act as fins to give cruise ships increased verticality.
While airliners typically depend upon tail surfaces for horizontal stabilization, cruise ships need additional support to prevent themselves from rolling over. Unlike planes, though, boats cannot bank around tight corners or dive to avoid trouble. Instead, stabilizers help ensure stability by maintaining the angle of attack of each stabilator blade.
Ideally, the angle should remain constant throughout the entire stroke of the device, allowing the craft to respond quickly and accurately to changing conditions.
Each stabilizer consists of multiple blades attached to a central hub assembly. A typical configuration includes four separate, triangularly shaped sets arranged symmetrically around a single axis. Each blade usually measures 4 feet (1 meter) long and 2 feet (0.6 meters) wide.
From the center, the blades diverge toward the stern of the ship. The thin edges taper into rounded points at the tips to increase hydrodynamic efficiency. Between the outer edge of each blade and its corresponding rail lies a slot cut deep enough to accommodate a spar pin. Together, the pins and slots form a truss bridge that supports both sides of the stabilizer. This component provides strength and rigidity to the whole structure.
To attach the blades to the main body, welded joints hold together steel plates bolted tightly at the point where they meet the hub. Because of this arrangement, the length of the blades determines the pitch range available to the pilot.
Generally speaking, longer blades offer greater control because they span wider angles. Conversely, shorter blades perform better under acceleration because the smaller sweep area allows pilots to push harder.
Although it sounds simple, designing an efficient stabilizer requires many complex calculations. Engineers must factor in wave height, velocity, keel displacement, trim tab location, wake effects, and current speed. Once the optimal design is established, manufacturers build prototypes and test them thoroughly to see how well they perform. Once everything checks out, the company begins producing actual units for sale.
So far, stabilizers haven’t changed much over the years. Next, we’ll discuss the newest developments in this field.
One significant difference between cruise ships and aircraft concerns the orientation of the latter’s engines. Whereas jets revolve their propellers perpendicular to Earth’s gravitational pull, ships rely on propulsion systems to maintain balance. Since jet thrusts are generally directed straight ahead, they require larger power plants and often burn fuel inefficiently.
Although ships have more significant engines than airplanes, the same principle applies. Propeller forces naturally tilt sideways away from gravity, making them more energy-efficient. So although cruise lines currently prefer gas turbines over diesel engines, they’re working hard to develop alternative technologies that improve performance [Source: CNN].
Stabilizer Fins For Ships
Unlike conventional stabilizers, hydrofoils aim not to correct the roll but to reduce pitching. Hydrofoils consist of streamlined foil sections connected to a trailing vane. Like a car driving downhill, the foil accelerates past the leading edge of the hydrofoil, generating lift.
This causes a reaction opposite gravity, lifting the vehicle slightly higher than usual. Meanwhile, the vane maintains contact with the water to stabilize the machine against tilting. The key to hydrofoils’ success lies in keeping the foil shape as sleek as possible. A ship weighing 100 tons (90 metric tons) can achieve speeds comparable to small yachts.
Hydrofoils represent only half the story behind cruise ship stability. Some designs include rudders mounted directly underneath the hull. Other vessels steer left and right via thrusters located amidships.
Yet other models feature adjustable flaps designed to adjust the flow of water coming into the steering nozzle. All of these techniques function similarly to handle turns. Changing the direction of incoming streams of water alters the amount of lift generated.
As mentioned earlier, conventional stabilizers primarily focus on preventing roll. Nevertheless, newer versions can also compensate for transverse movement, i.e., side-to-side swaying. Such improvements involve adding gyroscopic sensors that detect changes in pitch and roll. Additionally, stabilizers can lock automatically whenever excessive lateral movement occurs, reducing the risk of injury.
Perhaps the most outstanding innovation occurred in 2009 when researchers unveiled a prototype for a particular type of stabilizer dubbed SeaFoil. Its distinctive aspect is that SeaFoils sits atop the ship’s superstructure, unlike regular ones.
Moreover, SeaFoils contain a series of hydraulic pistons that press down evenly. Thus, the device doesn’t touch the deck but sits 3 inches (7 centimeters) above it. Under ideal circumstances, SeaFoils can counteract motions ranging from 1 to 15 degrees per second.
With all of these advancements simultaneously, it’s easy to conclude that cruising might cease to be fun anymore. Fortunately, some experts say otherwise. According to Mark Sorensen, president of the American Marine Corps, a cruise passenger wouldn’t notice any differences.
“It depends on what you want to do,” says Sorenson. “If you’re looking to go from Point A to B, you won’t notice anything different, except maybe the ride gets smoother.” Still, whether consumers will embrace the idea of traveling by sea again remains to be seen.
For more information on marine engineering, please check out the links on the following page.
Why waste precious batteries propelling submersible vehicles? Some scientists believe that hydrofoils could prove useful for submarines. Rather than forcing the craft through the water, a hydrofoil lets it float passively beneath the waves. Submarines already possess great maneuverability thanks to sophisticated sonar equipment.
