Why does a cruise ship go so slow? Can they go faster?

ByRick Deutsch

Why does a cruise ship go so slow? Can they go faster?

Cruise ships are as long as football fields. Ever wonder how they are able to push a brick with thousands of passengers, crew of a fourth of that, all their luggage, the food they’ll devour and the miscellaneous support equipment?

Big ships go about 22 knots

Big ships go about 22 knots

These boats can move at over 20 knots. A ship needs a ton of energy to overcome the drag of the ocean that tries to slow it down. Through mathematics, experience, and testing, hydrodynamic engineers figured out that if you mount a large “bulbous” projection just under the bow, it will “push” stagnant water aside. Less resistance, the faster you go. Look for these on cruise and container ships.

Paint also can be a source of drag. The smoother the blend, the faster the ship can go. The paint is a special blend that resists corrosion, salt water infusion and sea life adhesion. During scheduled dry dock stays, the hull is scrubbed, blasted and repainted. Less drag.

Cavitation is also a source of drag. When you look at a fast spinning propeller, those white bubbles are actually air coming of the water due to reduced pressure around the props. Design here minimizes this source of drag.

A new idea is the use of tiny bubbles that are shot out of the surface of the bow and hull. The ship thus rides on a tiny layer of air. This makes the whole ride smoother and faster. Royal Caribbean has tested this on the Celebrity Reflection. Look for it on their new Quantum class ships rolling out soon. If you get a speaking slot on one of these…look over the side and let us know what you see.

Contact us – we KNOW the facts, jack! :>)



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