The Limits of Bulbous Bows
2017-May-22
Ten Forgotten Uses for A Catamaran
2017-Jun-19
If you use a catamaran hull in the right way, it has almost limitless applications. The classic image of a catamaran may conjure some high-speed ferry or dainty yacht, like this.
Myself, I imagine industrial catamarans, with huge amounts of stability. Something more like this.
Credit: Offshore Energy Today
The skinny amas are not what makes a catamaran unique. We have plenty of commercial catamarans with wide, fat amas. In this video, I discuss the unique physics of a catamaran. If you understand the physics, you gain a new insight into the applications for catamarans.
Nomenclature
When we say “hull”, we normally refer to the single part of the ship that provides buoyancy and helps it float. But now we have two floating objects. What do we call them? Each individual floating object is called an “ama”, or a “demi-hull”. Even with catamarans, we still use “hull” when referring to all the buoyant objects.
The Physics of Catamarans
Catamarans have two major advantages.
- Waterplane stability
- The cross deck.
The separation between amas provides ample stability. This allows us to create skinny amas without compromising vessel stability. And the cross deck provides huge amounts of real estate for our internal arrangements. This is why catamarans are so popular on ferries. People weigh very little, compared to normal ship cargoes. But people do require a large amount of space. The catamaran, with its massive cross deck is a natural choice for ferries.
Conclusion
The catamaran is not a perfect hullform; it has strengths and weaknesses. A good naval architect can properly apply these strengths and compensate for the weaknesses. Ultimately, the catamaran offers flexibility, by separating several design elements that traditionally conflict on monohull designs. This allows several untapped applications of the catamaran hullform, which leads to untapped cost savings for you. Given the myriad of ways to adapt the catamaran hullform, it is almost always worth considering and talking to your naval architect about your next vessel.
