Trimaran vs Normal Ships
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Advantages
The trimaran offers several capabilities to bridge the gap between monohulls and catamarans:
- Excellent for high speed
- Moderate weight carrying capacity
- Good seakeeping capability
- Larger available deck area
- Moderate space below the main deck
- Heavier loads can be carried on the cross deck
- Less structural weight required for the cross deck
- Deadweight coefficients closer to monohulls
The long length of the center hull also offers great advantages for seakeeping. This length greatly reduces pitch motions in a wave, and the narrow center hull reduces chances of slamming. To improve things even more, the side amas reduce roll motions. They add stiffness to prevent large roll motions. But they also act to reduce roll accelerations. All together, trimarans make for gentle seakeeping.
The trimaran offers major advantages for damage survival. The side amas provide excellent protection to the center hull, which military designers find especially useful. But the cross deck also helps with damage survival by containing massive reserve buoyancy. Imagine a damage situation where the ship sinks down to its cross deck. On a monohull, that would be game over. But on a trimaran, the cross deck suddenly becomes a barge, easily supporting the entire ship weight.
In catamarans, you lose stability once a single ama completely leaves the water. Push a catamaran past that point, and stability is a losing battle. A fact that scares many vessel operators. Trimarans do not have this problem. They get stability mainly from submerging the amas. The center hull always stays in the water, and the leeward ama continues to submerge. This creates a predictable increase in righting moment. In normal cases, trimarans never experience the sudden loss of stability.
Disadvantages
The biggest disadvantage for trimarans is lack of experience. There are few trimarans in military applications, and even less in commercial use. That lack of exposure instills wariness in many operators.
Trimarans do have a few genuine detractors. Due to their complexity, they require some extra design effort. The cross deck introduces a few extra ways to twist and bend the ship, and the engineers must check each of these extra scenarios.
Cost definitely factors into trimaran construction. The cross deck and extra hulls do add extra steel to the design. You have to pay for that extra steel as part of the build cost. But don’t assume this drastically increases the total build cost. Adding extra structure is far less expensive than adding extra machinery and power.Consider the alternative to a trimaran: an equivalent monohull. For the monohull, we strip off the side amas and widen the center hull to maintain ship stability. But bad news. A wider hull requires a larger engine, and associated support machinery.
Adding larger machinery costs twice as much as adding extra structure.
The hull shape does not drive the price tag, and trimarans are not limited to high speed.Trimarans are just a hull configuration. How you use the hull is up to you.
Conclusion
Don’t let the previous trimarans limit your imagination. The trimaran hullform bridges the gap between monohulls and catamarans. It offers some advantages of both deadweight capability and larger deck area. Primarily, trimarans deliver ship stability in a very power efficient package. What uses can you imagine with that flexibility?