How to Rig Purchase on Ships: Advantages and Disadvantages Explained

# How Will You Rig Purchase to Advantage and Disadvantage?

Introduction: Why Does Rigging Matter at Sea?

Life at sea is all about getting the job done efficiently, safely, and with the right use of resources. Shipboard rigging is one of those fundamental skills every seafarer should master. But when it comes to lifting heavy loads using tackles (or “purchases”), did you know you can rig your blocks in more than one way? That’s where the terms “rigged to advantage” and “rigged to disadvantage” come in.

Understanding the difference isn’t just about textbook knowledge—it directly affects your daily tasks, your safety, and the smooth running of deck operations. In this post, let’s break down the subject with simple terms, practical explanations, and examples from real shipping life.

What Is a Purchase (Tackle) Onboard Ships?

Before diving into “advantage” and “disadvantage,” let’s recap what a purchase is onboard ships. A purchase—or tackle—is a system of blocks (pulleys) and ropes that helps you lift or move heavy loads with less effort. You’ll find them everywhere—on cranes, lifeboat davits, cargo gear, and even mooring arrangements.

Whenever you need to shift a load that’s too heavy for sheer muscle, a tackle system does the trick by distributing the weight and multiplying your force.

Want more in-depth definitions? Try this [IMO PDF on terminology and definitions](https://wwwcdn.imo.org/localresources/en/OurWork/Safety/Documents/232(82).pdf) for further reference.

What Does “Rigged to Advantage” Mean?

So, what do we mean when we say a tackle or purchase is “rigged to advantage”? Simply put:

• “Rigged to advantage” means: The movable or “live” end of the rope is attached to the moving block (the block closest to the load).

When you pull on the running end, you’re closer to the load and can use both the mechanical advantage of the tackle and the direction of the force to your benefit. It’s called “advantage” because you get the maximum lifting power from your tackle.

• Example: Let’s say you’re hoisting a lifeboat with a block and tackle, and you want to make lifting easier. If you fix the upper block (to the davit or overhead) and let the hauling part of the rope emerge from the block closest to the lifeboat, you’re “rigged to advantage.”

What Does “Rigged to Disadvantage” Mean?

On the other hand, “rigged to disadvantage” means the running end (the part you haul) comes out of the fixed block, not the moving block.

• “Rigged to disadvantage” is: When you pull from the stationary block (overhead), usually further away from the load.

This setup doesn’t make full use of the tackle’s mechanical advantage (ironically named, right?). You actually lose some efficiency in this arrangement.

• Example: If you haul a cargo net using a fixed deck block and the rope you pull emerges from this overhead block—not the net itself—you’re “rigged to disadvantage.”

How Do You Rig a Purchase to Advantage or Disadvantage?

Let’s break it down step by step:

Rigged to Advantage

1. Fix the upper block (usually to a strong overhead point like a beam or davit).
2. Attach the lower (moving) block to the load itself.
3. Thread the rope through both blocks. The rope will exit from the moving block closest to the load.
4. Pull the rope from near the load—this gives you easier access and maximum force advantage.

Rigged to Disadvantage

1. Fix the upper block as before.
2. Attach the lower block to the load.
3. Thread the rope so the running end emerges from the fixed (upper) block.
4. Pull the rope from the top—usually more awkward and with less lifting efficiency.

Still unsure which is which? Remember this tip: Rigged to advantage always has the hauling part exiting from the moving (lower) block near your load.

Why Should Seafarers Care? (Advantages and Disadvantages)

Every crew member should know that how you rig a tackle directly impacts:

• Effort required to lift the load
• Safety of your operations
• Speed and convenience of deployment

Let’s break down the pros and cons of each setup.

Advantages of Rigged to Advantage

• Maximum Mechanical Advantage: You get the best use of your pulleys, and the load feels lighter to pull—with less effort wasted.
• Closer Control: You’re nearer to the load itself, so you can control positioning more accurately—useful for delicate jobs or where space is tight.
• Safer for Crew: Fewer “flying lines” overhead; less chance of injury if something slips or fails.
• Efficient Teamwork: Crew can work in sync and react faster if anything goes wrong.

Disadvantages of Rigged to Advantage

• Limited Space: Working close to the load can be tricky in cramped spaces, like holds or engine rooms.
• Obstructed View: Sometimes the load may block your view of the exit point for the rope—watch your hands and footing!
• Possible Obstruction to Load Path: The outgoing rope may interfere with the path of the load being hoisted.

Advantages of Rigged to Disadvantage

• Space Efficiency: Hauling from the overhead or away from the load means the crew isn’t crowded around the object being lifted.
• Clear View for Supervisors: Officers and bosuns can oversee operations with a better vantage from above.

Disadvantages of Rigged to Disadvantage

• Reduced Mechanical Advantage: Simple physics—your setup isn’t as efficient, and you work harder for the same result.
• Longer Rope Required: You’ll use extra rope for the same lift.
• Higher Risk of Injury: More lines overhead, and farther from the load, increases risk if things go wrong.

From my own experience during cargo operations on a container vessel, using a block and tackle “rigged to advantage” saved both time and crew energy when shifting heavy hatch covers during port calls. When we tried “disadvantage” for convenience, the crew was noticeably more fatigued and the risk of errors increased!

Where Are These Methods Used Aboard Ship?

You’ll encounter these setups in:

• Lifeboat and liferaft launching arrangements
• Anchor handling and mooring operations
• Deck machinery—cranes, winches, derricks
• Cargo handling gear: slings, chain blocks, and tackles
• Engine room lifting tasks: shifting motors, pumps, or spares

As per IMO’s guidelines on life-saving appliances, the efficient rigging of tackle systems is a safety-critical task for lifeboat and survival craft lowering systems.

Who Decides Which Method to Use?

Typically, the Bosun, Chief Officer, or Duty Engineer, depending on the task at hand and the workspace available, will dictate which setup is needed. Surveyors, flag state inspectors, or class surveyors may also review arrangements—so make sure your rigging follows IMO cargo and safety standards!

Safety Tips Every Seafarer Should Remember

Rigging, even when done right, can become dangerous if not handled with respect. Here are some **simple safety checks** before you begin:

• Inspect your blocks, ropes, and shackles before use
• Ensure your “standing points” are secure (beams, rails, davits)
• Never exceed the safe working load of your purchase system
• Stay clear of the load path whenever possible
• Always communicate clearly with your team during lifts

Alternatively, refer to your company’s SMS and the classification society’s [rigging and lifting guidelines](https://www.lr.org/en/marine-shipping/lifting-appliances/).

When Should You Use Each Rigging Method?

During regular operations, ask yourself:

• Do I need maximum force and a closer view of the load? Go for rigged to advantage.
• Is space limited or do I need the team working from a distance? Opt for rigged to disadvantage, with a clear risk assessment.

Your choice may also depend on the nature of the work, number of crew, available space, and urgency.

Conclusion: Getting It Right Makes All the Difference

In summary, how you rig your purchase—“to advantage” or “to disadvantage”—can be the difference between smooth, safe, and efficient work, and a hard, risky, and potentially dangerous operation. Always assess your task, space, and manpower and—when in doubt—choose the method that gives you the safest, simplest, and strongest mechanical advantage.

In shipping, sometimes the simplest choices are the most critical. Happy rigging, and always keep safety first!

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