Bollards & Post Covers

Mooring Bollards

A series of colorful hawsers are draped over a staghorn bollard on a Scottish marina

The many types of marine bollards

A series of colorful hawsers are draped over a staghorn bollard on a Scottish marina

The term ‘bollard’ is believed to have derived from ‘bole,’ referring to the trunk of a tree. Its earliest documented usage traces back to a Scottish newspaper in 1763, where it was used to describe a marine bollard at a dock, used to secure boats. This terminology has since become integral to maritime vocabulary, with ‘mooring bollards’ being a familiar term among English-speaking seafarers. Moreover, the concept of ‘bollard pull’ has emerged as a standard metric for quantifying the towing power of tugboats, analogous to the use of horsepower for vehicles.

The Bollard Pull Test

Internationally, the certification of bollard pull follows remarkably consistent methodologies, although specific countries may designate one or more authoritative bodies for certification. Notably, the American Bureau of Shipping (ABS) sets a standard for such evaluations, detailed in part 5, chapter 3, section A1. This ABS standard delineates the testing procedure that is universally applied.

This procedure entails securing a tugboat in the water to a mooring bollard using a hawser (a durable marine rope), which is outfitted with a dynamometer. The dynamometer’s role is to assess the tension within the hawser as the tugboat propels forward, specifically measuring the force exerted at the propellers’ maximum thrust. The highest power output recorded by the dynamometer is then officially designated as the bollard pull according to the ABS standard.

However, implementing this standard in real-world conditions introduces additional complexity. The accuracy of the dynamometer’s load measurement can be affected by various environmental and operational factors, necessitating careful consideration to ensure a precise determination of the bollard pull. Some factors to consider include:

  • Water current: if the propellers are moving against water flow, it adds another vector of force to be accounted for.
  • Water salinity: the density of saline water is higher than fresh water, and density changes the total force required by the propellers. This must be measured and adjusted to compensate.
  • Angle of the rope: The dynamometer is set up based on the assumption that the rope is perfectly horizontal. Therefore, it’s necessary to measure any angle formed between the bollard and the vessel, and accordingly adjust for the resulting change in force.
  • Engine heat and output must be at a steady state.
  • Several trial runs should be averaged together, ignoring sudden pull forces that might be higher than continuous pull forces.

Types of Mooring Bollards

When visiting various docks and marinas, you’ll encounter an array of mooring bollards, each selected for its specific application. The choice of which bollard to install hinges on multiple criteria, ensuring the safety and stability of moored vessels. This decision is influenced by the unique demands of each maritime setting, including the characteristics of the dock and the types of vessels it accommodates. Selecting the appropriate bollard is crucial for effective mooring, as it directly impacts the ease of use for docking vessels and the long-term durability of the mooring infrastructure. Some factors to consider are:

  • Vessel Size and Power: The dimensions and engine strength of the ships that will be docked, influencing the required durability and load capacity of the bollards.
  • Mooring Line Angles: The angles at which mooring lines, or hawsers, will interact with the bollard. These are influenced by the ship’s loading conditions and tidal variations, affecting the choice of bollard design for optimal line management.
  • Water Chop: The condition of the water’s surface, particularly the presence of short, sharp waves. This factor affects the tension on mooring lines and, consequently, the stress on the bollards.
  • Available Space and Installation Surface: The physical space at the docking site and the nature of the ground or structure where the bollard will be mounted. This determines the feasible size and type of bollard that can be installed.
A cleat has a neat wrapped figure 8 style mooring line
Cleats are common on small commercial and pleasure craft and the docks they tie to.

Cleat bollard

Cleat bollards are compact, small bollards generally used for small watercraft. You’ll see them on small docks and marinas and in several places on the watercraft themselves.

Cleat bollards are a good choice for less experienced mariners with smaller boats to wrap their mooring line. Simple figure eights around the cleat are easy to manage with the smaller ropes used for these vessels. Cleats on the vessel are usually fastened by passing a loop through the center of the cleat and then over the “horns.”

One disadvantage to cleats is that the necessary wrap requires boats to be near the bollard to get secured.

A black post with a gold top has two pegs on either side: sea in background.
Single bitt mooring bollards are easier to lasso than other types of mooring bollard.

Single bitt bollards

Bitt bollards, also known as bitts, represent a traditional shape for mooring bollards. These bollards consist of a central pole with two protruding pegs on either side and typically feature a design that is either cross-shaped or resembles a lowercase “t.” The concept of bitts likely served as the inspiration for the earliest cannon bollards, where the cannon’s trunnions functioned as the side pegs when these cannons were repurposed and embedded on wharves. Modern iterations of bitt shapes include both cross-like posts and designs that feature a broader top and a narrower bottom, reminiscent of cannon forms, such as our R-7510 decorative bollard.

The term “Bitt” originates from a German word, and the phrase “Bitt bollard” is technically redundant since “bitt” already denotes a mooring post. Mariners may refer to these structures as bitt, bollard, or bitt-bollard when discussing this design.

Bitt bollards are available in single or double post configurations. Double bitts typically consist of two parallel posts connected by a single, long cross-post. Single bitts are designed for ease of use, allowing a looped hawser to be thrown over them without the need for precise wrapping. They can secure multiple mooring lines and effectively accommodate high rope angles, provided the bitt’s size and the width of its pegs are appropriately matched to the rope’s thickness.

A beautiful brass double bitt has developed a copper patina
Double bitts can hold more than one mooring line and are often used for heavier vessels.

Double bitt bollards

Double bitts are commonly used for larger vessels and variable tides, both on the vessel and off. The double bitt is usually hitched to a cleat with a series of figure eights; however, as with all large-ship mooring, an experienced sailor will consider the fiber of the mooring line and the direction of strain, and will modify their approach appropriately. After the cleat is hitched, one of the two bitts can be lassoed and from there further secured.

A T-bollard is bolted to a dock and wrapped with a thick chain
Although tee and kidney bollards look somewhat similar, tee bollards are better for high angle ropes.

Tee and kidney bollards

Tee and kidney bollards are similarly shaped, though they are used in different ways. Both are short posts with a flat top that protrudes off the main stem. With the T-top bollard, this lip juts out on only one side of the bollard post, away from the water. It looks a little less like the letter T than it does a bicycle seat, with the front of the seat flat to the post. The “back” of the bicycle seat is long enough to help trap a mooring line that moves to a higher angle, as with the tides.

The kidney bollard is similar, but generally has a lip on both sides, with one side slightly larger and bean shaped to help with mooring line positions.

Both can be used in heavy-duty applications, usually holding only one line: a large ship may more to many such bollards. However, kidney bollards are used in places without a huge range of tides as they have more tendency to slip.

Tee (also known as T-head) and kidney bollards serve distinct yet similar purposes as mooring devices, each featuring a unique design tailored to specific maritime requirements. T-head bollards, exemplified by Reliance Foundry’s R-7512 model, are characterized by their singular flat top that extends from one side of the main post, away from the water. This design, reminiscent more of a bicycle seat than the letter “T,” includes a flat front aligned with the post and a longer back end. This configuration aids in securing mooring lines, particularly as they adjust to varying angles due to tidal changes.

In contrast, kidney bollards boast a lip extending from both sides of the post, with one side larger and shaped like a bean to facilitate different mooring line positions. While both types are robust enough for heavy-duty applications, typically accommodating a single line for mooring large vessels, kidney bollards are preferred in environments with minimal tidal range due to their increased risk of line slippage.

This distinction underscores the importance of selecting the appropriate bollard type for maritime applications, ensuring safe and efficient mooring under varying environmental conditions.

Pillar bollards

Pillar bollards feature a straightforward design: they are posts with a top diameter that is slightly larger than the diameter of the post itself. Commonly found on wharves, pillar bollards are particularly easy for mooring lines to be looped or “lassoed” around, though they may not provide optimal security for mooring lines at high angles.

The “dipping the eye” technique makes It possible for two vessels to simultaneously use a single pillar bollard for lasso mooring while ensuring that the first boat can depart at any time without disrupting the mooring of the second. This method involves threading the eye (loop end) of the second boat’s mooring line beneath and then through the eye of the first boat’s line. This arrangement allows either vessel to depart freely without necessitating the other to be unmoored.

Staghorn castings sit on the foundry floor, ready for shipping
Reliance Foundry made staghorn castings until the early 2000s.

Stag horn bollards

Stag horn bollards are typically employed at large wharfs for mooring commercial vessels. These bollards are designed to accommodate multiple mooring lines, with their distinctive “horn” projections and complex shape providing enhanced security through the use of steep angle mooring ropes. Consequently, stag horn bollards are commonly found in locations with fixed docks and high tides, or where heavily laden ships dock for unloading.

Securing boats, securing people

Bollards have evolved from their original maritime use to their contemporary role in traffic management, where they serve to protect pedestrians from vehicles. However, mooring bollards continue to play a critical role beyond mere infrastructure. They ensure the safety of vessels, their cargoes, and people. Large vessels, in particular, require mooring at multiple points along their sides, with the capability to quickly adjust slack as needed. Marine bollards, designed to withstand harsh environmental conditions, are predominantly made from steel or ductile cast iron to provide maximum strength at a minimal cost, similar to their inland counterparts. Despite the corrosive effects of sea air, with minimal annual maintenance to prevent surface damage and corrosion, marine bollards can have an exceptionally long service life, reliably securing ships to port.

Rusty bollard by the ocean, narrower on the bottom and wider on top, with two short protruding pegs
A single bitt bollard with a traditional shape.