Cleats, Chocks and Fairleads

The integrity of a mooring system inevitably depends on the strength of the cleats, chocks, and fairleads installed on deck. In forty years of experience, we have learned that what matters is not just the shape of the fitting, but above all its ability to withstand multi-directional tensile loads and the corrosive assault of the marine environment. Using AISI 316 stainless steel is the minimum requirement to prevent rust from staining the gelcoat or compromising the grip of the fastening pins after just a few seasons.

When selecting a mooring component, the first question to ask is about the bearing surface and the thickness of the underlying structure. A robust chock is not enough if the fiberglass backing is thin or inadequately reinforced; the risk of pull-out under load is real. Always verify the presence of adequate backing plates and consider the fairlead footprint to ensure that the working angle of the line does not create dangerous chafing against the stanchions or pulpit.

At Nautiba, we work to give you clear information on delivery times, distinguishing between items we have in stock and those that require sourcing from Osculati warehouses. If you have doubts about the dimension or bolt hole spacing, contact us before proceeding. Our technical assistance helps you choose among flush, fixed, or fold-down models, ensuring you fit hardware appropriate for your vessel class.

Criteria for Correct Selection

• Always check the existing bolt hole spacing to avoid additional drilling on the deck.
• Choose AISI 316 cleats for extended offshore use and avoid non-certified alloys.
• Evaluate the line exit angle from the fairlead to prevent friction that deteriorates the rope.
• Make sure the chock base has a gasket or sealant to prevent water ingress into the laminate.
• Consider the theoretical breaking load of the fitting in relation to the size of your vessel.

How do I choose the right size chock?

The length of the chock should be proportional to the diameter of the line you intend to use. A rule of thumb is that the chock should be at least 10-12 times the line diameter to allow secure fastening without excessive overlapping.

Why prefer AISI 316 over AISI 304?

AISI 316 stainless steel contains molybdenum, an element that significantly increases resistance to chloride corrosion typical of seawater, making it far more durable than AISI 304, which tends to oxidize much more quickly.

Is it necessary to install a backing plate below deck?

Yes, it is always advisable. A stainless steel backing plate distributes the tensile load over a larger area of the fiberglass, preventing cracks or structural failures in the deck during demanding mooring maneuvers.

What do I need to check for a flush-mount fairlead?

You need to measure precisely the deck thickness and the free depth available below it. Also ensure that the internal radius of the fairlead is large enough not to stress the line under working load.

What does safe working load mean?

Safe Working Load (SWL) indicates the maximum tensile load the fitting can handle under normal operating conditions without permanent deformation. It is a critical technical figure that must always exceed the expected loads on your boat.