What’s Oakum?

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Oakum is a tarred fiber used in shipbuilding and repairing seagoing vessels. It can fill small cracks in various structures. It was traditionally made by prisoners and people in almshouses. Oakum has been useful in caulking and sealing gaps in wooden and metal ships, as well as in land-based projects. It is still used for decorative purposes in shipbuilding.

Oakum is a tarred fiber which has a long and illustrious history for use in shipbuilding and the repair of various seagoing vessels. Essentially, it is a blend of tar-coated fibers and can be used to fill small cracks in various types of structures. In past centuries, oak tar was often prepared by people serving time in prisons, as well as people who were forced to work in almshouses to pay off outstanding debts.

There is more than one form of Oakum available for use. In addition to the tarred version which is made using the jute or hemp fibers of old ropes, there is also white oak. This is created with the use of hemp fibers which have not been woven into ropes and is not impregnated with the pine tar which has been used in many cases to make the fibers resistant to water and the elements.

In use, Oakum has been extremely useful throughout the construction site. The substance served as an ideal packing material that could be used as a means of caulking or sealing the small gaps between the seams of ships made entirely of wood. As vessels built primarily of metal became more common, oakum was still used as a means of providing caulking and stability to the wooden deck plating which was often used to sheath the metal body of the vessel.

Over time, oakum has also found use in various land-based projects. Before the advent of plastic, it was often used to provide caulking and sealing around the seams on drain pipes and other forms of piping around the home. At a relatively low cost it has been possible to use the material over time to patch the exhaust pipes, thus delaying the need to replace the entire length of the pipe. This was usually accomplished by packing the joint with oakum, then applying a small amount of molten lead to the area. The lead would cause the fibers to swell and create an effective seal around the joint.

While the use of Oakum is rare today, the material is still used by shipbuilders looking to create a vessel that is a replica of the sailing vessels of yesteryear. However, it normally serves more of a decorative use than a practical one.

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