You will appreciate that the 'backbone' and most vital part of any ship's construction is the KEEL. If this becomes severely damaged in any way it could effectively render the vessel scrap. Therefore, in the days of wooden ships, shipwrights developed a way of protecting the keel. Using copper staples driven from each side, interlocking sections of timber were secured along the underside of the keel. This section of timber was known as the 'sacrificial keel', and was secured in such a way as to allow it to 'break away' from the main keel should the ship go aground or hit an underwater obstruction.

Whilst diving on the wreck in 1979 we came across a piece of ELM measuring some 20 feet in length. It was approximately 15" wide, 4" thick and had a series of very large copper staples 'set' into each side. Most were broken off at the end protruding away from the timber. Each end of the timber had a 'dovetail' type rebate where it clearly fitted into the next section when in situe. Clearly, this was a section of the sacrificial keel and the copper staples had broken in the manner in which they were so intended.
There are three reasons for using copper for the staples:-
1. It does not corrode
2. At this period in British maritime history, it was rapidly being understood that copper was an effective form of anti-fouling. The presence of copper tended to stop marine worms from attacking the timbers in close proximity.
3. Copper being soft, would have a tendency to 'break away' easily if the ship struck an underwater obstruction - typically coral reefs and rocky outcrops when sailing in uncharted waters.
  Above - Image taken from my original dive log. This clearly shows the 'broad arrow' stamped into a - albeit deformed - complete copper staple.

This last reason explains why nearly all of the staples were broken off at one end. The sacrificial keel did it's job as intended when Invincible struck the Dean Sand bank at 05:00 hours on that fateful - 19th February 1758. The unfortunate thing was the fact the Dean sand bank is exactly what it's name suggests - SAND.

Although the sacrificial keel broke away, the ship quickly became embedded in soft sand. The action of the hard tidal flow very quickly scoured a hole around the hull and her fate was effectively sealed.

During hundreds of years on the seabed, the staples have quite literally been worn down by the action of the sand particles being carried along in the strong tide. There was originally a BROAD ARROW stamped into each staple and this DEPRESSION has worn down at the same rate as the rest of the copper. See picture right:-

Left - The very first copper staple recovered from the wreck is beautifully mounted on a piece of Invincible oak. Manufactured exclusively for a collector of maritime antiqities, the package included:-
1/ A certificate of authentication signed by me as the diver who recovered the object.
2/ A sideview print of the Invincible on Parche Marque paper.
3/ A copy of the book by Brian Lavery - The Royal Navy's First Invincible'.
There were only a very small number ever recovered from the one remaining section of the sacrificial keel. The best examples are now in the National Invincible Archive exhibition in Chatham Historic Dockyard. There are however, two remaining staples that are not required by our National Heritage and are currently available for private sale.
These can be mounted on a superb backboard (right), which is suitable for either wall mounting or to have as a stand-alone item to enhance your office desk or mantelpiece at home. As with all original artefacts from the wreck each is fully authenticated with a certifcate signed by me personally.
For further information please write directly to me.