The Royal Research Ship 'Discovery'. Part 14.

More Surprises - More Original Material

The bottom plank fastenings problem was solved by inserting over-sized new 'dumps' (a historical name for the steel fastenings), hammered well home with a winding of cotton twine around the head of each. The head was hammered about a centimetre below the surface of the plank and capped with a wooden dowel (plug). The fitting of Zinc Anodes was left to be done just before the ship was re-floated.

Now we turned our attention to the hull plank seams. It had been estimated that about 40% needed to be re-caulked and sealed. Wrong! Closer examination showed that more than 80% needed to be treated as much of the sealant was no longer effective. The white or red lead mix used in the past as the final sealer could not be used again because of its toxic properties under Environmental Regulations. An alternative had to be found. There are very few supply companies remaining in the United Kingdom who stock maintenance materials used in historical wooden ships. After some investigation a small company was found that could provide the material to the specifications we required. It had to be flexible and remain flexible but at the same time, seal the seams. The supply company had experimented until it had found the right non-toxic mix, found it a marketable name and made it available to clients such as Discovery. It was the name of the material that raised and eyebrow and a laugh! Black Pudding Mix, it was called; black pudding being a favourite breakfast food for many Britons. Our Black Pudding Mix was not edible but entirely suitable for the work it was meant to do - seal the plank seams.

Black Pudding in a can!

The Shipwright sealing the plank seams with Black Pudding Mix.

A closer view of the sealant and application.

The process completed on 80% of Discovery's outer hull was delicate and oft-times awkward work. Each finished seam and joint was inspected. The outer hull consisted of three different types of wood, each having its own particular properties. English Elm formed the bottom planks giving way to Pitch Pine in the upper hull, however, Greenheart, that wood of all woods, that near-indestructible timber, that heavy, solid, super timber was used as a protective sheathing at the bow and down each side from above the waterline to meet the Elm planking below in order to provide protection from the ice.

You will gather that I am a great fan of Greenheart timber that grows in tree form to ah height of over 40 metres and can have a trunk diameter of more than a metre. A majestic hardwood found in Guyana and in parts of Venezuela, Surinam and Northern Brazil, it has the capacity to be nearly resistant to marine borers and decay fungi. All in all it is the ideal timber for underwater structures.

Again I have allowed myself to become distracted. Back to the Discovery and bottom repairs. Good progress was made after the initial set-backs and budget savings were made in relation to original estimates. The survey report had recommended that 14 bottom planks should be replaced but after further investigation, it was considered sufficient to rout out the surface decay and insert filling pieces where they were needed. In this way original timbers were restored and kept in place. But budget savings in one area were offset by overspend in another. The cost of re-caulking and sealing the plank seams rose by 100% and swallowed up any apparent savings from other areas.

Progress in restoring Discovery's hull planking.

It was known that water was leaking into the forward end of the ship where steel plates were mounted on top of the timbers at the bow to provide further protection from ice damage. The leak was discovered beneath a section of these plates. To remove them in order to repair the leak would be expensive, destructive and amount to vandalism of a historic artifact; it was out of the question. It was also known that Discovery's hull, especially at the bow, had been built exceedingly strong. Apart from the steel protection plates, Greenheart planks lay beneath and Pitch Pine below the Greenheart. Then there was an inner ceiling of Pine. Innovation had to be introduced and it was. A small hole was drilled through the Greenheart at the aft edge of the steel plates. When the drill penetrated the Greenheart to its whole thickness and entered the Pitch Pine, the reduced effort of drilling would be felt immediately. That was the moment to stop drilling. A long grease nipple was then inserted into the hole in the Greenheart timber and screwed home. Then an environmentally friendly sealant was pumped under pressure between the Greenheart and Pitch Pine plank layers. This spread out between the layers effectively providing a watertight membrane to seal the leak. The cost of doing this was minimal and the reward was that yet again the historic integrity of the ship had not been compromised and could remain preserved for the enjoyment of future generations.

It would be unwise of me to go into further detail of the work done to the lower hull, that would take too much space and could become boring to some. So I will move on in the next parts and explain what was found and done in the inner hull. I'll leave this one with a picture of Discovery's lower hull planking nearly completed.