More Surprises – More Original Material

5th, 2012
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The bottom plank fastenings problem encountered was solved by inserting oversized new ‘dumps’ (a historical name for the fastenings), hammered well home with a winding of cotton twine wound 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% would require to be re-caulked and sealed. Wrong! Close 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 could not be used because of its toxic properties under Health and Safety Regulation. A replacement had to be found. There are very few supply companies remaining in the United Kingdom that stock maintenance items used in historical wooden ships. After some investigation a small company was found that could provide the material to the specification we needed. It had to be flexible, remain flexible but seal the seams. The supply company had experimented until it 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 an 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.
The pictures show the Shipwright sealing the bottom plank seams. This process was completed on 80% of Discovery’s outer hull and was delicate and sometimes awkward work. Each completed seam and joint was inspected. The 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 below the waterline of the ship to protect her from ice.
You will have gathered that I am a great fan of Greenheart timber that grows in tree form to a height of over 40 metres and can have a trunk diameter of up to over 1 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 material for underwater structures.

Again I have allowed myself to become distracted. Back to the Discovery and the bottom repairs. Good progress was made after the initial set-backs and budget savings were made in relation to the original estimates. The Survey results had recommended that 14 bottom planks should be replaced but after investigation it was considered sufficient to rout out the surface decay and insert filling pieces where that was 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 in other areas.
The photo shows the progress made in restoring the Discovery’s outer hull planking.
It was known that water was leaking into the forward end of the ship where the steel plates were mounted on top of the timbers at the bow to protect them against 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 artefact; it was out of the question. It was known that the 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 one’s 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 Greenheart timber and screwed home. Then an environmentally friendly sealant was pumped at pressure between the Greenheart and Pitch Pine plank layers. This would 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 been preserved for future generations.
It would be unwise of me to go into further detail of the work done to the lower hull, that would take up too much space and time and could become boring for 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 with her makeup nearly completed.
© Captain John J Watson OBE January 2012 Fethiye

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