Caulking is a traditional technique used on wooden vessels to fill the gaps between the planks while still allowing the wood to flex and move. This involves driving a fibrous material, usually cotton or oakum (tarred hemp), deep into the gaps. Specialist tools (caulking irons) are required because it’s vital to drive the material evenly, gently so as not to damage the wood, yet firmly enough to stick fast in the gap without passing right through the seam.
Once the caulking material has been driven in, filling the seam to approximately half its depth, a stopping compound is used to fill the remainder of the gap. Traditionally this was red lead putty applied with a pallete knife, but some boatbuilders now use modern polyurethane mastics such as Sikaflex squeezed straight from the tube. Caulking of seams between planks is an essential task still required to keep traditionally-built boats watertight, vessels as diverse as the Götheborg or HMS Victory.
Seb broke his arm whilst working away from home about 4 weeks ago. Undeterred by this minor setback, he has worked the Caird every weekend since the accident with a little help from friends and family - the Shackleton Way of getting things done when adversity strikes! Approximately 250 meters of seams have been stopped with red lead and soon the boat will be ready for painting.
Its important to note that the boat has only been caulked and stopped using traditional 1914 boat building materials below the original top-strake. Once the boat is painted (inside and out), the additional topsides will be caulked and stopped using similar materials available to McNish on Elephant Island in 1916. Our material lists includes, frayed Shetland wool socks and Manilla rope, torn-up Gabardine cotton, oakum, and lampwick. The remaining seams will be stopped with something rather unique in the history of this vessel...watch this space.