Stage 4: Framing and Planking
The planking of a boat follows on from the framing and both processes rely upon accurate calculations from the lofter (the man in charge of all the drawings).
Dave Cockwell owner of the boatyard, personally chose the larch trees along with his chief shipwright, Johnny Mills. "It is imperative to pick the right trees as they are so important for the structure of the ferry," Dave said.
"The frame of a boat can be described as the ribs, and the planking is the skin," he added.
The boat yard has bought a sawmill especially for the building of the ferry to give them complete control over the way in which the timber is cut and which tree is used for which part of the vessel.
The framing up of the ferry took only three weeks to complete, using three teams of men for the three main stages. Dave started the process by taking all the plywood templates produced by the lofter out into the yard to help him decide which tree to use for which frame.
He said, "In order to make the most of the natural strength of the oak timbers, we select oak bends whose natural shape and grain is equivalent to each frame template. Once we have decided which piece of timber to use for each of the futtocks (the individual pieces that make up each frame), these rough-cut pieces of timber are passed on to the first team. They clean up the timber and cut it to the correct thickness.
"The second stage is to accurately mark the shape of the futtock using the template. The marked-out timber is then passed on to the second team, who cut the futtock out to the correct bevel (angle) using a bandsaw. It is then passed on to the next stage, where the frame bevels are planed. From here the futtocks are passed on to the team on the loft floor, where the individual futtocks are assembled into a frame and clamped while rivet holes are drilled and copper rod inserted. A brace is added and then the frame can be lifted clear and passed on to the final stage, which is the clenching of the copper rivet.
"Approximately two complete frames per day were produced. At the end of this process you end up with a large pile of complete frames, which should all be the correct shape. They are then craned on to the centreline (keel), checked for level and fastened with aluminium bronze bolts. It’s a bit like assembling a large Airfix model," Dave added.
Once the frames are in place, planking begins. The first stage of the planking process is called "lining off," in which the number and shape of planks needed each side is established. Flexible battens are temporarily fixed to the hull to work out the position of the plank edges. It is unlikely on any but very small boats that a single plank will be long enough to run from bow to stern, so joints will also be required between plank ends. These joints must be staggered between adjacent planks to avoid weakening the boat (in a similar way to the vertical joints in a brick wall). A "schedule of butts" (a drawing showing the positions of the butt joints between the plank ends) is produced to ensure this requirement is met. Plank shapes are then transferred to the timber that will form the planks.
When each plank has been cut to size, it is steamed to make it more flexible . Steaming can take up to two hours per plank. While it is still flexible, it is clamped into position on the frames and left overnight. The next day, it is taken off and will have curved to fit to the frame. Any final adjustments are made, then it is fixed permanently into place.
"Each plank is actually crafted into place. There were teams on both the port and starboard side of the ferry, working on the corresponding plank at the same time, starting with the garboard - the plank which is attached to the keel," Dave explained.
The planking of the St Mawes Ferry is completed up to deck height. The next stage of the build is the placing of the deck.