Boating NZ : FREE TO READ April 2014
64 Boating New Zealand April 2014 The practice of sheathing classic boats in epoxy and fibreglass is generating heated debate on whether it is best for the boat in the long term. L ast month we left our classic boat on its stands in the shed, with its timbers stripped, dried and free of salt. This was the first stage in preparing the hull and decks for sheathing in epoxy/fibreglass. The next stages require the expertise of a skilled boatbuilder. STIFFENING By definition a classic boat is built prior to 1950 and will be planked either in single-skin carvel or multiple skins, ie, double or triple-skin. In both cases, the planking is mechanically fastened to the frames with nails, rivets or screws; ie, not glued. These construction methods are relatively flexible, more so after six or more decades of use. Sheathing a flexible boat with a relatively rigid epoxy/glass skin inevitably leads to cracked or delaminated sheathing, allowing water into the structure to cause probable decay. Most, if not all, classic boats require at least some structural stiffening before sheathing. Every boat is different so it is essential to seek advice on how to stiffen the boat from a boatbuilder or marine surveyor experienced in traditional, classic boat construction. Recommendations typically include re-ribbing, extra frames, stronger maststep, and/or replacing the plank fastenings with the next size up. While on the subject of plank fastenings, all nails, rivets and screw heads will need to be exposed, and the heads scraped back to bright metal. Any defective fastenings need to be replaced, and the holes plugged with timber or epoxy. With a stiffened structure and tight planking seams, most multi- skin, planked classics are now ready for sheathing. Carvel-planked classics, however, will require splining. SPLINING Splining is the process of edge-gluing every carvel plank to its neighbour, essentially making the hull monocoque construction. First, a tapered groove is cut along every plank seam, removing all paint, putty and caulking cotton. Then a shaped timber batten, the spline, is glued into the groove. The grooves and splines are tapered so that glue can escape out the sides and won’t hydraulic the spline from being pushed snugly home. See diagram on page 76. While the spline grooves can be cut straight after stripping, splining should not be done until the planking has dried to the local ambient moisture content; in Auckland this is around 12% to 16%. Splining techniques vary. Classic boatbuilder Peter Brookes has splined many classic boats here and in the UK. He uses a modified biscuit joiner, similar to a mini circular saw, and a custom-tapered blade to cut his grooves. Local boatbuilder Wayne Olson is another experienced spliner. He uses a modified 100mm grinder, again similar to a mini circular saw, cutting a groove approximately 4mm wide at the top, narrowing to 2mm at the bottom. Brookes and Olson favour relatively narrow splines, as does marine surveyor Ray Beale, who splined many hulls during his boatbuilding years with Salthouse Brothers. Words by John Macfarlane Photos by John Macfarlane, Ian Kohler and Shane Anderson GLASSINGOVER PART II – SPLINING, SHEATHING AND PAINTING Practical boating REGULAR_PB_fibreglass PTII_April14.indd 64 18/03/2014 5:26:27 p.m.
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