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Boating NZ : FREE TO READ May 2014
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subscribe online at www.mags4gifts.co.nz/boating-nz 71 skins would be typical for a 12m boat. This procedure is labour intensive so it’s expensive if done professionally, however it’s well suited to amateurs working alone as it can be done a plank at a time. This method also suits classic purists who object to epoxy/glass sheathing on principle. An excellent example is the 8.5m gaff cutter Curlew, which owners Tim and Pauline Carr skinned in three layers of kauri in 1985. Over the next three decades, the Carrs sailed Curlew over the world’s oceans, including several years in the South Atlantic, without issue. ISSUE – MAJOR ROT/STRUCTURALLY UNSOUND SOLUTION – SHEATHING IN POLYESTER AND FIBREGLASS Timber boats requiring a full structural restoration can be given new life by laminating a new GRP hull over the old hull. The late Allan Vaitses, a boatbuilder from Massachusetts, developed this method during the 1970s and detailed it in his 1981 book, Covering Wooden Boats With Fiberglass. The book’s out of print but is often available secondhand. The key to the Vaitses method is that after stripping the hull of all paint, it is laminated over with a layer or two of chopped strand mat (CSM) with vinylester resin. The CSM layer is then nailed, screwed or stapled at 75mm centres, preventing future delamination. The remaining layers of CSM, alternating with woven rovings, are laminated with polyester resins to the desired thickness. For a 12m boat, for example, this might be 12mm thick or more. The hull is then faired, then covered with two, thin layers of CSM laminated with vinylester resin, and then painted. The Vaitses method should not be confused with the thin polyester/glass sheathing over plywood boats. This was often done in the 1960s and proved worse than useless. It’s now well understood that polyester resin doesn’t adhere well to timber and delaminates easily. However the Vaitses method of using polyester/glass works successfully because; • Mechanically fastening the first layers of CSM to the old timber hull prevents delamination • GRP lay-up is thick enough to provide the required structural strength on its own; essentially the old timber hull is a permanent male mould • fully encapsulating the old timber hull enables a moisture content lower than what is necessary to support rot, which prevents further deterioration of the old hull. Classic boat aficionados will probably choke if this method was used on a genuine classic boat, however it’s ideal for the likes of workboats where originality is considered less important. This method is not quick or cheap, but it’s still considerably less expensive than a full restoration of a timber boat in bad structural condition. SINGLE-PACK PAINTS Now that we’ve covered sheathing, let’s look at single-pack or alkyd, paints. There is a misconception among some owners that alkyd paints don’t last long on boats and use this to justify epoxy/ glass sheathing. “I didn’t want to be painting the boat every year,” is a commonly expressed motive for sheathing. But are alkyd paints ABOVE: Carvel planked yacht built 1958, recently sheathed with two skins of kauri. RIGHT, FROM TOP: Blistered alkyd paint must be stripped; Stripped and sanded timber ready for primer; An excellent finish achieved with roller and brush. REGULAR_PB_fibreglass PTIII_May14.indd 71 17/04/2014 7:17:15 a.m.
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