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 A Steep Learning Curve

Tim Tomlinson

In 1974 I was moulding glass fibre twelves to my Greyhound lines, using a 6mm P.V.C. foam sandwich construction. In 1975 carbon fibre was just becoming available as tows of carbon filaments. I happened on a hybrid tape made up of alternating fibre glass and carbon tows some 50mm wide - no woven carbon cloths in those days. So N2888 'Carbon Copy' was built using this tape on a forty five degree matrix instead of the foam between layers of chopped glass. A simple roll on polyester resin technique. That boat just made the Plymouth Burton Week in 1975. The highlight being the mainsheet slider coming out of the track going out to the start, returning to harbour, sorting, returning to the line start to begin the race five minutes late, deciding to keep clear wind, beating up to the wall turning right along the wall and rounding the first mark 5th!. The rest of the fleet had gone to Drake's Island and were plugging a foul flood tide pouring past the end of the wall. But I digress!.

In the winter of 97/98 I removed the keel and bilge keels from my Design Eight and altered the bow shape slightly. Not wanting the fiddle of returning to a gel coat finish I decided to body fill and go to a spray two pack white finish. I still liked the shape and it suits my inland type of sailing. So I thought why not wax it and take off a mould? A fatal decision! I then had to decide where to build. Why not the garage at home? Insulate it, erect a garden shed to put all the garage rubbish in. Be warned, a single garage is too small to build a Twelve in if you don't want to get short tempered or wear out trousers three fold as you scuff past it, crawl under it, over it and even through it.

The mould was then set up with ridged framing on a chipboard coffin with wheels - all eventualities now covered! At least it could be wheeled out on the warm dry days and worked round more easily.

Research then began into woven carbon fibre, its methodology of working, foams and resins. Many people were unstinting in their advice, not least Nigel Waller. It was obvious vacuum was going to be paramount, Nigel uses a milking machine pump 'two goat size'. My enquiries in this direction found one capable of milking a herd of fifty Friesians, too big, or a breast feeding pump from Boots, too small! I ended up with running a small compressor the wrong way round until it burnt out doing the decks. Then I moved to a pump out of my dentist's scrap spittoon unit that lay in his country garden! Works well but still smells of that pink disinfectant!

The actual lay-up techniques are not too dissimilar from my experiences with glass, except the spatula spreading of the resin because of the faster wetting out of the cloth. I elected to go for a polyester gel coat finish despite the known bond problems with the epoxy resin to be used with the carbon cloth. But I did use a glass-fibre tissue coat as a back up to the gel-coat before the carbon layers. Three layers of 160grm per square metre 90 degree woven carbon cloth for the main lay-up one of these placed at 45 degrees to the keel. 10 millimetre Divinycell H100 foam was used from just forward of the bulkhead to the rear of the plate case and 5mm H100 for the bow and stern areas to keep weight out of the ends of the boat. The 10mm in the area of maximum double curvature was a problem to pull down with the vacuum as it is so stiff. Two layers of 5mm would be better. The hull then received one more layer of carbon on top of the foam with a second layer to go on above the floor from transom to bulkhead. The hull was then released from the mould. Do use a water soluble release agent ! A hose pipe and a bit of water pressure and patience and out the boat pops with a very satisfying sound. I had calculated, by check weighing resins and mats, that the hull would weigh 21.222 Kg. It actually weighed 20.5 Kg. Other weights that might be of interest were plate case and first capping 2.7Kg., bulkhead 1.16Kg., floor supports, torsion tubes and wooden mast compression pad under the floor 3.15Kg., floor 9Kg., deck 6Kg, fittings 3.5Kg.,topsides final carbon 1Kg., Thwart and final case moulding 3.5Kg. A total of 50.5Kg.for a fitted out hull ! I'm sure this could be reduced further, a Paint finish not a Gel coat one for instance.

So what next? The target is to put the old Design Eight back in the mould after weighing. Remove the decks, ply frames, (which are rotten), teak case capping and thwarts and possibly the bulkhead; weigh again and decide what can go back as carbon fibre mouldings. Whether it goes as far as double bottom remains to be seen. I love the self draining aspect of the new boat but not the stress on ancient knees, Monday mornings can be painful.

I have kept a photographic record of the various stages and someone's muttering about the building manual needing updated information. We shall see !

Tim Tomlinson N3459 Carbon Copy

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