Caulking seam
Quarter sawn decking
Tosh Nail Beam
Spike
Figure 17 Hidden (or Blind) Fastenings Figure 17 Hidden (or Blind) Fastenings
skew nailing. When two such nails are driven at an angle to each other the process is referred to as dovetailing or tusk nailing.
Washers
All nuts have to be bedded down on washers so that, when tightening the nut, the wood or other material underneath is not torn to pieces. Sometimes, in order to spread the load, washers are also fitted under the heads of keel, bilge keel, stem and sternpost bolts as well as under the nuts. Washers, which have to be fitted the correct way, are of two main types:
• plain or ordinary washers. • plate washers.
Engineering bolts or studs would have machined washers but these are unlikely to be found in wooden boat construction. Plain washers are the standard washers purchased from any ironmongery shop and are usually of about 2 to 2½ times the diameter of the bolt for which they are to be used in diameter. They are punched out of mild steel sheet about 1½ mm to 2 mm thick. Plate washers are sheared out of 6
Rounded edges Bolt diameter Ragged edges (+ 1 mm) Washer diameter
Figure 18 Section through a Ring Washer (Exaggerated) Figure 18 Section through a Ring Washer (Exaggerated)
A treenail mooter was the specialist artisan often a retired shipwright employed to produce the different treenails at the shipbuilding site and to smooth them and make them the proper size Mooting was the name given to the process of making a treenail exactly cylindrical or octagonal to the given diameter or size called the moot using a tool similar to a pencil sharpener and called a mooting plane. The word moot was also used as a noun to describe the treenail’s diameter. Hence, when so made, it was said to be mooted. In Chatham dockyard in 1698 there were two treenail mooters to 2,593 shipwrights. It was all done by hand and must have been an extremely boring even though a highly skilled job. These days treenails are turned by lathe. The etymology of the verb to moot is unknown. Trennels were often called pags and the task of fitting and driving them, pegging off.
2. The Report • September 2020 • Issue 93 | 47 Ragged edges
mm (¼”) thick mild steel plate and are of about 75 mm to 90 mm (3” to 3½”) square area. Whether they are punched out plain washers or sheared out plate washers they have a smooth (slightly rounded) edge and a sharp edge and should always be laid with the sharp edge faying to the timber. This is a small point often ignored by the amateur builder or repairer and is often the give away to poor construction. The diameter of the hole through the washer is usually the diameter of the bolt plus 1 mm. Where they are required to be watertight, washers are fitted underneath with a boat cotton or oakum grommet. Plate washers are also fitted with a layer of felt. Both grommet and felt should be well luted with a suitable material which, in the author’s youth, was white lead but, these days, may be a resin, epoxy paint or something like Sykaflex. Nuts requiring extra security because of their purpose may be fitted with a split pin but that is rare in boat construction. Usually such bolts are fitted with a lock nut i.e., a second nut on the same bolt or a nylock nut. The lock nut is usually about three quarters of the thickness of the main nut and should be fitted first with the main nut on the outside.
Fit this way down
3 mm maximum
Spike 2t/3 t
Treenails2
To overcome the difficulties of iron spikes or clenched copper nails, boats, particularly those built in Scandinavia, are often fastened by a very ancient form of fastening called treenails (pronounced along the London River as trennels or trunnels). They are most commonly used to hold the planking of wooden boats on to the main framing or timbers. Treenails, as the name implies, are nails turned out of wood. They may be of oak, ash, locust or other tropical hard woods of durable quality. Where beech is used it must be confined to the bottom not higher than the floor (wrung) heads. The treenails must be straight and of regular octagonal or round form, being either machine cut, compressed or planed, not grain cut or knotty and must be free from sap. The marine surveyor should note that treenails should be of good quality and of a description equal to the best material through which they are driven. They must be tightly driven and in all cases the treenails should be efficiently caulked or wedged on the outside. Not less than two thirds of the treenails should be driven through the inside planking, clamps or other structural items. The lay and spacing of the treenails depends upon the width of the plank being secured and whether or not the frames behind are sistered. They can be of plain, wedged or wedged and fox wedged types. The simple types are called plain treenails and have no wedges in either the head or the toe. Plain treenails are, however, incapable of closing a joint and the marine surveyor should bear that fact in mind when surveying repaired boats with that form of fastening. In all cases planks above eleven inches in width must be double fastened and those betwen eight and eleven inches in width must
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