producing a blind hole. Before the treenail is inserted into the hole the point end is split and a hard wood wedge inserted. The so-called fox wedge should lie transversely to the grain of the frame timber. The treenail is then driven home and the head wedges fitted as for ordinary wedged treenails. The head and point wedge slots are laid at right angles to each other. If driven correctly, this method of fastening is very strong indeed and, once fitted, a wedged treenail is virtually impossible to remove.
If
such a treenail is properly driven, it will draw the plank close up to the timbers.
If when driving a treenail,
the wood through which it is driven splits along the grain because the treenail is too tight, the wood is said to be rent. Such rents or rendings are very difficult to caulk or chinse especially so in softwood planking. Where the timbers are laid in pairs i.e., sistered, the treenails are fitted at each frame with one treenail fitted into each sister. The length of the treenail that actually grips the wood through which it is driven is called its drift. Long treenails could be best driven with two drifts instead of one - the hole being bored with two augers of different sizes, instead of one. To improve the grip of the plank the treenails are often dovetailed i.e., with the point of the treenails leading alternately forward and aft3
.
Table 5 Details of Treenails
Thickness of Plank mm
Diameter of Drift mm
Width across Flats Eight Squared Treenail mm
12 25 30 50 60 75 10 12 12 20 22 25 6 7 7 8 9 10
exactly of the same size. For if that is not the case, it will be almost impossible, without a great deal of trouble, for even an expert workman to drive the treenails. The marine surveyor should be aware that treenailing off was often frequently performed by the less skilled workmen. On Scandinavian built vessels the treenails are not cross cut with slots but drilled with a small diameter hole down
SURVEYING TIPS: The marine surveyor is recommended to look carefully at the treenails to see that
they are not driven from both inside and out in the same holes, that they do not check the plank and are properly wedged on both ends.
The author does not recommend round treenails - the best form for every purpose being eight square - whether hand or machine made.
Once the shipwright has started to drive the treenail he must not stop for, if he does, he will not be able to start it moving again and they are the Devil’s own job to bore out. A treenail cracked, bent or nipped between the plank and the frame due to bad driving was said to be necked and must - often with some difficulty - be drilled out and replaced. The treenail should be about ¾ mm (1/32”) greater in diameter than the drilled hole. To ease entry and the driving of the treenail the toe is slightly chamfered and the treenail dipped in linseed oil. The treenails should be made from well open air seasoned wood and should be made and driven with accuracy and care. They should be properly rounded and of equal diameter from the point to within a quarter of their length from the head where they should begin to swell a little. When treenailing off (or pegging off as it was sometimes called) the bottom and topsides, it was the general custom to double bore each timber on the breadth of a strake if it exceeded 10 inches and to double and single bore all narrow strakes; that is, to double bore one timber and single bore the next alternately. One thing which should be particularly attended to by marine surveyor at this time, is to see that all the augers for any particular part of the vessel are
the centre which is then wedged open with a spike or peg of shaped hardwood – usually a different timber to that from which the treenail itself is fashioned. They are said to be pegged or spiked rather than wedged. After fitting, a short time is allowed to settle the timber and then the ends of the treenails extending outside the surface of the hull are dubbed off leaving a smooth surface. When pegging treenails or driving spikes the marine surveyor should be aware of the following points:
• the form of the point of the common spike is such that it inclines not to follow the hole.
• spikes driven close to the holes, but not into them, will have their withdrawal resistance lowered.
• if the holes are not too large and the spikes follow the holes closely, the resistance to withdrawal usually will be increased.
• if the pegs or spikes do not follow the holes, the resistance to withdrawal may be greatly reduced.
• the driven end of the treenail is usually slightly reduced in diameter to form a lead.
3. It is fancied by some that one of the factors that resulted in the general superiority of the
Royal Navy over the French in Napoleonic times was that the British ships were fastened with treenails which were stronger and lighter and the French ships were fastened with iron spikes resulting in much weakness due to nail sickness. A moot point but see Dr. Sam Wlillis’ Hearts of Oak trilogy. When the author as a young man was working as a shipwright the gang was given orders to break up two old badly rotted wooden lighters, which had been fastened by fox wedged treenails. They also had hooked wedged scarphs in the keel and other longitudinal timbers. It was found impossible to break the vessels up and, eventually, to get rid of them, they had, with much difficulty, to be burned.
The Report • September 2020 • Issue 93 | 49
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