Number and arrangement of fastenings for planks from 5 to 16 inches in width are shown in Fig. 161. It should be noted that two spikes count as one fastening.

As a rule, the number of fastenings to be driven is regulated by the width of the plank, while the diameter is regulated by the thickness of the plank, and the material of the fastening. It is also customary in some localities to keep the diameter of the largest fastening down to about one-eighth the siding of the frame timbers, which in some cases might require an increase of the number to be driven.

Figure 161. Plank Fastenings.

Hardwood treenails, are generally made from selected black locust, and may vary in diameter as driven from 1¬ inches to 1« inches, depending upon the thickness of the planking. All treenails, where possible are driven through the ceiling inside, then cut off flush on both ends and wedged with small oak wedges made for that purpose and called treenail wedges. The wedges must be set across the grain of the plank through which the treenail is driven. Where treenails are not driven through, a wedge is inserted in the end of the treenail which, when the treenail is driven, backs up against the bottom of the hole and wedges the treenail fast.

There are three general types of treenails in use. The first is straight, and is driven in a hole about 1/16 inch smaller than the treenail. When it is necessary to drive treenails of this type longer than about 24 inches, it becomes rather difficult to get them in with the proper amount of drift. Hence a second type has been devised where about one-half of the length of the treenail is sized about ⅛ inch smaller than the other half. These are driven in holes bored first about half-way through the hull with an auger 1/16 smaller than the large end of the treenail, and the rest of the way with an auger 1/16 smaller than the small part of the treenail. This in effect shortens the required length of drift and makes it possible to drive much longer treenails than would be the case with the first type. Such treenails are known as two-drift treenails. The third type is tapered and is driven in a two size hole bored in the same manner as described for the two-drift treenails. The large end of the treenail is about ⅛ inch larger than the larger portion of the hole, while the small end is the same size as the smaller portion of the hole. It is claimed that these treenails when driven properly cannot be backed out and that they actually hold the planking up against the frame.

All holes are bored, and all treenails are driven, from the outside.

In some instances button-headed bolts have been substituted for treenails, the same number being driven, and about one-half of them driven through the ceiling inside and clinched over rings.

The spike fastening is commonly known as the working fastening; as it is used to hold the plank in place until the planking gang can get clear for the fastening gang. It will be noted that two spikes are driven to each frame in Fig. 161 for all widths of planking. This is a maximum number and very often fastening arrangements call for not more than one spike to the frame.

The size of the spike is regulated by the thickness of the plank, the old rule being - ⅛ inch square and 2 inches long for each inch thickness of plank. Thus a spike for 5-inch planking would be % inch square and 10 inches long. Another rule adds one inch to the length thus obtained. Where the vessel has diagonal planking, the thickness of this must also be added to the length as obtained by the above rule.

Each plank butt must be extra fastened with two button-headed bolts, driven through and clinched over rings inside the ceiling. These may be arranged as shown in the figure.

Alternate arrangements of some of the fastenings are shown by arrows. The arrangement shown here is but one of several in use, and where plans show detail fastening arrangements, they should of course be carefully followed.

The shift of butts shown in Fig. 161, is the minimum customarily permitted, and where possible greater shifts should be used. The rule for minimum shifts may be stated as follows:

Butts in adjoining strakes shall have three frame spaces between. Butts in the next strake but one, shall have two frame spaces between. Butts in the next strake but two shall have one frame space between (as shown in the figure). Butts in the next strake but three may land on the same frame, or butts landing on the same frame shall have three strakes between. Butts shall not be arranged in even sequence or steps.

The above shift of butts will, with a frame spacing of three feet, require an average length of planking of only about 36 feet, hence it will be seen that it can easily be maintained in any locality, and very much bettered where long timber is available.