Hold bulkheads in wood ships are fitted for two general purposes. The first is, to subdivide the interior of the hull into small compartments so that if any one of the compartments is flooded, through damage to the hull, etc., the ship will still remain afloat. The second purpose is to provide additional thwartship stiffening against what is known as keel hogging and also against torsional strains.

Two types of hold bulkheads are in use, that shown in Fig. 105 being known as the "diagonal" hold bulkhead and that shown in Fig. 106 as the "solid log" bulkhead. The figures are practically self-explanatory and will require very little discussion.

It will be noted in Fig. 105 that the diagonal bulkhead planking in the lower hold is placed between two stanchions, which are opposite each other, these stanchions being heavily bolted together. Between decks, in the same bulkhead, stanchions are shown on but one side of the planking, the lighter construction here being due to the fact that the water pressure, should the hold become flooded, would be much less at the top than at the bottom of the bulkhead. If there were no decking laid on the lower tier of beams to stiffen the bulkhead at this point, then it would be necessary to extend the stanchions on both sides to the deck above.

To insure watertightness two thicknesses of tarred felt are laid between the courses of diagonal planking, care being taken to properly break joints. The border coamings are calked in the usual manner.

In general, the fastening will be as shown in the figure. The diagonal planking fastening, which is not shown, consists of standard boat spikes. Each plank should be well spiked not only at the ends but to each stanchion on one side. Obviously it would be impossible to spike this planking to stanchions on both sides.

These bulkheads are generally faced toward the expected source of water pressure, hence, bulkheads forward of midship would be faced forward and those aft of that point would be faced aft. The term "face" as here used is taken to mean the side of the bulkhead opposite the deck beam against which it is built. The bulkhead in Fig. 105 would under this rule face to the reader's right, and it will be noticed that the single stanchions between decks are on the back side.

Figure 105.

Figure 106. Solid Log Hold Bulkhead.

Solid log bulkheads, such as that shown in Fig. 106 may be put down without the extra heavy border timbers, or coamings, which have been shown in the figure, though it may be considered the best practice to use these heavy coamings as they afford room for additional fastening around the border which is often quite essential. It will be noted that at the side of the ship the bulkhead timbers are not landed on top of the coaming timbers as at the bottom, but are continued past them to and against the ceiling.

The arrangement of edge drift bolts in the bulkhead timbers as shown here is typical. Each bolt passes through two and one-half strakes. Those bolts at and near the bottom of the bulkhead should be close spaced as shown in the figure, the reason for this being much the same as that for adding the extra set of stanchions to the diagonal bulkhead in the lower hold.

These bulkheads must be calked all over and for this purpose calking seams must be run on all timbers. These seams should be small, that is not over one and one-half inches deep with a total opening of about three-sixteenths of one inch.

The ceiling, in way of all bulkheads, whether diagonal, or solid log construction, must be made water tight either by wedging or calking. Calking and paying heavily with pitch seems to be the most highly approved procedure.