February 13, 2019

So You Want to Build a Battleship - Construction Part 1

So what was actually needed to build a battleship? How was a pile of metal turned into a vessel capable of ruling the waves?1

Iowa takes shape on the building slip at Brooklyn Naval Yard

It all started with a piece of land. This land needed to be firm enough to support the vessel as it was being built, and next to a body of water into which the vessel could be safely launched. It also needed good access to the sources of building materials, and to skilled workers. Once the land was secured, a building slip was constructed. This sloped gently towards the water, usually at about 3°, to make it possible to launch the ship when it came time for that. The ways, the main supports for the ship under construction and the rails which she would slide down at launch, were then laid. These were built primarily of timber, and for a battleship were approximately 8' wide and 30' apart. In the center, a line of wooden building blocks was placed to provide the primary support for the vessel as it was assembled. These allowed men to work underneath the ship, and provided clearance for the launching cradle when it was installed.

The building slip for USS Washington (BB-47). The keel blocks are visible towards the bottom of the photo, while the ways are under construction towards the top.

The next task was producing the various pieces of metal that make up the basic fabric of the ship. Raw material was bought from commercial sources and formed into the necessary shapes on-site. The yard would prepare working drawings from the master plans supplied by the navy, and these would then be converted into full-scale wooden templates in the mould loft. The mould loft was a large, well-lit area, usually above a workshop, where skilled men filled in the gaps in the drawings and produced templates for the plates and frames. Plates were cut to shape with giant shears, rivet holes were punched or drilled,2 and rollers were used to bend the plate to the correct shape. The much stiffer frames were bent hot, using hammers, presses, and metal templates based on the wooden ones produced in the mould loft. Specialized pieces like shaft brackets and the stem (bow) and stern castings were cast or forged to their final shape by outside specialists and shipped in.

The Mould Loft at John Brown's Clydebank shipyard, 1901

The metal pieces would then be taken out to the slip, where they would be fitted into the growing hull. They were hoisted into place by a light derrick or crane, usually with a capacity of no more than 3-5 tons, and temporarily bolted into place.3 A riveting gang would then arrive to fasten them permanently to the ship's structure.4 Each rivet would be heated in a nearby furnace by the rivet boy, then passed to the catcher, who would place it in the hole. A holder-up would then hold the head of the rivet against the riveter(s), who would buck the tail of the rivet to hold the plates together. Through about 1910, rivets were bucked by a team of men, usually two, armed with hammers. Later on, a single man armed with a pneumatic riveter was used instead.

A man uses a pneumatic riveter, c.WWI

There were several drawbacks to riveting. Besides being labor-intensive, it tended to produce heavy structures. To provide enough space for the rivets, plates had to be overlapped or strapped, and stiffeners had to have extra flanges for attachment. The lines of holes also weakened the plates, the usual assumption being that this cost 1/7th of the plate's normal strength. More than that, riveted joints were not inherently watertight. Any watertight joints had to be caulked, with the edges of the plate split, and one side forced down into the other plate. Joints that had to be oiltight, such as fuel tanks, had to be caulked even more carefully, and welding was enthusiastically adopted for these areas.

Laying the keel of USS Florida, March 8th, 1909

Actual assembly began with the keel, the structural backbone of the ship. Its laying was usually the subject of some ceremony, as the official start of the ship's construction. After that, the double bottom with its frames, longitudinals, and inner and outer bottom plates was assembled. The frames that defined the ship's sides followed, along with the side framing and plating. Throughout assembly of the ship's structure, great care was taken to make sure that it matched the designed shape. Once enough structure was in place, to make sure it wouldn't shift, important structures like machinery mounts and shaft brackets were installed and aligned. These, and other heavy fittings like the stem and stern castings and transverse armored bulkheads, were usually erected using temporary wooden shearlegs, as the permanent derricks lacked the capacity for them.

HMS Dreadnought's frames show in this view two days after her official keel-laying5

For most battleships, the next step was to install the strength deck in preparation for launch. At this point, there would be several obvious components still missing, most notably belt armor, machinery and turrets. There were several reasons for this. First, this made the ship lighter at launch, which reduced stress on the ways and made the hull easier to control. Second, these components were heavy and would have required much more powerful lifting apparatus than was traditionally installed on the slipways. By waiting until the ship was afloat,6 the builder could make more efficient use of the expensive heavy cranes. This changed towards the end of the battleship era. Internal belts had to be installed before launch, and better cranes made it practical to add machinery and fully seal the hull before launch, instead of just bolting on some of the upper deck for later access.

Iowa two months before launch

But ultimately, the day would come when it was time to send the hull sliding down the ways and into the water for the first time. I'll discuss that process, and what followed it, next time.

1 Two notes on the following. First, I'm describing practice during the battleship era, and modern shipbuilding techniques are very different. Second, this is based almost entirely on British practice, due to the limitations of my sources when I wrote it, although American practices were broadly similar. I've since gotten more information on WWII USN methods, but will probably put that in a separate post.

2 Punching was much more efficient, but it cold-worked the holes, making them more likely to crack. Drilling was used on critical holes in the structure instead. Where accuracy was critical, practice was to punch undersized holes, then clamp the pieces together on the slipway and drill the holes to final size.

3 This is where modern practice differs most radically from that of the battleship era. Today, most ships are constructed using modules. Large blocks are assembled elsewhere in the shipyard, including things like cables and piping, and only then assembled. These modules can be up to 1,000 tons, as on the new Ford class carriers. Towards the end of the battleship era, heavier cranes were often used, which allowed more assembly to be done in shops instead of on the slipway.

4 Structurally, all battleships were riveted. Even the Iowas, which were extensively welded topside, had most of their structural elements riveted. Illinois and Kentucky would have had much more extensive welding, but neither was completed.

5 Fisher essentially cheated to get Dreadnought credited with a very quick building time. A lot more work was done than normal before the keel was formally laid.

6 The contracts the Admiralty issued to commercial builders specified that the ship had to remain afloat at all times while being fitted out.

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