The last five years of shipbuilding have focused the industry’s spotlight on the rapid development of the rivet’s lusty rival, welding. The premium placed on weight by the naval limitation treaties has been a powerful influence in the development and increasing acceptance of welding. Now that the naval treaties are dying we may well pause and consider how much we should continue to favor welding at the expense of riveting.
Strength, speed of construction, appearance, and final cost of ship should be the points upon which to evaluate our position. Let us consider strength first.
The reliability of riveted joints is a matter of history. We can calculate their performance within reasonably close limits. We know what they can do. Welded joints have no background of long usage to soothe the mind looking for unquestioned reliability. Calculation of their strength is considerably clouded by the locked-up stresses or shrinkage; but a generous factor of safety does much to lay this ghost. Under impact, the welded joint seems to be at a disadvantage compared with its more flexible riveted counterpart, but for general purpose jointure, in most structural work, the welded joint has the outstanding advantage of approximating the intact plate standard that the riveted joint strives to reach but never achieves.
Considering time of construction, welding comes off a bad second. The erection schedule of the welded ship is the slave of the welding sequence. Machinists must wait until shrinkage has done its work. Shipfitters cannot work too far ahead of the welders if dimensions are to be maintained. Structural material cannot be cut neat in the shop if one is to make ends meet. In the event of a shortage of ship- fitters, work must lag to suit because the welded ship is more of a job for the trained mechanic than for the more plentiful bolter-up. Thirty-day riveted destroyer hulls were war-time phenomena, whereas six months for a welded job would be optimistic under the same circumstances.
Coming to the question of appearance, welding is again a bad second in the case of ships of light scantlings, such as destroyers. Even the most careful fitting and welding sequence will result in some hollows, bulges and washboard effects in decks, bulkheads, and shell plating. Some can be removed by straightening gangs, but when the sun shines on the paintwork the remains can still be seen. Welded sterns and bows have a habit of trying to resemble a crumpled sheet of paper carefully straightened out. Even the keel and stem refuse to stay put unless vigilance is unrelaxed.
So finally we come to the question of cost. Is welded construction cheaper than riveting? Welding saves punching, drilling, reaming, calking, and material. A riveting gang costs more than a welder. But a riveting gang turns out about double the daily footage of laps and butts that a welder does, and this is a very large item of expense. What the welder saves in calking is largely neutralized by the extra chipping involved in leaving structural material long for good fitting. Welded construction requires a much higher ratio of high-priced shipfitters to lower-priced artisans than does the riveted ship. Welding undoubtedly makes an easier job of making the skin water-tight and makes it stay tight longer, but riveting can do the job, too, and moreover it gives us a smoother hull and consequent slight reduction in resistance. Finally, because the erection schedule must serve the welding sequence, the most economical order of work cannot always be followed. All in all, it does not seem that welding is cheaper than riveting if the final cost of the ship is considered. It would be interesting to build two sister-ships, simultaneously, one welded and one riveted, and compare the time and cost conclusively.
The issue might well be raised that the increased weight of additional riveting would require an increase in displacement of two to four times the increase in hull weight if the military characteristics are to be preserved, depending on the type of ship under construction. Additional displacement means a larger ship and correspondingly greater cost. The answer to this question would be some accurate figures on the real net saving in hull weight effected by welding in each type of vessel. It might be that the net increase in weight is not large enough to require increased dimensions to maintain military power, if the revision of the distribution of welding and riveting is carefully considered.
No consideration of the question of cost is complete without giving thought to the galvanized fumes encountered in welded construction. In ships built mainly of galvanized plates, such as destroyers, this is a serious problem because of the time lost in fighting the fumes, the time lost when the fumes win the fight, and the 165 general slowing up effect that the fumes exert on everyone working in the vicinity; not to mention the equipment and power required to keep the fumes under control.
So far the argument seems to favor riveting. But we have been talking only in terms of the structural portion of the ship. When the hull proper is built there remains a great mass of work still to be done—piping, miscellaneous foundations, fittings of various kinds, thousands of hangers—the million and one things that compose the interior gingerbread work of every ship. Here welding comes in an easy first. Welding is quick, easily varied to suit unforeseen conditions, eliminates much piercing of water-tight boundaries and when piercing is unavoidable it makes water-tight sealing easy. Not only is welding ideal for the great mass of miscellaneous stuff that must be fitted all around the interior, but it is unexcelled in making oil-tight boundaries, water and oil stops, many subassemblies replacing castings, and last but not least, it is the only putting-on tool available when necessity demands one.
It would seem then that the amount of welding in the hull proper can be profitably and properly cut down. Perhaps the pendulum, under the impetus of weight saving, has swung too far toward the new technique and the time has come to reconsider the case of welding versus riveting in ship construction and to give each its due, to the end that better ships may be built faster and more economically. The day may soon come when it will be recognized that the riveted joint is the best one for the skin and skeleton of the ship, while the welded joint is unexcelled for tying together the internal organs.