Don’t attempt any of the finish welding until all the hull plating is tack-welded into position. Before you start the final welding, give your hull a final check for irregularities. They will be easier to correct before the welding is completed. Bumps can be removed by any one of several metalworking techniques, including using a rubber mallet on one side while a helper holds a suitably shaped timber backing-piece on the other. Hollows on the hull are most unsightly, and must be removed. Small wrinkles along the chine can be removed from inside with the careful use of a large plastic-faced mallet and a person holding a suitable backing-piece from outside the hull.

Final welding consists of short welds laid down in the proper sequence for that particular plating. As mentioned in Chapter 5, Welding, different techniques are required to weld steel, aluminum, and copper-nickel. You must be fully conversant with the method best suited to the plating of your hull.

   Much of the work, up until the running of the finish welds, can be handled by a person with a minimum of welding experience, but the final welding of the plating is another matter. If you’re not a fully experienced welder, this may be the time to hire a professional. If you plan to take this route, we recommend that you seek help before you start the project. Discuss with the professional how much you can do yourself, and when and where you will need his or her assistance.

   If you’re going to seek outside assistance, make sure the person understands the problems of welding a pleasure boat. Welding a boat is quite different to commercial welding. In commercial welding, strength is important but laying down a considerable amount of weld per hour also has a high priority. A commercial welder might not consider a fine finish to be so important. Explain your expectations to the professional before you enter into a firm agreement. If you find that the person you’ve chosen doesn’t come up to your expectations, make other arrangements before the job gets out of hand.

   When the welding of the plating is completed, you’ll need to grind off some of your welds from the outside of the hull. If you have laid good-quality welds with good penetration, you’ll have the minimum of chipping and grinding before repairing or re-welding any unsatisfactory joins in the plate. It’s normal practice to grind only those welds above the waterline. Most classification societies insist that the welds below the waterline are left ungrounded so they retain all the strength of the original weld. Do not over-grind the welded seams above the waterline, otherwise you may weaken them to such an extent that you compromise the strength of the vessel.

Keel Plating

   If you’ve built your hull upside down, now will be the time to plate the keel. The keel’s leading edge (usually pipe or split pipe), the webs, and the aft end of the keel will already be in place. Your plans will instruct you about the order in which to plate the sides and the bottom. In the past, we’ve usually specified 1/4-inch (6 mm) material for the sides, and 1/2-inch (12 mm) for the bottom plate. Today, we’d be happy to have the whole structure built of 1/4-inch (6 mm) plate; this means that at the intersections of the sides and the bottom, you’ll be welding material of the same thickness. Also, in the case of boats built inverted, you’ll not have to struggle with the heavier 1/2-inch (12 mm) plate at the bottom of the keel.