The pattern thus drawn out is, of course, for one-half of the oval vessel, two pieces off this being required to form the body of the article. It will be necessary to add laps as required for grooving, wiring, and knocking up.
It will be seen that the joints are at the end of the article, the reason for this being that that part having the sharpest curvature, it will be somewhat stiller and stronger than the sides, hence the best position for placing the joint. Another reason that assists in determining the position of a wire joint is that, if possible, it should be covered with a lug, ear, or handle. In the present case, if the vessel is to be used as an oval tub or bath, the handles would be riveted over the end grooves, and thus materially assist to strengthen this part. Perhaps a further reason for fixing the grooves at the ends is that the pattern comes out much flatter when the joints are in this position than when on the sides; consequently the material will cut up to greater advantage. The economical cutting up of sheets and plates should always be taken into account when thinking of the position of joints. Also when stock sizes of sheets or plates are being used a little thought bestowed on the pattern will often save a large amount of waste in material.
When it is required to make the pattern for the body of an oval article in one piece, a little consideration of Fig. 139, will show how this can be done.
Before concluding it might be here pointed out that the lengths of both the radii used on the pattern can be calculated by the method shown, in connection with the cone, in Chapter XII (Conical Articles Of Short Taper).
Bodies of oval articles are usually shaped by bending in the rolls to the curvature of the ends, and then flattening out the side parts.