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. RULES FOR THE CONSTRUCTION OF STEEL VESSELS. STERN FRAME WITH PROPELLER APERTURE. 15. When an aperture stern frame is adopted, the sectional area of the pro- peller post and the sternpost should be of size given in Table 1. They must be of one solid forging and connected to the transom and keel as set forth in Sec. 18, Par. 7 to ro. 16. The rudder gudgeons should be forged to the sternpost, or they may be riveted thereto, but the sectional area of the sternpost in way of the gudgeons must be increased equal to the reduction by rivet holes, the distance between gudgeons not to exceed five feet. 17. The prevailing type of stern frame for single screw steamers navigating the Great Lakes is described in the preceding rules--Sec. 18, Pars. 7 to 10. RUDDERS FITTED WITH GUDGEONS AND PINTLE. SECTION 19. 1. The rudder frame with suitable cross stays must be in one forging. 2. The diameter of stock and heel pintle are given in Table 1. The spacing of the intermediate pintles to be governed by the length of the rudder blade and not to exceed five feet. 3. The rudder plating to be from to to 17% pounds to the superficial foot, and, in high speed steamers, double riveted to the frame, the head of the rivets to be full, and wood fitted between the plates. See Sec. 20, Par. 6. 4. The rudder pintles should be properly turned and fitted independently in the frame. 5. A proper rudder post casing and stuffing box must be fitted to the stern frame and transom and the rudder made to ship and unship with the vessel afloat. 6. To the stock must be fitted a suitable quadrant or tiller with rudder chains, steering rods, and blocks, and all must be to the satisfaction of the surveyor. ; 7. See drawing of stern frame and rudder, Figs. 34, 35, 36 and 37, Pages 10g, Itc. a3 BALANCE RUDDER. SECTION 20. 1. The sectional area of the balance rudder stock will be same as that given for rudder heads in Table 1. 2. The forward and after bow of the rudder blade, together with the cross stays, must be forged to the stock and may be 25 per cent. less in section than the tabular dimensions of the stock to which they are connected. 3. The head of the stock must be machine turned to conform to the stuffing box and head supports, which must be fitted and secured to receive the rudder head in the same manner and under the same conditions as described and set forth in Sec. 19, Pars. 5 and 6. 4. The foot pintle must also be machine turned to a diameter equal to one-half the tabular rudder head, and a brass or composition bushing must be fitted in the hub at the end of the shoe to receive it. 5. The rudder plating may not be less than 10 pounds, or more than 20 pounds, to the superficial foot, and should be secured to the frame by full or snaphead rivets of a diameter in proportion to the thickness of the plating, and the latter supported by a solid wood filling. 6. In steam vessels whose average speed exceeds 14 miles per hour, the plating should be double riveted to the frame. 7. Balance rudders, at the present time, are the prevailing type on the Lakes for single screw steamers, and the best results are obtained from those that have 20 per cent. of the width of the blade, forward of the rudder post. See drawing, Figs. 34, 35, 36 and 37, Pages 109, 110. FRAMES. SECTION 21. 1. Frames of various types and equivalent bending resistance are given in Table 3, and their spacing to be as per Table 1. 2. The tabular angle frame in double bottom vessels only, may be used in the bottom below the upper turn of bilges in conjunction with any special form of frame that may be used above the bilges.