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October, 1917 3.—To make such an allowance for the ex- cess, if any, in the declivity of the launching ways over that of the blocks as will prevent the forefoot of the ship from touching the ground when she has reached the end of the ways, as previously explained. In order to obtain the required height of the foremost block with great accu- racy a sketch of the ground or slip upon which the ship is to be built should be made in elevation and. sec- tion, and two pieces of cardboard should be cut, one to the shape of the transverse and the other to the _ longi- tudinal section of the ship, both draw- ings and cardboards being on the same scale. By placing the cards on the sketches and trying them in various positions, all risk of error in deciding the height of the foremost block can be avoided. The launching ways usually are set at a greater declivity than the keel blocks and the amount that the forefoot of the ship falls below the line of the blocks when it reaches the Jowest part of the slip can be found by a simple mathematical calculation. Clearance be- tween the forefoot and the ground should not be Jess than 9 to 12 inches. Now in the case of a ship built on a slip 300 feet long, on blocks at an in- clination of 5 inch to a foot, and launched at 34 inch to a foot, it is evident that the bow falls % inch below the line of the blocks for every foot the ship slides down the ,ways. Hence, in the 300 feet, there is a total relative fall of 37% inches, and therefore, the foremost block, if at the head of the slip, must be kept 37% inches plus 12 inches, or 49!4 inches above a line, FIG. 51—ASSEMBLING FRAME FUTTOCKS ON FRAMING STAGE THE MARINE REVIEW 367 FIG. 50—FRAMING STAGE LAID ALONGSIDE KEEL—THE FRAMES ARE HOISTED INTO POSITION BY MEANS OF A SIMPLE TACKLE which, at an inclination of 54 inch to the foot just touches the after end of the ship. From these data the foremost block can be readily built to its correct height. In order to lay the other blocks, in- stead of using the string or cord pre- viously mentioned, a declivity batten may be prepared. This is a batten about 20 feet long, the edges of which are straight and inclined to each other at an angle equal to the required declivity of the blocks. Now put up a block at 20 feet abaft the foremost one to such a height as will cause the upper edge of the batten to be level, as indicated by a spirit level, while the lower edge rests upon the two blocks. These two blocks will now have the proper de- clivity with reference to each other. The other blocks are laid in a similar manner, or by sighting them with the two first placed, and when this is done they can all be proved by stretching a line along their upper surfaces or by trying. the declivity batten along the whole range of blocks. After the blocks are laid out, in some yards they are secured to the ground by nails, dogs, etc., and if necessary, to each other. Spur shores also are recommended, reaching from the fore- side of each block near the ground. to the upper part of the after side of the one in front of it, in order to prevent the blocks from tripping, a casualty which has at times occurred when such precautions have not been taken. The keel rests on short blocks about 10 inches thick which are supported on wedges as shown in Fig. 55. These wedges serve a double purpose. They make it easy to bring the blocks ex- actly up to the line so that each pier supports its proper proportion of the weight and. in addition, when the ship is to be launched they may be readily knocked out of position with a sledge. FIG. 52—RESAWING FRAME JOINTS TO A PROPER FIT