The boy mechanic, book 3

by Unknown

Cutting Thin Wooden Disks

Draw the Strip with Its Saw-Tooth Brads around the Center, Cutting Out the Disk

Instead of cutting thin wooden disks with a coping saw, making it necessary to smooth off the circumference of the disk, more satisfactory results may be had by the following method: Determine the center from which the circumference of the disk is to be struck. Drive a nail through a strip of wood about 1 in. wide and ¹⁄₄ in. thick, and into the center of the proposed disk. At a point on the strip, so as to strike the circumference of the disk, drive two sharp brads, as shown in the sectional view of the sketch, arranging them to act as saw teeth, by driving them at an angle, with a slight space between the points. By grasping the end of the strip and drawing it carefully around the center a number of times, the disk may be cut cleanly. By cutting from one side nearly through the board, and then finishing the cut from the other, an especially good job results.—S. E. Woods, Seattle, Wash.

A WISHBONE-MAST
ICE YACHT
by John F. Pjerrou

Large spread of canvas and great speed when running with the wind, or “free”; stability under heavy wind, and adaptability to sailing under conditions similar to those of the common, single-boom-and-sheet ice boat, are the features of the ice yacht shown in the [illustration]. The runner and frame structure is in general typical of ice-boat construction. The double, or wishbone, mast is distinctive, as is the double-boom and sail arrangement, shown in Figs. 1 and 6. The booms are pivoted at the bow of the craft, and controlled at the stern by the usual line and pulley rigging. The booms may be spread so that a V-shaped cavity is afforded for taking the wind when running free, or they may be brought together and both sails manipulated as a single sheet. Reefing and lowering of the sails are accomplished in the usual manner. The framework is very substantial and the proportions are of moderate range, so that the craft may be constructed economically for one or two passengers. The double-boom feature may be omitted if the craft is to be used where little or no opportunity is afforded for running before the wind, by reason of the particular ice areas available. For the experimenter with sailing craft, the wishbone-mast ice yacht affords opportunity for adaptation of the various elements of the craft described, and is a novelty. The dimensions given are for a small yacht, and care must be taken, in adapting the design, to maintain proper proportions for stability and safety. A side view with working dimensions is shown in Fig. 1; inset into it is Fig. 6, showing a front view of the mast and sail arrangement. Figure 2 shows a view of the framework from below. A detail of the fastening of the backbone and runner plank is shown in Fig. 3; a detail of the fastening of the masts and the forward runners into the runner plank, in Fig. 4, and the fixture by which the booms and the yard are attached to the forward end of the backbone, in Fig. 5.

The construction should begin with the making of the lower framework, as shown in Fig. 2 viewed from the lower side. The main frame consists of a backbone, of spruce or white pine, 4 in. thick, 8 in. high at the center, and 16 ft. long, clamped accurately at right angles to a runner plank, of the same material, 2 in. thick, 10 in. wide, and 12 ft. 6 in. long. The backbone is tapered from the middle portion, 5 ft. 6 in. from the forward end, and with a ridge, 8 in. high and 2 ft. 6 in. long, measured from the end of the taper at this end, as shown in Fig. 1. It is tapered to 4 in. at each end, and the bow end is fitted with a three-eye metal ring, as shown in detail in Fig. 5. The runner plank and the backbone are clamped together firmly at their crossing, the backbone being set upon the plank, by means of two strap bolts, with washers and nuts, as shown in detail in Fig. 3. Only the best material should be used in the backbone and runner plank, and the stock should be straight-grained, to give the greatest strength.

The runner plank is tapered down to 8 in. at its ends, to which the guides for the forward runners are fixed. The guides are of straight-grained oak, 1¹⁄₂ by 3 by 14 in., bolted to the runner plank with ⁵⁄₁₆-in. carriage bolts, as shown in the detail sketch, Fig. 4, and in Fig. 2. The guides and the ends of the plank are reinforced with oak chocks, bolted in place at each of the tapered edges of the plank. The forward runners are of oak, 1¹⁄₂ by 5 by 36 in., shaped at their ends as shown, and shod with half-round strap iron. The heads of the screws used for this purpose are countersunk carefully. The runners are pivoted on ⁵⁄₈-in. bolts, the nuts being set to the inner side. Washers and jam nuts should be provided, or the ends of the bolts riveted slightly, to prevent the nuts from becoming loosened.

The stern runner is of oak, 1¹⁄₂ by 5 by 30 in., shod like the forward runners, and is pivoted in a forged wrought-iron hanger. The lower portion of the hanger may be made of a strip of heavy iron, bent into a U-shape, and drilled to receive a ³⁄₈-in. bolt, on which the runner pivots. The U-shaped piece is riveted firmly to a vertical shaft, provided with a heavy rubber washer, protected from wear by a metal one, as indicated at the right in Fig. 1. The upper end of the shaft is threaded to receive a washer and nut. A section of pipe is fitted over the shaft, and the steering handle, fitted to a square section of the shaft, is clamped securely.

The cockpit is fixed to the lower side of the backbone, and is 5 ft. long and 3 ft. wide, with coaming, 4 in. high. It is shown with square corners, since this construction is convenient, though not as good as the type having the ends of the cockpit rounded, and fitted with coaming steamed and bent to the curve. The floor of the cockpit is fastened to the backbone with lag screws, and the coaming is also fastened securely; this construction, if carefully made, will afford ample strength. If desired, especially in larger craft, ribs may be fixed to the backbone, to carry the cockpit.

The runners, the runner plank, and the backbone must be alined carefully, so that they are at right angles, and track properly; otherwise the craft will not keep a true course, and cannot be controlled properly by the rudder runner. The backbone and runner plank are held rigidly by four ¹⁄₄-in. wire-rope stays, shown in Fig. 2. They are fixed to eyes on the bands at the bow, near the ends of the runner plank, and to an eyebolt below the cockpit. The stays are provided with turnbuckles, so that they may be adjusted as required. The bands near the ends of the runner plank are fixed to the lower ends of the masts, as shown in detail in Fig. 4, and are reinforced with oak blocks. The ends of the guy wires are fastened to the eyes by looping them and clamping the resulting eye with steel clamps made for this purpose. Metal thimbles may be fitted into the loop of the rope, to make a better finish; other fastenings may easily be devised by one skilled enough to make such a construction.

The wishbone mast is made of two poles of hickory or ash, 3¹⁄₂ in. thick at the base, and tapered to 2 in. at the top. The poles are joined carefully at the masthead, bolted together, and fitted to an oak breast hook, as shown in Fig. 6. An iron strap reinforces the joint, and an eye, fashioned at its upper end, affords a point of attachment for the forward stay of the mast. The lower ends of the poles forming the mast are fitted into sockets in the runner plank, which is reinforced with mast blocks, as shown in Fig. 4. The ends of the mast, projecting beyond the lower side of the runner plank, are fitted with eye bands, used in guying the runner plank and backbone.

The sails are carried on a yard and two booms, of the same material as the masts, each 16 ft. long, 2³⁄₄ in. at the middle and tapering to 1¹⁄₂ in. at the ends. They are fitted with metal rings at the ends to prevent splitting. The yard and booms are fitted to the backbone at the bow by means of loops bolted to them and engaging an eyebolt and ring on the backbone. The eyebolt is fitted into a slotted plate of ³⁄₁₆-in. sheet iron, and fastened by a lever nut, as shown in Fig. 5. The sheets are fastened to the yard and booms in the usual manner, being fitted with grommets, and tied with line. The yard is suspended from the masthead by means of a line and pulley, the former being cleated to the backbone. The booms are controlled by the operator from the cockpit, by the use of lines and pulleys, similar to the arrangement used on sailboats, except that a duplicate set is required for the additional boom. The lines are cleated on the backbone convenient to the cockpit.

Fig. 1 Fig. 6
Fig. 5	Fig. 2	Fig. 4
Fig. 3		The Wishbone Mast Provides a StrongConstruction of Marked Stability, and theDouble Booms and Sails Permit of GreatSpeed When Running before the Wind.When Tacking, the Sails and Booms areUsed as One Boom and Sheet. Figure 1Shows the Side Elevation; Fig. 2 a View ofthe Lower Side, and the Details are Shownin the Other Figures

The sails are of the lateen type, and should be made of 8-oz. unbleached cotton duck. The breadths are sewn together by lapping one edge over the other about 1 in., and sewing or stitching along the edge. Yard-wide material is satisfactory, and if narrower laps or bights are desired, simply fold over 1 in. of the goods and double-stitch the seam. The bights should run parallel with the after, or leach, edge of the sail, as shown in Fig. 1. Each corner of the sail should be reinforced with a triangular patch of duck, so that it will stand up under the severe strain of winter usage. The edges of the sail may be bound with ¹⁄₄-in. tarred rope, which is not difficult if a sailor’s palm and a diamond-pointed needle are used. Sail twine, well waxed, should be used for the sewing of the sails.

The edges of the sails adjoining the yard and booms are provided with grommet holes by means of which the sails are attached to their supports. The grommets are made by punching holes in the sails, at the proper points, fitting two ³⁄₄-in. brass grommet rings into the holes, one at each side, and overcasting them with a buttonhole stitch. The sail needle and waxed sail twine are used. The reef points are of the usual type, and are made of ¹⁄₈-in. cotton rope, whipped at the ends to prevent raveling, and sewed to the sails at intervals.

The craft is designed to be taken down when not in use, particularly between seasons, and can be stored in comparatively small space, in the knockdown form. The method of setting up the ice yacht will serve to illustrate, also, the method of taking it down, in that the process is practically reversed. First, the backbone is fitted with the forward ring and the strap bolts are fastened at the crossing of the backbone and runner plank. The runners are fitted into place, and the steering rigging is adjusted. The wishbone mast is set into its steps, clamped at its masthead, and the bands fitted to the lower ends. The guy wires at the bottom and that at the masthead are then set, by means of the turnbuckles. The sails are attached to the yard and booms, and the forward end of the latter supports are fixed into place. The pulley at the masthead is fitted with ³⁄₈-in. rope which is fastened to the yard, at the proper point, as indicated in Fig. 1. The rigging by which the booms are controlled is threaded through the pulleys at the stern and the ends fixed on the cleats. The yard may now be hauled up and the craft trimmed so that the sails “set” properly. The halyard is fixed to the yard, as shown, and run through a pulley at the masthead, then down through a second pulley fixed to the runner plank, from which it is conducted to cleats convenient to the operator in the cockpit.

The main sheets are rigged as shown in Fig. 1. The ends of the lines are lashed to the ends of the booms, passed through pulleys, at the stern of the backbone, on the booms, about 1 ft. from the ends, and 5 ft. from the ends, respectively, then down to the cleats at the cockpit. This rigging gives good purchase on the lines and makes it convenient for the operator to attend to the helm and the lines at the same time. The fittings are, as nearly as possible, designed to be standard and may be purchased from ship chandlers, or dealers in marine hardware and fittings. The special metal parts may be made by one of fair mechanical skill, or may be made by local blacksmiths. The woodwork is all comparatively simple. The masts, yard, and booms should be smoothed carefully, sandpapered lightly, and finished with several coats of spar varnish. The other woodwork may be painted suitably, and the metal fittings should be finished with two coats of red lead, or other good paint for use on metals exposed to the weather.

The manipulation of this craft is in general similar to that of the common lateen-rig, or other sail and ice, boats. When running before the wind—free—the booms are separated and the wind acts against the sails in the pocket between them. When tacking, the booms are brought together, and the sails act as one sheet, on a craft of the ordinary type.