Wishbone-Mast Ice Yacht: 16 ft Backbone, Twin-Pole Mast and Double Lateen Booms (Boy Mechanic, 1919)

"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."

Use only the best straight-grained spruce or white pine. Backbone: 4 in thick, 16 ft long and 8 in high at the centre, with a ridge 8 in high and 2 ft 6 in long; taper it from the middle, 5 ft 6 in from the forward end, to 4 in at each end, and fit a three-eye metal ring at the bow (Figs. 1, 5). Runner plank: 2 in thick, 10 in wide, 12 ft 6 in long, tapered to 8 in at the ends. Set the backbone on the plank at right angles, 6 ft from the bow, and clamp them with two strap bolts, washers and nuts (Figs. 2, 3).

Bolt guides of straight-grained oak, 1-1/2 by 3 by 14 in, to the plank ends with 5/16 in carriage bolts, and bolt oak chocks at each tapered edge (Fig. 4). Make the forward runners of oak, 1-1/2 by 5 by 36 in, shaped at the ends as drawn, and shoe them with half-round strap iron held by screws with carefully countersunk heads. Pivot them on 5/8 in bolts (5 in long in Fig. 1), nuts to the inner side, with washers and jam nuts, or rivet the bolt ends slightly so the nuts cannot work loose.

Make the stern runner of oak, 1-1/2 by 5 by 30 in, shod like the others. Pivot it on a 3/8 in bolt in a hanger of heavy iron strip bent into a U and riveted to a vertical shaft. Put a heavy rubber washer, protected by a metal one, on the shaft; thread its upper end for a washer and nut, slip a section of pipe over the shaft, and clamp the steering handle (2 ft 10 in in Fig. 1) on a squared part of the shaft. The hanger may be forged, or made by a blacksmith.

Fix a cockpit 5 ft long and 3 ft wide, with 4 in coaming, to the lower side of the backbone toward the stern; fasten its floor to the backbone with lag screws and fasten the coaming securely. Square corners are easiest; rounded ends with steamed, bent coaming are better. Larger craft may carry it on ribs.

Line up runners, plank and backbone at right angles so the craft tracks true. Hold them with four 1/4 in wire-rope stays with turnbuckles, from eyes on the bow band and on the bands at the plank ends to an eyebolt below the cockpit (Fig. 2). Loop each rope end and clamp the eye with steel clamps made for the purpose (wire-rope clips); metal thimbles in the loops make a better finish.

Shape two poles of hickory or ash, 3-1/2 in thick at the base and 2 in at the top (12 ft in Fig. 6). Join them carefully at the masthead, bolt them together into an oak breast hook, and reinforce the joint with an iron strap with an eye at its upper end for the forward stay. Step the lower ends in sockets in the runner plank, about 8 ft apart, reinforced with oak mast blocks, and fit their projecting ends with 3 in two-eyed bands for the stays (Figs. 4, 6).

Make the yard and two booms of hickory or ash, each 16 ft long, 2-3/4 in at the middle tapering to 1-1/2 in at the ends, with metal rings on the ends against splitting. Bolt loops to their forward ends to engage an eyebolt and ring on the backbone at the bow; set the eyebolt in a slotted plate of 3/16 in sheet iron, fastened by a lever nut (Fig. 5).

Make two lateen sails of 8-oz unbleached cotton duck: lap the breadths about 1 in and stitch along the edge (or fold 1 in and double-stitch), the seams parallel to the leech. Reinforce each corner with a triangular patch of duck and bind the edges with 1/4 in tarred rope, using a sailor's palm, a diamond-pointed needle and sail twine, well waxed (the wax is ours: beeswax). Along the yard and boom edges punch holes, set two 3/4 in brass grommet rings in each, one each side, and overcast them with buttonhole stitch. Sew in reef points of 1/8 in cotton rope, whipped at the ends.

Fit the forward ring and strap bolts, the runners and steering, then step the mast, clamp the masthead and fit the bands; set the bottom stays and the masthead stay with the turnbuckles. Lace the sails to yard and booms and fix the forward ends at the bow. Run a 3/8 in halyard from the yard through a pulley at the masthead and a second on the runner plank to cleats by the cockpit, and haul up so the sails set. Lash the main sheets to the boom ends, through pulleys at the stern of the backbone and on the booms about 1 ft and 5 ft from their ends, then to cleats at the cockpit; the second boom needs a duplicate set. Taking down is the reverse.

Smooth the masts, yard and booms, sandpaper them lightly and give them several coats of spar varnish; paint the other woodwork. He gives the metal fittings two coats of red lead "or other good paint for use on metals exposed to the weather": red lead is a lead poison, so use the other paint.

From "A Wishbone-Mast Ice Yacht" by John F. Pjerrou, in **The Boy Mechanic, Book 3**, Popular Mechanics, 1919 (Project Gutenberg 71856; checked on the archive.org scan boymechanic0003unse, pp. 17-20). He gives no sail outline sizes. The tools, the metric figures and the choice of the non-lead paint he allows are ours.