Making Spars for the Schooner Jeanette

Transcription

1 Making Spars for the Schooner Jeanette..... by Byron Rosenbaum Figure 1. Byron Rosenbaum s 1:16-scale radio-controlled model of the schooner Jeanette. All photographs by the builder. The spars required are: (fore to aft) Bowsprit projects six feet forward of the bow peak Jib Boom attached forward to the forestay turnbuckle (Figure 3) Fore Mast with one set of spreaders and an aft sail track (Figure 4) Staysail Boom set on wire from the base of the foremast to mid-mainmast (Figure 5) Main Mast with one set of spreaders and aft sail track (Figure 6) Mainsail Boom attached to the main mast (Figure 7) Boomkin projects five feet aft, to receive a backstay wire (Figure 8) NAUTICAL RESEARCH JOURNAL 3

2 Figure 2. Sail and rigging plan of Byron Rosenbaum s 1:16- scale radio-controlled model of the schooner Jeanette. Bowsprit Solid clear straight grained spruce wood projecting 5 feet (3¾ inches on the model) forward of the stem. The dimen- sion at the aft end is 5 inches square (5/16- inch), continues forward 10 inches (5/8- inch). Aft to fore, the first 2 feet 8 inches (2 inches) is a square shape with beveled edges, until forward of the bow by 2 inches (1/8-inch). Thence forward, the stick is round, tapering from 3½ inches (7/32-inch on the model) in diameter to 3 inches (3/16-inch), then sharply reduced to 2½ inches (5/32-inch) diameter and tapered further to 2 inches (1/8-inch) diameter. A circular metal fitting with four tabs for hardware attachment seats against the last sharp reduction. (Figure 9) The aft end the bowsprit passes through two wooden sampson posts and is secured by a through bolt through the three pieces. Above the stem the bowsprit is anchored down with a metal strap that runs up the stem, over the bowsprit, then down on the opposite side of the stem. The strap is held by several screws through the strap on each side into the stem. The strap has one metal tab, centered on top, that provides a place to fasten the (beginning of) the jib s sheet Figure 3. 4 Vol. 58, No 1 SPRING 2013

3 Figure 5. Figure 4. line. (Figure 10) Four wire cables stabilize the bowsprit, attached to the four tabs of the circular metal fitting. Jib Boom sectional shape, equal to the largest mast diameter specified. The wood is clear straight grained basswood (Sitka spruce is often the choice for real boat wood masts). This differs from the usual solid wood whole tree selection of a real mast. In a model, the laminated method is a good substitute that adds the strength and helps Made from two pieces of opposing straight grain spruce, glued side to side. The length and shape of the boom is shown on the sail plan drawing. It is attached forward to the fore stay turnbuckle with a custom gooseneck fitting. Aft, the boom has an internal sail outhaul sheave. The boom is trimmed using a series of blocks attached to the boom and then, finally, to a deck-mounted traveler. A metal sail track on the boom is used to bend the jib sail to the boom. Fore and Main Masts Construction is four equal full length square section shaped lengths of wood glued together, with the end grain of each piece arranged in a sun burst radial pattern, to make up into a larger square Figure 6. NAUTICAL RESEARCH JOURNAL 5

4 to prevent warping. The centered glue lines help to do the layout for shaping purposes. Getting Out A Mast From Solid Stock by The Commonwealth of Pennsylvania guides me. Figure 7. Figure 8. Step 1: From the glue centerlines, mark the various diameter widths on all four faces at locations called, swell points. Connect the marked points with a long straight edge to define the taper of the mast. Remove the wood to the lines. With the stock mounted in a wood vise, I use a (medium cut) wood rasp to remove the bulk of excess wood. Then finish with a small, sharp, palm-held wood plane. The shaped planes must be parallel and square with the other faces. The mast is now tapered per plan, but still square in section shape. Step 2: Draw a paper layout to change the square shape into an octagonal shape. Using a 45/90 degree triangle, draw two square shapes at 45 degrees to each other, with the lines touching the mast diameter circle at each of the swell points. One diagram is needed for each swell point. (Figure 11) The main mast diameter at deck level is 7¼ inches (29/64-inch) The diameter at the spreader it is 7 inches (7/16-inch) The diameter halfway up to the head is 6¼ inches (25/64-inch) The diameter at the head is 3¾ inches (15/64-inch) Figure 9. Figure 10. Step 3: Mark dots at the eight intersections of the two square figures. Transfer these points to the 6 Vol. 58, No 1 SPRING 2013

5 Figure 20. Figure 11. stock at all the swell points on all faces. Draw the tapered shape on the mast by connecting the points with a long straight edge. Remove the wood outside those lines. The mast is now a tapered octagonal shape. Figure 12. Step 5: Round the mast into a sixteen-sided shape. Divide each octagon face at each swell location into four equal parts: 0, 1, 2, 3, 4. Connect marks 1 and 3 on the four sides. Remove the excess wood. The mast is now a sixteen-sided tapered shape. Step 6: Sand off the pointed ridges. Use a long sanding stick, rotating the strokes over the mast stick and eyeball the shape until round. Follow the same procedure to make the fore mast. The wood masts are left natural to receive a urethane varnish finish. To prevent the wood from becoming dirty, I paint a single coat of clear wood filler on the Figure 13. stock before proceeding further. At the base of the mast, carve a square indented tenon seat, angled for the proper mast rake as shown on the sail plan drawing. Rake is stated on the drawing as 7 inches in 20 feet for the fore mast, and 8½ inches in 20 feet for the main mast. Make NAUTICAL RESEARCH JOURNAL 7

6 Figure 14. a paper layout then, using an adjustable triangle or the paper template, make the tenon angle cuts on the masts. Match this shape to the internal mast receiving seat on top of the keel. Mast Fittings The masts are now marked to receive the mast details. Measure the locations on the scale drawing and, if necessary, convert the dimensions to the model s scale, then make the marks on the stock. For the internal halyard sheave at the mast head, locate and drill one hole for the through bolt that becomes the sheave shaft. Then using, that hole as a guide, locate and drill two holes, at right angles to it, at the top and bottom of the sheave location. Then cut away the connecting wood with a pointed knife. The finished slot hole is completed with a small flat file to make sure the width is accurately sized for the thickness of the sheave, plus the thickness of two thin washers. The bottoms of the slot hole are grooved downward with a round file to keep the halyard line from chafing on the wood as the line enters and leaves the sheave slot. The sheave diameter should match the mast s diameter at the sheave s location. Select the proper diameter brass sheave. Measure the sheave thickness, plus two washers thickness to determine the mast hole width. The hole s slotted length equals twice the sheave diameter. I used a through bolt and nut as the sheave shaft with a washer at both ends. (Figure 12) 8 Vol. 58, No 1 SPRING 2013

7 Locate the spreaders on each mast. For the main mast spreaders, also locate the lifts cheeks. Cutting and carving the wooden main mast spreaders follows the plan dimensions. Use basswood or spruce wood for these parts. The spreaders for the fore mast are metal. Appropriate parts from a metal eyeglass frame were modified and adapted for this use. Custom metal hardware was used to attach the spreaders to the masts. Cheek stops for the loops of the standing rigging wire that encircle the masts are made of spruce wood. A single nail inserted through an angled drilled hole reinforces the glue holding the cheek stop to the masts. The location of these cheeks is shown on the drawing. Bands around the masts for block attachments are made of inch copper sheet. Glue holds them in place, reinforced by the bolts or nails that are used to attach the blocks. The bands around the masts at the gooseneck fittings also carry a series of four belaying pins that surround the masts. These bands and pins are custom made of brass. The Booms These are two-part laminations using spruce wood, glued together side by side. The length and sizes are shown on the sail plan. Locate the many hoops and cleat locations. I like to provide a sheave for each outhaul. The aft end of each boom is slotted to receive a brass sheave of the proper size. Cut the slot to match the sheave width. (Figure 13) Connecting the fore end of a boom to a mast requires allowing the boom controlled freedom to move from side to side and up and down. Hinged gooseneck hardware connections are needed. Fabricating hinges from scratch for a 1:16-scale model is a difficult task, but there are manufactured hinges of a proper size in eyeglass frames. Finding the best shapes that can be used and modified saves a lot of work. Used and broken eyeglass frames usually are discarded and often are available at local eye glass retail stores just ask with a smile and a thank you, then collect the loot free. Getting rid of the plastic casings surrounding the metal parts is not that difficult. Some shapes are more useful than others. Keep your eyes open for shapes that will fit the needs. Grind away the excess to get to usable shapes. Preformed hinge parts from eye glass frames save a lot of labor and function well. Most metals used in these frame are cold-bendable and solderable; all my joints are silver soldered. The U shaped strap that surrounds the boom is custom made. I use copper plate cut and bent to the shape required. Drilled holes are for through bolts to attach it to the boom. The bolts are size. In this gooseneck assembly design I made a brass hoop to surround the mast and added drilled ball-shaped parts to provide seats for the belaying pins. The top of the main pin receives the sail. (Figure 14) The masts and booms are equipped with metal sail tracks. HO-gauge brass track comes in lengths long enough to require no butt seams. The bulbous shape, opposite the T-shape base, is let into the wood of the spars by slotting them in a Jerry-rigged set up. This is done with a table top jig to guide the stick and a device made by Foredom that holds the hand piece in a fixed position. A thin metal cutting disc used in the hand piece grinds out the material along a glue seam line. Tilting the stick as it is fed through the table top jig allows accurate adjustment of the depth of cut. The track is fitted so that the top and bottom stop short of the outer sheave and far enough from the inner end to allow the sail track slides to be slid onto the track. When the marking of stays is completed, holes must be drilled through the track before it is installed in the mast. These holes permit the stay wires passage NAUTICAL RESEARCH JOURNAL 9

8 Figure 15. under the track so as not to interfere with hoisting a sail. When that pre-drilling is completed, insert the mast track into the slot, pressing it into place with the T-shape parallel to the mast. Flood the entry on both sides with glue, being careful to keep it off the vertical metal. The Boomkin This was designed to attach a permanent back stay that would be aft of the long wooden main boom. I designed two side shrouds to stabilize the boomkin to prevent side movement. The two boomkin legs are bolted down to the aft deck. Finishing The set of spars was prepared for the addition of hardware by applying several coats of clear urethane varnish finish, lightly sanded between coats. As far as possible, hardware was attached after all the finishing was completed. (Figure 15) I began modeling with aircraft kits in the late 1930s to the early 1940s. In the mid-1950s through the late 1980s, as an architect, I built models to illustrate proposed designs. My first boat model was built in 1992 after I retired. Many of my models have been boats that a family member either owned or sailed. I now build original designs that are scratch-built radio-controlled sail boats. 10 Vol. 58, No 1 SPRING 2013