A Marblehead Model Sailing Yacht by Claude W. Horst – 1939

Fig. 1. The completed model By Claude William Horst, M.A. Instructor, Extracurricular Boat Building Milwaukee Vocational School, Milwaukee, Wisconsin; Member of Milwaukee Model Yacht Club THE BRUCE PUBLISHING COMPANY MILWAUKEE iealititaieaitiaaie SAILING YACHT itrieune ee MODEL a A MARBLEHEAD A MARBLEHEAD MODEL SAILING YACHT Fig. 3. When cutting out the lifts provide for a lug plate stock (Fig. 2A), using the dimensions as Given on Plate I. With the aid of a try square draw lines through these points and across the template stock (Fig. 2B). The distance given in the half-breadth table for these stations should be measured from the working edge (Fig. 2C). With the aid of a bat- ten, about 4% by 3/16 in. and 4% ft. long. tacked along the points just measured, draw a line through the points. Cut the template on the outside of the line and finish to it. Remove the Y-in. strip, which represents the keel thickness, and the template for lift 7 is ready to use. All other lift templates are made likewise. The Lifts. Select fine-grained, well-seasoned material, finished to 34 in. thickness. One of the edges of the lift stock must be perfectly straight and at right angles with the flat surfaces. This edge will be used as the working edge. Place the straight edge of the template along this edge of the lift stock and draw the outside curve of each lift. Cut away the surplus material and finish very carefully to the line with a plane or a disk sander. and lay out a lug about 1 in. wide to be left at station 6 on lifts 4, 5, 6, and 7. In cutting out the interior of the lifts leave the lugs (Fig. 3) and save the interior stock as it must be put back into its original place for the gluing-up process. By this method no distortion can take place when the clamp pressure is applied. Shellac the interior pieces to prevent glue from adhering to them. Gluing the Lifts Together. To simplify the gluing process make a rack of heavy material ~) ah 2 Material. A Nverevact yee i ion Locate the positions of the stations on the tem- Le i Z| Fig. 4. A glue rack as shown in Figure 4. The pieces are glue fas- tened and they must make a right angle with each other. Mark station 6 on the edge of each outside lift curve and place all the lifts for one hull half on edge and in their proper order on the rack. After the outside curves of all the lifts have been finished check each one of them with its mate to see that they are identical. Then mark Lift 8 is continued full length for gluing with a the interior cuts of all the lift pieces carefully of all the lifts and apply glue to all the contact station 6 very accurately according to Plate I on all lifts. Following the same drawing, mark spacer piece exactly the same thickness as the lift 8 stock. Adjust the lines of all the lifts at station 6 making a straight line across the entire structure (Fig. 5). Mark the overlapping A MARBLEHEAD MODEL SAILING YACHT 9 Fig. 5. The lifts adjusted forming a straight line at station 6 surfaces. Place all lifts from 1 to 8 back on the rack with the interior pieces in place and if necessary nail the front and aft ends of each lift to the rack by driving small nails through the lower corners of the lifts so that the nail Shaping the Outside. First shape both hull halves according to profile as shown in Plate I, which includes shaping the deck sheer line and the rabbet line. Figure 8A shows a batten tacked along the deck sheer to aid in marking it. Figure Fig. 6. All of the clamps applied to the lifts holes will be removed when the halves are shaped to profile. See that the center lugs are in contact with the rack when the clamp is being applied at the center. Then the rest of the clamps should be applied. Figure 6 shows all 7 shows the rabbet line marked at both ends. Figure 8B shows a half shaped to profile. To aid in shaping the contour of the outside, screw a lug to the hull halves by which they may be held in a vise (Fig. 9). Fig. 7. The interior of the glued-up lifts clamps in place and Figure 7 shows the interior of the glued-up lifts. The second hull half is assembled in the same manner. Be sure that its lifts are arranged to make a hull half for the opposite side. Figure 10 gives full-sized station curves from which station templates may be taken directly by using carbon paper and transferring the station curves to the template stock. Locate the stations on the hull according to Plate I and 10 IN A Covering Board NOTE Woe All = MARBLEHEA D s Lifts of 2 Stock. MODEL, SAILING natin YACHT As Kee/ of # Stock 6 Sheer HALF BREADTH SvRAA Ga VABLES ES —— PROFILE. CROSS Breodths SIONS ere are tak en given in from Inches the and Center Line. Hundredths, Plate I Nz and SECTIONS Par : A a wD a L A MARBLEHEAD MODEL SAILING YACHT ll nm Fig. 8B. A half shaped to profile ae uel bs I | 16 Sia Ad ar f +t LZ z 2 inf EET i z SC FEN te coe es Topvor Lead. Bolts. fy LEAD 22° Hinge T ie (a <| oe 4 i Suey = = er Rudder Stock 0.0, Tubing Plate iB 2 sR 28 Section for Metal Plate I Rudder }Ep my SSS Section of Wood Rudder f YACHT. pote Line Length — — oe r—2# Sara uf H 50° MARBLEHEAD 1 : 4 iN TY Line 2 N 1 5 Zi Sed “uke ae ary = Z 5 appeal i ah Uy SUB UST Fa bol ost al a Raber * A pause ome = Hn: al ( — — — —- 9 Drought.— — — — ——T7# eam— —— ¥ Sail Area — — — — 800°" By Claude W. Horst. A MARBLEHEAD MODEL SAILING YACHT 12 = a = - - ie IISMWIS GCS —_ADTM_R”m®’ Fig. 10. The full-sized station templates SSS) GW'%§wwwwfW FF gS 14 A MARBLEHEAD MODEL SAILING YACHT LZ mee SSS SS SS Sv SSswWw cies | y Fig. 10. The full-sized station templates shape the outside to fit the various station templates as they are applied to their proper places on the hull. Figure 11 shows the application of a template. in assembling the hull halves, lugs are left along the keel edge to which clamps are applied later in assembling the two halves. Figure 13 shows Shaping the Inside. To shape the inside, clamp the hull half to the bench top. Then use wedges, lugs, and other clamps to hold the job Template. securely in position (Fig. 12). Check freque ntly for an even thickness. Outside calipers are a great help for this work. It is very little troubl e to remove the hull half for check ing since only one clamp is needed to hold it in place . To aid Fig. 11. The application of a station template A MARBLEHEAD MODEL SAILING YACHT 15 Fig. 9. A lug screwed to the hull half to hold it in a vise a hull half ready for the fin to be attached and top of the stem, but do not cut off the stem top shaped later as shown on Plate I. at this time. Shape the transom and finish the The Backbone Structure. Cut the backbone inside by removing the clamp lugs or the clamp structure somewhat oversize to start with (Fig. ridge, as the case may be. Figure 16 shows the 14). The backbone is made of three pieces and hull completely shaped both inside and out. fastened to either one of the two halves with The Stand. After the shaping has been com- casein glue and '4-in. No. 20 brads. The bot- pleted, a temporary stand should be made to tom edge of the keel must be even with the hold the hull in an upright position during the bottom of the hull-half fin to which it is being rest of the construction process. fastened. stand should be made when the job is finally Fastening the Hull Halves Together. Apply glue to the keel surface of the second hull half A permanent finished. Rudder-Port Hole. Drill the hole through and to the keel which is already attached to the the hull for the rudder port which is made of first half. 3/16-in. I.D. tubing as shown on Plate I. Place the two halves against each other on the bench top making sure that both The Lead Portion of the Fin. Make a split halves are even at the bow. Apply the necessary pattern of a fine-grained wood, for both the left clamps, using several on the fin. Figure 15 shows and right half. The two halves are held together a cross section through one set of lugs. with dowel pins. The pattern must be made very Trim and shape the accurately according to the dimensions given in entire outside of the backbone, including the Completing the Shaping. Plate I. Station templates should be made of Fig. 12. The hull half clamped to the bench top for shaping the interior A MARBLEHEAD MODEL SAILING YACH T 18 ticular about the others. Before using the mold be sure that it is thoroughly dry. Figure may be removed very easily, and is allowed for 24 in the drawing to permit trimming, fittin g, and shows half of the mold ready for use. some lateral balancing. Mark very carefu lly the Casting the Lead. Before pouring the lead, place the bolts in position on frame A with a nut screwed to the lead end. The bolts should location of the holes for the lead bolts on the fin. Bore from the outside of the fin in towar d the center of the hull. Since the fin is narro w great care must be taken that the boring is done accurately. The lead also must line up perfect ly with the fin. Sometimes it is necessary to use a Fig. 26. The mold ready for pouring the lead Fig. 27. Cross section through the hull at the deck beam be held so that the nut will be about the center of the lead. Then place frame B in position on frame A (Fig. 25). Hol d the two frames to- gether with clamps at eac h end, or tie them with wire. Set them on edge as shown in Figure 26 and pour the lead. It is well to melt nearly 11 Ib. as there is more or less waste. Fitting the Lead. from When the lead is removed the mold, or brought back from the foundry, it must be smoothed and weighed. Ii it weighs less than the required 934 lb. it must be recast, first, of course, rechecki ng the pattern for accuracy. A small amount of excess weight A. Sib B Wb C. Rack Treveler Blocks. D. Mest & Shroud * Step. Prlotes. Spinnaker Hook G 4. Deck rattail file and enlarge one side of the hole to accomplish this. When this is done tighten the nuts and then fair-in the lead with the wood part of the fin. Trimming the Boat for Lateral Balance. Re- move lead and apply at least two coats of paint to the outside of the hull. After the last coat is dry attach the lead again and place the hull in a tub of water to check for lateral balance. Since the mast, rigging, deck, and deck beams are not in place the hull will float higher than shown on the drawing. If the thickness of the hull shell is as shown on the drawing, this will be about Beam. Fairlead Ll. Hatch J dSibing Guy Hook. K Steering” 4. Main DECK Quadrant Traveser. Fig. 28. o / aS VIEW SHOWING ARRANGEMENT OF DECK BEAMS. GENERAL FITTINGS AND A MARBLEHEAD MODEL SAILING YACHT 19 3/32 in. at the bow and 1/16 in. at the stern. on the deck piece and, whether the impression If the hull floats slightly too deep after all the is exactly on the center line or not, drill the hole rigging is attached the balancing may be per- on the line. Apply at least three coats of spar fected by using a file and removing the slight varnish to each side of the deck piece leaving a \%-in. border all around on the underside of excess from the fin. If one end or the other floats too deep for correction the pattern will med Hd EIN have to be changed and the lead recast. Fitting the Deck and the Deck Beams. Rab- ve = eH ete, =z} al) nz bet the top edge of the hull so the deck will fit as shown in Figure 27. Put in the deck beams 7 i stiff Wire —— B Fig. 31. Two types of jib travelers. Mainsail travelers are the same except that they are % in. high Fig. 29. The members added under the mast plate placing them as shown in Figure 28, and notching them into the hull as shown in Figure 27. the deck. This border must be kept free of varnish as it must be smeared with glue when the deck is being attached to the hull. 2 | Spinnak Cla Fig. 30. A jib rack =e Add two lengthwise structural members under the mast step (Fig. 29). The deck is made of Sy. eS a [Deck | Sar - | 1-in, board or 1/16-in. plywood. To determine its shape it is advisable to fit a template of heavy paper to the hull and mark out the deck piece from it. Cut holes in the deck piece for the hatch and a slot for the jib rack (Figs. 28 and 30). The Rudder Port. To cut the hole for the rudder port, tack the deck piece temporarily in place, and spot the hole by pushing the rudder tube, which at this stage should be extra long, Fig. 32A. The hatch details Apply at least three coats of paint to the inthrough the hole already drilled through the not to smear any bottom of the hull. When the end of the tube side of the hull being careful is to be attached comes into contact with the deck, tap the other on the top edge where the deck end with a hammer so that an impression will later. Attaching the Deck. Screw the jib rack in be left on the deck piece. This locates the fore e of the deck as shown and aft position of the tube. Draw a center line place on the undersid A MARBLEHEAD MODEL SAILING YACHT the stock is fastened to the blade. The heads in Figure 30 using 1-in. No. 1 roundhead should be countersunk slightly and then rounded 20 screws, Figure 31 shows two types of jib travelers. Either type works very well. Mainsail travelers are made in the same way except they are 34 in. high instead of 3 in. as shown. The travelers may be fastened to the deck with small wood screws or small bolts. Fasten the deck to the hull with 34-in. No. 20 brads and casein glue which is applied to the underside border. Attach the covering boards with /%-in. No. 20 brads. The Hatch. The hatch may be elliptical as shown in Figure 32A or square as shown in Fig- off with a file. If a metal blade is used, bend 26-gauge, nonrusting sheet metal around the stock, and solder it on. The rudder is attached at the bottom as shown in Plate I. To prevent the rudder port from turning, a small plate should be soldered to it at the deck by which it may be fastened. The Adjustable Deck Mast Step. Figure 33 shows a very popular type of adjustable mast step. The rack is made of a piece of T brass the required length, and slotted as shown. The mast ure 32B. Figure 32A shows a coaming around the hatch opening which has a rubber-band gasket stretched around it. The square hatch elim 1 2s7. ilepause Made of ZOD. TubingzZ Long. Slot Lower 5 ze over Slide. i Ferrule End Sloted fo Fit T-Brass 7% Pin Holds the in Position. Fig. 32B. A section through a square hatch Fig. 33. An adjustable mast step shown in Figure 32B has structural members ferrule has a slot which fits over the slotted all around the hatch opening on the underside T-brass rack and a pin which fits into the slots of the deck. This hatch is almost flush with the in the rack and holds the mast in position. deck, being raised above the deck proper only by the thickness of the hatch-cover material. A rubber gasket should be placed between Final Hull Paint. Several coats of enamel or good marine paint should be used on the out- _ the side. It adds a great deal to the appearance of hatch cover and the deck to prevent leaking. the model if the underwater body is painted a The hatch cap of either design is held in place by a spring or a rubber band attached to a wire different color from the topsides. The underwater paint should project about TM%4 in. above hook which in turn is hooked into a screw eye the floating water line of the hull. in the bottom of the hull, as shown (Fig. 32A). The Rudder Port. Drive the rudder port down through the deck and into the keel, allow- ing the tube to project 3g in. above the deck. The rudder blade may be made of wood or metal. The wooden blade has a slight advantage in that its tendency to float reduces friction. For one having metalworking equipment the metal blade is much easier to make. For either type of blade the stock should be made of 3/16-in. O.D. brass tubing with heavy walls. If the blade is of wood the stock should be drilled for the 114-in. No. 20 brads by which The Spars. For the straight-grained spruce. spars choose good Figure 34 shows the mast. Figure 34A shows the details of the upper part of the mast and Figure 34B the take-up. The aft side of the mast to which the mainsail is attached is shaped perfectly straight. The details of the main boom are shown in Figure 35 and those of the jib boom in Figure 36. All collar fittings for the jib and main boom are made of different size tubing as specified on the drawings (Figs. 35A and 36). The fittings are completed by soldering small brass angle pieces to them. The brass angle pieces are made of ~ MODEL SAILING YACHT A MARBLEHEAD ‘si 22 ake Ts i ip Head Board | Jack Line [eel rae ; a Dy Take—Up. a |_Main Halyard oy illo (| oy Rod— N Back— : mY N HE al = a z 5 F/G. 348 Bowser Sta y E r VU, ; Jack Line Screw Eyes it se eee A part. 7 cal ED pe Jack Line: YA a\«— Double Loop Hook. Sib Halyard and Bowser. Head Make Bip Heod Boards 20-Gauge Sheer Aluminam. small the Board —> Drifl Holes 15 across Base for Fastenings. Fig. 34A. simple take-up so that the jack line can be kept good swivel joint permitting the jib boom to taut at all times. Figure 36A shows a simple swing without binding. Nonrusting brads should tack hook made of a 1%-in. No. 16 brad. The be used for all boat work. strap holding the tack hook is made of 20-gauge A combination gooseneck and rubber kicking brass bent as shown and is attached to the jib- strap is shown in Figure 37. This type of kick- boom collar (at 5, Fig. 36A) by a 34-in. No. 16 ing strap works very well and is less subject to brad. This tack-hook arrangement provides a damage because of its flexibility. The mast and 1 tension can be adjusted and the rubber can easily be renewed, which should be done every / & Gooseneck. to Mast Slide. Te Spinnaker Fit Slot 10. Tabing. rubber ends are held between two small metal pieces which in turn are held together by a small 3/64-in. bolt. With this arrangement the Mast Ferrule 10. Tubing. 7% drilled for the boom pin, the spacing pins is the rubber-band attachment. The ‘%-in. rod ch whi supported by 1%-in. I.D. tubing pieces are soldered to the mast bands as shown. The S both ends then is slotted with a hack saw at , and The spreader arms are made of 4%-in. brass rod flattened at one end where small holes are drilled for the shrouds to pass through. The Tubing 1D. Tubing nze rod which gooseneck is made of a 1é-in. bro i all made of brass tubing. The LQ as L boom bands are A MARBLEHEAD MODEL SAILING YACHT © 24 Gooseneck—— |i gi season. a # Rubber Ge lt A-A Ea thy sy KICKING STRAP we al s EA ‘mim and GOOSENECK Ue Fig. 35. Fig. 37. The spinnaker-boom gooseneck is made by soldering a piece of 3/32-in. I.D. tubing to the mast band in which the spinnaker eye pin turns (see Fig. 37). Figure 37A shows a gooseneck with an extension to keep the boom from skying. It is very easy to make and works very other ends of the arms are fitted snugly and soldered in place in holes bored into the collar well. Solder a piece of ‘%-in. I.D. tubing 34 in. head wood screws. which is a piece of tubing the proper size to fit over the mast (Fig. 38). Attaching the Mast Step. long to a piece of %-in. I.D. tubing the same length into which the mast is fitted. At one end of a piece of 4-in. rod, 4% or 5 in. long, drill Tubing #12 make a right-angle bend parallel to the saw cut and at the other end bend a small hook. The Y-in. rod must turn freely in the %-in. I.D. tubing. Out of a piece of 20-gauge brass cut a wedge-shaped piece about 1 in. wide and 1% ey late ES As Drive Into Boom End. Detail of Boom Attechment Tubing $10 yes Metal Wedge Sow Cut coiger ge A. a 1/16-in. hole and cut a slot about 4 in. deep with a hack saw. Then 1 in. from the saw cut Fasten the mast step to the deck beams with 3£-in. No. 3 flat- sia ieee ae sRodZMust Fit riaeseley Into & 1D. Tubing Fig. 37A. A gooseneck and an extension to keep the boom from skying in. long. Drill a 1/16-in. hole at the large end and drive the pointed end into the mast end of The Steering Device. The steering quadrant the boom. The collar will prevent the boom is of the Braine type and is made of 18-gauge from splitting. When the boat is completely metal cut as shown in Figure 39. To the top rigged attach a rubber band to the boom and gooseneck extension. A few trials will determine side of the quadrant solder a short piece of tubing the proper diameter to fit very snugly over the tension necessary to keep the boom from skying. This device works especially well be- the rudder stock. The quadrant is attached to the rudder stock by means of a small pin for cause it swings with the boom. which a hole is drilled through both tube and 25% A MARBLEHEAD MODEL SAILING YACHT Make Brass. 18-Gauge -| 4g of Quadrant | | 20-Gauge Brass. sa Quadrant Quadrant Hook 7g Wire. #2 Rubber i /8-Gauge Metal xx 3 Strip Section B-B. Zi D. Tubing #L ong 3″ Rubber Adjusting Slide ae Quadrant. Soldered to Quadrant. Ss a) Egquo/izer. a Spocer Blocks. Block. [Loeeeer Stock. Fig. 39. The steering quadrant and tension slide stock. A series of small holes, 4 in. apart, are bored in the quadrant for the running-line hooks. The rudder port should extend 3 in. above the deck so as to keep the tension rubber rubber and the quadrant tail it is advisable to use a sheave as shown in Figure 39B. The Sails. Since the sails are the only means of propulsion great care should be exercised in of material, in laying out, in cutbelow any moving part of the quadrant. The the selection the sewing and hemming. Good sail rubber equalizer is made as shown in Figure ting, and in expensive, but it pays to get 39A, using a brass bolt. Fourteen inches of material is rather of the following are considered 1-in. round rubber is necessary for the tension the best. Any silk, longcloth, Egyptian cotton, requirements. This rubber should be renewed good: union every season as it has a tendency to deteriorate. and balloon silk. The yacht should have at least two suits of To do this simply loosen the small bolt and sails, or better still, three, to take care of various separate the plates (Fig. 39, Sec. A-A). weather conditions. The No. 1 suit (Fig. 40) should be the full limit of the allowed sail area — Equa Wee Quadrant Fig. 39A. Sheave. Fig. 39. and be cut somewhat full to be used in light r. The No. 2 suit should be perhaps 10 shown so that each side has its own adjustment. weathe smaller ‘and cut with less roaching to The spacer blocks under the ends are used so the per cent The tension slide is made in two parts as the sails more flat and to be used in sliders will clear the deck. By pushing the ten- make weather. The No. 3 suit should have sion sliders to the extreme forward position the heaviter20 per cent less area than the No. 1 sail quadrant tail will be locked in position between abou bad weather. It is important is for use in them. To reduce friction between the tension and A MARBLEHEAD MODEL SAILING YACHT 26 that the center of effort of suits 2 and 3 check hooks are not necessary on the jib since it is exactly with the center of effort of suit No. 1, attached to the jib boom only at the tack and The laying out of the sails must be done carefully and accurately. Spread out the material on a flat even surface such as a drawing board Rigging the Ship. Along the aft side of the mast and the top side of the main boom, ar- otherwise they will be out of balance. or a piece of plywood, and hold it in place with thumbtacks. Lay out the sails as triangles, drawing first a straight line from the vertex to vertex. Then add the roaching to the leech; a %-in. outward curve to the luff and the foot of the mainsail, and the same to the foot of the jib. This small outward curve on the sails permits them to belly out somewhat instead of being flat. The selvage of the goods should run parallel to the leech. Since the luff and the foot must be bound with cotton ribbon tape, they are cut on the line as laid out, but allowance must be made on the clew. range a series of small screw eyes, or staples, spaced as shown on the drawings, through which the jack lines are passed for attaching the sails to these spars (Figs. 34A and 35). The mast jack line extends from the top of the mainsail to 1% in. above the gooseneck and should have a take-up at the top as shown. These jack lines are made of stainless-steel wire. The jack lines under the main and jib booms, which are used in adjusting sheet bowsers, are made of cord or fishline. They should have a second bowser at one end to hold the desired tension. the leech for a narrow hem about % in. and for a double hem on the head where the sail is fastened to the head board and extra strength is needed. The ribbon tape for the luff and the foot should be preshrunk before it is used by boiling it some five or six minutes. After it is dry crease it with a hot iron along the center for its full length. When sewing it on, be sure to keep the edge of the sail material in the full depth of the crease, so the seam will not pull out, and be careful not to stretch the sail ma- terial while keeping the ribbon taut during the sewing process, otherwise the sail will pucker. Small eyelets should be placed at the tack and the clew of both mainsail and jib to take out Flee Bonscx Ring Fig. 41A. Bowser Fig. 41B. Shrouds and stays when of strong cord or fishline should all have bowsers to hold the tension. Figures 41A and 41B show a hauls and lacings. Battens for both sails are best made of celluloid strips 3/32 by 3/16 in. flat anda ring bowser. If wire or airplane cable is used turnbuckles are more practical. Chain plates and the required length as shown on the draw- (Fig. 42) may be screwed to the edge of the ing (Fig. 40). They are held in place on the sails by pockets made of tape TM% in. wide stitched to the sails at regular intervals. The leech end of the pockets is left open so the batten may be inserted and then a few stitches put in to keep them from coming out. Small hooks of rustproof material, used a) 9) Chain Plate. Fig. 42. by dressmakers, should be sewed to the luff and the foot of the mainsail. These hooks are used to attach the sail to the mast and boom jack lines. These deck into the hull, or screw hooks, spaced as shown in Figure 28, may be used for fastening the shrouds. Halyards may be made of strong – SU A MARBLEHEAD MODEL SAILING YACHT fine cord or of fishline. Bowsers are again used to adjust the tensions. Running-line blocks must have free-turning sheaves and be located as shown in Figures 28 SS Farrleed. Fig. 43. ==, Spinnaker Hook. Fig. 44. and 39. The blocks may be attached to the deck with %-in. No. 1 screws. The boom-running sheet block should be a double-sheave special block so that the sheet lines may be removed without unfastening anything. These are available at most model-boat supply houses. Running-line hooks are made of stiff 1/16-in. wire and bent as shown in Figure 39. For the sheets and the running lines use a light strong fishline. ST 27 Figure 43 shows a fairlead through which the jib steering sheets pass. A good fairlead may be made of a piece of %-in. brass tubing soldered to a small flat base 14 by % in. Figure 44 shows a spinnaker hook made of a piece of stiff 1/16-in. brass wire soldered to a piece of brass }4 by 1 in. Figure 45 shows a deck view with the complete rigging. Spinnaker. The spinnaker is an additional triangular sail used when sailing before the wind. According to the rules the spinnaker has only two restrictions when used; namely, that its boom must not extend more than 12 in. beyond the center of the mast, and its height is limited to the top point of the forward triangle. These meager restrictions permit a great deal of leeway in the shape and the rigging of the spinnaker. Since each design has its own pecu- liarities under weather conditions various spin- naker arrangements should be tried out on a \ Fig. 45. A deck view with the rigging A MARBLEHEAD MODEL SAILING YACHT 29 SAILING TECHNIQUE area of the hull. The pressure of the wind on the sails must be so distributed that a point representing the resultant force, called the cen- Desirable sailing performance of a model boat involves the use of considerable science, but the underlying principles are really quite simple and if they are understood and kept in mind during the period of building and rigging, individual models will have a great deal less tendency to be temperamental. Fig. 49. Template of underwater body Even when a model has been built carefully and accurately according to authentic specifications it is frequently found that it will not hold its course. Sometimes it is the stern and some- Intersecting Center of Medians Effort Determine of each Sail Fig. 50. Determining the center of triangular sails effort, will be almost directly over the times the bow which is blown around causing ter ofl point of the submerged area of the hull, the boat to head into, or away from, the wind. centrad the center of lateral resistance. Holding true to a course requires a perfect calle Center of Lateral Resistance. On authentic balance between the sails and the submerged Reference Line- Mainsail. Area 1/62 Area Maonsatt Sib Finding Sails 162 1B 200 X19 = 2106 X4,252, SONS. 2267.5 22558 = 1.937 Common Center of Effort oF /}———_j3.5+ \ 12X27 +162 2 Finding Area of oX475 & Sails Two ter of Fig. 51. Determining the cen ation bin com sail re enti an effort of Fig. 52. Determining the area of the sails +38 30 A MARBLEHEAD MODEL SAILING YACHT designs the center of lateral resistance will have been accurately determined. It is usually its center of effort is from the reference line. Add together these products and divide by the marked C.L.R. One method of locating it when not indicated, is to cut a silhouette template of sum of the areas of all the sails. The quotient the underwater body of the boat and, using a reference line to the common center of effort pin, find the point where the template will balance (Fig. 49). This point of balance is the center of lateral resistance. Another metho d of locating it is to place the completed but not yet rigged hull in a tub of water and discover the point where a rather sharp stick push ed against obtained will represent the distance from the of the entire sail combination (see calculations in Figs. 51 and 52). If the sails are roached the area of the roaching must be added to the area of the sails and it is found as shown in Figure 53. the side of the hull will move it throu gh the water sidewise without turning it. A line projected down from this point will pass through the center of lateral resistance of the hull. Center of Effort. The cent er of effort is a term applied to the geometri c center of an indi- vidual sail or the calculated cent er, or balancing point, of a combination of sever al sails. To indicate the position of the center of effort on the sail combination, designers usua lly use the circle and cross marked C.E. The center of effort of a triangular sail is determined geom etrically by drawing medians from any two sides (Fig. 50). [ Ly Area 5 = a@ax2bh if + \ a 4 Fig. 53. How the roached area of a sail is figured The point of intersection is the center of effort. To determine the center of effort of two or more triangular sails in combination, first find the center of effort of each sail separately. Then draw what is called a reference line perpendicular to the water line. This line is usually drawn through the tack of the foremost sail. Measure the distance between the reference line and the certer of effort of each sail (Fig. 51). Multiply the area of each sail (Fig. 52) | (Area of a triangle — Base x Altitude ) by the distance Line Two X-Y Divides Triangles. Sail A into and B, Fig. 54. Determining the center of effort of a quadrilateral sail To find the center of effort of any quadrilateral sail, divide the sail into triangles (Fig. 54) and proceed as described for a combination of several sails (Fig. 51). The center of effort for a single sail may also be found quite easily by making a template of the sail and with a pin determine its balance point, which is also its center of effort. The same method used for a combination of several sails will not be accurate, but will give a fair approximation (Fig. 55). Placing the Sails to Secure a Balance Between the Center of Effort and the. Center of Latera l Resistance. Theoretically the mast of the model should be so placed that the center of effort on the sails would be in a perpendicular lire with center of lateral resistance as determin ed on the hull, but the balance is disturbed by a number of other forces. The wind exerts a force against the sails which tends to move the model in a certain direction, depending on the setting of the sails. Any movement of the boat in the water, regardless of direction, which is caused by any power except the movement of the water A MARBLEHEAD MODEL SAILING YACHT 31 GE. Sailing WL mm Normal WL, CLR Fig. 55. Determining the center of effort with a template of the sails Sailing CLR. Fig. 56. Showing the difference between the sailing and non-sailing water line itself, is met by the resistance of the water in its effort to keep the model stationary. This resistance increases inversely as the cube of the speed. Since these two major opposing forces are some distance apart, the resultant center of resistance of the underwater body being some Fig. 57. The center of effort should be slightly forward of the center of lateral resistance 1. The displacement and design of the hull. 2. The area and design of the sails. 3. The setting of the sails and other control factors. 4. The weight and depth of the ballast. 5. The velocity of the wind and the angle at distance below the water line, while the resultant center of the wind’s force on the sails is a considerable distance above the deck. This condition creates a powerful lever in a strong which it strikes the sails. moving the center of lateral resistance either point. wind which actually forces the bow of the model deeper into the water while the aft end is raised a corresponding amount, adding to the submerged area forward and subtracting from it at the after end (Fig. 56). With every change in the velocity of the wind and every change in course which will tend to increase or decrease the effective force of the wind on the sails, the submerged section of the model will change, forward or backward. From the foregoing it follows, then, that it is absolutely impossible to so place the sail com- bination to secure a permanent perfect sailing balance between the center of effort of the sails and the center of lateral resistance of the submerged area. The amount of shift in the center of lateral resistance and the amount of heel at which a model will actually sail depends on many factors of which the following are most important: All of these factors play their part in determining the sailing qualities of the model. The stronger the wind the more the model will heel, and the further it heels the less effective will be the force of the wind, but the more effective as a righting lever will be the weight of the lead on the fin, which is supported at an angle when the model heels. To the righting effort of the lead is added the center of buoyancy of the model which moves outward in the direction of the heel. This force decreases as the deck begins to submerge, but it is a strong factor up to this The relation between the center of effort and the center of lateral resistance is further disturbed by the adjusting of the sails which must be done to meet various sailing situations. As the sails are swung outward the center of effort is moved forward. The effect is far less than that of the forward shift of the center of lateral resistance when the model’s sails are fairly close hauled, nevertheless, it is a factor to be considered, except when sailing before the wind. It follows then, that the center of effort, in- T A MARBLEHEAD MODEL SAILING YACH the eae stead of beinlatgerapllacedresdiistreancctlye, ovsherould be placed 32 steering device is necessary. It is a rubber attachment through which the rudder is actuated center of of r forward, slightly aft some distance farthethe center of Jateral resisthe point to which this by the wind pressure on the sails through sheets, running lines, and a quadrant to which is attached a taut round rubber band whose function is to bring the rudder to its central posi- sailing. For tance is likely to shift when esc ape from the reason there seems to be no ts n sailnever-ending necessary adjustmen wheexpe ri- tion. There are a number of automatic steering ing under changing conditions, although devices ranging from a very simple tiller to ments have shown that most of this shift may be corrected by placing the sail combination so steering quadrants with combinations of complicated that the center of effort is forward of the cal- adjustments. The the more common types may be understood culated center of lateral resistance approxi- from a study of the simple tiller which is noth- Toggle Sheet Line Rudder functioning of all Screw Eye. Stock Traveler Band D, Rubber Boat Deck: Fig. 58. A simple automatic steering device mately 4 per cent of the water-line length of the hull (Fig. 57). The Sliding Mast Step. Since the relation- ship between the center of effort and the center of lateral resistance cannot be a fixed point due to changing sailing conditions, the use of a sliding mast plate and jib rack is recommended so the whole sail combination may be moved for- ing more than a small beam attached near the center of its length to the rudder stock. The mainsail sheet is attached to the aft end of the beam and a rubber band to the front end (Fig. . 58). As the wind pressure on the mainsail in- creases, the pull on the sheet line increases, pulling the rudder with it, which in turn pre- vents the aft end from swinging around with Line Slack. No Pressure on Sails. CE aehes Pull on Sheet Line Turns. Pressure Rudder, Fig. 59. How the simple automatic steering device works ward or aft to secure a more delicate sailing balance. The Automatic Steering Device. To aid in controlling the course of a model an automatic the wind, or causing the yacht to head into the wind. As the wind pressure decreases, the pull on the rubber band brings the rudder back to its central position (Fig. 59). 34 CHT A MARBLEHEAD MODEL SAILING YA | ”) Fig. 64. Fig. 65. Mainsail steering resistance when the boat is at rest, but it should be remembered that the estimated 4 per cent of the water-line length of the hull is seldom accurate for any given model. The most efficient setting of the sails for sailing at various angles to the direction of the wind can only be done by actual experiment, but a few diagrams may not be out of place at Figure 62 shows the yacht still close hauled with the sails trimmed to make an angle of about 30 deg. with the wind for a close reach. Since very little rudder action is necessary to hold the yacht on its course, jib steering is very effective over a small range and is commonly used for close reaching. Figure 63 shows the arrangement for jib steering. gee this point. The direction of the wind remains the same for all the illustrations but the yacht is shown sailing at various angles to the wind with the sails trimmed for each course. Figure 60 shows the yacht with the sails close hauled beating about 15 deg. on the wind with the sails eee Je trimmed about 5 deg. with the wind. It is understood, of course, that no sailing craft of any kind can sail straight into the wind, and that all must sail at some angle to it. The angle varies, with the yacht, the trim of the sails, and the velocity of the wind. A yacht can be pointed higher into the wind in heavy weather because the lateral resistance increases with the speed of the yacht through the water. The stronger the wind the better the yacht will beat. For beating, the sails are close hauled with the sheets attached to the travelers as shown in Figure 61 and the rudder is not used, but is locked in a central position. | Fig. 66. Yacht on a broad reach Figure 64 shows the yacht reaching with the sails trimmed to make an angle of about 50 deg. with the wind. The jib is now hooked to the traveler as it is unable to handle the steer- ing, and the mainsail is attached to the rudder quadrant through the boom running sheets. Figure 65 shows the arrangement. Figure 66 shows the yacht on a broad reach A MARBLEHEAD MODEL SAILING YACHT 35 with the sails trimmed to make an angle of boom and the rudder. The jib is likewise fully about 75 deg. with the wind. Here again main- let out but it is of practically no value unless it sail steering is used. The arrangement is similar to that shown in Figure 65 except that the boom is swung farther outward. Reaching is more is swung over to a wing and wing position as difficult to control than beating and a great deal of experimentation usually needs to be done using many different combinations involving quadrant, sheet, rudder-tension, and slide ad- ignes! —_~ justments, and the like. ee Wind Figure 67 shows the yacht on a run. In this part = aaeet a — ree, sik YW AN ANS \ iN Fig. 68. Wing and wing position Fig. 67. A yacht on a run case the boom is let out approximately 80 deg. shown in Figure 68. On a run a spinnaker can to the center line of the boat, being careful that also be used if the winds are steady. Figure 69 the stays do not interfere with the action of the shows the spinnaker arrangement. The spin- Occasionally Mainsail Swings re | /f{ . Speget Wt will \ will Operate Rudder Sheet ll/is Hooked Since be /dle. to Outside of Quadrant giving it the Turning the Maximum Leverage fof Rudder, Causing the /Boat to continue aces Side. When this happens Sheet = ean pinnaker always Boom on a Left Turn untjl the Mainsail again Swings te Starbodd when the Boat will again Follow its Original Course. BS “7% When Mainsail is Set To Starboard. Sheet, ll Operates SB Rudder. Sheet Il is /dle. Fig. 69. Spinnaker arrangement 18 Set Forward A MARBLEHEAD MODEL SAI LING YACHT naker boom is always set opposite of the main- sail and forward of the mast. It is held forward by a rubber band which is fastened to the outer end of the boom and then attached to the jib rack. The spinnaker peak is attached to the jib halyard hook. The spinnaker sheets must have bowsers for adjustments. When running, the rudder plays a most important part as a greater amount of turning effort of the sails is 37 to move the mast aft and restep it. Rather than do that it is often easier to try some other method of accomplishing the same result. 2. The center of effort of the sail combination may be moved aft by moving the jib aft, or by making a new and larger mainsail and decreas- ing the size of the jib accordingly. exerted on the hull. To make the steering more effective the idle running sheet should be hooked at the extreme end of the quadrant to jibe the boat back on its course in the event of the boom swinging over the opposite side. Figure 69 shows a top view and Figure 70 a perspective view arrangement. Figure 71 shows the jibing guy which is used for bringing the boat about rather than for making a long tack. This arrangement is very effective for looping over the finish line which would otherwise mean a long tack. Figure 71A shows the course that would be taken Fig. 72. The sail combination too far forward without the use of the guy and the short circular course taken when the guy is used to bring 3. The center of lateral resistance may be the boat about putting her on the opposite tack. moved forward by decreasing the blade area of The course taken with the use of the guy is the rudder. This is often sufficient if the correc- much shorter than the one which must be taken tion needed is not too great. 4. The area of the fin may be decreased by without it as shown. Improving the Sailing Qualities of a Model. A model already built which consistently heads cutting away the aft end and this has the same effect. into or away from the wind instead of keeping 5. The entire shape of the underwater body its course is by no means hopeless, as any one may be changed by making a new fin which of several things may be done to correct the extends further forward, if a thin fin, which can difficulty, be replaced without any great effort, has been once the underlying causes are used. understood. The Model Which Heads Away From the Wind (falls off). As already explained this con- 6. Sometimes a combination of several different corrections may be used. dition is due to the position of the sail combination being too far forward which causes the front end to be blown around with the wind Conversely this condition is due to the position (Fig. 72). the aft end of the boat to be blown around with 1. The most fundamental correction, of course. is to move the whole sail combination aft. This is easily done if an adjustable mast step has been used in the construction of the model. If the correction is small increase the aft rake of the mast, otherwise it is necessary The Model Which Heads Into the Wind of the sail combination too far aft which causes the wind (Fig. 73). The corrections are just the reverse of those already given. 1. If the correction is small decrease the aft rake of the mast. 2. Move the jib forward. 3. Move the whole sail combination forward. T A MARBLEHEAD MODEL SAILING YACH s Bc been: e mast step haple If an adjustabl s is not the sim st cot ‘a 38 this sometime sail combina 4. The center of effort of the mak ing a new tion may be shifted forward bythe size of the and larger jib and decreasing mainsail accordingly. made longer or deeper or both. There is no remedy for a small amount of crabbing in light winds; all yachts do it more or less. Repair Kit. for a sail, Whenever the yacht is taken out especially when participating in a contest, it is advisable to take along a small / Sea Fig. 73. The sail combination too far aft 74 shows the effect of the proper balance. The Model Which Moves Sidewise Through the Water. This peculiarity, called crabbing, is sometimes noticeable in a boat that is sailing in a direction other than before the wind. It indicates that the model is not making sufficient headway or does not have sufficient submerged area to counteract the natural tendency of the wind to move an object in a straight line before it. The deeper the submerged body the harder it is for the wind to move the boat sidewise and the sails then can utilize the force of the wind to move the model ahead. A model built with insufficient underwater body may be improved by increasing the size of the fin which may be turnbuckles, thread, and a sponge for soaking up any water that may get in through the hatch. Key to Fittings Jib rack. Jib boom. Jib traveler. Mast. Blocks. Steering quadrant. Jib steering sheets. Main boom. Main traveler. Beating sheets. . Running sheets. . Jibing guy. . Spinnaker. . Spinnaker boom. . Spinnaker sheets. . Spinnaker-sheet hooks. . Rubber band. re 7. If feasible a new fin which extends further aft may be made. It will accomplish the same purpose in an even more marked degree. Figure spare parts, such as stay wire or cord, bowsers, SIAN FP WBNHH OO ONAN BP WY 6. The area of the fin may be decreased by cutting away the forward end of the fin to shift the center of lateral resistance aft. box containing a few tools, such as pliers, screw driver, sewing needles, small wrench, etc., and ee 5. The center of lateral resistance may be by increasing the blade area of the rudder. shifted Fig. 74. The sail combination in proper balance INDEX Backbone structure, 15 Beating close hauled, 33 Mainsail steering, 34 Mast step, adjustable, 20; sliding, 32 Mold, lead, for fin, 16 Center of effort, 30, 31 Center of lateral resistance, 29 Paint, final hull, 20 Deck, attaching, 19; fitting, 19 Repair kit, 38 Deck beams, fitting, 19 Rigging the ship, 26, 27 Fin, lead mold for, 16; lead portion of, 15; Rudder-port hole, 15 mold for lead, 16 Rudder port, 19, 20 : Gluing, lifts, 8 Sail, area of, 29, 30 Sail arrangement, 21 Hatch, 20 Sailing technique, 29 Hull halves, fastening together, 15 Sails, 25; placing to secure proper balance, 30 Shaping, completing, 15; inside, 14; outside, 9 Jib-boom rigging, 23 Jib steering, 33 Sliding mast step, 32 Jibing guy, 36 Sailing qualities, improving, 31 Spars, 20 Spinnaker, 27, 28; arrangement, 35; attachment, 36 Stand, the, 15; suggestions, 28 Steering, mainsail, 34 Kicking strap, 24 Steering device, 24; automatic, 32 Lateral balance, trimming boat for, 18 Steering quadrant, 25 Lateral resistance, center, 29 Lead, casting, 18; fitting, 18 Lead portion of fin, 15 Templates, developing, 7; full-sized station, 12, TorelA Slitte7 Lift templates, 7 Lifts, 8; gluing, 8 39