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MODELING
Three secrets of the mast. Tips for a modeller
Directory / Radio control equipment The mast is the "foundation" of the ship's sailing armament, its main node. The role of the mast is multifunctional, the area, configuration and aerodynamics of the sails, the ability to control their thrust, the location of the centerboard and much more depend on its design and location on the ship. So the choice of the type and design of the mast predetermines both the design features of the vessel and the level of efficiency of its sails. This choice becomes more complicated when creating a small collapsible vessel, when one has to "reconcile" such contradictory requirements as the strength and reliability of parts with their minimum weight and compact packaging of a disassembled vessel. Especially when constructing a mast. The main tasks that are solved in this case are the following: the choice of the type of mast and materials for its manufacture, the choice of its design option (including the method of attaching the mainsail) and, finally, the choice of the step design. Secret one: choosing the type of mast Less than that of a "solid" ship, the strength of the hull of a small sailboat makes it necessary to increase the strength of the mast. The task of keeping its weight to a minimum narrows down the range of suitable materials. So, wooden masts are too heavy, warp and rot from moisture, are difficult to manufacture, and it is not easy to get high-quality wood for them. The same, except for "rabies", can be said about homemade fiberglass masts. Therefore, thin-walled duralumin pipes became the most suitable material. Especially after small sail enthusiasts have mastered two operations: assembling an overhead lip-pause and turning the mast into a truss. The latter significantly improves the strength/weight ratio. The mast is placed on the ship either with side and bow braces - shrouds and forestay (Fig. 1a), or with side braces (Fig. 1b), or freely (Fig. 1c) and fastened at two points. The location of the lower point (steps) does not depend on the type of mast, the upper one depends on: for a free one, this is a pärtners - a hole in the cross beam; for unfastened - the attachment points of braces or shrouds with a headstay, located above the partners. The shrouds significantly reduce the load on the mast and hull of the vessel (but complicate their design). The angle between each shroud and the vertical shall be at least 11°.
It is possible to turn ordinary masts into truss masts (Fig. 2) with the help of three stretch marks from a steel cable with a diameter of 2-3 mm - a rhombus and transverse struts - spreaders. (The stiffness of the truss will increase if two rows of spreaders are installed.) The angle between the diamond blades and the mast must be at least 8°.
Rhombuses can be used to adjust the bend of the mast, thereby changing the profile of the mainsail and, as a result, its draft. Do this with a screw lanyard. By turning the lanyard body, it is shortened or lengthened, and the rhombovant attached to it simultaneously changes the pressure on the spreader and, thereby, the mast bend. The overhead lippaz is assembled from a thin-walled U-shaped aluminum profile used in construction for fixing window panes. It is given the desired shape with a hammer and mandrels (Fig. 4) or by drawing between two rollers with grooves of the corresponding shape. Finished sections of the processed profile are attached to the mast with screws or self-tapping screws with a diameter of 3-4 mm. Holes for screws are drilled before the deformation of the profile begins.
The thrust of the mainsail depends on the way it is connected to the mast. Since a small vessel has a small sail area, and the drag of the hull and crew is relatively large, such an unfavorable ratio (compared to a large yacht) impairs the ability of a small vessel to move into the wind. Therefore, it is important to observe two "not". Firstly, do not allow gaps between the mast and the mainsail, because the air breaking through them from the windward side of the sail significantly reduces thrust, especially on sharp courses. This happens if the mainsail is mounted on rings (Fig. 3a), segar loops, lacing or sliders sliding along a rail attached to the mast. There will be no "holes" if the mainsail is fixed in a lippase - a longitudinal slot on the back side of the mast (Fig. 3b). Secondly, do not create a ledge between the mast and the mainsail, because a violation of the smoothness of the sail profile, especially at its beginning, also worsens traction. This issue is being addressed in stages. A drop-shaped mast helps to improve the smoothness of the profile, which is difficult to get or manufacture. But you can make the mast swivel, then the step between it and the mainsail will be lower. And if you use a pocket, then the sail profile will become completely smooth (Fig. 3c). Of course, the easiest way is to make the free mast turn. And what about the braced one? At first glance, the stay and shrouds interfere here. But if the fastening of the shrouds is moved to one point (Fig. 5b), then the mast will be able to turn left-right by 15-20°, which is quite enough. With the pocket mount of the mainsail, too, not everything is simple, since it gives rise to a whole bunch of problems. It is known that the mast better resists loads, including from the staysail, if its shrouds and stay are attached not to the top, but below it at a distance equal to 0,12-0,25 of the length of the mast. It is desirable to place the stay below the shrouds, in extreme cases - at the same level. So, the pocket on the mainsail forces you to attach the shrouds and stay only to the top and use only the top staysail, which loads the mast to the maximum. The same pocket does not allow equipping the mast with rhomboids, so it is necessary to significantly increase its strength and rigidity, and thereby its weight. Secret two: the choice of mast design The articulation of the mast knees (Fig. 6) depends on the method of attaching the mainsail to it. Option "a" - universal; "b" is used, as a rule, for a free mast; option "c" - for unfastened with lipase. The links of the lipase must be properly joined, therefore, during assembly, adjacent knees must be fixed in a strictly defined position. The simplest option is with the help of a screw head or a rivet that enters the slot on the lower end of the upper knee (Fig. 6, pos. 6).
The strength of the mast is also affected by the way the boom is attached to it. In particular, a thin-walled mast "does not like" to be perforated. This is taken into account in the presented version (Fig. 7). The boom is attached to the mast with an enclosing collar, which is easy to fix at the desired height.
You can attach the lower luff of the mainsail to the boom either with a lippaz or with a pocket (the latter is easier here - it does not create any difficulties). A cutout is made in the pocket for the passage of the boom guy, which is necessary for Bermuda, hafel (including guari), sprint and sometimes rake (if the luff is attached to the boom, and not to the rail) grottoes. It is best to tighten the stay, shrouds and guy line of the boom with the help of a soft lanyard - a nylon end with a diameter of 3,5-5 mm, passed several times between two rings; with a sail area of more than 10 m2, screw lanyards can be used. The third secret: the choice of step design If the mast does not have to turn, as in the rake and Latin grottoes, the holes in the steps are made rectangular or square (Fig. 8a). Spurs in these holes can enter either tightly or with a gap of 3-5 mm on the side. Steps installed on the transverse or longitudinal beams of inflatable boats and rafts, catamarans and trimarans allow, if necessary, to lay the mast horizontally in any direction (Fig. 8c).
Briefly about the application of the considered structures. For masts, pipes made of D16 or D16T alloys are usually used with a diameter of 35-70 mm and a wall thickness of 1,5-2 mm, less often - 2,5 mm. With a grotto area of less than 4,5 m2, rhomboids are unprofitable: some weight savings do not justify the costs of labor, materials, and, most importantly, time for their assembly and disassembly. The mainsail is fixed with a pocket, first of all, in the armament of the KET (mast plus mainsail) with a free mast, especially with windage up to 4 m2. Such a solution gives the maximum effect: the advantages of the design work, and there is nowhere for the disadvantages to appear - there is no staysail and shrouds. In addition, it makes sense to use a pocket on the mainsails in types of weapons with a short mast: hafel, sprint, latin and rake. The advantages of such a solution significantly outweigh the disadvantages: the top staysail, although it has the maximum possible area, does not load the hull too much. In this case, the mast is most often free, since the difference in weight with the unfastened one is relatively small. It is easy to take it off and put it on, put a grotto on it. A free mast is often used in an intermediate version, when the main windage - the armament of the KET - is supplemented with a light staysail in light wind (that is, they are converted into armament of the SLIP). At the same time, the staysail does not create large loads and the mast is relatively light. A few words about gear Standing rigging (shrouds and headstay, rhombus) use steel - it does not stretch, it is thin enough, which means it has a small parasitic windage. Usually these are galvanized or stainless steel cables with a diameter of 2-3 mm. At worst - just a wire with a diameter of 2-2,5 mm. It is stronger, but can suddenly break (usually near the fire - a point at the end of the tackle). The cable “warns” about destruction: at first, its individual wires break. Running rigging - halyards (rigging for raising sails), sheets (for sail control), tacks and quickdraws are made from vegetable or synthetic (most often nylon) cables. The latter are preferable, they are more durable and are not afraid of moisture. The halyards are made from a braided cord type, since the twisted one (usually of three strands) stretches under load and the sails "sink", losing their shape. A cable with a core of a bundle of threads in a thick and strong sheath is allowed, such that when the halyard is stretched under load and then compressed without load, the core threads do not break through the sheath. The diameter of the halyards is 6-10 mm (with a grotto area of more than 7 m2, the halyard is sometimes made of steel cable). Sheets have a diameter of 8-12 mm. It is also possible to make them, especially with a small sail area, from a twisted cable, the hood is not so important here, but it is more convenient to hold in your hands. Good staysail sheets are made from polypropylene rope, it is noticeably lighter than others, which improves the control of the staysail in light winds. The sail area of a single-hull vessel can be approximately determined by the formula: Smax=kLB, where Smax is the allowable sail area; k - coefficient of stability (depends on the design of the vessel: for kayaks k=0,6...0,7, for inflatable boats k=0,7...1, for rowing boats k= 1...1,2); L and B are the length and width of the vessel along the waterline. Depending on the characteristics of the vessel, the result obtained can be adjusted. But it is not safe to "inflate" the windage. It is better, dividing it into main and additional, to expand the sailing "wardrobe", using main sails in medium wind, additional - in weak, stormy - in fresh weather (first of all, the mainsail, the area of \u2b\u3bwhich should be XNUMX-XNUMX times less than at the main). Sometimes a staysail is used instead of a storm mainsail if its area is suitable and its strength is sufficient. As additional sails, first of all, staysails with an increased area and from a lighter (than the main) fabric are used. With a main sail area of up to 6 m2, it is possible to increase the "wardrobe" without significant financial costs and at relatively low labor costs - due to staysails made of ordinary polyethylene film. Author: Yu.Kuzhel
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Comments on the article: Valery A very useful read for the teapot. I decided to make the simplest sailing equipment for the boat, like a centerboard with a sail of 1.5 square meters. It turned out I don’t even know what it’s called. Thanks to the author.
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