Cruising and racing sailboats of the quarter-ton IOR class have already gained quite wide popularity among the sailboatsmen of our country. .The indisputable advantages of sailboats of this class include relatively low cost, small overall dimensions and draft, the ability to maintain the vessel and manage it with a small crew. In the annual competitions for the Onega Lake Cup, for example, more than 30 sailboats start in this class. Representative are also the races held with the participation of quarter-tonners on the Black Sea, on the Volga and in a number ofe other regions of the country. In the last two or three years, almost all these competitions are dominated by the Konrad-25 type sailboats (Polish built), which, being quite difficult to manage and adjust, require constant attention of the crew to maintain maximum speed.
Basic data of the sailboat "ST-25"
|Overall length / on design waterline, m||7.62/6.00|
|Width overall / on design waterline, m||2.70/1.98|
|Displacement in the state of measurement, t||1.34|
|Fake weight, t||0.54|
|Sail area (mainsail + 150% staysail), m||37.0|
Ideas underlying the project
Produced at the Tallinn Experimental Shipyard of Sports Shipbuilding since 1973, the quarter-ton wooden structure is obsolete. In order to achieve good results in racing, these sailboats are upgraded by individual enthusiasts. Thus, the designers of the student design bureau "Yakhta" at the Nikolaev Shipbuilding Institute, who have been engaged in the modernization of the project for several years, have achieved a significant improvement in the racing qualities of sailboats. However, there is clearly a need to create a new, more moderna small quarter-ton project that would use the latest research in the field of hydroaerodynamics of sailboats and the experience of cruising races. Such a project was developed by the joint efforts of the designers of the Tallinn Shipyard and SKB Okean of the Leningrad Shipbuilding Institute. The development of a technical design for a new sailboat in this SKB (under an agreement with the shipyard) was accompanied by experimental studies in the field of hydromechanics, aerodynamics and ergonomics, as well as a comparative analysis of the design characteristicsa large number of foreign analogue sailboats. General trends in the development of this class were identified, those features of the sailboat that can be considered promising: these are high power-to-weight ratio with sails, low displacement, 7/8-type rigging with a developed mainsail, a slightly increased IOR racing score of 5.5 m.
The new quarter-ton boat, which received the ST-25 index (sports and tourist, 25 is the largest hull length in feet), has an architecture typical of modern cruising and racing sailboats. Characterized by a low freeboard, a developed aft overhang, a large camber, a short high deckhouse and a long, open cockpit from the stern. The keel line has a smooth rise in the bow and a gentle, with a slight bend, exit in the stern. Experiments in the LCI basin have shown that such a hull shape is most advantageous at the design speed. At the same time, in full coursesThe surf mode can be easily achieved, which is also facilitated by the wide flat stern. On sharp courses, both careful trimming and heeling of the sailboat by the crew are necessary to achieve maximum speed. To improve driving performance in light winds, all measures were taken to reduce the wetted surface of the hull through the use of radial contours of the frames in the underwater part.
The technological processes mastered at TEVSS determined the main design features of the project. The fiberglass hull, glued in the matrix, has a skin of variable thickness, reinforced with a transverse set. In the cheekbone area, the frames rest on a stringer, which is also a support for the bed decking. The middle part of the bottom plating is reinforced with developed fiberglass floors that take the load from the ballast headboard. Eyelets are also installed here, for which slings are attached when lifting and lowering the sailboat. deck, haveThree-layer construction with foam core, supported by three transverse frames and pillars under the cockpit. The outer surface of the flooring has a non-slip coating made directly in the matrix. In the future, it will probably be possible to apply a sandwich construction for the hull, which will reduce the labor intensity of building a sailboat and achieve a reduction in the weight of the hull.
The sailboat is equipped with four permanent berths - two sofas in the central part and a double bunk located forward of the mast (it is used to store sails on the move). The galley is located near the midships, which ensures the convenience of cooking and good ventilation. A dining table can be fixed in the galley berth; during races and campaigns, it is stored under the cockpit and, when extended, is used as a navigator. On the starboard side under the cockpit there is a place for wet clothes.
In general, the level of comfort on our sailboat seems to be higher than on the racing version of the Konrad-25. The felling is large; the size of the entrance hatch has also been increased, since in racing it is used for supplying and cleaning sails. The forluk is significantly reduced, since it serves mainly for ventilation.
The deck layout is typical of a modern racing sailboat. To adjust the front sails, two pairs of transverse shoulder straps are used (a scheme that has proven itself well on the Forward monoton). All halyards are brought out to the wheelhouse in the area of the entrance hatch, where cam stops on ball bearings are installed. The developed epaulette of the boom-sheet is located in the center of the cockpit; the running ends of the backstay and backstay hoists are also brought here. The applied rigging scheme allows for fine-tuning of weapons depending on the course of the sailboat and speed.awns of the wind.
It should be noted that at present in foreign sailboat building there has been a tendency towards a narrow specialization of sailboats according to their main purpose. All ton class sailboats are designed, built and used exclusively for competitions, and their cruising versions, although they are often created on the basis of the same hulls, differ from racing ones in deck layout, equipment and general arrangement. When creating our project, we took into account that the same sailboats will be used for purely cruising, as well as the fact thatRatsmen during long competitions live on sailboats and need a certain comfort. Therefore, the final version of the ST-25 is a compromise solution with all its advantages and disadvantages. However, the preference is still given to racing qualities, so you can expect the sailboat to be quite strong in the races. This is confirmed by the fifth place taken by the lead sailboat "Polaris" in her first competition among 27 participants in the traditional regatta in Muhu-Väina. This is the success of both the "Ocean" complex and the TEVSS team, withwho created a sailboat of excellent quality. The crew of the Polaris also deserves high praise, who managed to master a new sailboat in a very short time (directly in the races),
The operating experience of the prototype will undoubtedly reveal the weaknesses of the project, which will be eliminated on subsequent ships of the series.
The crew of the Polaris testifies
Built on the TEVSS according to the ST-25 project, the quarter-ton Polaris was launched just before the start of the Muhu-Vaina regatta, so the entry into the race on it for the crew, which was headed by master of sports Eino Tuvike, was the first exit on the new sailboat. (In addition to the captain, the crew included two more masters of sports in sailing.) This regatta was held in moderate and light winds. In the same group with Polaris, 26 Polish-built sailboats of the Konrad-25 and Koirad-26 types started. Comparing the driving performance of the new sailboat with rivals, it was possible to establish that "PLaris goes steeper to the wind and develops a higher speed not only on steep, but also on full courses. On the excitement that met the participants of the competition, the sailboat did not take water on deck and showed good germination on the wave. Water did not enter the sailboat's hull, except for a slight leak through the forluk (due to a defect in the rubber seal). The sailboat rolls relatively easily and requires constant heeling by the mass of the crew, which may be evidence of insufficient stability. There is nothing superfluous inside the Polaris, neverthelessThe level of comfort, even during a relatively long voyage, completely satisfied us. A good interior layout creates a sense of space; the sailboat does not seem cramped even when there are guests in the cabin in addition to four crew members. The Polaris was armed with a light alloy mast of the same profile as that used for the Tornado; the boom was used from the Star class sailboat, and the spinnaker boom was used from the Soling sailboat. Rigging with two forestays and two pairs of backstays allows you to set the sailboat to any course and almost any speed intra. By the way, setting up the front sails on the go with the help of two transverse shoulder straps turned out to be very convenient; it can be performed through the bow hatch without leaving the deck. It is also convenient to concentrate the running ends of the halyards at the entrance hatch. The helmsman has the opportunity to “tune” the sailboat from his place, since the running ends of the backstay and backstay are led to the epaulette of the boom-sheet located in the center of the Cockpit.