Home>>> Boat projects for self-construction>>> Motor-sailing mini-yacht «Dugong». Project and drawings for the construction of a yacht

Motor-sailing mini-yacht «Dugong». Project and drawings for the construction of a yacht

Motor-sailing mini-yacht «Dugong». Project and drawings for the construction of the yacht

Basic data of the yacht «Dugong»
Longest length, m 5,90
KVL length, m 5,34
Maximum width, m 2,30
Width by KVL, m 2,00
Freeboard minimum/in the bow, m 0,73/1,00
Full displacement, t about 1.5
Sail area, mainsail + staysail, m² 13,05
Engine power, hp 12-25
Passenger capacity, pers. 6

The major rivers of Russia for the most part represent a chain of vast reservoirs connected by sections of a channel of limited width and with a strong current. For tourist voyages on such rivers, motor-sailing vessels are very convenient and most economical, equipped with a sufficiently powerful engine with a good supply of fuel, which allows you to overcome purely river sections (especially against the current), and developed sailing armament, which makes it possible to use free wind energy when crossing large reservoirs, lakes and ples. The distinctive features of such vessels should be increased seaworthiness and high habitability, so that the crew can make transitions even in fresh winds, when planing motor boats and boats are forced to wait out bad weather near the shore.

Note that sailing vessels, as a rule, are relatively slow-moving; their speed is limited by the upper limit V = 5.25 VL km/h, where L — length along the waterline, m. The «power» provided by the sails is not enough to overcome this barrier due to a sharp increase in the wave resistance of water.

The same patterns are true for a sailboat as for a motor vessel. In particular, in order for a vessel under sail to switch to planing mode, it must be relatively light and carry at least 60 m of sailage per ton of displacement (compare with the engine power required for this — 40 hp per ton). It is impossible to increase the sail area arbitrarily — only depending on the displacement of the vessel: the more sails, the greater the risk that a gust of wind will tilt the vessel to a dangerous limit or even capsize. To counteract the heeling moment from wind pressure, the vessel has to be supplied with a heavy ballast bulkhead, i.e. to further increase its displacement and draft, which is associated with an increase in water resistance. Therefore, the real speed that a boat with a waterline length of about 6 m can develop under sail usually does not exceed 5 knots — i. e. 9-11 km / h, and the average speed at the passage of such a sailboat is 6-7 km/ h. To overcome this distance of 6-7 km, a planing boat of the same displacement and size as, for example, the proposed project of a motor-sailing mini-yacht «Dugong» will take about 12 minutes of time and 6 liters of fuel. The owner of the boat, of course, will gain time — the same path will pass five times faster, but the benefit of the crew of the sailboat will be a calm, silent sailing, which, moreover, will not have to spend a drop of fuel. The motor-sailing option allows you to combine the advantages of both types of vessels.

Having a sail on the mast, the skipper is freed from constant worries about refueling along the way; there is less danger of being left without running if the engine malfunctions; it becomes possible to rest on the boat itself, and not necessarily on the shore. With a favorable wind, a 6-meter sailboat can cover 100-150 km of the way in a day, and with the combined use of the engine and sails, these figures become guaranteed.

The yacht «Dugong» is an economical motor-sailing vessel of minimal dimensions, carrying a moderate sail area with a small draft (0.75 m), which does not limit the captain too much in sailing on inland waters. At the same time, there is no mooring line on it, which requires constant attention of the crew and creates certain inconveniences — the well takes up space in the cabin. The armament of the «Dugong» is designed to be controlled by a person who may not be sophisticated enough in sailing, but who wants to use a fresh tailwind. It makes no sense to maneuver on such a motor sailboat, especially with short tacks and in the presence of an oncoming current — it is easier to start the engine and overcome an unfavorable section over the shortest distance. Therefore, in this case, it is possible to put up with a developed (relative to the hull) cabin, which, of course, would be unacceptable on a purely sailing vessel. The high deckhouse, open from the stern and being a weather-protected part of the cockpit, is convenient for accommodating the ship's control post and a small galley, which can be equipped with a gas stove. It is well ventilated; cooking can be supervised by a person standing on watch; the dining table is located nearby — in the cockpit.

The general location of the yacht «Dugong»

General location of the yacht «Dugong»
zoom in, 1864x2207, 467 KB
1 — steering wheel feather glued from boards δ=30 mm; 2 — steering wheel sector; 3 — cockpit coaming with plywood internal stitching δ=6 mm; 4 — side niche; 5 — 60x28 rack; 6 — handrail made of aluminum pipe or oak, Ø23 mm; 7 — side porthole, plexiglass δ=6-8; 8 — upper porthole, plexiglass, δ=6-8; 9 — mast steps; 10 — staysail-sheet shoulder strap; 11 — reinforced beams; 12 — mooringtow bollard; 13 — bow rail made of pipe Ø22-25 mm; 14 — butt of the staysail; 15 — double berth; 16 — locker; 17 — galley table with drawers; 18 — falshkil weighing 150 kg; 19 — bunk flooring, plywood, δ=6 mm; 20 — gas stove; 21 — shelf for dishes; 22 — galley table, locker at the bottom; 23 — folding seat; 24 — removable table; 25 — divai; 26 — afterpeak — motor compartment; 27 — engine; 28 — storm wiring blocks; 29 — muffler and exhaust pipe; 30 — semi-disassembly; 31 — wardrobe; 32 — steering seat; 33 — steering drive; 34 — glass shelf; 35 — door to the forecastle; 36 — opening porthole.

The length of the sailboat was chosen as the minimum with the expectation of using standard length lumber for the construction of the hull. At the same time, bearing in mind the dependence of the maximum speed of the yacht on the length of the waterline, it can be advised, if appropriate materials are available, to slightly increase the length of the «Dugong» (up to 7.5-8.0 m).

Driving qualities corresponding to the speed developed under sail, i.e. about 10-11 km/h, could be provided with an engine of very low power, but developing a torque sufficient to apply a propeller of increased diameter. Abroad, diesel engines with a capacity of 7-12 hp are installed on such vessels. However, domestic diesel engines installed on lifeboats and fishing vessels will be too heavy and large in size for the «Dugong». From stationary engines, 13.5-horsepower «SM-557L» (now not produced) and various gasoline engines from motor pumps and portable power plants can be used. It is important that such engines are not too bulky and there is a device for reversing (for example, an adjustable pitch screw or gearbox), since without it the vessel will not be allowed to sail.

The most realistic, though less economical option is the use of outboard motors «Neptune-23», «Whirlwind» and «Hello». A 20-25-horsepower engine with a well-matched propeller will allow you to reach a speed of about 15 km / h; at the same time, the operating mode should be working at slightly reduced speeds, ensuring the greatest efficiency. A 12-strong «Breeze», although it will allow you to get a speed of about 10 km/h on quiet water, but it will not have the power reserve necessary to overcome fresh headwinds and currents. Sometimes the efficiency of this motor when installed on sailing yachts can be improved by increasing the gear ratio of the gearbox or by using an annular profiled propeller nozzle.

The builder is given to choose one of three options for installing an outboard motor. The easiest way is to hang it on the transom, making a recess in it. In this case, it will be necessary either to shift the motor from the DP to the board, or to perform a steering device with two rudders located on the sides of the motor. A positive property of installing the motor on the transom is the ability to flip the motor when sailing, but one should not forget about such disadvantages as the vulnerability of the motor when mooring, the low location of the engine relative to water, inconveniences during repair and start-up.

It seems most expedient to perform a power plant according to the type of «Saildrive» by disconnecting the motor head from the gearbox. The gearbox with the propeller is attached to the bottom from the outside, and the engine is mounted inside the body on a simple spacer-foundation. The installation turns out to be compact, well protected from damage and flooding by a wave, convenient for maintenance. An additional step-down gearbox can be mounted in the spacer. Since at the same time the exhaust pipe of the motor is deeply submerged under water, it is necessary to mount a separate exhaust pipe with a muffler and remove the exhaust through the transom. To prevent water from entering the engine, the pipeline should be bent in the form of a knee almost to the deck level.

Not every amateur shipbuilder is capable of making such an installation, so we can offer an intermediate option — to put an outboard motor in a special well mounted in the cockpit. In this case, it is not difficult to make some kind of sliding suspension for the motor, which will allow it to be raised above the level of the bottom when sailing and close the lower hole of the well with special flaps or a flap. The well should be placed as close as possible to the transom so that the recess of the exhaust pipe is not too large.

The contours of the hull, designed for sailing in the upper speed limit (13-15 km/h), have a full stern and a slightly submerged transom; the large width of the hull provides the necessary stability and comfort of the vessel.

Theoretical drawing of the hull of the yacht «Dugong». Projections: half-width and side

Theoretical drawing of the yacht hull
zoom in, 1760x1056, 168 KB

Theoretical drawing of the motor-sailing yacht «Dugong»

Theoretical drawing of the motor-sailing yacht «Dugong»
zoom in, 720x568, 52.7 KB
Completeness coefficients: δ=0,42; α=0,73; β=0,68

Table of plaz ordinates

Line frame no.
0 1 2 3 4 5 6 7 8 9 Tr.
  Heights from KVL, mm
Side line — LB 950 890 646 808 780 759 746 732 726 732 746
Batox B3 256 11 -65 -89 -63 27 237
Batox B2 673 68 -122 -171 -205 -210 -178 -133 -56 66
Batox B1 753 11 -179 -253 -274 -288 -271 -230 -193 -137 -48
Keel — LC 0 -248 -312 -343 -344 -332 -304 -260 -214 -154 -86
  Half-width from DP, mm
Side line — LB 392 684 897 1040 1120 1152 1150 1130 1070 992 876
Waterline 7 176 511 766 944 1063 1125 1130 1112 1045 952 835
Waterline 6 110 473 733 919 1045 1160 1130 1096 1030 930 800
Waterline 5 96 426 696 890 1015 1080 1110 1078 1006 896 753
Waterline 4 55 364 638 835 970 1045 1070 1040 959 826 660
Waterline 3 20 295 549 753 892 980 1000 970 876 718 493
Waterline 2 199 418 616 740 821 870 815 677 426
Waterline 1 55 233 397 480 573 602 411
Keel — LC 15 25 48 69 69 69 69 69 69 62 55

The main place where the crew stays on the move is the cockpit and the wheelhouse. The height under the «rigid awning» is 1.6 m. The steering seat is equipped with a folding seat. It is desirable to make the side window of the wheelhouse sliding for a better view of the course during the roll. When sailing, you can switch to steering the tiller from the cockpit, and if the helmsman prefers to stay in the wheelhouse at the same time, then a plexiglass window is made in its roof to observe the sails. A wardrobe is installed behind the back of the steering seat, the upper part of which can serve as a table for a map.

The forward part of the hull serves as a «sleeping cabin». Closing the space between the bunks with a removable flap, you can lay out a sleeping place for three people here. Two more can stay overnight in the cockpit, especially if it is covered from above with at least a sail draped over the boom. Of course, it is best to sew a special canvas awning, which will be useful in the parking lot and on the move (under the engine) both in hot sunny and inclement weather.

It is important to provide the forward cabin with ventilation — to make an opening porthole in the frontal coaming or a small hatch in the roof of the cabin. A small, hermetically sealed ventilation hole in the nose itself (for example, combined with a biteng), removing stagnant air from the area near the stem, will not hurt. This is important to prevent rotting of the wooden case.

Although the drawing shows a variant of the cockpit equipment with a stern sofa and two folding seats on the sides, longitudinal banks are more convenient when sailing; here it is also necessary to provide sockets for installing a removable table.

It is desirable to place the main fuel reserve in flat gas tanks closer to the middle — under the cockpit floors between shp. 5 and 6 or on the sides under the stitching. Their total capacity should be 80-100 liters. The additional stock is conveniently stored in cans in the aft compartment, securing them from moving during roll.

The sheets of the main sails — the mainsail with an area of 9.15 m² and the staysail of 3.9 m² — are carried on transverse shoulder straps made of pipe or steel cable. To increase the speed in a weak wind, it is useful to additionally have a large staysail — a 7,0 m square².

General appearance and sailability of the yacht

General appearance and sailability of the yacht

Details of sailing armament and some deck useful things can be made according to the drawings of the «Sea urchin» shvertbot (see here). The mast is installed in the steps on the roof of the cabin; its design must be reinforced with an additional reinforced beam on the shp. 3. The book «15 projects of vessels for amateur construction» (L., «Shipbuilding», 1974 and 1976) can serve as a guide for the construction of the hull. The hull design is almost identical to the Seal boat.

It is best to build the yacht «Dugong» with a rack-and-pinion covering on bent-glued or bent frames (see the specification of the set), followed by pasting the hull outside with one or two layers of fiberglass on epoxy or polyester resin. To increase the stability of the sailboat, a ballast false keel weighing 150 kg is attached to the bow of the outer keel, which can be made of reinforced concrete. The outer layer of concrete is reinforced with a thin steel mesh, and after mounting on the body, the false frame is glued with a layer of fiberglass. Four studs with a diameter of 10 mm, passed through reinforced floras shp. 3-5, are enough to attach the false frame to the body. The studs can be bent in pairs from one bar in the form of the letter P, to the «crossbar» of which it is desirable to weld plates or steel bars, zamonolichivaemye concrete.

Yacht hull Parts Specification:

Keel: cross-section in the middle part — 120x25; in the bow and stern — 80x25; rezenkil — 160x25 (120x25);
Internal privalny beam — 25x60;
Zygomatic stringer (with bent frames) — 25x40;
Collars -- 25x25, oak; beads — δ=22, oak;
Cabin and cockpit railings — 25x40;
Bent-glued frames — 25x40; spatula — 535;
Bent frames (oak) — 16x30; spatula — about 300;
Sheathing — a 20x60 rail or a board with a thickness of 18; blanks should be made 2-3 mm thicker for the final gouging of the case;
Deck decking, cabin coamings and transom — water-resistant plywood δ=8;
Cabin roof and bulkheads — plywood δ=6;
Strapping of the cabin — rails 24x40;
The rudder pen is a set of boards with a thickness of 28;
Payoles — plywood δ=8 or boards with a thickness of 14.

Project author: D. Antonov.

Boat projects for self-construction

Share this page in the social. networks or bookmark:

bookmark this page