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Free plans of the tourist motor boat Sea Lion

Free plans of the tourist motor boat Sea Lion

In editorial mail of Motor boats and yachts in recent years letters with request even more often appear to publish drawings for independent construction of the comfortable and economic motor boat expected 5-6 people, possessing rather top sea going qualities for swimming along the mixed tourist routes on the big rivers with exit in large water reservoirs and lakes. Such letters come to edition from coast of the great Siberian rivers, from the basins of Dnieper and Volga, from the northwest of the country.

As our correspondents emphasize, speed does not play especially large role: it is important that the motor boat was the cozy and reliable house on water which, however, could move irrespective of condition of weather. Also one more condition makes a reservation most often: that expenses on fuel were not too burdensome for the family budget.

The project of the similar motor boat interests as it has become clear, not only individual amateur boatmasters, but also trade-union collectives of number of the enterprises which have own recreation facilities on coast of the rivers and lakes and have the corresponding material potential for construction of the small vessel. It is represented to us that the published project can satisfy both categories of builders.

The motor boat is quite simple on design, nevertheless its construction demands presence at the builder of certain experience and in all cases accuracies in work. It is better if Sea Lion is for those who are going to form him, not the first boat; otherwise it will not be possible to avoid numerous alterations and excessive labor input. And in general it is very difficult to comprehend knowledge wooden (and any other) shipbuilding according to books a lot of things are comprehended only by own experience. Nevertheless books will be useful to the amateur shipbuilder starting construction of Sea Lion: 15 projects of vessels for amateur construction and G.V. Efremov Collector of wooden vessels (L., Shipbuilding, 1968).

Basic data of the motor boat Sea Lion
Length is the greatest, m 8,50
Length on KVL, m 7,75
Width is the greatest, m 2,88
Board height on a midship section, m 1,19
Draft is dimensional, m 0,7
Displacement on KVL, m³ 3,7
Engine capacity, hp. 20-50
Speed, km/h 12-18
Passenger capacity, persons. 10

General view of the boat Sea Lion
General view of the boat Sea Lion
1 accomodation ladder; 2 mooring duck; 3 tubular barrier hand-rail; 4 side lantern; 5 wooden hand-rail; 6 the illuminator (only on starboard); 7 rack of fore masthead light; 8 the opening illuminator in toilet; 9 ventilation cowl; 10 emergency and ventilating hatch; 11 nasal railing; 12 the roller for anchor line; 13 chock; 14 the round illuminator; 15 the opening illuminator in front wall of the cabin; 16 filling mouth of fuel tanks; 17 engine jacket, above table; 18 seat locker; 19 cockpit; 20 shield (ledge of sleeping cabin) seat; 21 movable cover of the hatch; 22 ring life buoy; 23 site for bathing and mooring.

The choice of measurings of Sea Lion was defined by desire to place 56 people in three certain kayutka, and one of them had to be located separately in fodder part of the motor boat. It was possible with length of body not less than 8.5 m. And with such length for receiving in after cabin of double bed of full length it was necessary to make insert in cockpit where the shield over legs lying serves as seat. Of course, width of the motor boat allows to arrange bed and across the motor boat at the transom, but as shows experience, cross beds always are less convenient (at least because of rolling and roll of the vessel).

The engine is offered to be installed in cockpit, having closed the part acting over its platform cowl. At such arrangement the builder has certain freedom in the choice of the engine and type of transfer on propeller shaft. The sizes of motor compartment allow to install in it the engine from the Volga car or from Moskvich with the regular gearbox or with angular reverse reducer. Here also the tractor diesel even with air cooling can be put (if to provide withdrawal of hot air from the diesel, for example, in dummy smoke pipe). The provided arrangement of the engine near centroid of the motor boat is favorable also in terms of ship sitting on water as the possibility of excessive running pitch angle on stern is excluded.

Generally speaking, it is possible to start construction of Sea Lion only after all issues connected with the choice of the engine and transfer are resolved. The diesel would be option, optimum for this motor boat, however to get special marine diesels from the fishing boats or abandon ship boats which have served the term it is possible only accidentally. At the limited power (18-23 hp) these marine diesels are bulky and have excessively solid weight, but they are already supplied reverse reducer and are cooled with outside water. The tractor diesel suitable for recovery and service on the motor boat, it is simpler to get, but at the same time it is necessary to equip it with thrust reverser and to upgrade the cooling system.

Are more available, but also automobile gasoline engines are less economic. They can be established on the motor boat after the corresponding completion of the gearbox and the cooling system. It is necessary to operate them at power not higher than 50-60% rated which they develop on the car. On such mode and at speed of 15-17 km/h will really expect about 0.5-0.6 kg/km fuel usage.

Hard-chine contours of the motor boat are expected swimming with relative velocity Froude number Fr = v : √gL = 0,40-0,57. The transom is only partially submerged in water; it provides smooth flow of the body without considerable turbulences on slow speeds and stall on maximum speed, upon transition to gliding.

Body line of the body of the motor boat Sea Lion

Body line of the body of the motor boat Sea Lion

Motor boat table of offsets

Line frame
0 1 2 3 4 5 6 7 8 9 10 11 12 (tr.)
  Heights from OP, mm
Kiel 230 5 0 0 21 46 79 118 160 198 215 235 272 305
Cheekbone SK 715 615 531 468 422 395 377 375 362 355 352 353 353 356
Board LB 1560 1515 1470 1423 1386 1351 1321 1297 1280 1269 1264 1262 1262 1270
  Semi-latitudes from DP, mm
Cheekbone SK 330 750 980 1134 1230 1280 1300 1304 1300 1286 1278 1265 1235 1190
Board LB 822 1152 1328 1410 1438 1440 1430 1421 1412 1395 1382 1370 1330 1290
Notes: 1. Are given ordinates on skin. 2. The base plane of OP is located 460 mm below than KVL. 3. Heights for transom are given in true look, taking into account its inclination. 4. Additional constructive frames 8' and 10' are made in the place in the assembled and sheathed body. 5. Spacing 630 mm.

Let's notice that if the builder has the diesel with power about 20 hp with the reducer providing rotating speed of propeller shaft about 1000 RPM it there will be very successful economic option it makes sense to install this engine. Speed of the motor boat will decrease to 12 km/h, but the screw of rather large diameter will provide the draft, necessary to overcome the added resistance to the movement at strong cross-wind or on nervousness.

And one more council. If there is opportunity to extend the body on 1-1.2 m, do it without hesitation. It is not so difficult it is necessary to remove transom back on 1-2 spacing. In addition to increase in payload volume of the body it will give approach of the mode of operation of the motor boat to the most favorable relative speed with which the share of wave resistance will be significantly lower (see article Measurings and Contours of the Water-displacing Motor Boat). In this case loss of speed because of increase in the size and weight will not be; on the contrary, at the same engine output speed will even increase a little.

At the same time it is necessary to warn against installation on Sea Lion of the engine more powerfully than 50 hp. Essential velocity increment will not turn out though the consumption of fuel will significantly increase; the motor boat will go with big trim by the stern. For higher, than 18-20 km/h, speeds are already necessary other contours of fodder part of the body.

Essential part of the body is the fin fixed to keel. It provides stability of the motor boat on course at strong side winds and also protects from breakdown propeller rudder system when beaching. By the way, for simplification of designs the wheel can be hung on transom; in this case need for the helmport device with the gland will disappear, also shturtrosovy wiring will become simpler.

Thanks to good stability and high freeboard Sea Lion can leave in open water reservoirs at nervousness up to 3 points (maximum height of wave 1.2 m). If to execute the platform of cockpit waterproof, and to supply hatch opening under the engine and cuts in partitions for doors with coamings 100-150 mm high, the motor boat will be almost not filled in. The platform of cockpit is lifted over waterline that allows to establish drain scuppers (it is desirable with non-return valves) for removal of the water which has got to cockpit overboard.

At open cowl the engine installed in cockpit becomes easily available to service. The fuel tanks located on boards from it should be separated from motor compartment longitudinal partitions. Compartments in which tanks are installed need to be equipped with reliable ventilation.

For convenience of survey and repair of tanks over them it is necessary to provide removable plates in the platform; these sheets it is necessary to fix to set by screws or screws without use of glue (certainly, with sealing gasket for sealing).

The exhaust pipeline from the engine can be removed in starboard, and it is the best of all to lead him on the right cheekbone to stern and to make exhaust port in transom at the level of waterline.

Several words about general arrangement of the motor boat.

General arrangement of the motor boat Sea Lion

The after cabin has small height only 1.25 m, however, as shows experience, it is quite enough, considering its basic purpose: to serve as the sleeping room. At family swimming it can be provided to children. In the presence onboard guests here, repaying debt to hospitality, the owner of the motor boat can move.

The lightest and high (about 2 m in light) the room in middle part of the vessel is allocated under salon. Here on port side are equipped control position with the motor boat and galley. The table on starboard needs to be made removable or falling to the level of cross seats; it will allow to turn lunch corner into berth for two people. The seatbacks stacked on table-top can serve as mattresses.

The nasal two-seat bunk room is separated from salon by double partitions between which the toilet and wardrobe are located. Height in bunk room of 1.6 m; in house top the air hatch of rooms and work with the mooring and towing ends fastening for nasal duck is made.

In all three cabins in runduchka (under beds and sofas) and on shelves there is enough place for placement of marching equipment and personal belongings.

At small lengthening of the body additional berths can be equipped also on the platform of cockpit under tent, but this option is recommended at exploitation of Sea Lion mainly in latitudes with warm climate.

Constructive longitudinal section, set of the deck
and view of set of the bottom of the motor boat Sea Lion

Constructive longitudinal section of the motor boat Sea Lion
to increase, 21282405, 203 CBs
1 house coaming, plywood δ = 8; 2 roof (deck) of the cabin, plywood δ = 6; 3 internal sewing of coaming within cockpit, plywood δ = 4; 4 seat shield of sleeping cabin, plywood δ = 6; 5 the layout of coaming 25X12, oak or the territory tree; 6 coaming binding, 15X25; 7 coaming stay, 25X30; 8 cabin carling, 25X50; 9 cabin beam, 22X30; 10 plexiglass, δ = 6-8; 11 rack, 25X30; 12 reinforcing rib, 25X60; 13 carling δ = 25; 14 lining of coaming 8X90, oak or the territory tree; 15 rack in DP, 50X35; 16 shell stringer, 20X60; 17 board covering, plywood δ = 8; 18 breasthook; 19 the shelf, plywood δ = 6; 20 stem; 21 the knot which is stuck together from rails 6X80; 22 chine stringer, 30X80; 23 keel, 40X180; 24 bottom plating, plywood δ = 8-10; 25 base stringer under the engine δ = 50; 26 base beam, δ = 50; 27 the fin, is gathered from bars 75X75; 28 screwshaft pipe; 29 bed wall, plywood δ = 6; 30 pillow for fastening of bracket, δ = 40; 31 starnknitsa-helmport; 32 pillow filler under efficient things, δ = 30; 33 cabin beam, 25X30; 34 house coaming, 25X60; 35 free bar, 30X60; 36 deck stringer, 25X40; 37 beam, 22X50; 38 midelveys, 180X28; 39 bottom stringer, 20X60; 40 removable plate of the platform of cockpit, plywood δ = 8; 41 platform flooring, plywood δ = 8; 42 floor, plywood δ = 6 from two parties; 43 bottom plating (option from boards on grooving rails), δ = 14; 44 grooving rail, 12X35; 45 floor-timber, 22X70; 46 gusset plate, plywood δ = 6; from two parties; 47 gusset plate filler, δ = 22; 48 upper futtock 22X70; 49 board covering (option from boards), δ = 12; 50 fillet, oak, ash-tree; preparation 30X30; 51 deck plating, plywood δ = 8; 52 decorative level, 25X30; 53 the shelf, δ = 25; 54 fillet, 20X20; 55 hand-rail, preparation 28X65; 56 pad, 16X35; territory tree or oak; 57 level 2,5X25; stainless steel or light alloy; 58 fiber glass fabric on epoxy binding; 59 fillet, 20X20; oak; 60 coaming pad, 25X30; 61 layout 8X40; 62 partition shp. 0, δ = 6; 63 beam, 22X90; 64 upper futtock, 22X90; 65 bar, 22X25; 66 korotysh-seal; 67 gusset plate, plywood δ = 6 from two parties; 68 basic bar of the platform, δ = 30; 69 bar, 30X30; 70 hatch coaming of motor compartment, 20X120; 71 partition of motor compartment, δ = 8; 72 bulhead stiffener, 20X25; 73 door box bar, 35X60; 74 floor, δ = 20; 75 basic rail of payol, 25X25; 75 partition panel, δ = 4; 77 partition rail, 20X25; 78 fillet, 1212; 79 rail, 12X12; 80 beam, 20X80; 81 filler δ = 20; 82 floor-timber and upper futtock, 2070; 83 floor-timbers shp. 1 and 3; 20X80; 84 cabinet bulhead stiffener, 30X30; 85 the designer of partition, 20X70; 86 partition beam shp. 3; 20X180; 87 latrine bulhead stiffener, 30X35; 88 the layout, 8X28; oak or territory tree; 89 basic rail of bed, 22X30; 90 gusset plate of binding of beds, δ = 4; 91 gusset plate edge wall of the shelf δ = 6; 92 beam shp. 1; 25X80; 93 transom floor, 28X150; 94 rack, 28X30; 95 the shelf bed support, 30X60; 96 gusset plate, δ = 6, on the one hand; 97 transom rack, 40X150; 98 sewing of transom, plywood δ = 9; 99 it is resistant 30X50; 100 transom binding parts, δ = 25.

The body of the motor boat can be sheathed by any waterproof plywood (bakelized 7 mm thick or aviation 8-10 mm thick) or boards by one of two options. More reliable option is covering on grooving connecting rails when all grooves between boards are blocked by the rails cut in frames and partitions from within. Sheathing boards 12-15 mm thick proklepyvatsya with edges of grooving rails. The distance between frames can be left to the same, as well as at plywood covering, i.e. equal 630 mm (except for fodder part of the body where in connection with installation of partition of sleeping cabin between shp. 9 and 10 constructive frames do not match theoretical). The covering on grooving rails turns out strong, easy and waterproof. Lack of this option is need to use long boards; also the amount of works as it is necessary to cut rails in frames increases.

Sections on frames (option with covering on grooving rails) and partition design

Sections on frames and partition design
to increase, 2132x2456, 158 CBs

Other option double diagonal planking levels about 7-8 mm thick allows to use short-length material which to get slightly more simply. The selected short pieces of boards without knots and other defects are adjusted and fasten (to keel and chine stringers on the bottom, to chine stringers and rubbing bands on boards) at an angle 45. Having laid first coat of covering, it is prostragivat outside, stack sealing layer of fine fabric on paint and sheathe the body the second layer of the same levels, having them at an angle 90 to previous. Then levels of both layers proklepyvatsya among themselves. Lack of this way is need of careful protection of end faces of levels (at keel and stringers) from moisture and also big labor input of mounting. For ensuring rigidity of covering at this option it is necessary to establish onboard and bottom stringer, the breaking skin panels on sites approximately of same width. Same additional stringer are necessary also at shell plating plywood.

Partition and transom


Partition and transom
to increase, 2090x846, 57 CBs

Stem assembled with keel
Stem assembled with keel
to increase, 1388981, 47.8 CBs
1 stem crown; 2 knot; 3 keel; 4 pad 14015, oak; 5 rail 4015, oak.

And again we will emphasize: before to start production of frame frames and preparation of other parts, the builder needs to work carefully installation in the body of that engine which it has. For this purpose it is necessary to draw in perhaps larger scale (1: 5 or even full-scale) longitudinal section of fodder part of the motor boat and, having imposed on it tracing-paper with gabaritka of the engine together with thrust reverser (naturally, in the same scale), to achieve the acceptable provision of shafting line. The origin is the provision of the fodder end of shaft. It is in the location of disk of propeller. Propeller diameter it is possible to accept 400-420 mm, and distance from shaft axle to keel about 470 mm. The angle of dip of the engine should not exceed 12 for providing reference conditions of operation of the lubrication system and the carburetor.

Then in the same scale two-three cross-sections of the body are drawn. It becomes to specify arrangement of the engine of rather longitudinal structural frame, to specify the necessary height of longitudinal bars of the base and their otstoyaniye from DP (on the provided drawings of frames it is designated by letter A), Most often the engine manages to be fixed on the base only by means of cross steel beams beam; they allow to install the engine as low as possible and to sustain height of longitudinal submotor bars demanded for reasons of rigidity of design.

It is important that submotor bars reliably fastened to longitudinals stringers which will carry loadings from the engine (including loadings of vibration character) on several frames and rigid partitions at perhaps big length of the motor boat, Otherwise shaking of design of the bottom at long engine operation will be inevitable, and as a result body vodotechnost. Besides, reliable connection with stringers promotes preservation of invariable lining of shafting line at different cases of operation (beaching, rise on the coast, etc.).

D. Antonov, Motor boats and yachts No. 112.

Free boat plans

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