A general idea of the shape of the outer surface of the housing is given by its section with three mutually perpendicular planes (Figure 5.1).
The vertical plane running along the vessel in the middle of its width and dividing the vessel into two symmetrical halves (port and starboard) is called the diametrical plane (DP). The surface of the water in a calm state, which crosses the outer skin of the vessel, carrying all the loads relying on the nature of its service, forms the plane of the cargo waterline (GWL). This plane separates the underwater part of the vessel from the surface part. The transverse plane that cuts the ship in the middle of its length is called the midship plane.
Figure 5.1 Location of the main planes. 1-plane midship frame; 2- diametral plane; 3 - plane of the cargo waterline
A number of planes parallel to the DP form lines of buttocks on the surface of the vessel (Figure 5.2).
Figure 5.2 Lines of intersection of the outer surface of the vessel by planes parallel to the main planes: 1 - buttocks; 2 - stem; 3 - waterline; 4 - frames; 5 - sternpost.
The intersections of the outer skin with horizontal planes form intermediate waterlines, and with vertical transverse ones - frames. When all the listed sections are combined in one drawing, a form of representation of the ship's surface, usual for shipbuilders, will be obtained - a theoretical drawing (Fig. 3).
An exhaustive idea of the shape of the ship's hull is given by its theoretical drawing (Figure 5.3). It consists of three projections, each of which depicts sections of the hull with planes parallel to those discussed above - DP, pl. MSH and OP. The theoretical drawing represents the theoretical surface of the hull, excluding the outer skin and protruding parts.
Figure 5.3 Theoretical drawing of the ship
The main overall dimensions of the body are usually called the main dimensions. This L is the length of the vessel; B - width; H - side height; T - sediment. The first three are unchanged and refer to the geometric characteristics of the hull as a whole, the last one - draft - can vary over a wide range and determines the submerged (underwater volume) of the vessel. Usually, when talking about the main dimensions of the ship, they take the draft according to the design, or constructive, waterline, corresponding to the design loading of the ship.
The length must also be specified. Distinguish the length between the perpendiculars L, according to the design waterline Lkvl, the maximum Lmax. The first two are close to each other, the last one is overall. When studying the seaworthiness of a vessel, strictly speaking, one should operate with the length along the waterline, but often instead of it they take a uniquely defined value - Lxx.
The largest modern ships reach very impressive sizes: their length can exceed 400 m, width 60, and draft in cargo is about 30 m.
Generalized characteristics of the form. Along with the theoretical drawing, an idea of the shape of the ship's hull is given by generalized dimensionless characteristics - the ratio of the main dimensions and the coefficients of completeness. Both seaworthy and other qualities of the vessel largely depend on these characteristics.
The main ratios of the main dimensions are as follows: . The ratio, or, as it is sometimes called, relative length, in to a large extent determines driving performance: the larger it is, the relatively faster the vessel. For modern displacement ships, this value fluctuates in the range. The lower limit is typical for some tugs, the upper one is for high-speed warships. Naturally, there are exceptions, for example, some rowing sports boats are > 25.
Attitude mainly affects stability and pitching. The larger it is, the better in terms of stability, although the pitching becomes more gusty. For modern marine vessels.
Attitude - affects handling: increasing it increases the stability on the course and worsens the agility.
Attitude - determines the stability at large angles of inclination and the unsinkability of the vessel. Growth has a positive effect on both of these qualities.
The ratio affects the strength of the hull, the higher this ratio, the more difficult it is to ensure the overall strength of the vessel.
There are three main independent coefficients of completeness. This is the fullness factor of the waterline area
where S is the KVL area;
midship frame fullness factor
where is the cross-sectional area of the midship frame below the overhead line
overall completeness factor
where V is the volume of the underwater part of the hull or volumetric displacement.
As follows from (5.1) - (5.3), all the coefficients of completeness are the ratio of the areas (volume) of the corresponding elements to the areas (volume) of the described rectangles (parallelepipeds). All these coefficients are less than one, their numerical values for sea vessels lie within: . Smaller values are typical for faster ships; the upper boundaries correspond to slow-moving vessels with very complete contours (formations).
In some ship theory calculations, it is more convenient to use the derivatives of the main, additional coefficients of longitudinal φ and vertical completeness, the physical interpretation of which is clear.
Example 5.1. Some of the theoretical positions and conclusions under consideration will be illustrated by examples. We will attribute most of them to one ship, which we will give the name "Engineer". The choice of the name is not accidental: firstly, the original meaning of the word engineer is an inventor, creator, and secondly, an engineer is the main driving force of scientific and technological progress, the fruits of which are not yet as weighty as one would like; thirdly, the purpose of this book is to contribute to the extent possible in the transformation of a student into a qualified engineer.
So, the multi-purpose dry-cargo vessel "Inzhener" is given, the side view of which is shown in Figure 5.4, and the main characteristics are as follows:
L max = 181 m; V \u003d 28700 m 3;
L++ = 173 m; D = 29400 t;
B = 28.2 m; G = 288000 kN;
T = 9.5 m; S \u003d 3700 m 2;
H = 15.1 m; sh msh \u003d 261m 2.
The vessel has a bow bulb, the engine room is shifted aft (intermediate position of the engine room of the MO). Combined recruitment system - the upper deck and double bottom are recruited along the longitudinal system, the sides along the transverse
Let's find the ratios of the main dimensions and the coefficients of the ship's completeness:
The coefficient of overall completeness according to (5.3)
The coefficient of completeness of the overhead line area according to (5.1)
The coefficient of completeness of the midship frame according to (5.2)
Figure 5.4 Vessel "Inzhener"
The values of the coefficient of overall completeness and the ratio - give reason to believe that the "Engineer" has rather sharp contours and belongs to medium-speed transport ships.
Elements of the theoretical drawing. The ship theory calculations include various characteristics body shapes. The main elements of the theoretical drawing include:
- -- volumetric displacement V;
- -- coordinates of the center of magnitude x c, z c ;
- -- waterline area S;
- -- abscissa of the center of gravity of the overhead line area x F ;
- - central moments of inertia of the area of VL I X and Iy;
- -- coefficients of completeness b, c, e.
The center of magnitude is called the center of gravity (center of mass) of the underwater volume of the hull (volumetric displacement).
Drilling along the waterlines is the dependence of the waterline area on the draft, by virtue of which we also characterize the volume distribution as a function of the draft. Most modern transport ships has a flat bottom, in this case the S(T) dependence does not come from the origin (Figure 5.5). It is obvious that the area bounded by the drill along the overhead line and the y-axis is the volumetric displacement at a given draft T. The drill along the overhead line is widely used in solving problems of receiving and spending a small load.
The cargo size is the dependence of displacement on draft. On this graph, in addition to the volumetric displacement V, determined according to the theoretical drawing, the displacement is also applied, taking into account the skin and protruding parts V i, as well as the mass displacement D (Figure 5.6). The load dimension is used, in particular, in solving the problems of receiving and removing large loads.
Figure 5.5 Line-up along the waterlines
Figure 5.6 Load dimension
The Bonjean scale represents the totality of the dependences of the areas of all theoretical frames on their immersion u(z). The values of the indicated areas are determined: in the form
The Bonjean scale is built on the transformed contour of the section of the hull by the diametral plane. The transformation lies in the fact that for ease of use, the linear scales along the x and y axes are chosen differently (Figure 5.7). From the vertical lines, traces of the corresponding theoretical frames, the values of the areas of the frames w(z) brought to the height of the upper deck are laid off.
Using the Bonjean scale, you can determine the displacement along any, including the inclined (for a ship sitting with a trim), waterline. The Bonjean scale is used in calculations of unsinkability, longitudinal descent of the vessel, and also for other purposes. The drill by frames characterizes the distribution of volumes along the length of the vessel and represents the dependence of the frame area on its location along the x-axis at a given draft (Figure 5.8).
Figure 5.7 Bonjean Scale
Figure 5.8 Drill on the frames
A framing line can be built using the Bonjean scale for any waterline. It is obvious that the area enclosed between the drill and the x-axis is the volumetric displacement. Drilling along the frames, in particular, is used in the calculation of the moments bending the ship.
Stability and metacentric height. The ship, the yacht are subject to the action of forces and moments of forces, tending to tilt them in the transverse and longitudinal directions. The ability of a ship to resist the action of these forces and return to a straight position after the termination of their action is called stability. The most important thing for a yacht is lateral stability.
When the ship floats without a roll, then the forces of gravity and buoyancy, applied respectively in the CG and CG, act along the same vertical. If during a roll the crew or other components of the mass load do not move, then with any deviation the CG retains its original position in the DP point G in the figure, rotating with the ship.
At the same time, due to the changed shape of the underwater part of the hull, the CV is displaced from point Co towards the heeled side to position C1. Due to this, a moment of a pair of forces D and gV arises with a shoulder l equal to the horizontal distance between the CG and the new CG of the yacht. This moment tends to return the yacht to a straight position and is therefore called the restoring moment.
With a roll, the CV moves along a curved trajectory C0C1, the radius of curvature r of which is called the transverse metacentric radius, r the corresponding center of curvature M is the transverse metacenter. The value of the radius r and, accordingly, the shape of the C0C1 curve depend on the contours of the hull. In general, as the roll increases, the metacentric radius decreases, since its value is proportional to the fourth power of the waterline width.
It is obvious that the shoulder of the restoring moment depends on the distance - the elevation of the metacenter above the center of gravity: the smaller it is, the smaller the shoulder l, respectively, with a roll. At the very initial stage of inclination, the value of GM or h is considered by shipbuilders as a measure of the ship's stability and is called the initial transverse metacentric height. The larger h, the more heeling force is needed to tilt the yacht to any particular heel angle, the more stable the ship. On cruising and racing yachts, the metacentric height is usually 0.75-1.2 m; on cruising dinghies - 0.6-0.8 m.
Using the GMN triangle, it is easy to establish that the restoring shoulder.
The restoring moment, given the equality of gV and D, is equal to:
Thus, despite the fact that the metacentric height varies within rather narrow limits for yachts of various sizes, the amount of righting moment is directly proportional to the displacement of the yacht, therefore, a heavier vessel is able to withstand a larger heeling moment.
The restoring shoulder can be represented as the difference between two distances:
lf - shape stability shoulders and lv-weight stability shoulders. It is not difficult to establish the physical meaning of these quantities, since lb is determined by the deviation during the roll of the line of action of the weight force from the initial position exactly above C0, and lb is the displacement to the leeward side of the center of the immersed volume of the hull. Considering the action of the forces D and gV relative to Co, one can see that the weight force D tends to roll the yacht even more, and the force gV, on the contrary, straightens the ship.
From the CoGK triangle, you can find that, where CoS is the elevation of the CG above the CB in the upright position of the yacht. Thus, in order to reduce the negative effect of weight forces, it is necessary to lower the yacht's CG as much as possible. Ideally, the CG should be below the CG, then the weight stability arm becomes positive and the boat's mass helps it resist the heeling moment.
However, only a few yachts have this characteristic: the deepening of the CG below the CG is associated with the use of very heavy ballast, exceeding 60% of the yacht's displacement, excessive lightening of the hull structure, spars and rigging. An effect similar to the reduction of the CG is given by the movement of the crew to the windward side. If we are talking about a light dinghy, then the crew manages to shift the overall CG so much that the line of action of the force D intersects with the DP significantly below the CG and the weight stability arm is positive.
In a keel yacht, due to the heavy ballast false keel, the center of gravity is quite low (most often, under the waterline or slightly above it). The stability of the yacht is always positive and reaches its maximum at a list of about 90 °, when the yacht is sailing on the water. Of course, such a list can only be achieved on a yacht with securely closed deck openings and a self-draining cockpit. A yacht with an open cockpit can be flooded with water at a much smaller angle of heel (a Dragon class yacht, for example, at 52 °) and go to the bottom without having time to straighten up.
In seaworthy yachts, the position of unstable equilibrium occurs at a list of about 130 °, when the mast is already under water, being directed downward at an angle of 40 ° to the surface. With a further increase in the roll, the stability arm becomes negative, the capsizing moment contributes to the achievement of the second position of unstable equilibrium at a roll of 180 ° (up with the keel), when the CG is located high above the CV of a sufficiently small wave for the ship to take the normal position again - down with the keel. There are many cases when yachts made a full turn of 360 ° and retained their seaworthiness.
Combatant on frames and waterlines. To characterize the distribution of displacement forces along the length of the vessel, a special diagram is built, called a drill diagram along the frames. To construct this diagram, the horizontal line, expressed on the accepted scale of the theoretical length of the vessel, is divided into n equal parts, equal to the number of spacings on the theoretical drawing of the vessel.
On the perpendiculars restored at the division points, the values of the areas of the immersed parts of the corresponding frames are plotted on a certain scale and the ends of these segments are connected by a smooth line. The area of the drill on the frames is equal to the volume of the ship's displacement.
In the absence of a theoretical drawing, the volumetric displacement of the vessel can be approximately determined by its main dimensions:
V=k*L*B*T,
where L, B, T are the length, width and draft of the vessel, respectively; k - coefficient of completeness of displacement or overall ratio completeness. The values of the coefficient of completeness k for various types of ships are taken according to reference data.
Construction on the frames.
Since the center of gravity of the vessel is located in the center of gravity of the underwater part of the vessel, and the front area expresses the volume of the underwater part, the abscissa of the center of gravity of the drill along the frames is equal to the abscissa of the ship's center of magnitude.
A similar diagram characterizing the distribution of displacement forces along the height of the vessel is called the drill along the waterline.
Construction on the waterlines.
The area of the combatant along the waterlines is also equal to the volumetric displacement of the ship, and the ordinate of its center of gravity determines the position of the ship's center of magnitude along its height.
If we take into account the properties of the combatant along the frames and waterlines, then determining the location of the center of magnitude of the vessel will be reduced to calculating the abscissa of the center of gravity of the combatant along the frames and the ordinate of the center of gravity of the combatant along the waterlines.
Calculation of the area of the submerged part of the frame using the trapezoid method. To calculate the roll and trim, it is necessary, in addition to the mass and position of the vessel's CG, to know its volumetric displacement and the position of the center of magnitude, CV, which is the center of gravity of the volume of water displaced by the ship's hull. The simplest way to calculate these quantities is to construct drill on frames.
As a basis for constructing this curve, the DP line at the half-latitude of the theoretical drawing serves as the basis, while the lines of the theoretical frames are extended downward. On each of these lines, on a certain scale, the submerged area of the corresponding frame should be set aside. For sharp-chinned ships with flat bottoms or deadrise, it is not difficult to calculate the area of the schnaigout: it is enough to divide it into simple geometric shapes - rectangles, triangles, trapezoids.
The same principle can be applied to calculate the area of frames of round bilge hulls, but a more accurate result gives trapeze way. Its essence is as follows. If a figure bounded by a curved line is divided by equidistant straight lines into a sufficiently large number of equal parts, then the area of \u200b\u200beach part can be calculated as for a trapezoid:
Then summing the areas of all trapezoids, you can get the area of the whole figure as the sum of the areas of all trapezoids:
Thus, to calculate the area of the frame, it is necessary to find the sum of all ordinates yi along the waterlines, minus the half-sum of the ordinates of the extreme waterlines - at OP and DWL, and multiply the result by the distance DT between the waterlines and by 2, since the calculation was carried out for half of the frame. A similar principle can be used to calculate the area of any waterline, which is divided by theoretical frames into sections of equal length DL.
Having found the immersed areas of each frame Wi on the projection of the hull, they are laid down from the DP on a certain scale, then a smooth curve is drawn. It is easy to figure out that if, for example, add up the ordinates of the areas sp. 5 and 6 and multiply by the distance between the frames DI, then you get the volume of the hull part as a truncated pyramid, having bases in the form of submerged parts of shp.5 and 6.
Here all quantities must be expressed in m and m2. Using the rule of trapezoids, you can also find the position of the center of magnitude - CV, since it must coincide with the position of the center of gravity of the combatant along the waterline relative to the midship. To do this, the static moment of the area limited by the front along the frames is calculated relative to the midsection - the frame, with the abscissas of the bow frames being taken with a plus sign, and the stern frames with a minus sign. With ten theoretical frames:
The CV abscissa from the midsection is:
Calculations to determine the coordinates of the ship's center of gravity. Calculations to determine the coordinates ship's center of gravity it is convenient to keep in tabular form, which is called a weight log. This journal records the weights of all elements of the ship itself and all cargoes on it.
If we take into account the properties of the combatant along the frames and waterlines, then determining the location of the center of magnitude of the vessel will be reduced to calculating the abscissa of the center of gravity of the combatant along the frames and the ordinate of the center of gravity of the combatant along the waterlines.
Using the definition known from statics for the static moment of the area, you can write formulas for determining the coordinates of the ship's center of magnitude:
where wi and wi* are the areas of combatant parts enclosed between two adjacent frames or waterlines; Xi, Yi, Zi are the coordinates of the centers of gravity of the corresponding areas.
At indicative calculations you can use approximate formulas to determine the location of the center of gravity, center of magnitude and metacenter in the height of the vessel.
The ordinate of the ship's center of gravity is determined by the expression:
where:
k - practical coefficient, the value of which, for example, for boats lies in the range of 0.68 - 0.73
h is the height of the vessel.
Center of magnitude ordinates. To calculate the ordinate of the center of magnitude, the formula of academician V. L. Pozdyunin is recommended:
Zc \u003d T / (1-b / a).
where T is draft
b(betta) - coefficient of completeness of displacement
a(alpha) coefficient of completeness of the load waterline.
Diagram of static stability. Static stability diagram. Obviously, the complete stability characteristic of a yacht can be a curve of change in the restoring moment Mv depending on the angle of heel or a static stability diagram. The diagram clearly distinguishes the moments of maximum stability (W) and the limit angle of heel at which the vessel, being left to itself, capsizes (3-angle of sunset of the static stability diagram). Using the diagram, the captain of the ship has the opportunity to evaluate, for example, the ability of the yacht to carry that or other windage with a wind of a certain strength. To do this, curves of changes in the heeling moment Mkr depending on the angle of heel are plotted on the stability diagram. Point B of the intersection of both curves indicates the angle of heel that the yacht will receive under static, with a smooth increase in the action of the wind. In the figure, the yacht will receive a roll corresponding to the point D - about 29 °. For ships with pronounced descending branches of the stability diagram (dinghies, compromises and catamarans), navigation may only be allowed at angles of heel not exceeding the maximum point on the stability diagram.
Comparison of the contours of various ships. When comparing the contours of various vessels and performing calculations of their seaworthiness, dimensionless coefficients of completeness, volumes and areas are often used. These include:
— displacement coefficient or general completeness — δ , linking the linear dimensions of the body with its immersed volume. This coefficient is defined as the ratio of the volumetric displacement V along the waterline to the volume of a parallelepiped having sides equal to L, B and T;
The smaller the coefficient , the sharper the contours of the vessel and, on the other hand, the smaller the useful volume of the hull below the waterline;
- coefficient of completeness of the waterline area - α and - β midsection - frame; the first is the ratio of the area of the waterline S to a rectangle with sides L and B;
Completeness of the assortment - the number of varieties of goods within the type.
The greater the completeness of the assortment, the higher the likelihood that consumer demand for goods of a certain group can be satisfied.
The increased completeness of the assortment can serve as one of the means of stimulating sales and satisfying a variety of needs due to different tastes, habits and other factors.
The assortment completeness ratio reflects the ability of goods homogeneous group meet the same needs and is calculated according to following formula:
Kp = (Pb: Pd), where Kp is the coefficient of completeness;
Pb - basic completeness, a list of goods depending on the volume of packaging in three competitive outlets;
Pd - actual fullness, the actual amount of juice products, depending on the volume of packaging, pcs.
The study revealed that when buying milk powder, consumers pay attention to such a feature as the volume of product packaging. It depends on the needs of each consumer (size and composition of the family, etc.). As a result, it is advisable to take this feature as a basis for calculating the assortment completeness ratio.
Moreover, in order to calculate the completeness coefficient, the range of products of the Troitsky Food Processing Plant brand was considered.
Calculation of the completeness indicator: Kp = (3: 5) = 0.6
In the assortment of the Vinnaya Karta outlet, consumers can find products of the Troitsky Food Plant LLC brand in far from all types of packaging, depending on its volume.
The probability that consumer demand will be fully satisfied is not very high. Such a low indicator of the completeness of the range of juice products, depending on the volume of packaging, is explained by the fact that the buyers of this store, who are mostly regular, prefer to purchase powdered milk in paper containers of a standard volume (0.5 kg).
Novelty coefficient
For many consumers, it is important to see the latest innovations in the range of outlets. This is due to the emergence of new species that are improved. So for integrated assessment assortment it is also important to determine the indicator of the novelty of the assortment.
The novelty of the assortment is the ability of a set of products to meet changing needs through new products.
The novelty indicator is defined as the number of new products in the general list. Updating the assortment is one of the directions of the assortment policy of the organization. It is carried out, as a rule, in a saturated market. The reasons that prompt the manufacturer and seller to update the range are:
Replacement of obsolete goods,
Development of new products of improved quality;
Expansion of the range through
Increase in completeness to create competitive advantages.
However, it should be borne in mind that the constant updating of the assortment is associated with a certain risk that the costs may not be justified, and new product will not be in demand. Therefore, the update must be rational.
To calculate the novelty coefficient, it is necessary to calculate the novelty indicator.
By interviewing sellers about the arrival of new products over the past 4 months, it was found that 1 new brand name of powdered milk was received.
The calculation of the novelty coefficient is performed according to the following formula:
Kn \u003d (N: Shd),
where Kn is the coefficient of novelty;
H - the number of new products that went on sale in the last 4 months;
Shd - the actual breadth of the range.
Calculation: Kn \u003d (1: 4) \u003d 0.25
The novelty coefficient for this outlet was 0.25. Such a small value of the coefficient is explained by the fact that at present the SMS market is saturated and new brands of powdered milk practically do not appear.
Updating the range of this product is mainly due to the emergence of new flavors.
Stability factor
Assortment stability is the ability of a set of products to satisfy the demand for the same products.
Among consumers there are those who rarely change their tastes and preferences throughout their lives.
To a greater extent, this category of consumers includes older people who are generally distrustful of everything new. Based on this, the task of the outlet is, among other things, to meet the demand from this category of consumers.
In the outlet under study, the Monetka store presents brands of powdered milk that are constantly in demand and are on sale. The number of stable brands in this outlet is 3. The value was given by the seller.
The assortment stability coefficient is calculated using the following formula:
Ku \u003d (U: Shd),
where Y (sustainability index) - the number of brands of juice products that are in steady demand among consumers;
Shd - the actual breadth of the range;
Ku - coefficient of stability.
Calculation:
Ku \u003d (3: 4) \u003d 0.75.
The stability coefficient of the assortment, calculated by the formula (4) was 0.75.
That is, more than half of the entire range of the Vinnaya Karta outlet is in steady demand from consumers.
It is this part of the assortment that the entrepreneur orders first of all when purchasing the next batch.
outlet you need to take into account the fact that tastes and habits change over time, so the sustainability of the assortment should be rational.
LECTURE №2
The geometry of the ship's hull. Main dimensions. Completeness coefficients. Classification of ships. The role and tasks of classification societies.
The bounding surfaces and planes of sections of the ship's hull, as well as volumes, are almost impossible to describe with mathematical functions. Therefore, to depict the shape of the body, it is cut by a system of planes (Fig. 1, 2).
Fig.1 - The system of planes of the ship's hull
The geometric shape of the outer surface of the ship's hull is depicted in the form of a theoretical drawing (Fig. 3).
The following are taken as the projection planes of the theoretical drawing:
The main plane (OP) passing through the middle straight section of the keel line
Diametral (vertical-longitudinal), passing along the entire vessel and conditionally dividing it into two symmetrical parts - the starboard and port side. The projection of the ship on this plane - side.
The plane of the cargo (GVL) or structural (DWL) waterline, coinciding with the surface of calm water when the ship is sailing along the design draft. The projection of the ship on this plane - half-latitude.
The plane of the midship frame (vertically transverse), passing in the middle of the estimated length of the vessel and dividing it into two asymmetrical parts - bow and stern. The projection of the ship on this plane - frame.
Fig.2 - Image of the ship's hull on the theoretical drawing:
a - side, b - frame, With - half-width, 1 - bow body, 2 - diametral plane, 3 - aft body
Sections of the vessel with planes parallel to the planes of projections form three systems of main sections: frames, waterlines and buttocks.
Fig.3 - Theoretical drawing of the ship's hull
Theoretical drawing- the basis of all shipbuilding drawings, for example, the position and contour of structural frames (plaza drawing), sheet developments, as well as theoretical ship calculations (for example, stability and trim calculations).
The main geometric dimensions of the vessel is its length L, width B, board height H and draft T(see Fig.4).
Overall length
- the distance measured in the horizontal plane between the extreme points of the fore and aft ends of the hull without protruding parts.
Design waterline length
- the distance measured in the plane of the design waterline between the points of intersection of its bow and stern parts with the centreline.
Length between perpendiculars
- the distance measured in the plane of the design waterline between the bow and stern perpendiculars.
Fig. 4 - The main geometric dimensions of the vessel
Length at any waterline
measured as 
.
Length of cylindrical insert
- the length of the ship's hull with a constant section of the frame.
Width
- the distance measured between the extreme points of the body, excluding protruding parts.
Width at midship frame AT- the distance measured on the midship frame between the theoretical surfaces of the sides at the level of the design or design waterline.
Board height H- vertical distance measured on the midship frame from the horizontal plane passing through the point of intersection of the keel line with the plane of the midship frame to the side line of the upper deck.
Depth to main deck
- the depth of the side to the uppermost solid deck.
Draft (T) - vertical distance measured in the plane of the midship frame from the main plane of the design or design waterline.
Draft fore and aft
and 
- are measured on the bow and stern perpendiculars to any waterline.
Average draft T Wed- measured from the main plane to the waterline at the middle of the ship's length.
Bow and stern sheer h n and h to- smooth rise of the deck from the midships to the bow and stern; the magnitude of the rise is measured on the bow and stern perpendiculars.
Beams die h b- the difference in height between the edge and the middle of the deck, measured at the widest point of the deck.
Freeboard F- distance measured vertically at the side at the middle of the ship's length from the upper edge of the deck line to the upper edge of the corresponding load line.
The shape of the vessel is to a certain extent characterized by the following coefficients of completeness and ratios of the main dimensions (see Fig. 5):
Fig.5 - Determination of the coefficients of completeness of the ship's hull
The coefficient of the total displacement of the displacement
- volume ratio 
of the underwater part of the hull to the volume of a rectangular parallelepiped with the dimensions of the ribs 
,
,
, into which this volume fits (Fig. 5, a):
.
Waterline area completeness factor 
- the ratio of the area of the constructive (cargo) waterline 
to the area of a rectangle circumscribed around it with sides 
and 
(Fig.5, b):
,
The coefficient of completeness of the area of the midship frame 
-
the ratio of the submerged part of the midship frame area 
to the area of a rectangle circumscribed around it with sides 
and 
(Fig.5, c):
,
Vertical completeness factor
corps
- the ratio of the volume of the underwater part of the hull 
to the volume of a straight cylinder with a base bounded by the contour of the design waterline and a generatrix equal to the ship's draft 
:
.
Longitudinal completeness coefficient 
- the ratio of the volume of the underwater part of the hull 
to the volume of the cylinder, the base of which is outlined by the midship frame, and the length of the generators is equal to the length of the vessel 
:
.
The main ratios of the main dimensions are 
,
,
,
,
, as well as their inverse relations.
The increasing flow of goods transported by sea, the desire to reduce transport costs and to maximize the loading of available ports, the variety of goods transported, the development of shipbuilding technology, as well as the increasingly popular tourism - all this has led to the fact that the traditional, which operated half a century ago the division of ships into passenger and cargo is no longer accepted.
Vessels are classified: by ACT, by area of navigation, by type of propeller and engine, by nature of movement, and, finally, by purpose. According to the ACT, full-set and shelter-deck ships are distinguished (Fig. 6).
Complete ships have a deck that runs from stern to bow, which simultaneously serves as a freeboard deck and a bulkhead deck, since transverse watertight bulkheads are brought to it (Fig. 6, a). Varieties of full-set ships: three-island, well and well with a quarterdeck. The three-island vessel (Fig. 6, b) has three superstructures: in the stern (poop), in the middle of the vessel (middle superstructure) and in the bow (tank). This type of ship was common between the two world wars. Sometimes the stern and middle superstructures were combined into a continuous stern superstructure. At the same time, a so-called well was formed between the aft superstructure and the tank. Hence the name "well vessel" (Fig. 6, c). The volume of holds is limited in the stern by the propeller shaft tunnel and the shape of the aft end. To compensate, the main deck in this place was sometimes raised (Fig. 6, d), usually by half a tween deck, and the so-called quarter deck arose.
a - full ship 1 - upper deck and bulkhead deck; 2 - buoyancy margin; 3 - bulkheads; 4 - tween deck
b - three island ship 1 - yut; 2 - middle superstructure; 3 - tank; 4 - main (upper deck)
With - well boat 1 - upper deck; 2 - elongated poop; 3 - well; 4 - tank
d - well boat with quarterdeck 1 - quarterdeck; 2 - upper deck; 3 - middle superstructure; 4 - well; 5 - tank
e – shelteredvessel 1 - main deck and shelter deck; 2 - measuring hatch; 3 - freeboard deck (bulkhead deck); 4 - bulkheads
Fig.6 - Architectural and structural types of ships
For full-set ships and their varieties, the buoyancy margin is determined by the volume of the ship's hull between the waterline at maximum draft and the bulkhead deck. In the figure, the shaded area corresponds to the reserve buoyancy of full-size vessels. Shelter deck vessels (Fig. 6, f) have a significantly lower margin of buoyancy than full-set ones. The upper deck of shelter deck ships serves simultaneously as the main deck, and the bulkhead deck (freeboard deck) is located below. There are superstructures on the upper deck, but they are not taken into account when measuring the vessel, since they are not impenetrable and solid. These add-ons are shown in the figure by dark rectangles.
By sailing area Distinguish between ships of unlimited navigation, which are sometimes also called ships of long-distance navigation or seagoing ships, and ships of limited navigation (ships of coastal navigation, ships for navigation in sea bays, etc.
Type of main engine distinguish ships with a steam engine (with a piston steam engine and steam turbine) ships with an internal combustion engine (with an internal combustion engine and with a gas turbine); ships with nuclear power. This division of ships by engine type is quite rough.
By type of propulsion ships with a mechanical drive are distinguished: ships with paddle wheels (nowadays almost never occur; ships with a propeller (fixed-pitch screw and variable-pitch screw), which can also be located in the nozzle; ships with a special propulsion (vane and jet).
Other, less important principles for the classification of ships are by type of material used(ships made of wood, light alloys, plastics, reinforced concrete) and by number of buildings(single-hull, double-hull - catamarans and three-hull - trimarans).
With the development of shipbuilding, the classification of ships is becoming more and more relevant. on the principle of movement on water. There are displacement ships (the vast majority of sea-going ships belong to them) and ships that are supported when moving by dynamic force (hydrofoils and hovercraft).
From the point of view of operation, the most important is the division of ships according to their purpose, since in recent times the specialization of the courts is developing rapidly.
By appointment distinguish between passenger ships, including: linear passenger liners, cruise and coastal passenger ships (for excursions and cruises) and cargo ships, including universal ones for general cargo, container ships, ro-ro ships (ships with horizontal cargo handling), barge carriers, for transportation bulk cargo, tankers, refrigerated and other vessels for the transport of special cargo (for example, for the transport of timber, machinery, extra heavy cargo, etc.).
Cargo ships can also be subdivided according to the type of their operation: into line ships that run between ports on a schedule, and irregular ships (tramps), which go depending on the accumulation of a consignment.
We should also mention fishing vessels (fishing research, fishing, processing factory ships and transport vessels for fish and fish products), as well as special and auxiliary vessels (for hydrographic and oceanological research, cable, tugboats, icebreakers, firefighters, rescue, etc.).
maritime shipping- transportation of people and goods by sea has long been associated with a certain risk. The ship was not always able to withstand the elements of the sea. And in our time, not only damage occurs, but also the death of ships due to unsatisfactory strength, stability, reliability of equipment and equipment of the vessel, improper placement of cargo, navigational errors, as well as due to fires, collisions and groundings. Therefore, improving the navigation safety of ships has always been a serious task. In the 18th century, the first national classification societies arose, which distributed sea vessels of that time - sailing - into the appropriate classes, depending on their seaworthiness. After the sinking of the passenger liner Titanic, which was participating in the Blue Ribbon race, in 1912, a number of international conferences on ship safety were held and relevant conventions were adopted.
After the Second World War, the Intergovernmental Maritime Consultative Organization (IMCO) was formed within the framework of the UN, the competence of which includes international cooperation on security issues in the field of shipbuilding and shipping. The International Convention for the Safety of Life at Sea of 1960 and the new International Load Lines Agreement of 1966 are recognized by almost all governments of shipping states and are reflected in legal bulletins, regulations, etc. Along with this, there are other national regulations that relate to the safety of navigation and ships. Compliance with the rules for the construction of ships, which are contained in the above contracts and agreements, is controlled by national classification or other state bodies.
Since the safety of a ship depends mainly on its strength, stability, reliability of equipment and equipment, insurance companies, when concluding a contract, determine the characteristics and condition of the ship. In order not to be mistaken, insurance companies in the past kept their own experts in the service, who were supposed to judge the technical condition of the ships. The associations of experts that arose later divided all the ships into classes depending on their seaworthiness and assigned a certain sign to each class. The first printed list, in which the characteristics of ships were indicated by certain characters, appeared in 1764 in England - it was published by Lloyd's Register. This classification society arose in 1760 and, along with the French Bureau Veritas, founded in 1828, is the oldest. All countries with developed shipping have their own national classification organizations, which, based on the experience of building and operating ships, issue the Rules for their classification, construction and safety of ships.
Main goals classification societies:
Development and publication of the Rules;
Checking the classification documentation (drawings) on new and converted ships;
Acceptance of ships at shipyards and supervision of the construction of new ships, as well as the repair and re-equipment of old ones;
Classification and classification (revision) inspections of ships in service;
Registration of ships in the Ship Register.
The publication of the Rules is necessary in order to inform shipping companies, design offices and shipyards about the conditions of classification. They contain requirements for materials, dimensions and conditions for manufacturing parts of the ship's hull, rules for the installation of mechanical and electrical installations, technology for performing welding and riveting, rules for equipment and fittings, ensuring the necessary stability and protection against fires. In addition, Rules are issued for special types of ships and installations (tankers, ore carriers and bulk carriers, yachts, hold refrigeration units, etc.). There are Rules that relate to the safety of the operation and movement of ships, such as Rules for ensuring unsinkability, Rules for the maintenance of radio, television and navigation installations, Regulations or recommendations for the placement of goods - grain, ores, etc. The scope of the rules published by the classification organizations, depends on the tasks assigned to them and the rights given to them.
When supervising the construction at the shipyard and classifying ships, the classification authorities proceed from the relevant documentation. The documents (drawings, calculations, descriptions) must contain all the data necessary to assess the strength and reliability of the ship as a whole or individual installations and parts of equipment. The construction of new and converted old ships can be carried out only after the approval of all the necessary documentation for this.
When classifying a ship, it is assumed that its hull, installations, equipment and arrangements must comply with legally binding requirements. The class is assigned to a vessel for several years if it is in satisfactory condition. Regular classification inspections - revisions are carried out on the vessel. Typically ships are inspected once a year afloat to confirm class and every 3-5 years in dock to renew class. There are deviations from this rule: ships with more wear and tear and old ones that no longer have the highest class are inspected at shorter intervals. Passenger ships once a year, and cargo and other seagoing ships, once between two class renewal inspections, are subject to a bottom inspection in the dock. Along with these regular inspections, special inspections are also carried out after an accident, fire or other damage to the ship.
Vessel classification is confirmed:
By assigning a class to it;
Drawing up a ship class certificate (certificate) and other documents, as well as transferring them to the owner of the ship (ship owner, captain).
The list of ships to which the Register class has been assigned is published annually by classification societies.
With the increase in the intensity of shipping, the number of maritime disasters has also increased, as a result of which people and great material values \u200b\u200bare killed. The reasons for many accidents include the unsatisfactory condition of safety devices, insufficient strength and defective equipment of ships, as well as poor professional training of crew members. Therefore, the maritime countries have agreed on the minimum requirements that should be placed on ships with regard to their safety. The first agreement of 1914 was replaced in 1929 by the London Convention for the Safety of Life at Sea (SOLAS 1929), which in 1948 and 1960 reprinted. New changes were developed by a conference held in 1972. SOLAS contains requirements that are mandatory for all ships (with the exception of military ones) of the states parties to the treaty.
These requirements mainly concern:
Current inspections and inspections of ships, including machinery, devices and equipment, as well as the preparation of safety certificates;
Ship structures in relation to the separation of the hull of passenger ships by bulkheads and the stability of damaged ships;
Execution and installation of bulkheads of peaks and engine room, propeller shaft tunnel, double bottom;
Closing of openings in watertight bulkheads and in outer plating below the maximum draft;
Drainage systems on passenger ships;
Stability documentation for passenger and cargo ships, as well as water ingress safety plans for machinery and electrical installations;
Fire protection, detection and extinguishing of fires on passenger and cargo ships, as well as general fire fighting activities;
Equipment of passenger and cargo ships with life-saving appliances;
Equipping ships with telegraph and radiotelephone installations.
There are design, design, largest and overall dimensions of the ship's hull. The design dimensions, which are understood as the main dimensions, include:
H - forward perpendicular, K - aft perpendicular, L - length of the vessel, B - width of the vessel, H - depth of the side, F - height of the freeboard, d - draft.
- vessel length(L) - distance along the DWL between the extreme points of its intersection with the DP. -
ship's width(B) - the largest width of the design line.
- board height(H) - the distance measured in the plane of the midship frame from the main plane to the deck line at the side.
- ship's draft(d) - the distance between the planes KBL and the main one, measured in the section where the midship and diametral planes intersect.
The dimensions corresponding to the immersion of the vessel along the design waterline are called calculated. The largest dimensions correspond to the maximum dimensions of the hull without protruding parts (posts, outer skin, etc.). And the overall dimensions correspond to the maximum dimensions of the case, taking into account the protruding parts.
The shape of the hull is determined by the ratios of the main dimensions and the coefficients of completeness. The most important characteristics are the relationships:
L/B- which largely determines the propulsion of the vessel: the greater the speed of the vessel, the greater this ratio;
V/d- characterizing the stability and propulsion of the vessel;
N/d- determining the stability and unsinkability of the vessel;
L/H- on which the strength of the ship's hull depends to a certain extent.
To characterize the shape of the hull contours of various ships, the so-called completeness factors. They do not give a complete picture of the shape of the hull, but allow a numerical assessment of its main features. The main dimensionless coefficients of completeness of the form of the underwater volume of the ship's hull are:
- displacement coefficient(total completeness) δ - this is the ratio of the hull volume immersed in water, called volumetric displacement V, to the volume of a parallelepiped with sides L, B, d:
Completeness factor midship frame areaβ- the ratio of the area of the midship frame ω F to the area of a rectangle with sides B, d;
Coefficient vertical fullness χ - the ratio of the volumetric displacement V to the volume of the prism, the base of which is the area of the waterline S, and the height is the ship's draft d:
| χ = V/(S×d)=δ/α |  |
The above coefficients of completeness are usually determined for a ship sitting at the load line. However, they can also be attributed to other drafts, and the linear dimensions, areas and volumes included in them are taken in this case for the current waterline of the vessel.
Ship architecture.
Ship architecture is the general arrangement of hull elements, equipment, devices, layout of ship premises, which must be carried out in the most rational way, in compliance with safety requirements.
The main architectural elements of any ship are: the ship's hull with its decks, platforms, strong transverse and longitudinal bulkheads, superstructures and deckhouses.
deck is called a continuous overlap on the ship, going in a horizontal direction. A deck that does not run along the entire length or width of the ship, but only on part of it, is called platform. The internal space of the hull is divided in height by decks and platforms into inter-deck space, which are called tween decks (minimum height 2.25m).
upper deck(or design) is called the deck, which makes up the upper belt of the cross section of the strong part of the ship's hull. The name of the remaining decks is given from the top deck, counting down, depending on their location (second, third, etc.). The deck that goes over the bottom for some part of the length of the vessel and is structurally connected with it is called second bottom. Decks located upward from the upper deck are named according to their purpose (promenade, boat, etc.), the deck above the wheelhouse is called the upper bridge.
The hull is divided along the length strong transverse watertight bulkheads, forming watertight spaces, which are called compartments.
The rooms located above the second bottom, and designed to accommodate dry cargo in them, are called holds.
The compartments in which the main power plants are located are called engine room.
Any container formed by hull structures and designed to accommodate liquid cargo in it is called cistern. A container for liquid cargo placed outside the second bottom is called deeptank.
tanks called compartments on tankers intended for the carriage of liquid cargo.
Some compartments have special names:
End - the first compartment from the stem is called forepeak, and the first transverse waterproof bulkhead is called forepeak or ram.
Terminal - the last compartment before the afterpeak is called afterpeak, and the bulkhead is called afterpeak.
Narrow compartments separating tanks from other rooms are called rubber dams. They should be empty, well ventilated and convenient for inspection of the bulkheads forming them.
To separate the ship's hull in width, in some cases, strong waterproof longitudinal bulkheads.
Enclosures on ships, all kinds of light watertight bulkheads separating rooms are called.
mines- compartments are called, limited by vertical bulkheads, passing through several decks, and not having horizontal ceilings.
superstructure called a closed structure on the upper deck, extending from one side to the other, and not reaching the side for a distance not exceeding 0.04 of the ship's breadth. The space on the upper deck from the stem to the bow bulkhead of the bow superstructure is called tank. The space on the upper deck from the aft bulkhead of the aft superstructure to the sternpost is called yut. The space on the upper deck between the bow and stern superstructures is called waist.
felling any kind of closed space on the upper or higher decks of superstructures, the longitudinal outer bulkheads of which do not reach the sides of the main hull at a distance of more than 0.04 of the width of the hull, is called.
bridge called a narrow transverse platform running across the ship from one side to the other. The part of the bridge that protrudes beyond the outer longitudinal bulkheads of the deckhouse located below it is called bridge wing.
bulwark is called a continuous fencing of the open deck, made of sheet material. On the upper end edge, the bulwark is trimmed with a horizontal strip called gunwale. The bulwark sheathing is reinforced to the hull by oblique struts, which are called buttresses. Along the length of the bulwark, holes are made for the rapid drainage of water that has fallen on the deck, which are called storm porticoes. The space at the bulwark running along the side on the upper deck around the entire perimeter, which serves to drain water is called waterway chute(waterway). A hole with a tube that serves to drain water from a waterway chute is called scupper.
Spars are called round wooden or steel tubular parts of the armament of ships located on the open deck and are designed to carry signals, structures of communication devices that serve as supports for cargo devices. The spars include masts, topmasts, arrows, yards, gaffs, etc.
Rigging - the name of all the cables that make up the armament of individual masts. Rigging serves to hold and permanently unfasten the spars in the proper position is called standing rigging. The rest of the rigging that can move through the blocks is called running.