about carene...and software

[Special-one]

hi to all the naval and sympathizers, I am new of this community I take care of design and realization drawings in particular yacht, the famine is the part according to me most influential on the project and the successful outcome of the ship.

in talking about large boats it has generally taken to illustrate what are their characteristics of style and design and it is perhaps a little neglected the exquisitely technical part, which is, instead, basic to allow these queens of the sea to carry out crossings in serene and safe navigation. I would like to illustrate the state of art in this area of construction and start from the base, from the hull, which can be displaced or semi-dislocated, according to the purposes of use.

round hull plans

the famine is, as it is known, the immersed part of the hull, called, with essential and very effective marine definition, also work alive, as with its forms directly influences the resistance and behavior of the boat during its motion and represents the vital part of each boat.
the choice of a displacement or semi-dislocating hull for a great motoryacht, as every designer knows, but also the owner with a little experience, the greater discriminants are dictated by two fundamental parameters: from the size of the hull and the speed at which you want to navigate. these, undoubtedly, are input that the designer receives directly from the owner and are the foundations on which to first develop the living work and then, subsequently, the internal and external layouts of the boat.


slender hulls

when to prefer one or the other? for an analysis on the choice of a certain form of hull, therefore, we begin to illustrate few simple concepts, which concern the resistance to the motion that a boat meets in water.
the resistance to the motion of a boat or ship, whatever its speed, size and type, depends mainly on two main phenomena:

water friction against the surface of the hull (strength resistance)
the generation, to the passage of the boat on the water, of surface waves (wave resistance)

to these two main factors should be added other, less conditional, but nevertheless important that we state below:

shape resistance
air resistance
resistance of appendages
resistance of dirty hull
resistance by sea

wave resistance and form resistance are commonly called globally residual or wave resistance.

the resistance of the dirty hull has much influence on the resistance of the ship especially with the going of time. in order to prevent the formation of dirt due to marine vegetation and microorganisms that are formed after long periods of sea especially in warm waters, the surface of the living work is treated with special antivigetative paintings, which periodically must be renewed.

is perhaps a difficult language to the most, but demonstrates in a concise and effective way the concept, accessible to all, that the friction resistance of a hull increases rapidly with the increase of speed, while the wave or residual resistance decreases, at equal speed, with the increase of the length to the float, that is the length measured on the "line that tracks the water level on the hull of the boat and separates the part immersed from that. In poor words, the more speed increases the more resistances increase to its progress, the longer the boat the greater is its speed of navigation.

the one who has to design a new ship or megayacht, therefore, is first faced with the problem of the consequences that will have on the power to install the possible choices of the shape of the hull and its proportions.

generally the problem is so formulated:

to seek, for the desired displacement (i.e., as far as you want to transport) and for the speed or speed you want, the forms and proportions of hull that will lead, without prejudice to the indispensable conditions of stability, to the least power consumption.

the project, according to operational requirements, can be developed following three basic directives:

the weight criterion
the volumetric criterion
the criterion for taxes dimensional limitations (which may be from time to time, depending on the needs of particular needs, width, length or dive).

the weight criterion is followed when the displacement of the ship is imposed by the loads of high specific weight, plus the weight of the hull and the motor apparatus. in this case (which only exceptionally can affect the nautical), the hull must have as much volume to contain the total weight listed above. we will find ourselves, therefore, in front of a ship with a pronounced immersion and therefore with a high volume of hull, remembering that the hull is the immersed part of the ship.

the volumetric criterion is followed when the ship must carry bulky loads, but of specific weight not elevated. in this case, ensured the necessary metacentric stability, it will be possible to carry much of this bulky load in spaces above the floating line; therefore, much of the useful volume of the ship will be over the float and the hull will be assigned that enough volume to bear the total weight.

However, the problem, in its more general formulation, will be to make travel a certain displacement at a certain speed, realizing or a fair of minimum length possible or of minimum power. as always in a boat, a compromise must be identified between the various needs, which meets the priorities of the shipowner.

the first case, which affects shipowners of ships, has advantages in the construction costs: Shorter ship however with a worse behaviour with rough sea, certainly more expensive in the exercise, as the apparatus requires more power to reach the same speed of a longer boat.

the second case, which affects the naval architect (i.e. the designer specialized in the study of static and dynamics of the hull), of the times is a little more expensive in the construction, for the greater length, but considerably less expensive in the exercise and with a better seal to the sea.

the third case, affects the shipowner who must travel the ship or the megayacht in low seabeds or passages in zones that bind the width, or particular constraints that condition the length. This third case could also affect those who, having sold a volume (a volumetric space) to a shipowner and stipulated the relevant contract, bind the main dimensions and then condition the coefficients of the hull.

This last case, sometimes, becomes the worst case for the naval architect, since the compromise in the choice of hydrodynamic coefficients will not be optimal.

but we examine one of the very frequent cases in the nautical, that of the priority of speed regarding the rest. If the speed becomes the primary data of the project, that is, there is a number of fades f > 0,6 or a quotient of taylor,
you should consider the shapes of edged famine that allow you to have a dynamic boost and achieve high speeds.

until now we have studied the resistances that meets the hull during his motorcycle; we see now the forms that best meet the various needs.

the forms that a carena can take are essentially two: round or corner.

the round hull, called displaced hull, with the increase of speed, has a wave resistance greater than that of friction, therefore it adapts better to the low and medium speeds. On the other hand, the edge hull, reached certain speeds, has a friction resistance that significantly exceeds the wave. The latter type of hull, called the planant hull, is therefore suitable for high speeds.


for the means that by weight, length and speed have intermediate characteristics between a round hull and a planant, the semi-planning or semi-dislocating hull is adopted. the latter compromise, used in the means of small tonnage, begins to be considered also for the ships of great tonnage and the hull is defined deep-v.

However, regardless of the forms of hull, a ship must maintain operational capacity under rough sea conditions.
However, it remains the fundamental consideration that the naval project, beginning with the choice of the hull and the very first forecasts of power, is not only a strictly mathematical study, determined and defined, but it is in reality how much more free and open can desire a creative mind.

the software has a relatively important function for the realization of the carena, it takes a general knowledge of the problems.
It's important to me once you have a superfice, choose a software with naval applications.

 

[sampom]

ciao a tutti...

Hello special-one, welcome among us.
And good, nice "treatment." great ideas to examine the technical details, especially in this section of the forum that as you have noticed is not frequented by both operators and by simple enthusiasts (I while still moderate it are among the latter). needed just a little vitality also to give man strong to the good _exatem_ that bangs everything alone:smile:.

take a look around and don't mess with the interventions, see everything you can add.

greetings
Mar

 

[cacciatorino]

the first case, which affects shipowners of ships, has advantages in the construction costs: Shorter ship however with a worse behaviour with rough sea, certainly more expensive in the exercise, as the apparatus requires more power to reach the same speed of a longer boat.

the second case, which affects the naval architect (i.e. the designer specialized in the study of static and dynamics of the hull), of the times is a little more expensive in the construction, for the greater length, but considerably less expensive in the exercise and with a better seal to the sea.

Let me see if I understand, even displacement, a long ship has a smaller cross-section so it moves less water to the passage (like more 'to a cast) but it needs more iron to build it, unlike a short ship and tort that moves more water but requires less material for construction.

I mean, as a corollary: the wave generated by two ships with the same cross section (master section is called?) is roughly the same, though the length of the two is substantially different?

 

[Special-one]

It is not so, take into account that there are relationships to be respected between the dimensions of a hull; For example, the ratio between perpendicular length and maximum width must be between 5.5 and 7.1 and the ratio between lpp and construction height should not be greater than 10;
However with regard to wave resistance I attach this pdf file that can be clarified to you, but I advance that in these topics it is not easy to distract if you are not in the industry.
Hi, see also this link
http://wpage.unina.it/miranda/corsi/geometria/corso_2006/lezionecoefficienti.pdf

 

[sampom]

It is not so, take into account that there are relationships to be respected between the dimensions of a hull; For example, the ratio between perpendicular length and maximum width must be between 5.5 and 7.1 and the ratio between lpp and construction height should not be greater than 10;
However with regard to wave resistance I attach this pdf file that can be clarified to you, but I advance that in these topics it is not easy to distract if you are not in the industry.
Hi, see also this link
http://wpage.unina.it/miranda/corsi/geometria/corso_2006/lezionecoefficienti.pdf

Always interesting.
if you have documentation, news, curiosities and links related to the sector I invite you to insert them also in the specific thread Useful resources.

Hello
marco

 

[Exatem]

hi to all the naval and sympathizers, I am new of this community I deal with design and realization drawings in particular yacht, the famine is the part according to me most influential on the project and the successful outcome of the ship.. .

welcome to cad3d and especially in the naval area, a section that, as the dear friend sampon said, is not very frequent. naval we are few and therefore each additional user is welcome.
I read that you are resident in Liguria (conterranean) and work in the field of yachts. We will be able to compare our opinions on our subject.
something about the carenes I mentioned in "over and under..." around post 80 or down of them... but since we talk about this, I add mine on the subject.
the hull is rightly the most important part of the ship, "the living work" and its choice influences the dynamics of the ship.
the dynamics of the ship is constantly developing. naval art evolves and enriches, systematic experiences allow to establish which specifications assign to the hull so that it has the characteristics that correspond to the minimum resistance to motion. but a carena designed without having a scientific approach, it hardly will give a good result. only by trying in the naval tank we will be able to know its resistance.
while using the systematic series or comparative calculation, only the tank will confirm or not the forecasts and indicate where to intervene to further reduce the resistance to the motion.
in the context of the smaller ship, you hardly have the time and the money necessary to perform the tests in the tank therefore, nothing remains but to rely on the series above.
fade was the first that, having available a naval tank, including the problem of friction resistances.
taylor instead, was the first to design the research that resulted in the systematic series of hulls. on the studies of these two, the dynamics of the ship are based. taylor began with 80 famine models looking for the causes of motion resistance variations. obtained relationships between the size, weight and shape of the waxes. The dimensions are: the horizontal ratio between length and width (l/b) and the vertical ratio between width and immersion (b/t). to consider weight, taylor created the report: displacement in tons divided one cent of the length standing at the cube. this is called "relative dislocation". the shape of the hull is identified by the "prismatic coefficient" or longitudinal.
Thus the taylor managed to catalog the values of the so-called "unitarian resistance" of all 80 models detected at various speeds obtaining graphics that still cost the foundations of naval constructions.
the American military navy, reworked such data and modified them taking into account also the number of reynolds expressed by schoenherr coefficients.
all the hulls whose speed relaitva remains less than v/radl=1,3 (e.g. 30 meters at 13 knots), are "fast" those where the speed is higher than v/radl=2. at relative speed = to 2, we find the displacement or semi-dislocating hulls. are displaced the famines that keep unchanged the static loriùo (and therefore the volume of famine). a semi-dislocating hull, instead, will change the set "appoppandosi" taking advantage of the dynamic pressure of the water and thus becoming almost "semiplanant". increasing the propulsion, or decreasing the weight or applying appendices (flaps) to the stern, you can take a "planant" trim.
therefore it is not the famine to define its state.
there are yachts with starch hulls, therefore apparently planant, that instead are absolutely displaced.
therefore the definition of planant or not, is given to the assertion that the carena assumes during the motion and to the carrying effect of which it uses.
a correct definition is obtained by connecting the relative displacement, with relative speed. in principle a boat with relative displacement greater than 150, will rarely have relative speed greater than 2.

Hi.

 

[Exatem]

Let me see if I understand, even displacement, a long ship has a smaller cross-section so it moves less water to the passage (like more 'to a cast) but it needs more iron to build it, unlike a short ship and tort that moves more water but requires less material for construction.

I mean, as a corollary: the wave generated by two ships with the same cross section (master section is called?) is roughly the same, though the length of the two is substantially different?

It's not that simple.
every object moving in a fluid, finds a resistance that is said "the existence of the medium". to win it, it is logically necessary to apply a force. therefore to know the power necessary to achieve a certain speed to the ship, it is necessary to determine the resistance that it will encounter.
the goals of the designer are:
- to reach the speed of project with the minimum expense.
- ensure a good sea estate (seakeeping)
- ensure manoeuvrability and route seal.
to achieve this you need to optimize:
- famine design
- design of the propeller
- compatibility between two.
of the methods to predict the behaviour of the hull, I talked about it at the previous post. I repeat that the best is the test in the tub.
to determine the total resistance and therefore the force to be applied, a method used is that of fade according to which friction resistance and residual resistance, are independent among them.
friction resistance is the energy needed to advance the hull in a fluid.
the wave resistance is the energy that the ship gives to the system of waves that it generates (remember when we talked about the function of the bulb? ).
the resistance of skiing is the lost energy in the vortices created by the hull and appendixes (thims, anti-roll wings. . . )
the resistance of the air refreshes the dead work and the superstructures.
generally these last three are called "remained resistance".
the form of famine can be divided into three areas:
- Prodiera
- central
- poppiera
the prora is generally refined to fender the water but must take on increasing volumes at the increase of the dive in order to avoid "invigorating" of prora, damping the beaking, offering boost reserve in case of flooding and allow the installation of equipment for the maneuvers of blanket (argans, verricelli,...). the parameter that defines it is the "entry angle". bulbs are increasingly adopted as reductions of resistance to motion are obtained by creating an auxiliary wave train that suits to interfere with that generated by the hull. the central or master zone, as rightly said by hunting, can be a constant section zone in the case of ships with coefficients of limited or reduced to the minimum in the thin and fast ship. if this section extends longitudinally, the length of the ship increases and thus its displacement. wave resistance is maintained around a constant value for which the designer can choose a length that not only does not increase the resistance, but even decreases it despite increases the wet surface and therefore viscose resistance. not rare cases of ships that have been "longed" by inserting a central section (jumboization).
the forms of the stern are the subject of a particular study because they must facilitate the closure of the flow without creating vortices and turbulence. depend on the number of propellers and thymones adopted as well as on standards indicated by the classification registers that determine the position of the propellers in order to avoid the triggering of vibrations generated by the pressure forces caused by the blades and which can cause injury to the bottom plates.

 

[Exatem]

What?
Are you all gone?

 

[cacciatorino]

What?
Are you all gone?

I apologized for the explanation.

However, one point you have clarified, and that is, that the wave resistance is generated by the cracking water and the chuderla, while instead the central hull does not influence it considerably.

 

[Exatem]

I apologized for the explanation.

However, one point you have clarified, and that is, that the wave resistance is generated by the cracking water and the chuderla, while instead the central hull does not influence it considerably.

the wave resistance consists of two distinct systems, one due to the bow and one to the stern. the wave resistance, added to the resistance of skiing, risucchio, etc. is that which is called "resisting resistance" and is quantifiable, with good approximation, if the famines of the systematic series interpolate the values. the amount of residual resistance (lower wave) depends mainly on the weight, shape and speed of the ship. in naval architecture, it is not possible to relate similar famines, it is necessary to resort to parameters the most important of which is the " relative speed".
Let me give you an example.
a 30 meters long trailer, at a speed of 12 knots, has a remarkable ondous formation.
a cruise ship of 120 meters to 12 knots, barely smuove the surface of the sea.
the two hulls have the same absolute speed but not the same relative speed.
the relative speed (also called taylor quotient) expresses the relationship between two sizes. the speed divided the square root of the length to the float (remembering that it is expressed in feet and v in knots).
therefore the relative vel of our trailer is 12/rad100 = 1.2 while the ship has vel rel. = 12/rad394 = 0.6.
the trailer has a relative double speed regarding the ship. to create a comparable wave, the ship must run at 23,8 knots.
introduces a new parameter. the trocoidal wave caused by the wind.
it is a constant and worth 1,34. when a ship reaches a relative speed of 1,34, a strong increase of resistance occurs.
It is interesting to note that, thanks to appropriate tables, detecting the number of waves to the float and knowing the length of the hull, it is possible to determine its speed.
a ship that had a famine and an unsuitable weight and that reached values of 1.5 or higher, would be found to navigate between the ridges of a longer wave of itself and would take a very affluent thirst increasing of much residual resistance.
with the formation of the wave to prora that dispersed, they also form transversal waves, normal to the hull, and proportional to the speed of the ship.
these meet the waves created by the stern and sum up or subtract to them giving rise to the trail.
this lost energy, proportional to the square of the wave height, is called "wave resistance" to which increases and pressure decreases correspond. taylor was the first to realize that such pressure variations could be advantageously exploited.
the length will have to be such that at the speed of cruise, a wave with the crest aft. so the pressure will be positive and will push the ship forward.

 

[Drag]

to achieve this you need to optimize:
- famine design
- design of the propeller
- compatibility between two.

Good exatem,
I would like to know more than naval designers who think it as tea, unfortunately in the diporto (to speak of hulls up to 24 meters), and also in the field of fishing it is thought that the propeller is a mysterious object to be inserted last in the project, first comes the hull, then the motor (and go with horses to 3 digits) then the reducer and finally when the prediction sends you the package with the choices already taken and above reduced speed
I forgot, when you go to try the first time the boat you realize that there is no order, the displacement has increased magically by 20 %, but one thing is certain the fault is always of the propeller:angry:
a greeting to all

 

[Exatem]

The faults are always others...
Bye.

 

[Fulvio Romano]

Good exatem,
I would like to know more than naval designers who think it as tea, unfortunately in the diporto (to speak of hulls up to 24 meters), and also in the field of fishing it is thought that the propeller is a mysterious object to be inserted last in the project, first comes the hull, then the motor (and go with horses to 3 digits) then the reducer and finally when the prediction sends you the package with the choices already taken and above reduced speed
I forgot, when you go to try the first time the boat you realize that there is no order, the displacement has increased magically by 20 %, but one thing is certain the fault is always of the propeller:angry:
a greeting to all

but no, it's not true...the most important thing in the study of the minor ship, the one that faces first and imposes strict constraints on everything else, is the shape of the tuga, the hardtop, and the fact that these lines like the architect of turn.. .

Excuse me:

 

[Exatem]

but no, it's not true...the most important thing in the study of the minor ship, the one that faces first and imposes strict constraints on everything else, is the shape of the tuga, the hardtop, and the fact that these lines like the architect of turn.. .

Excuse me:

what, what wants to open a walled sea view window at all costs? that would make a glass boat? that, now where we put the engines, smoke and all that noise... there would be better a fitness gym or a tropical aquarium.
But let him make a couple of keel turns!

 

[Exatem]

Good exatem,
I would like to know more about naval designers who think it as tea...
a greeting to all

was my dream to make the ship designer...:36_1_4:

 

[sampom]

the wave resistance consists of two distinct systems, one due to the bow and one to the stern. the wave resistance, added to the resistance of skiing, risucchio, etc. is that which is called "resisting resistance" and is quantifiable, with good approximation, if the famines of the systematic series interpolate the values. the amount of residual resistance (lower wave) depends mainly on the weight, shape and speed of the ship. in naval architecture, it is not possible to relate similar famines, it is necessary to resort to parameters the most important of which is the " relative speed".
Let me give you an example.
a 30 meters long trailer, at a speed of 12 knots, has a remarkable ondous formation.
a cruise ship of 120 meters to 12 knots, barely smuove the surface of the sea.
the two hulls have the same absolute speed but not the same relative speed.
the relative speed (also called taylor quotient) expresses the relationship between two sizes. the speed divided the square root of the length to the float (remembering that it is expressed in feet and v in knots).
therefore the relative vel of our trailer is 12/rad100 = 1.2 while the ship has vel rel. = 12/rad394 = 0.6.
the trailer has a relative double speed regarding the ship. to create a comparable wave, the ship must run at 23,8 knots.
introduces a new parameter. the trocoidal wave caused by the wind.
it is a constant and worth 1,34. when a ship reaches a relative speed of 1,34, a strong increase of resistance occurs.
It is interesting to note that, thanks to appropriate tables, detecting the number of waves to the float and knowing the length of the hull, it is possible to determine its speed.
a ship that had a famine and an unsuitable weight and that reached values of 1.5 or higher, would be found to navigate between the ridges of a longer wave of itself and would take a very affluent thirst increasing of much residual resistance.
with the formation of the wave to prora that dispersed, they also form transversal waves, normal to the hull, and proportional to the speed of the ship.
these meet the waves created by the stern and sum up or subtract to them giving rise to the trail.
this lost energy, proportional to the square of the wave height, is called "wave resistance" to which increases and pressure decreases correspond. taylor was the first to realize that such pressure variations could be advantageously exploited.
the length will have to be such that at the speed of cruise, a wave with the crest aft. so the pressure will be positive and will push the ship forward.

great _exa_..
great technician as always:finger:. clear and simple exposure.
the beautiful is that these "phenomenes" are to a careful eye (..e ear and mesh), detectable just "going by sea" ( numeric values apart...after studies and calculations).

here, these considerations as and how much they apply for "strong" scaffolding, example the offshore. when at regime the living work is practically reduced to the sole poppieri feet (ok, propellers and final part of the axis line) and flaps?

greetings
Marco:smile:

 

[sampom]

was my dream to make the ship designer...:36_1_4:

years ago, when "diporteggiavo", I dreamed of my possible (and unreachable) new boat. And in the evening I dabbled the shapes on a block notes.
What do you say, so much at stake, you can't pull down a little project?

greetings
Marco:smile:

 

[Drag]

What do you say, so much at stake, you can't pull down a little project?

If you need propellers or some other famine appendage I can give you a hand so maybe exa pulls a little up.
ps. It wasn't my intention to make you cry.
ps.ps but what do you do if I can ask
greetings

 

[Exatem]

years ago, when "diporteggiavo", I dreamed of my possible (and unreachable) new boat. And in the evening I dabbled the shapes on a block notes.
What do you say, so much at stake, you can't pull down a little project?

greetings
Marco:smile:

Of course it could be fun. . .

If you need propellers or some other famine appendage I can give you a hand so maybe exa pulls a little up.
ps. It wasn't my intention to make you cry.
ps.ps but what do you do if I can ask
greetings

I cry because I regret (and this is an appeal to the boys who read the post... "study") of not following the indications of my uncle (disappeared for years) who was ing a finca designer and urging me to graduate. Unfortunately I did not listen to him and I stopped at the diploma (in mechanics, naval manco!).
I work today in an office of mm (the one with the gray ships) but now we only take care of refitting for the maintenance in service of the units.

 

[Er Presidente]

Of course it could be fun. . .



I cry because I regret (and this is an appeal to the boys who read the post... "study") of not following the indications of my uncle (disappeared for years) who was ing a finca designer and urging me to graduate. Unfortunately I did not listen to him and I stopped at the diploma (in mechanics, naval manco!).
I work today in an office studies of mm (the one with grey ships) but now we only take care of refitting for the maintenance in service of the units.

I've always been in love with the dealer, but how are they going?
When I was a kid, they talked about it like a jewel, and it seemed to me that way, but then I didn't hear about it anymore.