Mod-01 Lec-08 Structural Assemblies Double Bottom Construction

We will start with the double bottom construction, with the structural assemblies. If we look back, what we started with.


We will start with the double bottom construction,
with the structural assemblies. If we look back, what we started with the
plates and profiles, then we had the sub-assemblies units. So, decks, side shells, bottom shells, they
were under the so called assemblies. Gradually the things are growing, from the
plates we had small subassemblies, the brackets, floors and then we came to decks, bottom shells,
bilge plate. Putting these together, we are getting the
units, so another unit will talk about the double bottom construction, wing tanks and
these items. As per as double bottom construction is concerned,
as you can see that it comprises of the inner bottom plating, also referred
to as tank top. We have already talked about it, but just
taking relook; this part is the bilge plate, obviously this is bottom shell. Here, this is the entire double bottom; we
have drawn only one half of it. This is my ship centerline, so here, part
of the plating of the bottom shell that is referred to as keel plate of the total bottom
shell. The plate at the centerline is referred to
as keel plate, why different name? Because, it has some additional function,
the strength of the thickness of this plate is generally more than the adjacent bottom
shell plating. One can say, as if its forming so called backbone
of the entire ship, the keel plate will be extended like this, as well as the tank top
plating is also extended. So, along with this vertical member here,
which is refer to as center girder or also termed as center keel. When a ship actually is put on what you call
on the keel blocks, when the ship is under construction. You cannot really put it on the floor, is
not it. Then, it will be difficult to work. So, it should have a proper base over which
it can be put. So, if this is my floor line that means the
ground line, the ship sits on such blocks. These are blocks, generally you have three
rows of blocks to support, over it sits and they are referred to as keel blocks. Here, you can see the keel plate rests over
the keel block, so thereby here you have the double bottom, you have the center girder,
so there by the weight is supported. Because, when the ship floats, then situation
is different, the entire hall is supported by a distributed force. Here, it is supported at certain concentrated
locations, because keel blocks are not everywhere, at certain spacing it is there. So that needs the bottom most plating of the
double bottom unit, is referred to as keel block. Then, you have the bottom shell bilge plating
and so on. The construction inside the double bottom
unit is it looks something like this. As we are drawing it, these are the bottom
longitudinals, we are putting it. These are my bottom longitudinals, these are
inner bottom longitudinals or tank top longitudinal, these are bottom shell longitudinal or bottom
longitudinal. What tank top inner bottom plating or tank
top plating- I am writing tank top, well that is shorter than that word inner bottom any
way. Then, you see these green lines, what are
these? Struts – they are referred to as struts. What is
the function of these? They are essentially stiffening the floor
plate that is a floor plate here. The plate is in this plane, in the plane of
the paper. In the floor plate, what happens? You have such openings, only some of the openings
I am drawing, not all of them. But, in all the longitudinal, you will have
such openings, through which the longitudinal pass. Also, the floor plating has so called lightening
holes, right. In between the struts, you have these openings
cut, we have talked about it. Why these openings it looks like this? Then, what about the member here – in between
this black line? This is center girder, by this one continuous
line it refers; that means, there is some vertical member continuously going, so this
is referred to as side girder. This is in the centerline; this is on the
side, so you have a side girder. This is a port side girder; on the other end,
there will be starboard side girder. There can be more than one side girders, here
we have shown one side girder that does not mean that there is only one. Depending on the breadth of the vessel, the
number of side girders will depend. If the breadth is more, you will have more
than one side girder. More than one side girder means, more than
one side girder in each side. Port side one means, automatically starboard
side one, so there are two side girders. We are saying – that means, total side girders
could be 2 or 4 or 6 whatever. These are the side girders; obviously, you
will have in the floor such cuts, which are referred to as what you call the scallops,
so this whole thing would look something like this, a double bottom unit. So, this double bottom unit is manufactured
from or fabricated from this plating, this stiffened panel. The stiffened panel is the tank top panel,
then you have the bottom shell panel, this is my – we have talked about – even you can
have the bilge panel. Then, you have the separate side girders and
the center girders. This is the center girder, this is the side
girder. So what we mean to say is, first that means,
as we are moving from subassemblies – assemblies, then to units, once this assemblies means,
the tank top panel, the bilge panel, like that they are separately fabricated. That is what is referred to as prefabrication;
they are prefabricated, then they are put in place. The bottom shell is put in the place, place
means where that is what is called skid. Skid means, because here, what we are doing
is, drawing or showing you is, the bottom shell is absolutely flat; not necessarily
it will be always flat, isn’t it. If we look in to the entire ship, say the
ship structure, suppose you are fabricating this part, let us assume you also a have a
small bottom – double bottom unit here. So, in this section, the double bottom unit
may look like this. Here, you have your – some part of the double bottom unit can be
this way. The part of the double bottom here would look
like this. So, what happens is, as I said there, we talked
about keel blocks, the ship wind the blocks, are erected that means once this blocks are
erected, these blocks are transferred over the keel blocks and align individual block,
put them together. You have the whole ship, but when these units
are fabricated, those units are put over some – one can say the working bench here. Working bench should be – this is your say
the ground level, so working bench should be something like this. That means, some supports over which this
plate is – the structure is erected. So, these supports, they are properly connected
with each other, so that they have the necessary strength. This is referred to as skid, also termed as
jig, they not only serve the purpose of supporting the structure, but the top surface of this
skid or the jig, if I Put a sort of joint lines and develop the surface over the skid,
it will actually confirm to the ship surface. How the fabrication process goes? Here, the this assemblies that means the curve
panels -here you have the curve panels, the plates are bent in the plate bending machine,
they are checked for the bend shape, whether they have been correctly bend. Then, you bring and put on the skid, it should
match perfectly on the skid surface. Then, it is a double check, not only it support
seat on that but also you can see that well it is matching. That means, this skid pillars they are not
arbitrarily erected, they are erected at predetermine locations. That means, so that I have this coordinates,
where ever it is touching the surface, this coordinates are known. So, it is such that it will match perfectly
not – so, it serves the purpose of supporting the structure, but also checks whether the
surface is correctly done or not. The curve shells are put and then weld. The curve shells coming with the stiffeners,
then your further erection of the central girder. If there the center girder is erected, welded
then this inner bottom plating is put over it. Also, the necessary welding is done that means
there is proper sequence is followed. So, these buildings – all the buildings at
the end, you have to entire unit prefabricated. It is part of the bottom plating, can be the
part of that keel, whether the keel is narrowing down even. Keel means, it is nothing but no other special
thing, only this part of the plating at the center, is referred as keel plate. Generally, it is a little of higher thickness
compared to the additional, compared to the adjacent plate. The reason of this been higher is there is
a wire in; I mean it sits about the keel block. So that is why it is given little extra strength,
because concentrated load will come on this that is how. I mean, it is not a must that you will have
to have a keel plate of higher thickness, not necessary. If you provide a higher thickness, well the
separate name is given for this streak of the plate – keel plate. That is what your double bottom construction
is. The double bottom construction thereby comprises
of what? Essentially, the bottom shell – inner bottom
shell and the relevant stiffening members, what are the relevant stiffening members? Stiffening members of the individual panels
– inner bottom longitudinal and bottom longitudinal; this is a case in case of longitudinal framing
system, we are not going to discuss the transfers framing system, because for all practical
purpose, it is preferable to go for longitudinal framing system. Why because, in longitudinal framing system,
we have better buckling strength, may be this; we can once again look back to that the framing
systems, say a plate. If it is stiffened in this direction, identical
plate is stiffened in this direction, so that the top one longitudinally framed and bottom
line is transversely framed, isn’t it. This has been done by longitudinal framing
system, as if this is transverse framing system, both of them are under compressive load in
this direction. Obviously, the one with longitudinal framing
system will have a higher critical buckling stress, isn’t it? For the every arrangement, this will have
a higher critical bucking stress; that means, we will be able to sustain higher amount of
load. In other words, for the same loading, this
is P, this is also P for the same loading and I can have a structure in this case of
lesser scantling. That means, with longitudinal framing system,
I will have strength to weight ratio in longitudinal framing system, will be higher compared to
the weight ratio of the structures with transverse framing system, isn’t it. For the same weight, strength will be greater;
I will have a greater strength, so my structure will be more economical. So that is how we will have to see while arranging
or making a structural arrangement, so that we can maximize the use of longitudinal framing
system. But, in some places, there can be cases, where
for some other functional requirement we will have to deviate from longitudinal framing
system and take the course to transverse framing system. Anyway, so that is what – so that is how the
double bottom is, since double bottom space only usage is either it remains empty or you
use it for carriage of some liquid, not cargo, but say fresh water or fuel oil or lubricating
oil or ballistic purpose. So, if I am carrying liquid, then whether
it is longitudinal framing system or transverse framing system, it does not matter, isn’t. It only is said that – where longitudinal
is difficult, where it becomes difficult? Where you have interference with the cargo,
mainly which is the main cause of concern at times, when I have to shift from this to
transverse framing system. Otherwise, all longitudinal – that is why
in oil tanker, the entire framing arrangement is longitudinal framing arrangement. So, double bottom also is similarly will go
for totally. A framing system based on the longitudinal
framing system; so that is what I mean – whole this so called concept of the double bottom
construction, these are the 3 d units fabricated from the stiffened panels. Now, we have other 3 d units or wing tanks
– the wing tanks, before you go to wing tanks,
we can have a little look in the double bottom one aspect. Just to show how the things that they take
ship? Say, this double bottom has been fabricated
and then what happens? The other stiffened panels or the side shell
panels we have talked about – so side shell panels, once they are fabricated, they are
erected here that means you have the double bottom. So, the side shell panel is erected, side
shell panel erected means what? Physically placed in that position; when you
are placing it, well you will have to have all kinds of support to hold it there. This panel is either transversely framed or
longitudinally framed; let us assume it is transversely framed. That means, you have transverse frames, side
shell frames like this. The double bottom was longitudinally framed;
that means, this is my tank top plating, this tank top plating has longitudinally stiffness
below, so they can be shown by this dotted line – this dotted line indicates that they
are the longitudinal running below this. So, once they are put, then you provide the
so called it is connected with a bracket, brackets are coming like this; among this,
this is welded. As well as, because just the entire side shell
panel, if you just weld along the line, it does not get enough strength. So, you provide those brackets, we have talked
about brackets, they increase the load bearing area. They enable better load path, so you can see
this brackets are welded over the tank top. These brackets are welded here, to the side
shell and to the tank top. Where we are welding? See the drawing, where we are welding the
bracket? Where you have those longitudinal? That means, it is taking the support of the
longitudinals from there, then it is going on the tank top. Where I am ending the bracket toe on the longitudinal,
we are ending the bracket toe on the longitudinal. That means, you have this bottom shell plate
– inner bottom plating. Let us assume this is my longitudinal below
and I am providing the bracket, it is coming and it is terminating on the top, on the longitudinal;
it is the part of the bracket, is showing. This is called bracket toe, this is a vulnerable
point, because imagine, this bracket toe terminating here. Means, suppose instead of that you have a
connection like this, you have the bottom longitudinal here. Let us assume that I have the bracket coming
and terminating like this, this is not a good design. Why because, this bracket was the function
of the bracket, it is transmitting the load. So, all these forces are acting, here at this
point, it is acting, so the load is not effectively transferred. This may lead to a sort of a deflection of
the bottom plate like this. Whereas, in this case, it is taken up by the
bottom longitudinal that is much stronger load supporting member. So, always in construction, we have to keep
in mind that whenever these connections are done, you will to have the proper support
to the end points. So, the toe of bracket should land over some
stiffener below. That is how the side shell is erected; similarly,
on the other side also the side shell will be erected. Then, you have the – then, bring the deck
panel and erected over it. Deck also will have the necessaries in the
same fashion of longitudinal stiffeners. The longitudinal stiffeners will be there,
then the connection of this is my part of my side shell; this is
the part of the deck plating, this is side shell. We are talking about – if we are talking about
main deck plating, then this part of the side shell has a different name that is referred
to as sheer strake. Sheer strake means, here essentially this
is my – if you see the a section of a vessel, the top most part of the side shell plate,
we have named the plate – keel plate, bottom shell plate, bilge plate, side shell plate. This is also part of the side shell, but the
top most part of the side shell has a special name sheer strake. Why because, a special care is given to that
so just to identify that particular strake name – sheer strake. Why, what so special about this plate? What do you think what is so special about
this? The primary thing is, it is the strake, which
is one can say furthest away from the neutral axis. Because of the longitudinal bending, the maximum
stresses, as well as the side shell plates are concerned, the sheer strake will undergo
the maximum stress that is number 1. Number 2, the sheer strake is connected to
the deck plating, it is welded. Number 3 is, well it is more prone to some
damage – possible damage, why? You imagine a situation, you are loading the
cargo. Some cargo is coming, it is hanging, so it
may hit. Some accidental hitting could be there while
loading the cargo, unloading cargo. Any failure or flaw taking place in the main
deck, it may get propagated and goes to the sheer strake. If sheer strake cannot withstand the sheer
strake, it will fail the fracture or crack propagates, the whole ship will break in to
two. So that is how sheer strake needs a special
consideration. What are the special considerations? Well, the thickness is more a higher grade
steam is used. This particular welding, these are the welding’s
– this particular welding is thoroughly checked, so that there is no flaw there that is how
anyway, so this joint is also vulnerable, but the side shell – the sheer strake is welded
to the deck. Why this joint is important? Because, through this joint, the load of deck
is getting transmitted, so it should have a proper path. Now, what are the structural configurations
here? Our main deck is longitudinally stiffened. Suppose, it is going like this, let us assume
the side shell is transversely stiffened, in case of a general cargo ship – general
cargo carrier will see that the side shell, it is preferable to have transverse stiffening
– transverse stiffening means a stiffener will go like this. Also, let us assume, the side shell stiffener
is angle section, it is referred – named as side shell frame. So, there should be, if I just weld it, it
is not enough, isn’t it. For all load to get transmitted, it will be
better if I have a connection between the stiffeners. So that is, stiffener is given – that connection
is given to a proper bracketing arrangement and the brackets are like this. Well, it is preferable to have it sight here. These are welded, this we have already shown,
so that is how you get the proper load path. When the deck is erected, after erection means
what? We put in place, align it and then go on joining
this. This welding is done; all this brackets are
welded, so you get the full block, so that is how you end up in the full block. In this process, we have not done the wing
tank; this is a section of the general cargo ship we have shown, so wing tank now we are
coming to that. Wing tank, as you can see, the name, it is
kind of a tank. As if right this wing tank and that the tank
is in the wing that is how the name of the wing tank. In bulk carrier, we will see, we have already
when talking about the different type’s vessel, we have seen there is a kind of vessel,
which is referred to as bulk carrier. There is a kind of vessel, which is referring
to as bulk carrier. It carries cargo in bulk, well let us take
a look at the sectional view of a bulk carrier, wherein we have the concept of wing tank;
this is what the wing tank is. So, you can see the difference. Till such time we had been drawing mixed sections,
something like this. You had inside a double bottom, depending
on it was general cargo shape. You had a lower deck, now this is a different
kind of section, where in this is my hatch opening, so this is the part of the main deck. This section is drawn in line of hatch opening
– in line of hatch opening where the hatch opening is that there it has been drawn. We can see there is nothing there. As if in this part, the double bottom is only
this part, is the double bottom. This is my double bottom, its constructional
features and details are identical to what we have talked about. In that case, the double bottom extended further
to the bilge plate, it has stopped here. It has stopped in one of the side girders
that are the only difference. There we have seen the side girder. Well, there is one more word about these girders. The center girder is generally a water type
girder, totally water type plate. Means, this center girder divides the entire
double bottom, in port and start boat independent tanks. That means this port side tank. That is the port side tank they are independent,
it is divided by the central girder that runs water tight. Side girder may be water tight, may not be
water tight, depending on your requirement. Generally, they are not water tight, means
they will have the floor, you have these openings. Then, the side girder you will have openings
– side girder is a longitudinal member contributing towards longitudinal strength. Floor is a transverse member contributing
towards transverse strength. This side girder you assume in this case,
as if the double bottom as ended in the side girder. This side girder is also water tight, such
that this is a separate tank in that case. Similarly, here also I can see some tank like
space, so this is referred to as bottom wing tank
and this is top wing tank. This is a typical feature of bulk carriers
only, in bulk carries, you have such wing tanks, why this wing tanks are coming? Then, well in this context, probably, possibly
in better to talk about the bulk carriers, a bit, what is the function of a bulk carrier? To carry cargo in bulk, what does that mean? That means, you put the lose cargo in the
hold. How do I put the lose cargo in the hold? How the loading process through a hopper? Through the hatch definitely – through the
hatch head, but it will come through a hopper; naturally, it will be preferable to have automated
loading arrangement. That means, you can think of such an arrangement,
say you have a Conveyor sort of a thing or even without any hopper just you have conveyor
here, whatever thing is coming and it is falling. Suppose, you are loading wheat, so you have
arrangement here, this is a conveyor system. Here, you are putting the wheat say from the
trucks or trailers or whatever or from silo, if you have seen silo means, basically sure
containers of this wheat, sugar, bulk kind of things. So from that you put it or load it on the
conveyor, through the conveyors to the ship hold. You know, when such thing is dropped, it always
forms a heap, isn’t it. It will form a heap like this, so if the hold. If I keep the ship hold, in this fashion,
I go on loading with this in this way, what will happen ultimately? I will have a heap like this, isn’t it? This will be my cargo in the process, what
is happening? Some space – this particular space is remained
under, I mean not utilized – empty that is number 1; number 2, you think the reverse
process of it, unloading it, how do you unload these cargo? They are unloaded either by a hose – pump
it out or by grabs. You know, there are some grab, some such arrangement
– not properly drawn, some such arrangement. This opens up; you dip it, closed it and lift
it through the grabs. Either pumping it out or through grabs, in
both the cases, once the cargo is unloaded, then what will happen? A part of the cargo will remain here in this
corner. How much corner it will remain? If you lower the hose up to this, this will
remain. So again the problem of unloading-full unloading,
you would not be able to do and that will be quite substantial amount. It is not only the substantial amount; it
is going to contaminate the next consignment of cargo that can be something else. It is sugar, next consignment salt, may be
so loading and unloading, both creates problem. In loading what is the problem? If it remains empty, because as it is I cannot
load, it further load this much, it has already hit the so called planes of line. That means, the loaded draft, it is designed
for carriage of so much. You have loaded it, it was already in this
and this space remains empty, so no problem. If it remains empty, because as it is I cannot
shove, let manually pack more material, because it is already there. But, what problem is, it can give, if it remains
like that. So, it is not only the question of the space
is remaining unutilized, but it is some other is remaining, vacant – empty. So what problem could be there? Stability means not releases, stability in
these terms, not what stability? Yes, so there will be the direction of stability
problem, not the statically stability that much, but direction of stability. That means, suppose it hits a little bit of
rough weather and starts rolling. That means, executing oscillating – oscillatory
movement, so this cargo may shift. In one rolling motion, the cargo may shift
to the port site; in the next phase, when it is going in the starboard site, not necessary
the whole cargo will shift back, this is not water. So, it may so happen there will be a dis balance
in the weight distribution and the whole ship may remain healed condition – in an inclined
condition. If it remains in an inclined condition, then
it will have problem of maintaining directional stability. What does that mean? That means, suppose your ship is supposed
to heads straight, means your radar also will be of 0 angle. Now, what will happen? Since, it is healing, so it will have a tendency
to take a turn, deviate from the straight course. So, you will have to give a radar angle to
bring it back to the desired course. Giving a radar angle means you are wasting
power, so there will be drop in your speed. To boost this speed you will have to power,
means your fuel consumption will increase, operating cost will increase and so forth. So that is how – this is the problem; that
means, this space has to be looked into, as well as unloading time, this has to be looked
into. The solution would be that cut of that space,
provided a plate cut of this space and also provide a plate. That means now when I load cargo, the cargo
comes like this. When I unload also the whole things gets unloaded,
because this slope of course, I am drawing it very shallow. We will have a definite slope – required slope
such that the cargo will come down automatically to the central part, from where it is pumped
out or through grab, it is taken out. What should be the angle of this? So that angle is generally defined from the
angle of repose. This is a particular term use angle of repose,
means when you pore say sand or wheat or sugar, it forms a particular heap with a certain
angle, so that is what is referred to as angle of repose. Based on that the kind of cargo it is supposed
to carry – now the angle of repose of all those cargoes, some average angle is selected
and accordingly this configuration is even. So, in this process, what happens? That means, this is a fixed plate, this is
also a fixed plate. These plates are referred to as sloping bulkheads,
sloping bulkhead of top wing tank, sloping bulkhead of bottom wing tank, so I get a tanked
space. So, these are my wing tanks, what is the purpose
of this tank? Tanked these spaces, same as that of your
double bottom space; that means, otherwise, what was happening is, as it is we could not
use this phase, so by making a tank, it does not mean that I will carry extra cargo there. It may remain as well empty, absolutely empty
or in necessity, I can put some well fresh water, if necessary ballast water, whatever,
but it is not exactly that way that means it has to be decided, pre-designed. That means, in the design stage itself the
spaces has to be year mark, whether it will be is going to remain empty or whether it
is going carry fresh water or whether to carry ballast water, whatever. That means, I have additional space in addition
to the double bottom, I have bottom wing tank, I have top wing tank, they can be utilized. Now, if I just look into the top wing tank
or the wing tanks, the construction point of view, it is like this. This is the main deck, this is my sloping
bulkhead and then this can be the hatch side girder. So, deck is longitudinally stiffened, once
again we are using longitudinal stiffening of the deck. Similarly, you see here, this part of the
side shell; I can as well go for longitudinal stiffening, is not because this space is going
to be used for some liquid if at all. So, I maximize my longitudinal stiffening
arrangement, this is also longitudinally stiffened. There by this entire thing – this particular
wing tank, it becomes a quite strong structure. In the profile, say this is my engine room
and these are my holds – cargo holds. So, the top wing tank will run all along the
length of the holds, the bottom wing tank is also running all along the length of the
hold. Here, you have the double bottom. Like that it provides these both – the wing
tanks, it covers quite a substantial length of the ship, so it provides additional strength
also. Additional strength that means all these wing
tanks it is totally longitudinally stiffened, you have the sloping bulkhead, the hatch side
girder and the bottom plate of the top wing tank. All together provides a sufficient longitudinal
strength, what about the transverse strength? Then again the same question is coming that
these are longitudinally stiffened means, your longitudinal members are running like
this. Say, any longitudinal – this particular green
line represents one of the longitudinal, which is one of this longitudinal. It could be one of these, it could be these
and the longitudinals will run like this, isn’t it. So, again you need to provide necessary support
such that the span does not become too much, because otherwise your supports are at the
bulkheads. The questions of transverses come that means
transverse, so the spacing of transverse spacing is generally how much? It is generally 3 to 4 times the frame spacing
or in another words, the span of the longitudinal remains 3 to 4 times its spacing. Frame spacing – frame spacing is spacing of
the longitudinal, this is my frame spacing. If transverse spacing is represented by capital
S, it is 3 to 4 times the small s. Here, you will have the transverses, how? That means at intervals like this, you will
have the transverses – wing tank transverses; they will be refer to as wing tank transverses. How they look like? This red line is the – basically is the transverse
member, this are the cuts in the transverse plate. In the similar lines, as we have seen in the
floor plate, these intersections of the longitudinal and the transverse plating is same as that
of bottom longitudinal and the floor plating, the same logic is followed. Now, this is a plate in this plane, so where
ever you have a plate floor in the bottom shell, in the double bottom space – a plate
floor, you will have a bottom wing tank transverse, you will have a top wing tank transverse and
also you will have a web frame here, a side shell frame of higher scantling. So, it forms like a ring. When you see this, when you talk about this
transverses, right at intervals, so in the same interval, you will have a web front in
the side shell, a bottom wing tank transverse or a plate floor, top wing tank transverse
web frame, bottom wing tank transverse plate floor. So, such will be the deployment of the transverses
or the transverse stiffening members. These are taken all together, it forms a – as
if a ring structure like the reeves, at intervals you have the reeves, so they are forming the
reeves. Those reeves are as if supporting the longitudinal
members, so this is what. Then now for local strengthening, because
of this particular plate, these dimensions can be substantial. So, they may get buckled in between, because
of others loads coming on that. So, what we have is a Face plate welded to
this cut, this is the opening. Again, the opening is for lightning thing,
we have said that this place can be used as a tank head space. So, if I carry some liquid, the flow of liquid,
so the openings are needed. So, there are opening, if you cut an opening,
you stiffen it with a flat plate. Stiffen it with a flat plate. That means if I look a cross section here,
it is nothing but you have the transverse member plate, there a flat plate is welded. That means, a flange is welded all around,
a flat bar is welded all around. From here, like in floor, you had struts. These are my struts, those green lines – those
are a strut that means they are stiffing it that means, this transverse member, this particular
plate is top wing tank transverse. This is a plate in the transverse plane, it
is providing support to the wing tank longitudinal and all these longitudinals taken together,
I can refer to as wing tank longitudinals. They are providing support; these details
are the same as those details, we have shown in the floor longitudinals, so that is how. Now to provide strength to the transverse,
you have this struts welded, we have this flange welded here, so that is what the top
wing tank is. The similar configuration will be in the bottom
wing tank – identical configuration, all the shapes are different. So, we stop here today.

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