2. SCOPE
• Introduction
• Origin & History
• Today’s scenario
• Features
•New advancements
• Future prospects
• Backdrops
3. INTRODUCTION
•A multihull is a ship, vessel, craft or boat with
more than one hull.
•Comprise a great variety of types, sizes and
applications.
• Consist of various numbers of hulls and of hulls
of various common or uncommon shapes
and/or hulls with a SWA.
4. INTRODUCTION
• Different types of multi-hull ships differ from
each other and from mono-hull ships due to
their own specific features
• Firstly, it must be noted, that variously shaped
hulls can be applied as parts of multi-hull
ships, including SWA hulls, which have no
transverse stability, unlike single hulls.
• These hulls can be asymmetric relative to their
own longitudinal axes.
5. ORIGIN & HISTORY
• Prior to about 1850, the principal requirement
maximum stowage space.
• Speed - never an issue.
•Only since the introduction of mechanical
propulsion and the socio-economically-driven
development of international trade.
6. ORIGIN & HISTORY
• Today, greater speed can provide a
commercial edge in getting the product to the
market as well as suiting the modern rapid
lifestyle.
• Greater speed might be achieved by greater
installed propulsion power, but usually it is
more efficiently obtained by the minimization
of resistance.
8. ORIGIN & HISTORY
• Solution for a mono-hull to achieve low
resistance:
• Minimum displacement
• Minimum beam
• Greatest practical length.
9. ORIGIN & HISTORY
•Unfortunately these three hull
characteristics not only affect the
resistance, but the stability characteristics
and the payload capacity. A long thin
lightweight mono-hull may have the
minimum of resistance, but would exhibit
poor and probably inadequate stability.
10. THE NEED
•An obvious solution to this dilemma
of poor stability is to add one or
more stabilizing hulls to the main
hull, and this is the basic reason for
the success of the multi-hull as a
high-speed craft.
11. THE NEED
•The advantages of a high L/B ratio in
minimizing resistance, are such that a
catamaran (L/b = 15) will have
considerably less resistance than a mono-hull
(L/b = say 6) of equal Δ and L, despite
having two hulls.
12. TODAY’S SCENARIO
• A wide development of various multi-hull ships
began in the second half of the twentieth
century.
• small sized twin-hull boats for fishing, tourism,
pleasure, working
• twin-hull ships function as fast ferries (today
about half of fast ferries are catamarans)
13. TODAY’S SCENARIO
• Semi-submersible structures for drilling and
auxiliary services at sea.
• About 70 twin-hull ships with small water-plane
area.
• Some triple-hull ships and boats (the main hull
and two small side hulls – “outriggers”).
• Twin-hull ships with a main hull and one small
side hull (outrigger), known as “proas”.
14. Multi-hull ships with
traditional hull shapes:
1, 2 – catamarans,
symmetrical and
asymmetric hulls;
3,4 – trimarans,
symmetrical and
asymmetric hulls;
5 – catamaran with
staggered hulls;
6 – proa;
7 – ship with (two)
outriggers
15. FEATURES
•A great number of type and shape
options with various characteristics.
•Larger relative deck area.
•More or less higher seaworthiness.
•Any needed initial stability without any
restriction of the hull aspect ratio.
•Large above-water watertight volume.
16. FEATURES
• Possibility of wet deck slamming.
• A sufficient influence of transverse external
loads on strength.
• Deck area:
• 2.4 – 4 times larger for a catamaran;
• 1.9 – 2.3 times larger for a twin-hull SWA ship;
• 1.6 – 2.3 times larger for proa;
• 1.3 – 2.3 times larger for an outrigger ship with an SWA main hull.
19. WAVE-PIERCING’ TRIMARANS
•Doubled speeds (in comparison with
contemporary level).
•Increased seaworthiness and
minimal wash.
•Sufficient air-borne unloading
capacity.
20. WAVE-PIERCING’ TRIMARANS
•Restricted at the top speeds only by
the power capacity of existing gas
turbines.
•No mono-hulls can ensure such
speeds together at the required
level of sea keeping.
22. SEMI-PLANING SWA MONO-HULLS
WITH FOILS
• A higher level of sea keeping.
• greater speeds in waves.
• suitable for fast battleships.
• SWA corvettes.
24. CONTAINER-CARRIERS
•Small design draught.
•High degree of seaworthiness can
be ensured by an outrigger SWA
ship-platform as a feeder carrier of
containers.
26. BACKDROPS
•The wider overall beam of a multihull
vessel is often a problem for
conventional docking.
•Relatively greater total wetted area
increases the frictional component of
water resistance of the vessel, and thus
the total resistance at low speeds.
27. BACKDROPS
•Weight of hull structures per ton of
displacement is greater than that of
monohulls.
•Assembly of a multi-hull vessel in a
shipyard takes a wider area; as a result,
the construction cost and maintenance
(in dry dock) can be greater.
28. BACKDROPS
•All multihulls are less applicable
ships in ice than monohulls.
•The main problem of designing is the
restriction of all disadvantage results
and full application of advantages.
Simple definition
So when we r talking abt multihull vessels we r lookin at great variety of types, sizes n app
One thing to note here is variously shaped hulls r also accounted under multi hull.
How these kind of vessels came into existence,
Maximum cargo, as much as passenger etc,
Speed was never accounted for.
Designers started thinking of multihulls only since…………..
Speed can play a major role.
Two ways:
More power or less resistance
But more power means more investment and money
Now lesser resistance can be obtained by the following ways
But with these methods several problems also originates:
It compromises with stability and payload capacity.
Because of these reasons multi hull vessels evolved at a very fast rate.
Today, there is a large variety.
Now these are some features of multihull vessels that advocates their evolution and use.
Deck area comparision from mono hull ships.
There has been some new design breakthroughs recently in multi hull vessels
Can reach unbelievable speeds in water,
Only restricted by power capacity of existing GT
Can reach unbelievable speeds in water,
Only restricted by power capacity of existing GT
Semi planing : the hull form is capable of developing a moderate amount of dynamic lift
Very serious problem of dry docking,
Positioning of keel blocks on multihull is a challenge
It results in More stresses on cross structure
Displacement of of multihull is lesser as compared to monohulls, therefore weight of hull structures per ton of disp is greater.
We can summarize all the backdrops in one point that is to optimize the design keeping disad & advantages.
