Hovercraft have the ability to travel over land and water surfaces due to pressurized air being pumped into a plenum chamber and escaping out through a skirt. They consist of a hull, skirt, lifting fans, thrust fans and engines. Hovercraft operate by using lifting fans to create an air cushion that lifts the hull above the surface, while thrust fans provide propulsion. They have advantages like traveling over many surfaces and bypassing routes restricted to boats, but also have disadvantages like potential skirt damage and noise. Future applications of hovercraft in Egypt could include military transportation over the new Suez Canal or connecting lakes and tourist sites.

1. Advanced Marine Vehicles
with Focus on Hovercraft
Ahmed Hares Mohamed AdelKarim Kotb
Prof. Dr./ Mo’men Gaafary
Supervised by :-
Performed by :-

2. Ch. (1) Advanced Marine Vehicles
Table of contents
(Elements of Typical Hovercraft)
Ch. (2) Hovercraft
Ch. (3) Hovercraft
(Theory and Operation)
Ch. (4) Application of Hovercraft in Egypt
(Types & Characteristics)
(Case Study)

3. Advanced Marine Vehicles

4. Advanced Marine Vehicles, (AMV)
Contains a broad range of craft types
these types were invented
to attain higher speeds at sea than
conventional ship types.

5. Two exceptions to this rule are :-
•The SWATH
Invented to gain exceptional ride quality
among waves.
SWATH : Small Water plane Area Twin Hull
•The Hovercraft
Invented to gain very special capability,
on sea & land surfaces.

6. There is an important principle in ship design, that
goes something like
“Fast - Comfortable - Cheap”
Pick Only Two

7. Recently, Naval Architectural Challenge is
to balance between the following five parameters
• Speed & Power
• Sea-keeping & Sea-kindliness
• Comfort & Space
• Load Carrying Ability
• Economics
To Characterize the various AMV design concepts …

8. AMV – Types

9. What is Fast ? What is Speed ?
• Unfortunately, the answer depends upon size.
• It is important to begin by understanding
the relationship between speed and size.

10. This small 20- knot Jet-Ski is clearly
fast
This 20- knot Washington State Ferry is
Slow

11. The answer lies in the naval architect’s tool of
“Froude Number.”
Froude Number is, crudely put,
“speed divided by size.”
The “size” can be length or displacement.

12. Two Particular Formulations are The Most Common :-
• “Length Based” Froude number.
FnL = V/ (g.L)^0.5
( is the most common in conventional ship )
• “Volumetric” Froude Number.
Fnvol = V/ [0.5 .g(Vol)^0.33]
( is useful in some high speed ship problems )

13. Going to a higher Froude
Number requires more power
per ton of ship weight.

14. The NTUA-SDL FMV
Database Study
• 653 registered vessels
• Froude number over 0.7

15. Brief about The AMV Types :-
•Monohull
•Hydrofoil
•Catamaran
•Trimaran
•SWATH
•HOVERCRAFT*, or (ACV)
* Some Focus is given in Ch. 2 & 3

16. 1) Monohull
• Round bilge semi displacement hull
• Planing hull, hard chine.

17. Round Bilge Hard chine
Low lift Higher lift
High resistance Lower resistance
Low acceleration
(better ride comfort ) Higher vertical acceleration

18. • These vessels are characterized by slender narrow hulls.
• The planing hull form is commonly used for Patrol Boats.
• A length to beam ratio of around 3:1
• Planing craft are generally small, say less than 40 meters.
• Hard chine superior for Fn > 2.25
• These vessels are high speed and high maneuverable.
Characteristics of Planing Hull

20. 2) Hydrofoils

22. HOW IT WORKS ?
• At low speeds hydrofoils are totally submerged in the water.
• As the boat’s speed increases, the hydrofoils create lift.
• At a certain speed, the lift equals the sum of the boat and
passengers weight. Therefore the hull comes out of the water.
Lift

23.  Advantages
 High cruising speed up to 50 kts
 High level of comfort up to wave heights of 2.5 m
 After dynamic lift, the drag decreases which leads to
a better use of power in increasing the speed.
 Disadvantages
 Limited payload capability,
 Large wing draft.

25. 3) Catamaran
• The catamaran uses a very slender
hull to get low drag , but it overcomes
the stability problems by putting one
of these hulls on each side .
• The speed range of all catamarans is
about Froude Number = 2.0 .

26. .
• Disadvantages :-
.
The most important advantages of
a catamaran over a mono-hull are :-

27. 4) The Trimaran

28. .
• Trimarans are better than
Monohulls in minimizing
Wave resistance by 53% ,
And catamarans by 19% .

29. Their overall advantages compared
to monohulls are :

30. 5) SWATH
.
.

31. The advantages of a SWATH
.
Seakeeping superior to similar-
sized conventional.

32. German shipyard Abeking & Rasmussen is the
world’s most prolific builder of SWATH vessels
.
•SWASH
(Small Water-plane Area Single Hull)
It uses a single submerged hull.

33. • Concept
For rough waters .
Safe personnel transfer .
• Individual Particulars
Superior seakeeping
Maneuvering capabilities
Low motion parameters
Length over all LOA 20.42 M
Breadth Hull B 12.16 m
Draught dmax 3.10 m
Speed Vmax 16.5 kts
MATERIAL aluminum
Controllable Pitch Propeller (CPP)

34. • Traditional propeller configurations have a tendency to cavitate at higher
speeds. To maintain propulsion efficiency, designers have utilized a variety
of propulsion packages including specially designed propellers,
• variable pitch propellers,
• surface drive outdrive units,
• Water jets
•

35. Hybrid vehicles combine more than one source of
sustention or lift simultaneously.
The classification of advanced vehicles and their hybrid
derivations usually follows :-
The classical sustention Triangle.
The "sustention triangle" is a commonly used for
characterizing ship types.

36. The corners of this triangle
represent the vessels supported
by :-
The edges and the inside of
the triangle represent the
hybrids.

37. The Hovercraft
Ch. 2
Elements of Typical Hovercraft…

38. What is a Hovercraft?
• A Hovercraft, also known as:-
An air-cushion vehicle, (ACV) is a craft capable of
travelling overland, water, mud, sand, ice, or any
combination of these surfaces.

39. A hovercraft is a vehicle that:-
Flies like a plane,
Floats like a boat,
Drives like a car.

40. .
Invention
The first hovercraft SR-N1 by cockerel

41. SR-N1Used to transport soldiers
across English channel
Elevation, side view and plane
of the first Hovercraft SR-N1

42. • The principles of hovercraft operation is the use of
pressurized air to lift the hull off either the ground
or water surface.
• Normal atmospheric air is pushed into a plenum chamber by lift fans
and some parts of it escapes through a gap at the lower edge of the
cushion.
• This volume of high pressure air is surrounded by a skirt, that prevents
the pressurized air from escaping from the plenum chamber
The Principles of Hovercraft

43. Elements of Typical Hovercraft
•Hull
•Skirt
•Lifting fan
•Thrust fan
•Engine
•Control system

44. Hull
This is where the driver operates the hovercraft
and where the passengers or cargo are located.
Types of Hull Material:-
•Steel
•Aluminum alloys
•Magnesium alloys
•Titanium

45. The fiber glass and composite materials, such as PVC which
provide lightness, strength, and buoyancy in a single material.

46. Skirt
.
.

47. Major skirt design
Finger skirtBag skirt

48. Bag and finger skirt

49. Investigation of Skirt Dynamics under
Non-linear Wave Impact
A set of simulation
have been tested to investigate the
current results obtained reveal the
effect of the bag material stiffness
and bag thickness.
Water height 1(m)
Water width 3(m)
Wave-maker frequency 0.4(s)
Wave-maker amplitude 0.5(m)

50. The Young’s modulus of the rubber ranges from 0.01~0.27 (GPa)
Results
The simulation is stable when Young’s Modulus is larger than
0.03 (GPa) with thickness of skirt of 40 mm or more

51. Lifting Fan
.

52. Thrust System
This consists of propeller or ducted fan that moves
air from front of the craft and accelerates it out
through the back.
This accelerated mass of air generates thrust which
pushes the craft forward.

54. The Engine
A typical hovercraft uses one engine but larger sizes can use more
sometimes up six engines
Diesel engines are common but gas turbines are favor because this
type of engine is smaller and lighter for a given Horse power. And has
a higher weight to power ratio..
The engine should :-
 Cause low noise
 superb economy
 electric start
 air cooling and fantastic reliability

55. •Most hovercraft use two engines. One is used to lift the craft
and the other engine is used for thrust.
• Some smaller craft use a single engine for both lift and
thrust.

56. DE – Drive Engine
DG – Drive Gearbox
LE – Lift Engine
DLG – Distributing Lift Gearbox
LG1 – Lift Gearbox 1
LG2 – Lift Gearbox 2
Propulsion Plant Configuration of Zuber class hovercraft
Full speed – 63 knots
Full displacement – 500 tones

57. Control System
.

58. By means of moveable air
ducts as the bow thrusters
The bow thruster can be
swivel up to 180 degree from
their normal direction.
Advantages:-
Enhance maneuverability

59. Theory & Operation ...
Ch.3
Hovercraft

60. Working Theory of Hovercraft

61. • In case of open plenum theory :
.
• In case of momentum curtain theory:
.

62. Operation of The Hovercraft
• Hovercrafts work on two main principles of lift and propulsion
• Lift fan allows the craft to ride on a cushion of air.
• Thrust fan moves air from front of the craft and accelerates
it out through the back.
• Hovercrafts have no contact with the ground.

63. Law’s Acts in Hovercraft
•
•To lift the Air cushion vehicle, the pressurized air must push
against the surface of the water.
This law is sometimes referred to as the action-reaction law.
Aerodynamics is defined as the branch of fluid physics that
studies the forces exerted by air or other gases in motion.

64. Lift Calculation
Target of This Study
1) To calculate the exit velocity of the air (Vexit) from cushion
2) To calculate the flow rate of air escaping ( Q )
3) To calculate the clearance between the lower
end of the skirt and the ground (h)
4) To calculate the pressure inside the hull, Phull .
Pressure required inside the air cushion ( Pcu ) :-
Pcu = F/A
Where,
F = is the load imposed by the hovercraft weight
A = the hovercraft foot print

65. • According to Bernoulli’s equation,
Where
So that
Where,
Q = The flow rate of air escaping
h = The clearance between the skirt and the ground
L= Length of hovercraft
w= Width of hovercraft
Where:-
•Vexit is the exit velocity of the air
•Dc is the discharge coefficient
•ρair is the density of air
(1)

66. • To calculate the pressure inside the hull, Phull
• The flow rate of air escaping
• The clearance between the lower end
of the skirt and the ground
Where,
 X is the power of the engine
 ηengine is the efficiency of the engine
 ηduct is the efficiency of the duct
 ηfan is the efficiency of the lift fan.
(2)
(3)
(4)

67. Drag Theoretical Approach
• The various components of drag, which apply to a hovercraft are as follows:-
• Wave making drag,
• Aerodynamic profile drag,
• Momentum drag,
• Skirt drag.

68. Where,
• 𝒑 𝒄 is the cushion pressure
• 𝑺 𝒄 is the cushion area
• 𝝆 𝒔𝒘 is sea water density
• Fr is Froude number
• Lc is length of cushion
• Wave making drag
𝑫 𝒘 = 𝟐 ∙ 𝒑 𝒄
𝟐 ∙
𝑺 𝒄
𝝆 𝒔𝒘 ∙ 𝑳 𝑪∙ 𝒈
∙ 𝟏 − 𝒄𝒐𝒔(
𝟏
𝑭 𝒓
𝟐
) 𝑫 𝒂 =
1
2
∙ 𝑪 𝒂 ∙ 𝝆 𝒂 ∙ 𝑺 𝒂 ∙ 𝑽 𝒔
2
Ca: is the coefficient for the aerodynamic profile drag
its value is obtained from wind tunnel tests for detailed
design.
Sa (Cushion Area): the frontal projecting area of the hull
above the water Hovercraft's velocity.
𝝆 𝒂 : is the air density
• Aerodynamic profile drag

69. Where,
• Q is the cushion air flow,
• Vs is the speed relative to ambient air
• 𝝆 𝒂 is the density of air .
The momentum drag is that force due to the rate of change of momentum of
accelerating the cushion air and engine air to hovercraft velocity.
• Momentum Drag
𝑫 𝒎 = 𝑸 ∙ 𝝆 𝒂 ∙ 𝑽 𝑺
Skirt drag is a function of Hovercraft size, shape, skirt design and cushion pressure.
• Skirt Drag
There is no adequate theoretical treatment for the skirt

70. Advantages of Hovercraft
1) Travel over any surface.
2) Shortcutting routes.
3) Travel Rivers up as fast as down, irrespective of the
current.
4) Hovercrafts are very fuel efficient as Hovercraft do not
have to plough through the water but “fly” above
surface.

71. 5) At maximum speed fuel consumption of a Hovercraft is
about 70 % less than of a fast patrol boat
with similar payload capacity.
6) Access to 75% of coastal area instead of only 5% with
conventional vessels.
7) Can be launched from ship.
8) Sea life and coral reefs remains untouched as Hovercraft
propeller churns up the water .

72. •Disadvantages of Hovercraft
1) Potential of skirt damage/puncture.
2) They move a lot of air and can be relatively loud.
3) Steep grades can be issue.
4) Not exactly agile (e.g., cornering).

73. Modification and solution for the problems
FEA analysis indicated that a modification of the
Design would correct the deformation
1. Skirt Damage problems

74. Recommendations and Solution for Noise Problem
NASA deals with this problem as follows:
1-The first generation of hovercraft
The distance between a terminal and
the nearest houses should be at least 800 yd
2-New generation of hovercraft
• Reduction of the tip speed.
• Large numbers of blades and the use of devices such as shroud
rings are rejected
• Using aircraft soundproofing technique.

75. Why hovercraft?
Transport mode Maximum payload
( tons )
Speed
( knots )
Potential work
capacity (ton . knots )
Maximum range
(nautical miles)
Hovercraft 0.24 – 50.5 30 – 70 7 - 3280 60 – 310
Hydrofoil 1.3 – 23 32 – 48 40 – 897 145 – 300
Ferry 90 – 340 14 - 22 1260 - 7480 On cross channel
A comparison of some transport modes on a potential work capacity
Transport mode Lb of fuel required to transport 1 ton / mile
Hovercraft (amphibious) 2.3 – 3.7
Hovercraft (non-amphibious) 1.8
Hydrofoil 1.5 – 4.0
Fuel required to transport one ton of payload over one nautical mile

76. Future of The Hovercraft
•Hovercraft is the newest vehicle on Todays
transport scene as well as being new, this
vehicle is different from other, more
conventional, terrestrial vehicles in that it
requires no surface contact for traction.

79. Application of Hovercraft in Egypt
Case study…
Ch.4

80. Application of Hovercraft in Egypt
1- Amphibious Army transportation mean
at new Suez Canal region:
Suez Canal characteristics:
• The total length is 193 km from Port Said
to Suez.
• The depth is 24 m .
• The width ranges from 280 m to 345 m.
New Suez Canal Characteristics:
• The total length is 72 km , 35 km dry
digging & 37 km deepening the waterway.
• The sand island width ranges between
(500 to 1684) m approximately.

81. ‫االتصال‬ ‫قنوات‬ ‫عدد‬‫ا‬‫البحيرات‬ ‫عن‬ ‫لبعد‬
‫المرة‬
‫الطول‬‫العرض‬
‫االتصال‬ ‫قناة‬
‫االولي‬
8.1521.679.4
‫االتصال‬ ‫قناة‬
‫الثانية‬
11.6598.2131.1
‫االتصال‬ ‫قناة‬
‫الثالثة‬
20.11684.3124.5
‫االتصال‬ ‫قناة‬
‫الرابعة‬
30.4813.193.5

83. Application Of Hovercraft In EGYPT
2-As a fast ferry between EGYPT & SAUDI ARABIA :
THE HOVERCRAFT IS THE BEST ALTERNATIVE TO THE BRIDGE
Using a Hovercraft between “ Lara ” region in EGYPT & “ Sheikh Humaid ” region in SAUDI.
The distance between them is about 20 km .
• This will save about 12 hours for travelers by land in the way of Nuweiba & Aqaba.
2007

84. Application Of Hovercraft In EGYPT
3-As a fast ferry between Hurghada & Sharm
EL-Sheikh :
• The distance between Hurghada and Sharm
EL-Sheikh through the RED SEA is about
110 km.

85. Merits of using Hovercraft ferries in Red Sea
•Sea life and coral reefs remains untouched as Hovercraft
propeller churns up the water .

86. Application Of Hovercraft In EGYPT
4- Used for tourism purposes
Region : Lake Nasser
Target : To transfer tourists to and from the floating Hotel

87. Application Of Hovercraft In EGYPT
5-Land and maritime rescue in case of
storms and floods:
• manager of the maritime rescue and
environment protection organization
of RED SEA confirms the need of
Hovercraft to save people’s lives.

88. All References are under Request…
MKA Team at Ismailia City