report final

Hydrofoil Seminar Report 2010

1. INTRODUCTION

A Hydrofoil is a specially designed hydrodynamic surface that creates lift significantly

exceeding drag. The main function of the hydrofoil is to lift the ships hull out side the water. At

low speeds the ships hull sits on the water and the hydrofoils are totally submerged in water, but

as the speed increases the hydrofoils create lift, bringing the hull outside the water surface.

The basic principle of the hydrofoil concept is simply to lift a ship's hull out of the water and

support it dynamically on wing-like lifting surfaces, i.e. hydrofoils, to reduce the effect of waves

on the ship and to reduce the power required to attain modestly high speeds. Engineers and naval

architects have been intrigued with the possibilities of this concept for many years. A United

States patent for a hydrofoil was defined in the late 1880s, about the same time as the early

airplane and airfoil patents. The earliest record of a successful hydrofoil flight is 1894 when the

Meacham brothers demonstrated their 14 foot test craft at Chicago, Illinois. This compares with

the Wright brothers' first airplane flight in 1903. The early attempts to exploit the hydrofoil

concept were frustrated by lack of suitable structural materials and power plants. However,

advancement in these areas, much of it stemming from aircraft developments, has permitted

development over the past 30 to 40 years of the technology necessary to achieve and demonstrate

reliable and effective hydrofoil ships for both military and commercial below.

Dept. Of Mechanical Engg. 1 SBCE,Pattoor


2. HYDROFOIL BASICS

Many people are familiar with airfoils. Foil is simply another word for the wing (such as the

wing on an airplane). A hydrofoil is a wing that 'flies' in water. Hydrofoil is also used to refer to

the boat to which the water wings are attached. A hydrofoil boat has two modes of operation:

a. as a normal boat with a hull that displaces water and

b. with the hull completely out of the water and only the foils submerged.

Hydrofoils let a boat go faster by getting the hull out of the water. When a normal boat moves

forward, most of the energy expended goes into moving the water in front of the boat out of the

way (by pushing the hull through it). Hydrofoils lift the hull out of the water so that you only

have to overcome the drag on the foils instead of all of the drag on the hull.

The foils on a hydrofoil boat are much smaller than the wings (foils) on an airplane. This is

because water is about 1000 times as dense as air. The higher density also means that the foils do

not have to move anywhere near as fast as a plane before they generate enough lift to push the

boat out of the water.

The hydrofoils generate lift only when they are in the water; if they leave the water, the boat will

crash down onto the surface of the water (and thus submerge the foils) until the foils generate

enough lift to lift it back out. Like an airplane, a hydrofoil must be controllable in terms of pitch,

roll, and yaw. Unlike an airplane, a hydrofoil must also maintain a consistent depth. Whereas an

airplane has a range of about 40,000 feet in which to maintain its altitude, a hydrofoil is limited

to the length of the struts, which support the boat above the foils.



3. WORKING

3.1.MAIN FUNCTIONAL REQUIREMENT

Lift the boat's hull outside the water.

3.2.DESIGN PARAMETER

Hydrofoil (It is a foil or wing under water used to lift the boat's hull until it is totally outside the

water.)

3.3.GEOMETRY/STRUCTURE

Figure 1: Detail of Hydrofoil Geometry



Figure 2: Flow around a hydrofoil (aerofoil)

3.4. EXPLANATION OF HOW II WORKS/ IS USED

1. At low speeds the hull (body of ship) sits in the water and the hydrofoils are totally

submerged in the water.

2. As the boat's speed increases, the hydrofoils create lift.

3. At a certain speed, the lift produced by the hydrofoils equals the sum of of the boat and

cargo weights. Therefore the hull comes out of the water.

4. Instead of having an increase in drag with increasing speed because the hull is lifted out

of the water (contrary to what happens in traditional boats due to pressure drag), the hydrofoils

provide a more efficient way of cruising. Decreasing the drag contributes to the better use of the

power needed for the movement of the boat.



4. DOMINANT PHYSICS

How is the lift produced - Fluid Dynamics.

Bernoulli's Equation: Po = Pt + 1/2pv12 + Pgy1 = P2 + 1/2pv2

2 + pgy2

Variables Units

Po Stagnation Pressure

P Pressure

p Density

V Velocity

g Gravitational- constant

[Pa] or [lbf/ft2]

[Pa] or [lbf/ft2]

[kg/m3] or [lbf/ft3]

[m/s] or [ft/s]

[m/s2] or [ft/s2]



5. PRINCIPLE

This equation applies to flows along a streamline which can be modeled as: inviscid,

incompressible, steady, irrotational and for which the body forces are conservative. Also the

difference on the height of the foil (the distance from the bottom section to the upper one) is

small enough so that the difference pgy2 – pgy1 is negligible compared to the difference of the

rest of the terms. What is left is that the pressure plus one half the density times the velocity

squared equals a constant (the stagnation pressure).

As the speed along these streamlines increases, the pressure drops (this will become important

shortly). The fluid that moves over the upper surface of the foil moves faster than the fluid on the

bottom. This is due in part to viscous effects, which lead to formation of vertices at the end of the

foil. In order to conserve angular momentum caused by the counter-clockwise rotation of the

vortices, there has to be an equal but opposite momentum exchange to the vortex at the trailing

edge of the foil. This leads to circulation of the fluid around the foil. The vector summation of

the velocities results on a higher speed on the top surface and a lower speed on the bottom

surface. Applying this to Bernoulli's it is observed that, as the foil cuts through fluid, the change

in velocity produces the pressure drop needed for the lift. As it is presented in the diagram, the

resulting or net force (force= i pressure) (area)) is upward.

Detail of Hydrofoil:

a) Pressure Profile

b) Momentum Transfer

c) Circulation

d) Streamlines



This explanation can be enriched with the Principle of Conservation of Momentum. (Momentum

= (mass) (velocity)) If the velocity of a particle with an initial momentum is increased, then there

is a reactant momentum equal in magnitude and opposite in direction to the difference of the

momentums. (See diagram). (Mi = Mf + C1M)

Figure 3: Detail of Hydrofoil


a) Pressure Profileb) Momentum Transferc) Circulationd) Streamlines


6. FOIL LIFT AND DRAG

FOIL LIFT IS CALCULATED USING THE EQN:

Z = (l/2)p*V2*<Cl*S

FOIL DRAG IS CALCULATED USING THE EQN:

Z = (l/2)p*V2*<Cd*S

WHERE

p=DENSITY

V=VELOCIY

C=DRAG OR LIFT COEFFSHPROFILE C.S.AREA



7. ANGLE OF ATTACK

As it has been presented, lift comes from the dynamics of the fluid in the area surrounding the

foil. But the lift can be optimized by positioning the hydrofoil at an angle (relative to the

incoming fluid flow) called the angle of attack (See diagram). The goal is to optimize the lift to

drag ratio. This ratio depends on the shape of the foil, which in this case is considered to be a

thin foil. With a small angle of attack, the lift increases rapidly while the drag increases at a

small rate. After an angle of —10° the lift increases slowly until —15° where it reaches a

maximum. After ~15° stall can set in. 'When the angle of attack is 3° to 4° the ratio of lift: drag is

at it's maximum. So the foil is more efficient at those angles (3°and 4°) with lift to drag ratios of

— 20 to 25:1



8. LIMITING PHYSICS

8.1. DETAIL OF HYDROFOIL GEOMETRY

At first, people can think that stalling is likely to be a problem in hydrofoils as it is in airfoils, but

surprisingly it is not. A steep angle of attack is not needed in the design of the hydrofoil. On the

contrary, small angles of attack are used on hydrofoils to optimize the lift to drag ratio as

explained before.

What is a primary concern is the design of the foil, the struts/supports, and their positioning. All

these features have to be taken in consideration. So the features are designed to produce a

minimum speed that will lift the boat of certain weight and keep it foil borne.

One problem that a hydrofoil craft can experience is the height of the waves being greater than

the struts. Also, if the craft is traveling faster than the waves, the foils could break to the surface

and outside of the water, resulting in a loss of lift and a negative angle of attack when the foil

dives into the next wave, making the craft crash into the sea. Engineers have designed hydrofoils

to minimize these limitations and better the ship's performance.


e)


There are two particularly persistent problems faced by designers of hydrofoils:

Cavitation and ventilation

Ventilation occurs when part of a hydrofoil pierces the surface of the water and air gets sucked

down the lifting surface of the foil. Since air is much less dense than water, the foil generates

much less lift and the boat crashes down. Ventilation can occur at any air-water interface.

Ventilation occurs when air gets sucked down to the lifting surfaces. Although ventilation can

occur on -vertical struts, 'V foils are particularly prone to this problem because of the shallow

angle the foil makes with the water surface.

Cavitation occurs when the water pressure is lowered to the point where the water starts to boil.

This frequently happens with propellers. When a propeller is turned fast enough, the blades

generate so much lift (i.e. the pressure on the lifting surface of the blades goes down) that the

water flowing over the propeller blades begins to boil. When cavitation occurs, the foil no longer

generates enough lift and the boat crashed down onto the water.

Note that a hydrofoil is not a hovercraft. Hydrofoils fly on wings in the water that generate lift

whereas hovercraft floats above the water on a layer of air. In both cases the boat's hull leaves

the water, but the mechanisms by which this is achieved are completely different



9. CONFIGURATIONS

Hydrofoil configurations can be divided into two general classifications, surface piercing and

fully submerged which describe how the lifting surfaces are arranged and operate (see Figure 1).

In the surface piercing concept, portions of the foils are designed to extend through the air/sea

interface when foil borne. Struts connect the foils to the hull of the ship with sufficient length to

support the hull free of the water surface when operating at design speeds. As speed is increased,

the lifting force generated by the water flow over the submerged portion of the foils increases

causing the ship to rise and the submerged area of the foils to decrease. For a given speed the

ship will rise until the lifting force equals the weight carried by the foils. As indicated by the

terminology, the foils of the fully submerged concept are designed to operate at all times under

the water surface.

Figure 4: Surface-Piercing (Left) & Fully Submerged (Right) Foil Configurations

The struts which connect the foils to hull and support it when the ship is foilborne generally do

not contribute to the total hydrofoil system lifting force. In this configuration, the hydrofoil

system is not self-stabilizing. Means must be provided to vary the effective angle of attack of the



foils to change the lifting force in response to changing conditions of ship speed, weight and sea

conditions. The principal and unique operational capability of hydrofoils with fully-submerged

foils is the ability to uncouple the ship to a substantial degree from the effect of waves. This

permits a relatively small hydrofoil ship to operate foilborne at high speed in sea conditions

normally encountered while maintaining a comfortable motion environment for the crew and

passengers and permitting effective employment of military equipment. It is this desirable

characteristic which has caused the hydrofoil ship development in the United States to

concentrate on the fully- submerged foil concept.

The basic choices in foil and strut arrangement are canard, conventional or tandem as shown in

Figure 2. Generally ships are considered conventional or canard if 65°/o or more of the weight is

supported on the front or the aft foil respectively. If the weight were distributed relatively evenly

on the fore and aft foils, the configuration would be described as tandem.



Figure 5: Foil/Strut Arrangements

10.FEATURES

10.1. WEIGHT LIMITATIONS

Like the airplane designer, the hydrofoil designer must, at all times, be extremely conscious of

weight. The hydrofoil type of craft is weight critical, and every pound of weight saved in

structure, outfit, or machinery means weight available for pay load and fuel.



The structural engineer, in designing hydrofoils to conserve weight, uses aircraft techniques.

Relative to conventional ships, hydrofoil craft are subject to very high loadings, as caused by

high operating speeds. Likewise, lightweight, high strength materials are used. He also must

contend with fatigue and problems of hydroelasiticity, including both divergence and flutter.

10.2. HULL CONSIDERATIONS

The development of a satisfactory hull form for hydrofoil application represents a significant

challenge to the designer. The hull should perform well in the hullborne mode but also during

takeoff and during foilborne operation where impacts with waves are involved. In addition, the

hull configuration of a hydrofoil ship must satisfy all of the requirements for strength, freeboard,

and intact and damaged stability for any other ship.

Relatively high power requirements for high-speed operation, in common with other high

performance systems, pay a high performance dividend for achieving a minimum weight

structure. Therefore, hydrofoil ship hulls are generally constructed using high-grade aluminum

alloys, 5000 series weldable alloy being typical. Structurally, the hull must have the strength to

resist wave impact at high speed as well as distribute the concentrated load at the strut

attachment points. Although hydrofoil hulls may appear quite conventional, the required

compromises are more complex than for a monohull because of the many operating modes of the

ship. An efficient hull form for a lower speed operation requires a narrow beam. However, a

righting moment large enough to satisfy the stability criteria of reference [6] with the foils

retracted generally dictates a wide beam. Cresting the tops of waves while foilborne points

toward the use of a deep vee forward and high deadrise.

Another major consideration in hydrofoil hull design is the requirement for good seakeeping

characteristics in a heavy sea. If hydrofoil craft are to operate unrestricted in open ocean, they

must be capable of surviving storm seas in the hullborne condition. Furthermore, in certain

missions, it may be expected that the hydrofoil ship will spend the greater portion of its operating

lifetime in the hullborne mode. Thus, it is essential that close attention be given to the hull

seakeeping characteristics. With the foils extended during hullborne operation, which is normal



operation at sea, there is a significant reduction of craft motion in both the roll and pitch modes

which is normally not heavily damped. Thus the strut/foil system gives hydrofoil craft hullborne

motion characteristics of ships having much larger displacement.

10.3. FOIL SYSTEMS

Foil variable lift is obtained by either trailing edge flaps or variable incidence of the entire foil as

illustrated in Figure 5.

Figure 6: Hydrodynamic Force Control

10.4. WEIGHT TREND

A fundamental limitation is imposed by the so-called "square- cube" law, which impacts the

growth potential of hydrofoil ships. The lift developed by the foils is proportional to their

planform area (the square of a linear dimension), whereas the weight to be supported is

proportional to a volume (the cube of a linear dimension). It follows that as size of the hydrofoil

is increased, the foils tend to outgrow the hull. Aircraft solve this problem by increasing speed

and wing loading as size is increased, but practical hydrofoil speeds are limited by cavitation.

In the early period of hydrofoil development it was felt that an increase in the foil and strut

weight fraction by direct application of the square-cube law would inherently limit hydrofoil

size. More detailed design studies show that foil system weight fractions increase only slightly

with displacement, Figure 6.



Figure 7: Strut and Foil System Weight Trend

The principal reasons why the weight fraction does not increase as might be expected is that

required strut length varies with design sea state, not ship size, and larger foils are structurally

more efficient. For hydrodynamic efficiency, it is desirable to use as high a foil aspect ratio

(span/chord) as possible. The PHM aft foil extends almost 10 feet on either side of the hull.

Thus, a camel is normally used to hold the ship away from the pier for mooring. When no camel

is available the ship must be moored across the end of a pier or the transom of a larger ship with

the stern overhanging. PHMs have occasionally nested bow to stern. As ship size increases and

foils grow relative to the hull and in actual dimension, practical considerations dictate efforts to

limit the span. The trend will be to move toward tandem foil configurations to divide the weight

more evenly between the forward and aft foils.

11.PROPULSION SYSTEMS

Modern hydrofoil ships have been made possible by the development of lightweight diesel

engines and marinized gas turbine engines. Most of the European commercial ships using fixed

surface-piercing foil systems have used lightweight diesel engines driving subcavitating



propellers by means of an angled transmission system. This combination provides simplified

construction, relative ease of maintenance and low cost. However, the comparatively high

specific weight (6-8 pounds per horsepower) of the diesel engines and higher overall drag have

resulted in practical design speeds of these ships of about 35 to 40 knots.

Existing aircraft gas turbine engines slightly modified and coupled with specially designed free

powered turbines are available in sizes with power ratings up to about 30,000 horsepower and

specific weights of around 0.5 pounds per horsepower. The newer large engines employing blade

cooling techniques have specific fuel consumption rates at their design power about equal to

diesel engines. Gas turbine engines have been used in all major U.S. military and commercial

hydrofoil ships permitting practical design speeds greater than 40 knots. Propellers are the most

efficient propulsion device available for operating over the subcavitating speed range of current

hydrofoil ships. The power transmission systems required when using fully submerged foil

systems consist of right angle bevel gears, flexible shafts and possibly a speed reduction gearbox

in the propeller transmission pod. See Figure 7 as an example.

Figure 8: PGH-1 FLAGSTAFF Propulsion System

Problems encountered with gear transmission systems in early hydrofoil ships led to interest in

waterjet propulsion systems. While not entirely eliminating the need for gearboxes, these

systems consist of underwater inlets, water ducts in the struts, a pump located in the machinery

spaces and an above-water exhaust nozzle. The U.S. Navy's PHM waterjet system is shown on



Figure 8. The price paid to achieve these less complex waterjet systems is a decrease in

propulsive efficiency of about 20% at 45-50 knots and considerably more at takeoff speeds along

with an increase in propulsion system weight due to the water carried in the system.

Figure 9: PHM Waterjet System

12.AUTOMATIC CONTROL SYSTEM



As noted earlier, surface-piercing hydrofoil configurations are self-stabilizing in both pitch and

roll and thus do not require an automatic control system. However, to reduce the inherent

reaction to rough seas, a number of ships have added trailing- edge flaps to the surface-piercing

foils and have used autopilots for ride improvement.

In the United States, full automatic control of submerged foils has been deemed necessary to

attain the seaway performance desired for ocean-going hydrofoil ships. Typically, control is

accomplished by positioning trailing-edge flaps on the forward and after foils and by rotating the

swiveled forward strut (rudder), or by moving the entire foil surface and by using the power

driven aft strut as a rudder. See Figures 9 and 10 for schematic and pictoral diagrams of a control

system. The control surfaces are positioned by means of conventional electro- hydraulic servos.

The control system motion sensors consist of: 1) a vertical gyro which measures craft pitch and

roll angular motion, 2) a rate gyro which measures craft yaw rate, 3) three vertical

accelerometers, one accelerometer being located approximately on top of each strut (the two aft

accelerations work differentially to provide roll angular acceleration feedback, and they work in

unison to provide pitch and heave acceleration feedback), and 4) a height sensor which measures

the height of the bow above the water surface. The manual inputs consist of a foil depth

command, which the helmsman uses to select any desired foil depth (or flying height), and the

helm, which introduces the craft turning commands.

Figure 10: Hydrofoil

ACS Schematic



Figure 11: Typical Hydrofoil Automatic Control System (ACS )

The ACS provides continuous control during takeoff, landing, and all foilborne operations. The

pitch, roll, and height feedback loops provide automatic stabilization of the craft. The craft is

automatically trimmed in pitch by the pitch feedback, and roll trim is accomplished by helm

inputs. To steer the ship, the helmsman simply turns the helm, and the ACS automatically

maintains a coordinated turn, with turn rate being proportional to helm deflection. ACS system

requirements and operation are discussed in detail in References (7), (8), and (9).

13.HYDRAULIC SYSTEM



The hydraulic and automatic control systems are worthy of mention because: 1) they have

proven reliable and functionally well suited for a hydrofoil ship, 2) they combine proven aircraft

system equipment applications, and 3) they are essential to all operations: foilborne, hullborne,

and docking. Because the hydraulic systems are crucial to both foilborne and hullborne

operation, the design should employ multiple levels of redundancy to assure continued operation

in the event of system failures.

On the PHM, for instance, four separate systems supply the required power to the various

hydraulic equipment users which include the foilborne and hullborne control actuators, strut

retraction and lock actuators, bow thruster, anchor windlass, and emergency fuel pump.JSystems

No. 1 and No. 2 supply hydraulics to the forward part of the ship while systems No. 3 and No. 4

supply the aft part. Two separate supply systems feed each user with provisions included to

transfer (shuttle) the user from its primary supply to its alternate supply in the event of loss of

primary supply pressure. The hydraulic systems of the PHM operate at a standard 3,000 psi

(20.68 MN/m2) constant pressured Proven aircraft hardware, mostly from the Boeing 747

aircraft, was used where possible. The hydraulic pumps, tube fittings, tubing material, and filters

were all taken directly from the 747. In the case of the foilborne and hullborne steering actuators,

an automatic shuttle valve was specifically developed for the hydrofoil program which rapidly

transfers the user actuator from a failed supply to the alternate, thus assuring continued safe

foilborne operation. The hydraulic actuators on the PHM were for the most part specifically

designed and developed for this program. The four foilborne control actuators, the hullborne

steering actuator, two hullborne thrust reverser actuators and the strut retraction actuators all

were designed, manufactured and qualified to military specifications including rigorous

environmental and life testing.

The PHM hydrofoil program pioneered the use of a new hydraulic fluid, a synthetic

hydrocarbon. This new fluid provides a much greater resistance to fire and explosion than its

predecessor. At the same time it overcomes the serious shortcomings of phosphate ester base

fluids which have proven to be incompatible with the saltwater environment.

14.CHARACTERISTICS



14.1. RESISTANCE AND POWERING

Although the major reason for the employment of hydrofoils is to lift the hull out of the water to

reduce the effect of waves and to reduce the drag at high speed, a naval hydrofoil ship spends a

considerable portion of its life hullborne and must have an efficient hull form to keep the drag

low at low speed and through takeoff. Total drag just prior to takeoff is a significant factor in

establishing the power requirement. Careful attention must be paid to the hull design to minimize

this effect. Figure 3 shows a generalized smooth water drag curve for d hydrofoil craft with its

significant "hump" prior to takeoff. Comparison is also made with a typical planing craft to

illustrate the high-speed advantage of the hydrofoil even in smooth water. To overcome

additional takeoff drag which results from rough water, a power margin over the smooth-water

takeoff drag is required. Since the magnitude of this margin is a prime factor in the sizing of the

propulsion system,} it is essential that it not be arbitrarily overspecifled. Tests in design sea

states on well-instrumented U.S. Navy hydrofoils show that 20 to 25 percent margin is ample to

permit takeoff in rough water in any direction.

Figure 12: Typical Calm Water Thrust

14.2. SEAKEEPING



Some of the principle advantages of hydrofoil ships, over all other monohull or alternative ship

types are: (1) the ability of a ship, which is small by conventional ship standards, to operate

effectively in nearly all sea environments, and (2) an improved ratio of power to displacement in

the 30 to 513 knot speed range permitting economical operation at these higher speeds. The

submerged-foil ship can maintain its speed and maneuverability in heavy seas while

simultaneously providing a comfortable working environment for the crew.The ship's automatic

control system (ACS) provides continuous dynamic control of the ship during takeoff, landing,

and all foil borne operation In addition to providing ship roll and pitch stability, the ACS

controls the hull height above the water surface, provides the proper amount of banking in turns

and all but eliminates ship motions caused by the orbital particle motion of waves. Foilborne

operations only become limited as wave height exceeds the hydrofoil's strut length.] Figure 4

shows operating data points for three submerged-foil hydrofoil ships in actual sea conditions.

The data clearly show only a modest reduction in speed as wave heights increase. A hypothetical

operating envelope is drawn to represent hydrofoils designed to have a 50-knot speed capability

in calm water.

14.3. MANEUVERING

Besides a significant speed advantage, hydrofoils are more maneuverable and provide a more

stable platform than conventional ships. Foilborne turns are accomplished in a banked

(coordinated) fashion. This causes the centrifugal force required in turns to be provided

predominantly by the reliable lift capability of the submerged foils rather than by the

unpredictable side forces from the struts. Turn coordination enhances crew comfort during high-

rate turns because the accelerations due to turning are felt primarily as slightly greater vertical

forces rather than lateral forces. For example, a 0.4g turn is felt as only 0.08g vertical

acceleration increase while the lateral acceleration is zero. Therefore, hydrofoil ships have design

turn rates of 6 to 12 degrees per second, two to four times those of conventional ships, and they

can maintain these rates in both calm and rough seas. This makes the hydrofoil ship a more

difficult target for enemy missiles, guns, or torpedoes. The exceptional stability of the hydrofoil

ship makes it a superior platform in which to mount surveillance equipment and weapons while

maintaining crew comfort and proficiency.

15.ADVANTAGES



1. A hydrofoil requires only 50°/o of the power of a displacement vessel of comparable

size, for a given speed

2. The hydrofoil due to their small size and maneuverability, are target less vulnerable to

tactical military weapons like missiles

3. Greater platform stability and high speed

4. Can be maintained even in seaway due to better sea keeping ability

15.1. SOME HYDROFOILS AND THEIR USE

Hydrofoils have become very popular. They are used in various kind of sea traveling, from

military use to water sports. The high speed, smooth cruise and better turns delivered by

hydrofoils have been used in military ships. Sailing has also adopted the hydrofoils to gain more

speed. They enable new inventions that can satisfy people's desire to challenge danger, like the

sky ski. It is a water ski with a hydrofoil attached, which permits people to fly above the water

surface. Every day more hydrofoils are used, and in the future, they may be the dominate method

of sea traveling

16. CONCLUSION



Although the basic concept of hydrofoils has been around for 85 years, it has only been in the

last 35 years through advances in materials, light weight propulsion plants, and control theory,

they have become a viable open ocean concept. Involved. The design of a hydrofoil demonstrates

the very essence of engineering that is the trade-off and compromise among often-conflicting

requirements of many disciplines to arrive at a good balanced design.

17. REFERENCES



www.foils.org

www.howstuffworks.com


report final

Documents

hydrofoil boat

water surface

hydrofoil concept

water wings

water contrary

hydrofoil geometry

introductiona hydrofoil

hydrofoil aerofoil