Sample Phase 2 Report

7/30/2019 Sample Phase 2 Report

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Phase II Design Report Team Dozen 3/2/2012

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3/2/2012

Dr. Paul E. Labossiere

MECH 2012

TEAM

DOZENPHASE IIHOVERCRAFT DESIGN REPORT

Daryn Freier, Team Leader

Phillip Pearson, Technical Secretary

Steve Thomasson, Design Lead

Kirk Calvadores, Research and

Development

Clint Kaminshi, Materials Specialist


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Table of ContentsTable of Figures ............................................................................................................................................................. 3

1.0 Executive Summary ................................................................................................................................................. 4

1.1 Background.......................................................................................................................................................... 5

2.0 Introduction ............................................................................................................................................................. 6

2.1 Purpose Statement .............................................................................................................................................. 6

2.2 Problem Definition .............................................................................................................................................. 6

2.3 Goals .................................................................................................................................................................... 6

3.0 Research .................................................................................................................................................................. 7

3.1 What Others Have Done ..................................................................................................................................... 7

3.1.1 Commercial Use ........................................................................................................................................... 8

3.1.2 Military Use .................................................................................................................................................. 8

3.1.3 Personal Use ................................................................................................................................................ 9

3.2 Fundamental Equations and Analysis.................................................................................................................. 9

3.2.1 Lift ................................................................................................................................................................ 9

3.2.2 Thrust ......................................................................................................................................................... 10

3.2.3 Drag ............................................................................................................................................................ 11

4.0 Design Space .......................................................................................................................................................... 12

4.1 Client Needs ...................................................................................................................................................... 12

4.2 Target Specifications ......................................................................................................................................... 14

5.0 Preliminary Conceptual Designs ............................................................................................................................ 15

6.0 Conceptual Development ...................................................................................................................................... 17

6.1 Hull/Deck Concepts ........................................................................................................................................... 18

6.2 Skirt Concepts .................................................................................................................................................... 18

6.3 Lift System Concepts ......................................................................................................................................... 18

6.4 Thrust System Concepts .................................................................................................................................... 19

7.0 Concept Screening and Scoring ............................................................................................................................. 19

7.1 Concept Screening ............................................................................................................................................. 19

7.2 Concept Scoring ................................................................................................................................................. 24

8.0 Detailed Design ...................................................................................................................................................... 36

9.0 Summary ................................................................................................................................................................ 47

10.0 Recommendation ................................................................................................................................................ 49

11.0 References ........................................................................................................................................................... 50


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Table of Figures

Team Dozen Logo....1

1.1 SR.N1 General Arrangement [4].......53.1 Typical Skirt Designs [5].......7

5.15.8 Preliminary Concepts......15

5.95.15 Preliminary Concepts....16

6.1 Major components [12] ...17

7.1 Concept ATop Isometric View30

7.2 Concept AFront View..30

7.3 Concept ARear Orientation Isometric View31

7.4 Concept FTop Isometric View.32

7.5 Concept FFront View...32

7.6 Concept FRear Orientation Isometric View33

7.7 Concept GTop Isometric View34

7.8 Concept GCross-Section Side View34

7.9 Concept GBottom Isometric View...35

8.1 Final DesignIsometric View....36

8.2 Final DesignFront View...37

8.3 Final DesignSide View37

8.4 Final DesignSection View...38

8.5 Final DesignDetailed View..39

8.6 Final DesignComponent View.40


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1.0 Executive Summary

The goal of the design process is to produce and present a functional hovercraft that performsbetter than its competitors. The hovercraft must travel in a straight trajectory, have a minimal

cost, be aesthetically appealing, operate with no external interference, be user friendly and safe,easily manufactured, while being faster than its competitors. Things taken were intoconsideration when designing the hovercraft are the effect of aerodynamic forces, selection ofappropriate materials, shape and size of the hovercraft, arrangement of components, and themanufacturing cost. After extensive research we configured a series of concept scoring chartsthat aided us in narrowing down our concepts. Through this screening process we came up withten concepts that integrated the information we learned into their designs. As a result of furtherconcept screening and research from various sources we were able to narrow all of our designstyles to the following three concepts. From these three concepts we developed a final conceptthat was a combination of the three designs, the reason for this was to reduce manufacturingcosts, increase speed and meet the client needs as much as possible. The final concept has the

following design, materials and constraints: A fan hub with a fin attached on the back, both madefrom plastic, that has integrated aerodynamic contours to increase air control to desired direction,custom propulsion fan to increase thrust output, a custom lift fan for compatibility with thethickness of the hull while maintaining required thrust output, nine cell NiCd battery for thethrust fan, six cell NiCd battery for the lift fan, a tear drop shaped hull made with a two layerhigh density foam, a bag skirt made of tarpaulin bond between the two layers of high densityfoam, the motor for the propulsion fan is CN12-R-XC which has 25500 rpm and the motor usedfor the lift fan is the CN12-R-LC and has 15200 rpm. We found that our final design showedbetter theoretical performance capability than any other considered design. However the designwas restricted by its relatively high manufacturing cost, so research alternative manufacturingprocesses are needed before further development and production of the hovercraft.


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1.1 Background

Over the years, hovercraftshave been used in manydifferent areas. From personal

use, to public transit, tomilitary applications, theconcept has received a lot ofattention. The first mention ofhovering crafts was in 1716 bySwedish scientist EmanuelSwedenborg [1] but it wasntuntil 1915 that the first air-cushion vehicle was proposedby Dagobert Mller vonThomamuehl [2]. The year

1931 marked the recognitionof the first true hovercraft byFinnish aero engineer Toivo J.Kaario [3]. After World WarII, many groups began developing air-cushion vehicles. However, due to lack of funding andinterest, advancement in this field was limited. Finally in the late 1950s, Sir ChristopherCockerell designed and developed the SR.N1 [3] which set the standard for the hovercrafts wesee today.

Figure 1.1 SR.N1 General Arrangement [4]


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2.0 Introduction

2.1 Purpose Statement

The purpose of this design report is to gain a better understanding of the Engineering designprocess. From the problem definition, to selecting the appropriate manufacturing process andeverything in between, we will learn what truly goes into fulfilling our clients needs. Ourcreativity, knowledge, ability to work in teams and technical skills will be tested and presented ina fully developed, formal report, documenting the entire design process.

2.2 Problem Definition

The problem we have been presented with is to design and manufacture a functional hovercraftthat is fast (forward motion) and travels in a straight direction without user input, while

maximizing cost efficiency. The hovercraft is to be produced using obtainable materials andmanufacturing methods.

2.3 GoalsWe have determined the following list of goals for our hovercraft design:

Cost EffectiveWe aim to develop a design that requires inexpensive materials and low production costs.

Visually Appealing

The design should catch the consumers eye without compromising functionality.

Linear VelocityThe vehicle must be able to compete in a drag race-like setting.

LightweightA lightweight design will reduce the amount of material required and will increase portability.

DurableIn the event of a collision, the craft must remain intact or be easily repairable.

SafeAbove all else, our design should not put the user or observer in harms way.


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3.0 Research

3.1 What Others Have Done

As the design of hovercrafts developed over time, new features and modifications were added toexisting models, a major one being the addition of the skirt. The initial design was an extension ofthe hull, made of rigid material that was perpendicular or angled to the ground. When it was foundthat this only allowed for low clearance and the inability to clear obstacles, a change was made.

It was proposed to use a flexible, durable, and most often, waterproof material to create the skirt.This skirt would replace the rigid bottom of the hovercraft as the section of the unit that filled withair. The skirt of the hovercraft is typically made from neoprene coated nylon, thick vinyl sheeting orsynthetic canvas cloth. Thick vinyl sheeting is fairly inexpensive and good for light dutyapplications. Neoprene coated nylon is the recommended choice, but synthetic canvas cloth can beused for light duty hovercraft usage as well. Initially, a double wall design was proposed where air

travelled between two layers of material creating a channel of air. With this design, it was found thatupon contact with an obstacle, the walls would collapse at the point of contact, restricting air flow.Later, the two wall design evolved to a single wall that was more forgiving when coming into contactwith obstacles because deformation of the skirt at one point would be compensated at another.

The design of a hovercrafts skirt is determinedby its applications. Popular designs include thewall shirt, bag skirt, jupe skirt and finger skirt.A bag or wall skirt is a tube of material thatcovers the perimeter of the hull. Bag and wallskirts are ideally suited for larger/slowermoving hovercrafts. Finger skirts are made up

of many individual segments that press togetherwhen inflated and are typically used for speed.The jupe skirt is several cone-shaped tubes,attached to the bottom of the hull, surroundedby a wall of material around the perimeter.When designing a skirt, the height shouldalways be considered. The higher the skirt, thelarger the obstacles the hovercraft can clear.However, if it is too tall, the hovercraft willslide off the cushion of air, resulting indeflation of the skirt and causing the vehicle to

become extremely unstable.

In addition to skirt design, the shape of the hull was modified as well. Once again, this is dependenton the use of the vehicle. The hull is usually made from a combination of plastic, plywood,fiberglass, aluminum, and Styrofoam. The components of the hovercraft have to be well balanced onthe body to prevent one side of the hovercraft from dragging and possibly letting the air cushionescape from the opposite side deflating the skirt. Models used for carrying cargo will normally have aflat deck with an oval, or rectangular with rounded corners, shape. These models are usually for

Figure 3.1 Typical Skirt Designs [5]


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commercial or military use. Smaller models that have narrower hulls, with possibly chamfered decks,are normally used for speed. These models would be for personal use with applications such asracing, search and rescue and patrolling.

Hovercraft models also vary in the quantity and use of fans. Military or commercial hovercrafts mayhave as many as six fans for lift and two for thrust. Smaller models will either use a single fan forthrust and lift, called an integrated system, or a separate fan for both. In an integrated system, air isdiverted from the thrust fan to fill the skirt with air. Fins have been implicated with thrust fans inorder to control air flow. Fins prevent the air from coning after passing through the fan and focus it instraight channels maximizing forward momentum. Along with fins, rudders are used for steering.Normally attached to the fans, rudders control the direction of the air flow and therefore the directionof the hovercraft. Apart from fans, some hovercrafts are propelled by jet engines. Jet engines providemuch more speed than fans, due to concentrated air flow, but similarly require much more power.

Hovercraft power systems vary by scale and usage. As mentioned previously, hovercrafts aretypically propelled by fans or jet engines. The main use of commercial or military hovercrafts is formoving large amounts of cargo. As the weight of the cargo, and the vehicle itself, increases, more

power is required to lift it off the ground and move it forward, thus introducing the power-to-weightratio. The amount of clearance between the skirt and ground is determined by the power-to-weightratio. The thrust systems operate more efficiently when the ground clearance is high, but if theground clearance is too high the hovercraft will become unstable. Due to this power requirement,large hovercrafts rely on combustion engines. Smaller hovercrafts may run on combustion engines aswell but some can rely on electric power depending on scale and desired speed.

3.1.1 Commercial Use

The commercial hovercraft is used for many different tasks such as mass transportation. The firstcommercial hovercraft able to carry passengers was the Vickers VA-3 and began service in the

summer of 1962. In the English Channel, commercial hovercrafts are used as transport ferries forpassengers, automobiles and goods. The capacity of the commercial passenger hovercraft hasincreased over the years, for example in 1965 a SR.N6 carried 38 passengers and in 1983 theAP1-88 carried 98 passengers and more recently in 2007 the BHT130 carried 130 passengers.Scandinavian airline (SAS) used a hovercraft for a charter between airports in Denmark andSweden. In Alaska, the U.S. Postal Service uses a hovercraft to transport mail, freight andpassengers to remote towns with no road access. Also in Alaska, there is a cargo hovercraft, theSuna-X, that can carry up to 47 passengers and 47500 lbs of cargo and is used for transportbetween small remote communities.

3.1.2 Military Use

The hovercraft is well suited for military use because of the hovercrafts ability to move overdifferent terrains quickly. The military uses hovercrafts to transport equipment and soldiersacross land and water. Most military hovercrafts are armed with gun turrets and/or grenadelaunchers and are also armoured for protection. The Soviet Union designed and built the worldslargest hovercraft the Zubr. The first use of military hovercraft application was with the SR.N1


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and was built in England by Saunders-Roe and the United Kingdom joint forces used thishovercraft. The military hovercraft is included in the navy sector of a countries military force.

3.1.3 Personal Use

The personal hovercraft can be used to describe search and rescue, racing, model, and homemadehovercrafts. The personal hovercraft is used for search and rescue because of the hovercraftsability to ride over any terrain which no other ATV can. The hovercraft is used for search andrescue in Finland and the UK to rescue people from thick mud. The hovercraft is also used inCanada and the US for water and ice rescues. Also the hovercraft has a low impact on lifebeneath the water it hovers over which makes the hovercraft a good fit for research on sensitivewater systems. The personal hovercraft is also used as a means to inspect shallow bed offshorewind farms. The personal hovercraft is also used for racing on a land and water track. Thedrivers of racing hovercrafts have to wear helmets as well as a flotation device in case of a crashon the water. Model hovercrafts and R/C hovercrafts are typically made of plastic and areconsidered to be more of a hobby than any other hovercraft. Homemade hovercrafts are also

considered more of a hobby and are typically made from relatively cheap and lightweightmaterials.

3.2 Fundamental Equations and Analysis

In this section we will be analyzing three forces that will allow us to theoretically maximize theperformance of our hovercraft. First we will be analyzing the lift force produced by ourhovercraft. Creating this force reduces the friction between the hovercraft and the surface it is on;essentially allowing it to hover. We will also be analyzing the thrust produced by thehovercraft. Thrust is the force that allows the hovercraft to move forward. Lastly in this section

we will evaluate how the drag force affects the hovercrafts performance. This is a force thatopposes the forward movement of the hovercraft, essentially slowing it down. Ultimately in thissection we will be considering these forces when designing the hovercraft so that we canmaximize/minimize them for optimal performance of our hovercraft.

3.2.1 Lift

The lift force that we want to produce in our hovercraft is a force that is equal to or greater thanthe weight of the hovercraft. Lift is produced by blowing air into the hovercrafts skirt, creating ahigh pressure pocket. Since the pressure in the skirt is greater than the pressure produced by the

weight of the hovercraft, an upward force is created. Ideally, we want the lift force produced tobe equal to the weight of the hovercraft in order to maximize efficiency. If the lift produced isgreater than the weight, air will escape the skirt through the bottom, thus lowering the lift forceuntil equilibrium is obtained. The lift force can be calculated using the equation:

[8]


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Where A is the cross-sectional area of the skirt in m2, PC is the air cushion pressure within theskirt in Pa, and the lift,FL in N,should be equal to the weight of the hovercraft. When designingour hovercraft we need to take lift into consideration. The cross sectional area and the weight ofthe hovercraft will determine how much lift our hovercraft will need to produce. Therefore,considering the lift required is essential when determining the size and weight of our hovercraft.

We must also design our skirt so that it contains the air, but also allows air to escape from thebottom when the pressure is too high. To ensure perfect balance, we must control thehovercrafts pitch, vertical movement of the nose, and yaw, horizontal movement of the nose. Itis vital that the pressure is distributed evenly throughout the skirt and that the center of mass ofthe hovercraft is properly supported so that no unwanted moment will be created.

3.2.2 Thrust

Thrust, which is created by the propulsion system, is the force which pushes the hovercraftforward. Having maximum thrust is critical for our hovercraft, as we are designing it so that itmay travel a certain distance in the smallest amount of time.

The momentum of an object is given by:

Where Q is the objects momentum in kgm/s, m is the mass of the object in kg and v is thevelocity of the object in m/s. According to Newtons Second Law, the force acting on an objectis proportional to the rate of change of the objects momentum. The force on an object cantherefore be written as:

Where tis time in seconds. Mass, m, over time, t, is equal to mass flow rate, . For a fluid:

Where is measured in kg/s, is the fluid density in kg/m3 andA is the cross-sectional area ofthe propulsion system, such as a fan, in m2. The thrust force can then be written as:

[9]Where vi is the entrance velocity and ve is the exit velocity, to and from the propulsion system, inm/s. When the thrust is produced, we must insure that the force is applied collinearly to thecenter of mass of the hovercraft to prevent any unwanted yaw, thus allowing the hovercraft to gostraight. In selecting a propulsion system, we must consider these equations. As an example, ifwe were to use fans for thrust, we would have to consider in our design, the area of the fan, andhow fast we can make the propellers turn. This will increase the velocity of the air exiting thefan, thus increasing the thrust.


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3.2.3 Drag

Drag must also be considered when designing our hovercraft. Assuming that our design producesenough lift to essentially make the surface frictionless, drag is the only force that opposes thehovercrafts forward motion. However, we can reduce this force. The drag is caused when the

hovercraft moves through a fluid, such as air. The drag force can be calculated using thefollowing equation:

[10]Where is the density of the fluid, is the velocity of the hovercraft relative to the fluid,A is thecross-sectional area of the hovercraft, and is the coefficient of drag. The coefficient of drag isa unit-less ratio between the drag force and the dynamic pressure times the area. This coefficientis usually found through experiment and can be calculated through the equation:

[11]

From these equations, we can determine that drag must be considered when designing thehovercrafts body shape and size. Our goal is to make our hovercraft design more aerodynamicby reducing the cross-sectional area of the reference face and eliminating any flat surfacesperpendicular to the flow of air. Selecting a streamlined design with a thinner tail end will reducethe wake produced by our hovercraft. A smaller wake means less drag produced and therefore,lower opposing forces, resulting in a faster hovercraft.


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4.0 Design Space

4.1 Client NeedsWe have determined the following client needs for the hovercraft design. They are listed below in

order of priority:

Able to Hover

The ability to hover defines a hovercraft. The vehicle must be able to generate and maintain liftto even be considered a hovercraft.

Self-Propelled

The vehicle must have its own propulsion system. From the point of activation, the vehicle mustoperate without any interaction from the user.

Linear Trajectory

Once activated, the vehicle is required to travel in a straight line in order to stay on course.Following any other path could result in collision with obstacles or disqualification.

Speed

The hovercraft will be raced against other models and therefore must be fast.

Safe to Use Indoors

The hovercraft race will be located in a public place and there is the possibility of peopleobserving or being in proximity. Under no circumstances, should the hovercraft be able to hurtone of those individuals. Safety is a top priority.

Made From Attainable Materials and Processes

When designing a prototype, there are hundreds of materials and manufacturing processes thatcan be used. However, our resources are limited and our designs must take into account theselimitations.

Lightweight

Two main goals of the design are lift and speed. A heavy vehicle will make both of theseobjectives more difficult. A vehicle that is light will be easier to lift and propel and may reducematerial costs as well.


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Durable/Robust

The hovercraft must be made of strong materials and of a solid design. The vehicle has to be ableto complete multiple runs and withstand collisions and impact.

Cost Effective

Ideally, the cost of materials and manufacturing should be low in order to reduce cost. This willdecrease production costs and therefore, be more affordable for the consumer.

Designed for Manufacturing

The design should take into consideration, the manufacturing process. Complex geometry oftenrequires expensive machining processes and extended production times. The design should besimple and relatively easy to manufacture.

Self-Contained

The hovercraft is to be of a single piece design. Once assembled, no addition or removal of partsshould be required; excluding an interchangeable power source. No parts may separate from thevehicle upon collision or impact.

Portable

The hovercraft should be small and light enough to transport from finish line to start line, forrepeated runs, or from one race location to another.

Aesthetically Pleasing

Although the main requirement of our design is function, the hovercraft should be visuallyappealing. In the event that a tie occurs during the race component of evaluation, the determiningfactor could be presentation. We want our design to catch the consumers eye.


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4.2 Target SpecificationsWe have determined the following target specifications for the hovercraft design. They are listedbelow in order of priority:

Cost

The main goal of this project is to design and manufacture a hovercraft prototype whileminimizing cost. The budget for this project has been set to a maximum of one hundred dollars.This includes all materials, machining costs, components and power supplies.

Desired Distance Travelled

The hovercraft models will be raced against each other. It has been determined that the distancefrom the starting line to the finish line will be thirty meters and our design is required to travelthis distance in each trial.

Desired Speed

The winner of each trial will be the first vehicle to cross the finish line. We have determined theminimum speed obtained by our hovercraft to be three meters per second. A maximum speed hasnot been set in order to not impose any restrictions. Our goal is to win.

Weight

In order to obtain faster speeds, we have established a maximum total weight of five kilograms.The lighter the vehicle, the easier it will be to accelerate and achieve maximum velocity. Thetotal weight refers to our hovercraft being race-ready.

Fuel Source

The fuel source for our hovercraft must be reusable or interchangeable. The fuel source must berecharged or changed/swapped in less than five minutes in order for the hovercraft to be readyfor another trial.

Dimensions

Our hovercraft design is to be less than three tenths of a meter wide and less than one meter long.Reducing the size of the vehicle will reduce material cost, weight, drag and the power required to

obtain and maintain lift.


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5.0 Preliminary Conceptual Designs

This section contains sketches depicting our preliminary concepts. These drawings mark thebeginning of our conceptual development.

Figure 5.1 Figure 5.2


Figure 5.5


Figure 5.6


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Figure 5.13

Figure 5.14

Figure 5.15


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6.0 Conceptual Development

To initiate the formal design process, we identified four major components that are essential for ahovercraft to function properly. By dividing the hovercraft into different sections, it allowed us

to brainstorm ideas for individual features instead of taking on the burden of proposing completedesigns. This way, we were able to present designs that were made up of a combination ofconcepts from each component section.

The four main components are:

1. The Hull/DeckThis is the main body of the hovercraft, the foundation. All othercomponents are mounted to the hull.

2. The SkirtAttached to the underside of the hull, the skirt fills with air and houses thehigh pressure air cushion that maintains the hovercrafts lift.

3. The Lift MechanismMounted to the hull, this system generates the air that fills theskirt with air, therefore creating the air cushion.

4. The Thrust MechanismLocated at the tail end of the hovercraft, this system generatesthe high pressure air stream responsible for the vehicles forward momentum.

These components are illustrated in the following figure:

Figure 6.1 [12]

The following page contains a list of concepts we brainstormed for each major component.


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6.1 Hull/Deck Concepts

Ellipse shaped Rectangular

Standard shape (rectangle + semicircle) Triangular Rhombus shaped Circular Cylindrical Teardrop shaped Elongated Turtle shell shaped Think hull Thin hull Chamfered edges Fillet edges

Hull/Deck Material Options

Wood Plywood Particle board High density foam Low density foam Carbon fiber Fiberglass Cardboard Plastic Aluminum Titanium Plexiglass Rubber

6.2 Skirt Concepts Rigid wall skirt, extension of hull Flexible wall skirt Finger skirt Jupe (cell) skirt C skirt Porous bag skirt Vented bag skirt Enclosed bag skirt Thick/High skirt Thin skirt

Skirt Material Options Hull material Coated fabric Neoprene fabric Plastic Nylon Tarpaulin Rubber

6.3 Lift System Concepts Single motor, vertical fan Dual motors with dual vertical fans Air diverted from propulsion system Single power source for propulsion and lift systems Inverted hockey table design Wings attached to hull Nose design Magnetic field Angled fins attached horizontally to propulsion system


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6.4 Thrust System Concepts Single horizontal fan Dual horizontal fans Triple horizontal fans Single horizontal turbine Dual horizontal turbines Sails Jet engine Water jet Compressed air CO2 canisters Balloons Roman candles Rockets

7.0 Concept Screening and Scoring

7.1 Concept Screening

As a result of the brainstorming performed for the Section 6.0, we formulated a list of specificdesign concepts for each major component of the hovercraft. These design concepts werecomposed of combinations of features and materials. Examples of which include a C shapedskirt made of rubber and an ellipse shaped hull made of high density foam. In total, we

developed eighty-three design concepts. In order to identify which of these design conceptswould be the most beneficial, we presented them in a table. In this table, we screened eachconcept against the client needs of the hovercraft design, outlined in Section 4.1. A designconcept was assigned a +1 if it would have a positive effect on the corresponding client need.

A -1 was assigned to a concept that effected a client need negatively and a 0 was assigned toconcepts that had a neutral or no effect on the given need. The assigned values were tallied forevery design concept, resulting in a final score for the given concept. Positive final scoresrepresented beneficial design concepts, which would be given more consideration, and negativescores were dismissed because they would not benefit our design. The higher or lower the score,the greater benefit or detriment the concept would respectfully contribute to our design. We referto this process as Concept Screeningand it is presented in Table 7.1.


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Table 7.1 - Concept Screening

NEEDSSafe

Operation Durable

Light

Weight

Cost

Effective Manufacturable Trajectory Speed

Self-

Propelled

Self-

Contained Material Hovers Portable Aesthetics

Total

Score

SKIRT

CONCEPTS

Rigid Wall Skirt,

Extension of Hull

Material 0 0 1 1 -1 -1 -1 0 1 1 -1 0 -1 -1Flexible Wall

Skirt made of

Coated Fabric 0 0 1 1 1 0 0 0 0 1 0 1 0 5

Flexible Wall

Skirt made of

Neoprene Fabric 0 1 1 -1 1 0 0 0 0 -1 0 1 0 2Finger Skirt

made of Plastic 0 -1 1 1 -1 0 0 0 0 1 0 1 0 2Finger Skirt

made of Nylon 0 1 1 1 -1 0 0 0 0 1 0 1 1 5Jupe (Cell) Skirt

made of Nylon 0 1 1 0 -1 0 0 0 -1 1 0 1 1 3"C" Skirt made

of Rubber 0 1 0 -1 -1 0 0 0 0 1 1 0 1 2Porous Bag Skirt

made of Plastic 0 -1 1 1 -1 0 0 0 -1 1 1 1 1 3

Vented Bag Skirt

made of Nylon 0 1 1 1 -1 0 0 0 -1 1 1 1 1 5

Vented Bag Skirt

made of Plastic 0 -1 1 1 -1 0 0 0 -1 1 1 1 1 3

Enclosed BagSkirt made of

Tarpaulin 0 1 1 1 1 0 0 0 1 1 1 1 1 9Enclosed Bag

Skirt made of

Plastic 0 -1 1 1 1 0 0 0 1 1 1 1 0 6Thick/High Skirt

for Clearing

Obstacles -1 0 0 0 0 -1 -1 0 -1 0 0 0 1 -3Thin Skirt for

Stability 1 1 1 1 0 0 1 1 1 0 1 1 1 10


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HULL/DECK

CONCEPTSSafe

Operation Durable

Light

Weight

Cost


Self-

Propelled

Self-


Total

Score

Ellipse Shaped 0 0 0 0 -1 0 1 0 0 0 0 0 1 1

Rectangular 0 0 0 0 1 0 -1 0 0 0 0 0 -1 -1

Standard 0 0 0 0 0 0 1 0 0 0 0 0 0 1

Triangular -1 -1 0 0 1 0 1 0 0 0 0 0 0 0Diamond

Shaped -1 -1 0 0 1 0 1 0 0 0 0 0 1 1

Circular 0 1 0 0 -1 0 1 0 0 0 0 0 1 2

Cylindrical 0 0 0 0 -1 0 1 0 0 0 0 0 1 1

TeardropShaped 0 0 0 0 -1 0 1 0 0 0 0 0 1 1

Elongated 0 -1 -1 -1 -1 0 -1 0 0 0 0 -1 0 -6Turtle Shell

Shaped 0 1 0 0 -1 0 1 0 0 0 0 0 1 2

Thick Hull 0 1 -1 -1 -1 0 -1 0 0 0 0 0 1 -2

Thin Hull 1 -1 1 1 1 0 1 0 0 0 0 0 1 5Chamfered

Edges 1 -1 0 -1 -1 0 1 0 0 0 0 0 1 0

Fillet Edges 1 -1 0 -1 -1 0 1 0 0 0 0 0 1 0

Made of Wood 0 1 -1 0 1 0 0 0 0 1 0 1 1 4Made of

Plywood 0 1 -1 0 1 0 0 0 0 1 0 1 -1 2Made of Particle

Board 0 1 -1 1 1 0 0 0 0 1 0 1 -1 3Made of High

Density Foam 1 1 1 1 1 0 0 0 0 1 0 1 0 7

Made of LowDensity Foam 1 -1 1 1 1 0 0 0 0 1 0 -1 0 3Made of Carbon

Fiber 0 1 1 -1 0 0 0 0 0 -1 0 1 1 2Made of

Fiberglass 0 1 1 -1 0 0 0 0 0 -1 0 1 1 2Made of

Cardboard 1 -1 1 1 1 0 0 0 0 1 0 0 -1 3

Made of Plastic 0 0 1 1 1 0 0 0 0 1 0 1 1 6Made of

Aluminum -1 1 -1 -1 -1 0 0 0 0 -1 0 1 1 -2Made of

Titanium -1 1 -1 -1 -1 0 0 0 0 -1 0 1 1 -2


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Made of

Plexiglass 0 1 -1 -1 1 0 0 0 0 0 0 1 1 2Made of Stiff

Rubber 1 1 -1 -1 0 0 0 0 0 0 0 0 -1 -1

LIFT SYSTEM

CONCEPTSSafe

Operation Durable

Light

Weight

Cost


Self-

Propelled

Self-


Total

Score

Independent

Motor and

Vertical Fan 0 0 1 0 0 0 0 0 0 0 1 0 0 2

Dual Motors and

Vertical Fans 0 0 -1 -1 0 0 0 0 0 0 1 0 1 0

Air Divertedfrom Propulsion

System 0 0 1 1 -1 0 -1 0 0 0 1 0 1 2Single Power

Source for

Propulsion and

Lift 0 0 1 1 0 0 -1 0 0 0 1 0 0 2Rigid Flat Base

with Small Holes

like a Hockey

Table 1 1 1 1 -1 0 0 0 0 0 1 0 1 5

Wings on Hull -1 -1 -1 -1 -1 0 0 0 -1 0 1 0 1 -4

Nose Design 0 0 0 -1 -1 0 0 0 0 0 1 0 1 0

Magnetic Field -1 0 -1 -1 -1 0 1 0 -1 -1 1 -1 1 -4Horizontal Fins

Attached to

Propulsion

System 0 -1 0 0 0 0 0 0 -1 0 1 0 1 0

PROPULSION

SYSTEM

CONCEPTSSafe

Operation Durable

Light

Weight

Cost


Self-

Propelled

Self-


Total

Score

Single

Horizontal Fan 0 0 1 1 1 1 0 1 0 1 0 0 0 6Dual Horizontal

Fans 0 0 0 0 1 1 1 1 0 1 0 0 1 6Triple Horizontal

Fans 0 0 -1 -1 1 1 1 1 0 1 0 0 1 4Single

Horizontal

Turbine -1 0 0 -1 -1 1 1 1 0 0 0 0 1 1


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Dual Horizontal

Turbines -1 0 -1 -1 -1 1 1 1 0 0 0 0 1 0

Sails 1 -1 1 1 1 -1 -1 -1 0 1 0 0 1 2

Jet Engine -1 0 -1 -1 -1 1 1 1 0 -1 0 -1 1 -2

Water Jet 0 -1 -1 -1 -1 -1 -1 1 0 -1 0 -1 1 -6

Compressed Air -1 -1 -1 -1 0 1 1 1 0 0 0 -1 0 -2

CO2 Canisters -1 -1 -1 -1 -1 1 1 1 0 0 0 0 0 -2

Balloons 1 -1 1 1 1 -1 -1 1 0 1 1 1 1 6

Roman Candles -1 -1 1 1 0 -1 -1 1 -1 0 0 0 1 -1

Rockets -1 -1 -1 -1 -1 -1 1 1 -1 -1 0 0 1 -5

POWERSOURCE

CONCEPTSSafe

Operation Durable

Light

Weight

Cost


Self-

Propelled

Self-


Total

Score

NiCad Battery 1 1 1 1 1 0 0 1 1 1 0 1 0 9

Lithium Battery 1 1 1 0 1 0 1 1 1 1 0 1 0 9

Fuel Cell 1 1 1 0 1 0 0 1 1 1 0 1 0 8

AC/DC 0 1 -1 1 1 -1 1 -1 -1 0 0 -1 -1 -2

Hamster Wheel -1 -1 -1 -1 -1 -1 -1 -1 -1 1 -1 -1 1 -9

Monkey Crank -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 1 -11Gasoline

Combustion -1 0 -1 -1 -1 0 1 1 1 1 0 -1 1 0Diesel

Combustion -1 0 -1 -1 -1 0 1 1 1 1 0 -1 1 0Hydrogen

Combustion -1 0 -1 -1 -1 0 1 1 1 -1 0 -1 1 -2

Solar 1 0 -1 -1 -1 0 0 1 1 1 0 1 1 3

Steam -1 0 -1 -1 -1 0 1 1 1 1 0 -1 1 0

Coal Burning -1 0 -1 -1 -1 0 1 1 1 0 0 -1 0 -2

Elastic/Stored 1 0 1 1 1 0 -1 1 1 1 -1 1 -1 5

Explosive -1 -1 -1 -1 -1 -1 1 1 -1 -1 -1 -1 1 -7

Rocket Fuel -1 0 -1 -1 -1 0 1 1 0 -1 0 -1 1 -3

Nuclear -1 -1 -1 -1 -1 -1 1 1 -1 -1 -1 -1 1 -7

Compressed Air 0 0 -1 0 1 0 0 1 1 1 0 1 0 4

Hydraulic 0 0 -1 -1 -1 0 0 1 1 0 0 -1 1 -1

Water 1 0 -1 1 1 0 0 1 1 1 0 1 0 6

Methane -1 0 1 -1 1 0 0 1 -1 0 0 1 0 1


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7.2 Concept Scoring

The Concept Screening process carried out in Section 7.1 was extremely beneficial indetermining which component concepts should be incorporated into our final design. From theinformation we obtained from Table 7.1, we were able to identify our best ideas. Using thisknowledge, we developed ten potential hovercraft designs. Each design is presented below withits key features outlined.

Concept A:

Standard hull shape constructed from high density foamo Flat decko Approximately 3/4 thicko Can be cut by hand on a band saw or CNC machined for higher accuracy

Chamfered edges to remove sharp edges and increase aerodynamicso Cut by hand (low cost, low tolerance)o Cut by CNC (increased cost, high tolerance)

Enclosed bag skirt made of Tarpaulino Material can be cut by hand, low tolerance requiredo Anchored between pieces of foam

Single lift fan embedded in the middle of the hullo Independent power supply

Dual thrust fans mounted at the rear of the vehicleo Enclosed to focus air streamo Both motors powered by a single power supplyo Vertical fins centered behind each fan to prevent air from coning

Concept B: Standard hull design constructed from durable, light weight plastic

o Flat decko Approximately 1/8 thicko Can be cut by hand on a band saw or CNC machined for higher accuracy

Thin deck reduces amount of material and need for chamfering Porous bag skirt made of plastic (garbage bag material)

o Material can be cut by hand, low tolerance requiredo Holes are made in material by hando Skirt is fastened to perimeter and bottom of hull to enclose air pocket

Dual thrust fans mounted at the rear of the vehicleo Enclosed to focus air streamo Independent power supply for each motoro Vertical fins located in-between and on the outside edge of each fan to maintain a straight

air flow

Integrated systemo Air diverted from thrust fans through channels to inflate skirt


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Concept C:

Shell shaped hull made of fiberglasso Manufactured using a mold and laying up materialo Curved surfaceo Streamlined design

Finger skirt made of nylono Material can be cut by hand, low tolerance requiredo Individual air chambers allow use over may different terrainso Fastened to hull using an adhesive material

Single lift fan attached to the middle of the hullo Independent power supply

Single thrust fan located at the rear of the vehicleo Independent power supplyo Enclosed to focus air streamo Crosshair fins attached behind fan to prevent air from coning

Concept D:

Shell shaped hull made of carbon fibero Manufactured using a mold and laying up materialo Curved surfaceo Streamlined design

Enclosed bag skirt made of plastic (garbage bag material)o Material can be cut by hand, low tolerance requiredo Anchored to hull with use of adhesive

Single lift fan attached to the middle of the hullo Independent power supply

Single thrust fan located at the rear of the vehicleo Independent power supplyo Enclosed to focus air streamo Dual vertical fins located on either side of the fan to maintain straight air flow

Concept E:

Teardrop shaped hull made of high density foamo Large rounded end is the front of the crafto Flat deck, chamfered edgeso Can be cut by hand on a band saw or CNC machined for higher accuracyo Approximately 3/4 thicko Streamlined shape

Wall skirt made of nylono Material can be cut by hand, low tolerance requiredo Anchored between pieces of foam

Single lift fan embedded in the hull

o Located towards the front of the craft near the centre of masso Independent power supply

Single thrust fan located at the rear of the vehicleo Independent power supplyo Enclosed to focus air flowo Crosshair fins attached behind fan to prevent air from coning


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Concept F:

Bloated Triangle shaped hull made of high density foamo Triangular with rounded verticeso Single vertex is the nose end of the crafto Flat deck, chamfered edgeso Streamlined shapeo Approximately 3/4 thicko Can be cut by hand on a band saw or CNC machined for higher accuracy

C shaped skirt design made of rubbero Material can be cut and formed by hando Acts as a bumper, can collide with objectso Anchored between pieces of foam

Dual thrust fans mounted towards the rear of the vehicleo Enclosed to focus air streamo Independent power supply for each motoro Vertical fins centered on each fan to prevent air from coning

Large vertical fin located in-between thrust fanso Helps maintain linear direction of travelo Adds artistic appeal


Concept G:

Ellipse shaped hull made of high density foamo Flat decko Approximately 3/4" thicko Aerodynamic shapeo Cut by hand with difficulty, complex geometryo Cut by CNC machine, increased production time

Chamfered edges to increase aerodynamicso Can be cut by hand, low toleranceo Can be cut by CNC, high tolerance

Inverted hockey table skirto Extension of hull materialo Air passes through small holes in a flat surfaceo Uniform lift air distribution

Single lift fan embedded in the hullo Located at the origin of the ellipse to evenly distribute airo Independent power supply

Single thrust fan located towards the rear of the vehicleo Independent power supplyo Enclosed to focus air flowo Crosshair fins attached behind fan to prevent air from coning


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Concept H:

Ellipse shaped hull made of durable, lightweight plastico Flat decko Approximately 1/8" thicko Cut by hand with difficulty, complex geometryo Cut by CNC machine, increased production time

Thin deck reduces amount of material and need for chamferingo Lower manufacturing costs

C shaped skirt design made of rubbero Material can be cut and formed by hando Acts as a bumper, can collide with objectso Bonded to hull with use of adhesive

Single lift fan attached to the decko Located towards the front of the crafto Independent power supply

Dual thrust fans mounted towards the tail end of the vehicleo Enclosed to focus air streamo Single power supply to run both motorso Vertical fins centered behind each fan to prevent coning of air

Concept I:

Circular hull made of high density foamo Flat decko Approximately 3/4" thicko Aerodynamic shapeo Can be cut by hand with low toleranceo Can be CNC cut with high tolerance

Chamfered edges to increase aerodynamicso Can be cut by hand, low toleranceo Can be cut by CNC, high tolerance

Inverted hockey table skirto Extension of hull materialo Air passes through small holes in a flat surfaceo Uniform lift air distribution

Single lift fan embedded in hullo Located at the origin of the circle to evenly distribute airo Independent power supply

Dual thrust fans mounted centrally on either side of the lift fano Enclosed to focus air streamo Single power supply to run both motorso Crosshair fins attached behind each fan to prevent air from coning


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Concept J:

Circular hull made of durable, lightweight plastico Flat decko Approximately 1/8" thicko Can be cut by hand with low toleranceo Can be CNC cut with high tolerance

Thin deck reduces amount of material and need for chamferingo Lower manufacturing costs

Enclosed bag skirt made of plastic (garbage bag material)o Material can be cut by hand, low tolerance requiredo Anchored to hull with use of adhesive

Dual thrust fan mounted centrally on the decko Enclosed to focus air streamo Independent power supply for each motoro Vertical fins centered behind each fan to prevent coning of air

Large vertical fin located in-between thrust fanso Helps maintain linear direction of travelo Adds artistic appeal


In order to get closer to our goal of presenting a single hovercraft design, these ten potentialdesigns had to be further reduced. To accomplish such a task, we focused on what was trulyimportant. This involved reviewing the client needs outlined in Section 4.1 and the order inwhich we ranked them. The higher the priority we assigned to the client need, the greater theconsideration we gave the given need when selecting a design. To represent this thought process,we listed concepts A through J in a table, along with the client needs. The client needs weregiven a multiplying value, or weighted value, between 0.1 and 1.0, corresponding to its priority.

A client need was given a weight 1.0 if we felt that it was one of, if not, the most importantaspect of our design. A client need received a weight closer to 0.1 if, in our opinion, wasnt asimportant to the overall design of our hovercraft. Each concept was scored from one to ten inevery client need category. A score of ten was assigned to a concept if it was the best idea in aclient need category. Best could imply best performance, highest level of safety, highest materialavailability, etc. Every client need category was considered and ranked independent of the otherclient needs. The score awarded to the concept in each category, multiplied by the weightedvalue, produced a weighted score in that category. The weighted scores were summed for eachconcept and resulted in a total weighted score. The total weighted score determined the conceptsthat would be presented in the following section. We refer to this process as Concept Scoringandit is depicted in Table 7.2. In actuality, this process was a result of many in-depth brainstorming

sessions. We critiqued our designs according to logic, previous knowledge and information wegained from researching what has been done in terms of hovercraft design. The table below ismerely a numerical representation to communicate our thought to the reader.


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Table 7.2 - Concept Scoring

Able to

Hover

Self-

Propelled

Linear

Trajectory Speed

Safe to Use

Indoors

Made From

Attainable

Materials

and

Processes Lightweight

Durable/

Robust

Cost

Effective

Designed

for

Manufact-

uring

Self-

Contained Portable

Aesthetic-

ally Pleasing Total

Concept

Score1

Wegte

Score1(1

.0)

Score2

Wegte

Score2(1

.0)

Score3

Weighted

Score3(0

.9)

Score4

Weighted

Score4(0

.9)

Score5

Weighted

Score5(0

.8)

Score6

Weighted

Score6(0

.7)

Score7

Weighted

Score7(0

.6)

Score8

Weighted

Score8(0

.5)

Score9

Weighted

Score9(0

.4)

Score10

Weighted

Score10(0

.3)

Score11

Weighted

Score11(0

.2)

Score12

Weighted

Score12(0

.1)

Score13

Wegte

Score13(0

.1)

TotalWeighted

S c o r e

A 7 7 10 10 8 7.2 9 8.1 10 8 10 7 6 3.6 10 5 9 3.6 9 2.7 8 1.6 8 0.8 7 0.7 65.3

B 6 6 10 10 9 8.1 8 7.2 9 7.2 8 5.6 5 3 6 3 9 3.6 9 2.7 8 1.6 8 0.8 7 0.7 59.5

C 5 5 10 10 8 7.2 5 4.5 8 6.4 6 4.2 9 5.4 8 4 5 2 4 1.2 9 1.8 8 0.8 10 1 53.5

D 7 7 10 10 8 7.2 5 4.5 8 6.4 6 4.2 10 6 7 3.5 5 2 4 1.2 9 1.8 8 0.8 10 1 55.6

E 4 4 10 10 7 6.3 5 4.5 10 8 10 7 8 4.8 9 4.5 6 2.4 7 2.1 8 1.6 8 0.8 9 0.9 56.9

F 7 7 10 10 10 9 8 7.2 10 8 10 7 7 4.2 10 5 6 2.4 7 2.1 8 1.6 8 0.8 8 0.8 65.1

G 10 10 10 10 8 7.2 5 4.5 10 8 10 7 8 4.8 10 5 8 3.2 5 1.5 10 2 8 0.8 8 0.8 64.8

H 8 8 10 10 8 7.2 10 9 8 6.4 6 4.2 4 2.4 8 4 8 3.2 5 1.5 8 1.6 8 0.8 8 0.8 59.1

I 10 10 10 10 6 5.4 7 6.3 10 8 10 7 6 3.6 10 5 7 2.8 6 1.8 10 2 8 0.8 6 0.6 63.3

J 6 6 10 10 8 7.2 10 9 8 6.4 10 7 7 4.2 7 3.5 7 2.8 6 1.8 8 1.6 8 0.8 6 0.6 60.9

As outline in Table 7.2, we selected concepts A, F and G out of our proposed ten. Up until this point, we made our selections based on theoreticalperformance and aesthetics. We wanted to choose an idea based on the best design and not be restricted by manufacturing and material costs. Thisallowed us to maximize our creativity without limitations. Concepts A, F and G were modeled in SolidWorks and rendered to communicate visuarepresentations of the designs. These images and a description of why we choose each concept are included below.


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Concept A

Figure 7.1: Concept A Top Isometric View

Figure 7.2: Concept A Front View


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Figure 7.3: Concept A Rear Orientation Isometric View

Concept A

This hovercraft was chosen over the various other designs brainstormed because of thefollowing benefits: The shape of the hull is standard; this means that it can be cut out byhand without the use of machinery or expertise of a machinist, this will reduce costgenerously. Its made out of high density foam which will meet the strength requirements

while drastically reducing the cost in comparison to using a carbon fiber body or evenone forged from metal. The hulls edge perimeter is to be chamfered instead of filleted,this will reduce cost because less machining time is needed; only one pass of the bitrather than multiple passes. The bag skirt is made of a tarpaulin material which is notonly cheap but also is very durable and adds aesthetic appeal. There is also one lift fanpowered by a single Ni-Cad battery and two thrust fans that are powered by a singlelithium ion battery; this will ensure its speed is unrivaled. Overall this concept waschosen as one of the top three design concepts because it is cost effective, plausible,designed for manufacturing, fast and aesthetically appealing.


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Concept F

Figure 7.4: Concept F Top Isometric View

Figure 7.5: Concept F Front View


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Figure 7.6: Concept F Rear Orientation Isometric View

Concept F

This concept was selected as the one of the top three, because of its combination of greatcomponents. To start the hull of this hovercraft made of high density foam is a teardropshape which is aerodynamic as well as visually appealing. The reason for using highdensity foam for the hull is because the foam is lightweight, strong, and easy to cut by

hand or by using a CNC for more accuracy. The skirt of the hovercraft is made of thinrubber and is in the form of a C shape. The reason for using rubber as the skirt materialis because the rubber will act as a bumper if the hovercraft collides with anything andalso because rubber can easily be cut and formed by hand. The skirt is also anchoredbetween the double layer hull so that air does not leak from the top of the skirt and so theskirt is firmly attached and will not fall off. The propulsion system is composed of dualthrust fans located at the rear of the hovercraft. Each thrust fan motor is powered by itsown lithium ion battery for maximum output as opposed to a less powerful Ni-Cadbattery. The fans are also enclosed in a housing to increase their thrust power and focusthe air stream. An integrated system is used to supply the lift for the hovercraft, becausethis way there is no need for a separate lift fan and battery pack to power it. The

integrated system diverts air from the thrust fans through a channel to inflate the skirt.One other feature of this concept is the large vertical fin that runs lengthwise along thehull; this fin is not only artistically appealing, but also helps to stabilize the hovercraftand keep it going in a straight line. The fin would be made of high density foam and runbetween the two thrust fans. For these reasons concept F was chosen as one of the topthree hovercraft design concepts to meet the required needs.


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Concept G

Figure 7.7: Concept G Front Isometric View

Figure 7.8: Concept G Cross-Section Side View


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Figure 7.9: Concept G Bottom Isometric View

Concept G

This concept was chosen in the top three designs over the others because of its cost,manufacturing, and features. The cost of this design is lower than most other designsbecause the material used for the hull of the hovercraft is high-density foam. Using high-density foam as the hull material has a much lower cost than carbon fiber or fiber glass.The manufacturing of this hovercraft is also easy and cost effective. This design requiresCNC machining only for two features, the elliptical shape of the hull and the chamferededges. All other features on the design can be done by hand. The design uses two fans,one to provide lift for the inverted Air-hockey-table skirt powered by a Ni-Cad batteryand the other fan to produce thrust powered by a lithium ion battery. Having a skirt as aninverted air hockey table will create a pocket of air that would produce lift for thehovercraft. For these main reasons Concept G was picked as one of the top threehovercraft design concepts.

The representation of these concepts clearly indicates our conceptual development. We tookeverything we knew and proposed designs based on that information. In the following section,we put together our collective knowledge, including materials and manufacturing processes, anddeveloped a single design for recommendation.


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8.0 Detailed Design

The hovercraft design process began with researching what had been done by others. We lookedat the progression of the hovercraft design throughout history and the applications of todays

models. That research was followed by analyzing the key equations that must be consideredwhen designing and operating a hovercraft. With this information, we began brainstormingspecific design features and we identified the ones that we would consider for our design. Weused the condensed list of features to develop ten formal hovercraft designs. From these ten, weselected three designs according to theoretical performance abilities, complexity and aesthetics.As we became more familiar and educated with the different manufacturing processes availableto us, we were able to refine our design. We learned of tolerances, their importance in the designprocess and the level of tolerance obtained from the different manufacturing processes.Incorporating this information into our concept selection allowed us to refine our design. Wedeveloped a single, well thought out, hovercraft design concept according to available materialsand manufacturing processes. The details of this design and a preliminary manufacturing process

are as follows.

Final Design Overview

Figure 8.1: Final Design Isometric View


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Figure 8.2: Final Design Front View

Figure 8.3: Final Design Side View


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Figure 8.4: Final Design Section View

Final Design Components

Table 8.1Final Design Components

Component Description Manufacturing Process

Hull Two layer system in order to fastenskirt material

Made of Quick-Recovery NaturalGum Foam Rubber

Computer NumericalControl

Skirt Enclosed Bag Skirt Made from Tarpaulin Cut manually

Lift System Ducted Lift Fan and MotorAssembly

Purchased fullyassembled

Lift System

Power Source 7.2V 900 mAh NiMH Battery 6 Cell Shrink wrapped in plastic

Purchased

Thrust System

Mount Housing for securing thrust system Linear Trajectory Fin Rapid Prototyping

Thrust System Dusted Thrust Fan and MotorAssembly

Purchased fullyAssembled

Thrust System

Power Source 10.8V 650 mAh NiMH Battery 9 Cell Shrink wrapped in plastic

Purchased

Shell Carbon Fiber shell that provides anaerodynamic shape to our design

Vacuum Forming


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Figure 8.5: Final Design Detailed View


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Figure 8.6: Final Design Component View


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Final Design Cost Analysis

Table 8.2 Final Design Component Cost

Component Cost

10.8V Battery [15] $17.99

Thrust Fan [15] $11.73

Lift Fan [15] $11.14

7.2V Battery [15] $17.99

Total: $58.85

Table 8.3 Final Design Material Cost

Material Cost

Foam Sheet(36 x 12 x 0.5) [13]

$16.80

Tarpaulin Sheet

(10 x 12) [14]

$7.19

Carbon Fiber Sheet(12 x 12 x 1/16) [13]

$57.43

Resin for Carbon Fiber [13] $28.89

Total: $123.49

Table 8.4 Final Design Manufacturing Cost

Process Cost

CNC [16] $71.13

Rapid Prototyping [16] $79.90

Vacuum Forming [16] $5.28Total: $156.31

Total Design Cost: $338.65

Final Design Manufacturing Breakdown

Computer Numerical Control Cost:

The shape of our hull must be done by CNC due to its complex geometry. The cost for using aCNC for the deck can be calculated with the following equation:

[16]Our hull design consists of two pieces of high density foam. Since the hovercraft designs are notcontrolled by the user, we rely on symmetry to provide even air distribution. In order to obtainthis, the CNC process must be used to get the required tolerance. The first part is the top piece ofour design. It is a tear drop shape, with a profile consisting of a semi-circle and spline, which has


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an approximate area of 0.0387 m2. Excess material must be removed from the stock piece andthree holes added to the surface. These holes are for the two battery compartments and the liftfan housing. The cost of this machining process would be:

The second piece is the bottom of the hull and is of the same material and shape as the previousone. This implies that the same amount of area must be cut out. This piece has a hole in thesurface for the lift fan housing and two pockets for the remainder of the battery compartments.The cost for this piece would be:

Our design includes a carbon fiber shell of complex geometry to be produced using the vacuumforming process. The CNC process must be used to manufacture a mold for this process. Themold has an approximate area of .022 m2 and 6 slits that we classified as holes. It is made fromthe same material as the hull. The cost for the mold would be as follows:

$18.24The total cost for our use of the CNC is as follows:

Our decision to CNC the body of the hovercraft was influenced by multiple factors. We found

that having the best possible tolerance for the most important components (hull and the shell) ofthe hovercraft was necessary. The hull, which holds the hovercraft together, must be of the bestquality, and the shell is what protects the components of the hovercraft. The shell adds a majoraerodynamic feature to our design and is therefore very important. By using the CNC process formanufacturing parts, the complex geometry we defined is maintain, the tolerance of the parts ishigh and our overall quality is increased, resulting in a more aesthetically appealing design.


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Rapid Prototyping Cost:

Our design has three parts that require rapid prototyping; the fin behind the fan, the fan housingand the housing mount. We will be using the digital light printer process, the Zbuilder UltraMachine, for each of these parts.

Fin: [16]

Fan Housing:

Fan Housing Mount:

The total cost for rapid prototyping is: $79.90

During our design process we were shown rapid prototyping and it appeared to be a valid option.Initially, with lack of knowledge in the subject, we thought we believed rapid prototyping wouldbe more cost efficient and a quicker than other processes. The tolerance for rapid prototyping isextremely high. However, when we considered rapid prototyping above, we found that the costwas too high and the production time was quite lengthy [17]. Through other resources we foundan alternative method that would be more cost effective.

The process we were informed of still involved three components but produced from verydifferent manufacturing methods. This process is as follows [18]:

Laser-cutting the linear trajectory fin from a piece of fiber board would be much morecost effective than rapid prototyping.

The thrust fan housing could be cut from a stock tube of our required diameter. Thematerial would be ABS plastic and could be cut on a lathe.

CNC could be used to machine the thrust fan housing support out of an acrylic material. The three components would be bonded with an adhesive to produce the required piece.


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This process, from a reliable source [18], was an interesting alternative and a great way to reducethe manufacturing cost of our design.

Vacuum Forming:

The shell that encloses our hull design and its exposed components could be manufactured usingthe vacuum forming process. It is made out of carbon fiber and will be formed to the molddescribed previously in the CNC section. The shape will be set and strengthened with the use ofa resin. The cost will be as follows:

[16] The total cost for vacuum forming is:

$5.28For our design, we selected carbon fiber for the material for the shell. However, through ourexpert resources [18] we found that alternative material would be much cheaper and moreefficient. We wanted a strong material for the shell that looked aesthetically appealing; which iswhat was found in carbon fiber. We initially chose to vacuum form the material because of thecomplex geometry of our design and we believed it was a fairly simple and cost effectiveprocess. By vacuum forming the carbon fiber, it would allow for high tolerances, as it takes theshape of the mold produced in the CNC process section. With laying up carbon fiber over high-density foam, the mold would be a onetime use only as it is bonded to the carbon fiber with anadhesive. This is inefficient, and other alternatives would be better. By using ABS plastic as the

material for the shell and medium density fiber board for the mold, the mold could be usedmultiple times [17]. Having a reusable mold would allow us to produce multiple shells asrequired for mass production or in the event of a crash and a replacement was needed.

Ultimately, the manufacturing costs that we have presented in this section are merely apreliminary estimate based on guidelines provided to us. We have made reference to somealternatives to our initial thoughts on the manufacturing process, and without a doubt, manymore exist. Through more research, expert advice and testing, a much more thorough, costeffective manufacturing process could be determined and outlined for our proposed design.


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Performance Analysis

To begin applying the formulas found in section we first must calculate the mass. The mass ofthe total hovercraft is calculated by adding all of the components individual masses.

Mass of hovercraft body 13.28oz.Mass of lift fan +0.95oz.Mass of 6 cell Ni-Mh battery +4.6oz.Mass of thrust fan +1.1oz.Mass of 9-cell Ni-Mh battery +4.3oz.Total Hovercraft Mass 24.23oz. = 0.68736kg

The masses of the components are given in the descriptions of the specs for the product online[15]. The mass of the hovercraft body was drawn on solid works and we were able to get thevalue for the mass from the program.

With the mass we can calculate the amount of pressure that the lift fan must produce so that thehovercraft can perform effectively.

[8]

The next force that must be analyzed is the thrust force. This force will give us an idea of howmuch force will be pushing the hovercraft forward, and how fast it will go. It is calculatedthrough the following equation:

[9]The thrust of the hovercraft cannot be calculated without observing the performance of thehovercraft. However the theoretical thrust that the fan will produced is given in the description ofthe fans specifications. The thrust that is produced is:

= 90.0 g


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The final force that we must calculate is the drag force, which is calculated through the equation:

[10]

Calculating the drag force allows us to see how much thrust force must be produced. Byassessing if the drag is too high we can alter our design so that it will be minimized. Ourcalculation is restricted by the calculation of the velocity and coefficient of drag. Both of thesecannot be determined without performing any experimental analysis, so they are left as variables.The coefficient of drag can be calculated by the following formula:

[11]The calculations performed in this section are preliminary calculations that give us an idea of

how our hovercraft will perform. It should be noted that these numbers are rough and will notreflect the actual numbers that the hovercraft will produce. The rough estimate for performanceallows us to analyze our design and see what need to improved or changed for optimalperformance of the hovercraft.


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9.0 Summary

In the outlined report we were able to define several concepts of a hovercraft that met the clientsspecific needs constraining the hovercraft to being faster than its competitors, travels in a straight

line, minimal cost, maximum aesthetic appeal, no external interference on the hovercraft duringcompetition, user friendly and safe, meanwhile designing for manufacturability. Drag, power-to-weight ratio, lift, appropriate materials, shape that encourages aerodynamics and the cost toachieve all of the above were covered in detail in the report.

The included tables had the following focal points: lift/system concepts, skirt concepts, hull/deckconcepts, power source concepts, and propulsion system concepts. Through this screeningprocess we came up with ten concepts that integrated, the useful information we learned, into thedesign itself. We also learned, through various resources, that when manufacturing a small scalehovercraft, one propulsion fan will meet the speed requirements because if more than one isused, for the given size, there will be too much thrust for forward propulsion and there will be a

loss of directional control. The fins help direct the airflow to maintain moderate control. Havinga propeller hub increases thrust significantly by also directing airflow into a constant flow. Usinga curved shape on the front of the hull has less drag then a more square design because it cuts theair smoothly rather than coming against it, chopping the air with a flat edge. Lastly it wasdeduced that a bag skirt using a material such a tarpaulin was the best choice overall, this isbecause tarpaulin is a cheap, easy to acquire material, that is durable, forms to desired shape ifmanipulated appropriately and is very easy to assemble as part of the hovercraft.

We were able to reduce our list of potential design styles to three concepts. Concept A, thedesign is a standard hull with a flat deck that is approximately 3/4 (two layers, each 3/8 thick)thick made of high density foam, this can be cut by hand on a band saw or CNC machined for

higher accuracy. We decided on chamfered edges for increased aerodynamics without the extracost of fillets. Concept A has an enclosed bag skirt made from tarpaulin and attached by using anadhesive placed in between the two layers of the hull. A single lift fan is used in this conceptwith an Electrify T370 motor powered by a NiCad battery. Dual thrust fans using an ElectrifyT370 motor for each, powered by one lithium ion battery provide the thrust.

The next design chosen was Concept F. This includes a tear drop shaped hull made from highdensity foam that is approximately 3/4 (two layers, each 3/8 thick) thick, this can be cut byhand on a band saw or CNC machined for higher accuracy. The skirt chosen was a C shapedskirt that is made from rubber, which acts as a bumper if collision occurs. A single lift fanlocated in between thrust fans powered by a single NiCad battery does the lift portion for the

hovercraft. Dual thrust fans are used and are each enclosed by a fan hub to increase thrust output,each motor is powered by a lithium ion battery.

Lastly Concept G has an ellipse shape hull made of high density foam that is approximately 3/4thick, this can be cut by hand on a band saw or CNC machined for higher accuracy. Chamferededges were chosen for part of the hull design to increase aerodynamics and reduce drag. Thedesign for the skirt is an inverted hockey table skirt, which is simply an extension of the hull


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shape material. A single lift fan provided all the lift thrust needed to perform the hovering. Asingle thrust fan was made responsible for the forward motion of the hovercraft, to which it wasoperated by Electrify T370 motor powered by a single lithium ion battery.

The final concept that we decided upon was a combination of the last three designs, the reason

for this was to reduce manufacturing costs, increase speed and meet the client needs as much aspossible. The final concept has the following design, materials and constraints: A fan hub with afin attached on the back, both made from plastic, that has integrated aerodynamic contours toincrease air control for desired flow, a custom propulsion fan to increase thrust output, a customlift fan for compatibility with the thickness of the hull while maintaining required thrust output, anine cell NiCad battery for the thrust fan, a six cell NiCad battery for the lift fan, a tear dropshaped hull made from two layers high density foam, a bag skirt made of tarpaulin bondedbetween the foam, the motor for the propulsion fan is CN12-R-XC which has 25500 rpm and themotor used for the lift fan is the CN12-R-LC and has 15200 rpm. The next step is the actualmanufacturing and assembling of the hovercraft. Our superiors will choose the best six designsand we will commence the manufacturing process.


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10.0 Recommendation

In our design process we found that one particular design for our hovercraft was betterthan the rest. Although we did not cover the details of the other hovercraft concepts and designs

in as much depth, we found that the final design that we chose is superior in many ways. Weselected this design over the others because it showed that its features would allow it to performbetter than the other designs. Features such as its aerodynamic design, propulsion system, and liftsystem showed more promising results than the other designs when we applied the forceequations to the hovercraft. Also, we found that the material composition of this design wassuperior to the others. The materials were attainable and relatively cost efficient. Most parts ofthe design are easily fixed or replaced, and it is not costly to do so. We also found that thematerials used in this design are exactly what we needed for the hovercrafts purposes. Mainmaterials such as carbon fiber, high density foam, and tarpaulin are light, which will allow thehovercraft to achieve lift and speeds greater than the other designs. The materials are also sturdyand will be able to absorb any impact that might occur, allowing the hovercraft to make multiple

runs. The power source of the design was superior to others because it is able to supply theamount of power that we need, as opposed to being too much or too little, which is what wasfound to be problematic in the other designs. Not only is the designs theoretical performance

superior to the other designs; we found that it is much more aesthetically appealing. The smoothstreamlined design gives the hovercraft a slimmer and more aesthetic appeal. The hovercrafts

shape is unique to other designs, aiding in its aesthetical appeal.

Although the hovercraft is much more promising than any other design that we haveconsidered, it has flaws and must be further evaluated. The materials for the hovercraft arerelatively cost efficient, however the manufacturing cost for many of the hovercrafts features aremuch more expensive than many of our other designs. Because it has a streamlined design many

of the parts have to be produced by a CNC, which allows for better tolerances, but it increases itscost for manufacturing. In our report, we chose to rapid prototype and vacuum form various partsfor better tolerances and higher quality products. These two processes drastically increased themanufacturing cost, and the cons of the processes outweighed the pros. In spite of the majorflaws, we found through other sources that these prices can be significantly reduced by usingalternative materials, which would provide us the same functionality as the current, and by usingalternative manufacturing process which would be more cost efficient for specific parts.

Ultimately the designs specifications are promising and show exceptional theoreticalperformance. The hovercraft is also more aesthetically pleasing and unique than any other designwe have considered. However, the designs manufacturing cost is way too high and must be

reduced significantly. Since alternative manufacturing processes show that the manufacturingcost can be significantly reduced, our recommendation would be to perform more research onthese processes and materials before proceeding with the development and production of ourdesign.


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11.0 References

[1] (May 1968).Hovercraft Bill[Online].Available: http://hansard.millbanksystems.com/commons/1968/may/16/hovercraft-bill

[February 18 2012].

[2] E. Bilzer, E. Sieche (1981, Nov 17). VersuchsgleitbootThe Worlds First Hovercraft[Online].Available:http://homepages.thm.de/~hg6339/data/ah/minor-crafts/1915_ah-gleitboot/tec_versuchsgleitboot-1.htm [February 17 2012].

[3]Hovercraft[Online] Available: http://en.wikipedia.org/wiki/Hovercraft [February 20 2012].

[4] SN.R1 [Online]

Available:http://upload.wikimedia.org/wikipedia/commons/b/b1/SRN1_General_Arrangement.jpg[February 19 2012].

[5] Mark Porter (2006).Paper presented to The Hovercraft Society [Online].Available: http://www.model-hovercraft.com/thspaper.html [February 17 2012].

[6]Military hovercraft[Online].Available: http://links999.net/hovercraft/mem_hov/hovercraft_military.html [February 18 2012].

[7]Hovercraft in use [Online].

Available:http://links999.net/hovercraft/mem_hov/hovercraft_in_use.html [February 16 2012].

[8]Hovercraft: Lift Using Air Only [Online].Available: http://www.hovercraftcentral.com/article/only_air.html [February 19 2012].

[9] General Thrust Equation [Online].Available: http://www.grc.nasa.gov/WWW/k-12/airplane/thrsteq.html [February 20 2012].

[10] The Drag Equation [Online].Available: http://www.grc.nasa.gov/WWW/K-12/airplane/drageq.html [February 20 2012].

[11] The Drag Coefficient[Online].Available: http://www.grc.nasa.gov/WWW/k-12/airplane/dragco.html [February 20 2012].

[12] J. Benini (2004). Why A Hovercraft Hovers: Pressure and Lift[Online].http://www.discoverhover.org/infoinstructors/guide4.htm [February 14 2012].

[13]McMaster-Carr[Online]. Available: http://www.mcmaster.com


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[14] Orange Tarpaulin, 10 x 12-ft[Online]. Available:http://www.canadiantire.ca/AST/browse/5/SportsRec/Camping/Tarpaulins/PRDOVR~0405000P/Orange+Tarpaulin%2C+10+x+12-ft.jsp?locale=en [February 27 2012]

[15]Hobby Fever[Online]. Available: http://www.hobbyfever.com

[16] N. Balakrishnan, PHASE II: CONCEPTUAL DESIGN REPORT: CNC AND RP COSTING

ANALYSIS, unpublished.

[17] C. Laing,Expert, In-person communication, March 2012.

[18] N. Balakrishnan,Expert, In-person communication, March 2012.

Documents

Sample Phase 2 Report