aerodynamics-front & rear wings - final report · aerodynamics-front & rear wings - final...

Aerodynamics-Front & Rear Wings - Final Report

by Mikael Sedlacek

2013-09-08

1


by Mikael Sedlacek

2013-09-08

2

Abstract Grass grows, birds fly, waves pound the sand and wings deliver lift.

In 2013 Chalmers Formula Student set out to design and deliver a reliable yet lightweight formula

racing solution. To achieve this goal it was determined that negative lift was needed for the car to

have enough traction on the track. Thus it was decided to design and deliver a front and rear wing to

fit the application.

There is no definite way how to design wings for a race car because of the amount of variables that

affects aerodynamics. They are affected by the turbulent flow around the car created by the wheels

and body. Also in play is the ground effect which is not present in for instance airplane wings. So

when looking at aerodynamics for a race car one has to see it as a unified whole.

This report will present how the wings were designed and delivered by going through each phase of

the project. It will present the variables of each phase and give motivations for why certain choices

were made.


by Mikael Sedlacek

2013-09-08

3

Contents Abstract ................................................................................................................................................... 2

List of figures and tables ......................................................................................................................... 4

1. Pre Study ......................................................................................................................................... 5

Introduction ......................................................................................................................................... 5

Functional model ................................................................................................................................. 6

Benchmarking ...................................................................................................................................... 8

Solution model .................................................................................................................................. 14

Final discussion .................................................................................................................................. 14

2. Design ............................................................................................................................................ 16

Technical Background ........................................................................................................................... 16

Analysis .................................................................................................................................................. 31

Material selection for the wings ....................................................................................................... 31

CFD ........................................................................................................................................................ 33

3. Manufacturing ............................................................................................................................... 34

4. Manufacturing coordination ......................................................................................................... 40

5. Costs .............................................................................................................................................. 44

6. Testing/ Validation ........................................................................................................................ 44

7. Improvements/ Conclusion/ Recommendation ............................................................................ 45

8. References ..................................................................................................................................... 46

9. Appendices .................................................................................................................................... 46


by Mikael Sedlacek

2013-09-08

4

List of figures and tables Figure 1: Functional model ...................................................................................................................... 6

Figure 2: Undertray and Diffuser setup ................................................................................................. 11

Figure 3: The effect of an Airdam (Barnard, 2001) ............................................................................... 11

Figure 4: Solution model for Aerodynamics .......................................................................................... 14

Figure 5: This is a sketch made to illustrate the concepts evaluated during the pre-study phase. The

sketch is not at all a final design. ........................................................................................................... 15

Figure 6: Sketch of S1223 Airfoil with endplate .................................................................................... 16

Figure 7: Simplified figure of how an airfoil works ............................................................................... 17

Figure 8: Explanation of the key terms of an airfoil .............................................................................. 18

Figure 9: A sketch of the flow on an airfoil without endplates ............................................................. 19

Figure 10: A table with the design targets for the aerodynamic subgroup .......................................... 21

Figure 11: A CAD rendering of the parts current for this report ........................................................... 22

Figure 12: A picture of the flow field around the S1223 airfoil ............................................................. 23

Figure 13: A CAD rendering of the concept front wing without a middle segment.............................. 24

Figure 14: A CAD rendering of the concept with a neutral middle segment ........................................ 25

Figure 15: A CAD rendering of the concept with small end plates ....................................................... 26

Figure 16: A CAD rendering of the concept with endplates close to the chassis .................................. 26

Figure 17: A CAD rendering of the final front wing concept ................................................................. 27

Figure 18: A CAD rendering of the rear wing with a neutral middle segment ...................................... 29

Figure 19: A CAD rendering of the rear wing with plates in the middle ............................................... 29

Figure 20: A CAD rendering of the final rear wing concept .................................................................. 30

Figu e : A g aph ith ate ials ith ou g’s odulus plotted agai st de sit ............................... 32

Figure 22 A CAD of the top part of the front wing main element mold ............................................... 34

Figure 23 Twill weave Figure 24 Textreme weave ............................................................................. 35

Figure 25 A picture of using vacuum infusion for the top part of the rear wing .................................. 36

Figure 26 A picture of the ribs placed out on the top part of the wing ................................................ 37

Figure 27 Picture of a part of the BOM initially set up .......................................................................... 40

Figure 28 A picture of the overall planning document ......................................................................... 41

Figure 29 A picture of the overall planning setup ................................................................................. 42


by Mikael Sedlacek

2013-09-08

5

1. Pre Study

Hereby a briefing of the pre study part of the project can be found. It involves a problem definition,

functional model, benchmarking, solution model and discussion revolving the same.

Introduction

In order to develop a concept it is first of all important to identify the main functions for the

subsystem. The functions are first presented in a functional model. In order to fulfil these functions,

data collection and benchmarking has been made to find existing solutions and developing new. The

identified concepts were then evaluated in order to choose the best alternatives, and these solutions

are then presented in a solution model.

1.1 Problem Definition

The main responsibilities for the Aero subgroup within Chalmers Formula Student is reducing drag

and creating down force. Drag refers to the resultant force acting in the stream wise direction, and it

has a direct effect on the fuel efficiency (Clayton, 2010). Down force refers to negative lift which pulls

the a do a ds. This ea s that the a ill e a le to ake o e effi ie t use of its ti es due to the i eased t a i g ge e ated do fo e. Opti al diffuse design for Formula SAE Race

Car) (Ehirim,2012,p.2) In addition to this cooling is to be generated for the engine and protection is to

be created for the driver and the car. The Aero subgroup is also responsible for the aesthetics of the

car.


by Mikael Sedlacek

2013-09-08

6

Functional model

The functional model was created in order to identify the different functions which each separate

subgroup is responsible for. Thus the functional model for the aerodynamics subgroup can be found

underneath.

1.2 Presentation

By starting from the customer needs we can determent functions to be able to find solutions. The

functional model shows inputs and outputs to the system, e.g. air comes in and is used in order to

generate down force. Further on the model describes how the identified functions interact with

other subgroups and the boundaries between different subgroups.

Figure 1: Functional model

1.3 Explanations

The functions that the Aero subgroup are responsible for, is (1) the aesthetics of the car, which are

important in order to attract customers and create a winning concept. (2) To protect the car, focuses

mainly on the engine and (3) the driver during the race. (4) To create mass flow for cooling vital parts

of the vehicle, such as brakes and engine. (5) To reduce drag, which reflects on the performance and

the fuel efficiency of the vehicle. Additionally (6) to generate down force, improving the overall

handling and grip of the vehicle while it is cornering.

1.4 Discussion


by Mikael Sedlacek

2013-09-08

7

A o di g to i dust ial desig e Diete Ra s; The aesthetic quality of a product is integral to its

usefulness, because products are used every day and have an effect on people and their well-being.

Only well-executed objects can be beautiful.

Therefore, in order to make an aesthetically pleasing product for the costumer, close collaboration

with the Communications subgroup is needed to understand what the customer wants and needs,

and also that the car fits the Chalmers Formula Student team visual brand identity. Collaboration

regarding the aesthetics will also be dependent on every subgroup in the team, since every part of

the car will make a total package. Although, if Dieter Rams third rule of good design is followed, that

only well-executed objects can be beautiful, then the car will be aesthetically pleasing. Well executed

means that not only every part should be thought through, but also how they are put together, in

order to form a unified whole.

To protect the car, collaboration with the Chassis subgroup is needed for design and stiffness. The

collaboration is dependent on whether a monocoque chassis will be used or not, but it will be highly

different according to the choice. If a monocoque chassis is used the Chassis sub-group will design a

stiff monocoque with the aerodynamics defined by the aero-subgroup, in this case Chassis will have

the responsibility to protect the car. If a space-frame is used collaboration will circle around how the

space frame is formed and how the panels will fit onto the frame.

In order to protect the driver, collaboration with the driver, as well as the EDSC subgroup is needed.

Collaboration is needed to define where the seat, panel and steering wheel will be placed. The seat

height will have a factor when it comes to how high the front body of the car can be, since the driver

has to have a free line of sight.

Handling the air flow around the vehicle could be beneficial for many sub groups. Strong

collaboration with Powertrain and Unsprung mass is required in order to be optimized the cooling of

the engine and the brakes respectively. At the same time the electronics cooling will be taken into

account.

Reduce drag is linked to the Suspension and Powertrain subgroups. Information regarding drag force

will be revived by the Suspension subgroup and the Powertrain subgroup. The drag will be minimized

so that the Powertrain will spend as little energy as possible. Additionally, collaboration among

subgroups is needed when it comes to mounting the aerodynamic devices.

Generate down force is linked to the Suspension, Unsprung mass, Chassis and Powertrain subgroups.

Information regarding the down force will be received by all these subgroups, and down force will be

generated for the Unsprung mass and Suspension subgroups


by Mikael Sedlacek

2013-09-08

8

Benchmarking

In order to find solutions to the functional model different technical solutions were benchmarked.

Knowledge from previous years Chalmers formula student, formula student cars in general and

racing cars were used.

1.5 Benchmarked solutions

In the end of benchmarking a Weighted Pugh matrix have been used to evaluate, rate and compare

the different concepts. In this matrix different weight-parameters have been used in the evaluating

process. The general parameters are shown below and the specific parameters are discussed in the

corresponding subsystems.

Mounting – Refers to how the mounting will be done, and if it is already tested and easy. It is

important to get the parts in the right position where it works in an optimal way.

Drag – It’s ital to de ease the o e all d ag of the a i o de to i ease the maximum

speed of the car and to reduce fuel consumption.

Down force – The main function for the aerodynamic devices is to create down force. More

down force will give better grip between the road and tires which is an advantage when

cornering.

Manufacturability – It is required that the solution can be manufactured under the

conditions and time limits of this project.

How it affects other subgroups – A solution may interact with other subgroups and make

collaboration between aero and the affected subgroups necessary. The effect of this is that

both groups may get more to do and maybe some changes of different parts are required.

Development time – The time for development are restricted and many parts are to be

designed. The development means the time for making a computer model, simulations and

manufacturing.

Adjustability – By this the Aero group refers to the opportunity to tune the solution on the

physical car.

Cost – The weight of the cost for the CFS team is set to 7 since the team is on a budget.

CFS Cost –The importance of cost will be 7 for all the subsystems since the cost report is part

of the points that can be gained.

Weight – The weight will always have an importance of 8 since it is stated that the CFS13 will

deliver a reliably and yet lightweight car so the weight must be investigated in order to fulfil

the team goal.

Support/previous experience – It is valuable with previous experience but it should not be

forgotten that you are allowed to do something totally innovative.

Handling – The solution should not be unpredictable and should also be reliable to the driver.

Reliability – The solution should not break during driving and the team goal states that we

are going to build a reliable racing solution, therefore the importance was set to 10.

Aesthetics – Aesthetics refers to the perceived look of the car with the chosen solution. The

first thing that the customer will see is the look of the car and because of that, the aesthetics

are important to consider.

Assembly – It should be easy to remove the chosen solution from the rest of the car in order

to do some work with another part of the car, or make some repairs.


by Mikael Sedlacek

2013-09-08

9

Maintenance – The maintenance for the different parts of the car is important; it should be

easy to fix broken parts and to check if repairing is needed.

Sustainability – Refers to the total material use to create a working solution and effect on the

fuel consumption. Sustainability is important to be competitive at the competition and as

well an important issue for Chalmers University of Technology

1.5.1 Subsystems 1: Body

The body consists of the nose, the body around the driver (but not sidepods, if these are used) and

engine cover. The subsystem is also responsible for how the parts are put together. The reference

used was CFS 2012 car.

Solution 1: Smooth shape

Smooth shape is a solution that will bring well-designed continuous lines for the vehicle, aiming to

give the sense that the different aligned parts create one homogeneous surface. An important aspect

of a smooth shape vehicle is the reduction of drag and increase of down force due to the less flow

separations on the surface of vehicle. (Katz, 1995) The solution comes from the CFS 2011 car, which

has a u h s oothe shape tha the CF“ a ; it a also e see i Delft’s Formula Student

2012 car.

Solution 2: Engine cover

Engine cover is a solution that would be used to optimize the air flow at the rear part of the vehicle,

reducing the turbulent flow and increasing the efficiency of the rear wing. The solution can be seen

i CF“ a , Delft’s Fo ula “tude t a a d o e.

Solution 3: Slope in front of the driver

This solution refers to that the body directly in front of the driver would be formed so that air flow is

directed over the drivers head and into the engi e o e if su h is used. It a e see i Mo ash’s 2009 Formula Student car and more.

1.5.1.1 Discussion and Final solution(s) 1

For the body the PUGH matrix clearly displays the advantages of having a smooth shape, using an

engine cover and having a slope in front of the driver in reference to the CFS 2012 car, which had

o e of these. “i e the solutio s do ’t ou te a t ea h othe , all of the a e used i the sa e concept. It can be seen though, that a smooth shape is more important than using a slope in front of

the driver and the same relationship between slope in front of the driver and engine cover. So more

energy should be put into making a smooth body than developing an engine cover, since this gives

more benefits.

Not much weight to the car will be added by the body solutions themselves, so therefore no

compromises would have to be made regarding weight and optimizing drag.

Having a smooth shape does allocate more time to manufacturing, but the gain overcomes the time

spent.

Considering whether the Chassis is going to be a monocouqe or a space frame has a big impact on

how the nose and front body will be developed. Both require collaboration with the Chassis


by Mikael Sedlacek

2013-09-08

10

subgroup, but in different ways. If a space frame is used, the aero subgroup needs data considering

how big the frame is and where to mount the parts. If a monocoque is used the aero subgroup will

define the shape and the Chassis subgroup will make calculations from this shape.

So therefore the final solution for the body will contain: a smooth shape, an engine cover and a slope

in front of the driver. The smooth shape will be accomplished through attention to details and a close

collaboration with the other subgroups. Collaboration between subgroups is also needed in order to

use an engine cover, this first and foremost refers to the Powertrain subgroup regarding engine

placement and volume. A slope in front of the driver will also be used in order to lessen the drag

force on the car and to lead air to the engine cover.

1.5.2 Subsystems 2: Underbody

By properly channelling the airflow under the car, significant down force can be gained to the

expense of very little additional drag; the down force/drag ratio for ground-effect cars can be up to

300:1 (Faul, 1980). The under body of a race car can thereby be shaped to, with a varied

effectiveness, create this phenomenon with different concepts. According to Formula SAE rules the

car must have a floor close-out to protect the driver (Formula SAE® Rules, 2012), and if a

monocoque is used the engine must be protected by the under body.

Solution 1: Flat undertray

The simplest and cheapest solution is having only a flat undertray that makes the underbody smooth.

This will lessen the drag and create a low pressure and faster traveling airflow under the car.

Bernoulli’s p i iple tells us that ai t a eli g ith highe speed, o pa ed to the f ee st ea velocity, will create a pressure drop (Barnard, 2001). This low pressure will create down force, but

not significant enough due to the abruptly change of air velocity – back to free stream speed – and

separation in the airflow when the air emerges from under the rear of the car would cause a stall and

consequentially reduce the down force (Mahon, 2004). The complexity, manufacturability and

development time of a flat undertray is low. There are not many teams that are using only an

undertray without the diffuser due to the negative effects on the down force it would give.

Solution 2: Undertray with diffuser

A diffuser, or venturi, is an add-on to a simple undertray and will help the airflow under the car to

decrease its velocity back to the free stream speed without separating from the diffuser walls, which

would cause a reduction in down force. This concept will give better down force, compared to only

an undertray, and the same drag. The cost will be higher due to the more complex form. Many top

teams in Formula Student are using this solution.


by Mikael Sedlacek

2013-09-08

11

Figure 2: Undertray and Diffuser setup

Solution 3: Airdams

Air dams are used in the front of the car to reduce the pressure on the under body of the vehicle, and

at the same time increase the down force. When the car is in motion the lower front of the car is

creating a low pressure zone and by adding air dams the airflow is restricted locally and the airflow

will be accelerated. This will increase the down force, but towards the rear of the car air is flowing in

through the sides and reduces the down force. None of the benchmarked teams are using this

solution.

Figure 3: The effect of an Airdam (Barnard, 2001)


In the Pugh matrices the reference for the under body was CFS12 with an undertray and small

diffuser. Air dams are a good add-on but may interfere with other aerodynamic. The winning

concepts were a big and effective diffuser that could, without separating the airflow, de-accelerate

the airflow back to free stream speed. Through these studies and through extensive discussions

within the subgroup and to alumnae we have decided to go for an undertray with diffusers.

The negative effects with this concept are the cost, manufacturability and development time. It will

be more complex and harder to simulate, but considering the benefits and the ratio of down

force/drag that can be gained, this area is important to analyse and give a lot of consideration.


by Mikael Sedlacek

2013-09-08

12

1.5.3 Subsystems 3: Cooling

When benchmarking Formula Student cars three main solutions regarding cooling were observed; (1)

A radiator without something to direct the air (2) A single sidepod with a duct used to direct the air

(3) Two sidepods, either one or both used for a duct. The most common solution within the top 20

teams at FS 2012 and FSG 2012 were two sidepods.

The goal is to build a reliable car that can perform well on the track. This requires the engine to run

at its best performance at all times, which consecutively requires that the radiator always provides

enough capacity. For the radiator to work efficiently it demands sufficient air flow through the heat

exchangers. In order to get enough flow through the radiator, it is therefore important to review the

lo atio of the ai i let a d the ae od a i effe ts. The adiato ’s apa it depe ds la gel o the air flow passing through and thereby the mass flow rate is the important factor. Studies show that a

properly designed duct can provide 154% better mass flow rate compared to a simple baseline

shape, and a duct is also said to provide better mass flow compared with drag ratio. Additionally, a

more effective duct will need smaller heat exchangers and can thereby reduce both drag and weight.

This in itself can lead to reduced fuel consumption and hopefully also to faster lap times.

(Christoffersen, 2008)

Since the power train subgroup has specified that they most likely will use one radiator it was

decided to benchmark two alternatives; one single sidepod or two sidepods.

Solution 1: One sidepod

In order to fulfill the need for cooling and based on the fact that the car only will requires one

radiator, only one sidepod is needed. The solution with one sidepod has the advantage that it is

a light alternative and moreover it requires less resources in terms of manufacturing time,

materials and money.

Solution 2: Two sidepods

The solution with two sidepods gives the opportunity to use the one not needed for cooling as

packaging. This sidepod could be used either for the exhaust, electronic or other equipment,

something that the future will show. Further on two sidepods will make the car symmetric which will

have benefits regarding aerodynamics. Last but not least a car with two sidepods is more aesthetic

attractive.


There are a few things that are vital to consider when discussing one or two sidepods; aerodynamics,

weight and adjustability. The weight of one sidepod is quite small compared to the overall weight of

the car. The impact on aerodynamics that one sidepod and a non-symmetric car have is hard to

calculate, but it could lead to sideforces acting on the car. A Sidepod can have a streamlined shape

that will direct the air flow in a way so that the drag from the wheel will be reduced. Effects

regarding downforce and the cars behaviour when cornering could also be affected by a non-

symmetric car. Considering the alternatives the benefits of two sidepods will be clearly higher than

the expected negative effects.


by Mikael Sedlacek

2013-09-08

13

1.5.4 Subsystems 4: Wings

Wings are not necessary for running a Formula Student car but can be used to increase down force.

Wings are commonly used in Formula 1 and some of the teams competing in the Formula Student

competitions are using wings. The idea with the wings is to reduce pressure at the lower surface of

the wing. The pressure difference between the upper and lower surfaces will give the wing negative

lift (down force) that increases the grip between the road and the tire. The increased grip will

increase the performance when cornering and the car can go with a higher velocity in the corners.

There are some important parameters when evaluation the best solutions:

Solution 1: No wings

One simple solution is to not use wings. Wings will increase the drag on the car and the maximum

velocity for the car will decrease. The no wings solution is commonly used by other teams in the

Formula Student competitions. The CFS11 team and also Delft University of Technology, that finished

second after CFS12 team in FS12, used this solution in their cars.

Solution 2: Front wing

A front wing will increase the down force on the front wheel. No benchmarked cars did use this

solution.

Solution 3: Rear wing

A rear wing will increase the down force on the rear wheel. No benchmarked cars did use this

solution.

Solution 4: Front and rear wing

A wing in the front and rear will increase the down force both in front and rear. This solution was

used by the FS12 CFS12 and also Monash University that finished third in the same competition used

this solution.


The t o solutio s f o t i g a d ea i g a gi e a ad fo e dist i utio to the a hi h a make the car behave strange and unpredictable. The car will be over steered or under steered and

these properties will vary with the velocity of the car. The two other solutions are both common in

Formula Student competitions. Both solutions have pro and cons, for example the no wing solution

will have less drag which leads to a higher speed at straight line driving and lower fuel consumption

than for a car with wings. A car with wings will have more down force that will increase the possible

velocity when cornering.

Which solution that is the best depends on the events at the competitions. Some investigations had

been made to find out the advantages and disadvantages with wings. A SAE report called

Aerodynamics for Formula SAE: Initial design and performance prediction (2006) from the Monash

University was studied. The report investigated how wings on the Monash 2003 car would affect the

results in the different dynamic events in Formula Student competitions. The results of the different

events were compared with simulations in the software OptimumLap that were made by the CFS13

Suspension subgroup. The Aero subgroup has summarized the result and calculated that a car with

wings can gain approximately 130 (129.17) points in the competitions compared to a non-winged car.

How these calculatio s e e ade a e ead i Co petitio s “ o es Ae o s No Ae o i the


by Mikael Sedlacek

2013-09-08

14

Appendix. A conclusion from the report showed that an aero package that can provide much down

force will gain more points at a Formula Student competition. Also the result from the Pugh matrix,

hi h a e see i the appe di , sho s that the solutio f o t a d ea i g is the est solutio .

Solution model

The solution model describes the different solutions for the subsystems and how they interact with

each other and other subgroups. Due to the decisions for the concepts needs to be analysed and

thoroughly developed in the design phase before mountings can be decided, the different arrows

sho i g Mou ts o a e just p eli i a a d ill e de ided i the desig phase.

Figure 4: Solution model for Aerodynamics

Final discussion

Throughout the pre-study phase concepts and solutions have been evaluated to find preliminary final

concepts for the aerodynamics of the CFS 2013 car. These concepts will be evaluated throughout in

the design phase with computational fluid dynamics (CFD) and wind tunnel tests. Since aerodynamic

parts work together in a total aerodynamic package, it is hard to evaluate the solutions and concepts

by themselves, and also in combination, without using simulation software (CFD). Time constraints

also contributed to the fact that assumptions where made. The assumptions made where that every

part would work perfectly by themselves and together. This is not always the case in reality,

therefore adjustments will be made to the final solution, and concepts may be added or removed

from the final car. Therefore collaboration with other subgroups is needed, and this will also make a

difference in the final design.


by Mikael Sedlacek

2013-09-08

15

Figure 5: This is a sketch made to illustrate the concepts evaluated during the pre-study phase. The sketch is not at all a

final design.


by Mikael Sedlacek

2013-09-08

16

2. Design

Hereby a briefing of the design part of the project can be found.

Technical Background

As stated in the problem definition of the pre study part (1.1) the main responsibilities of the

aerodynamic subgroup is to generate down force, reduce drag and generate cooling for the engine.

The parts referred to here are all connected to these three responsibilities. The pre study part also

explains what could be used in order to achieve high down force, low drag and cooling for the

engine. However it does not explain technically how the parts work in order to achieve this.

Therefore a short summary of the physics behind each part will be found beneath.

Front and rear wing

Both front and rear wing are built up from several parts; so o e i g refers to the assembly which

makes up one front or rear wing package. The wing packages specifically used here consist of;

1. Ai foils; Airfoils are bodies designed to produce lift (or negative lift: down force) from the

o e e t of fluid a ou d it. E gi ee i g Fluid Me ha i s, The airfoils can also be

referred to as elements, they are divided up into one main element and one or more

secondary elements, also known as flaps

2. End plates; which can be used with different sizes and/or shapes

Figure 6: Sketch of S1223 Airfoil with endplate


by Mikael Sedlacek

2013-09-08

17

As stated in the pre study part the wings generate a downwards force by a pressure difference; this

pressure difference comes from the top and lower surface of the airfoils used. To understand why

such pressure difference creates down force one must first understand;

1. Pressure

2. Ne to ’s se o d la

3. Specific weight

4. Eule ’s e uatio of motion of a fluid 5. The Bernoulli equation

I sho t ou appl Ne to ’s se o d la a d the k o ledge of spe ifi eight in order to reach

Eule ’s e uatio fo otio of a fluid. You the appl Eule ’s e uatio alo g a path line to get

Be oulli’s e uatio . If ou egle t is ous effe ts i Be oulli’s e uatio the su ill al a s e

constant along a streamline.

This means that if the flow velocity decreases the static pressure increases; on a race car wing the air

flows faster on the lower surface then on the upper. This results in down force, also known as . The

down force can be calculated through the equation where * is the coefficient of lift,

is the fluid density, is the free-stream velocity measured relative to the body and is the reference

area to the body.

Figure 7: Simplified figure of how an airfoil works

*However to gain more knowledge about all the reasons why specific airfoils generate different amounts of lift (or negative

lift) one must understand the Concept of circulation ∮ . Which combined with ideal flow theory and the Kutta


by Mikael Sedlacek

2013-09-08

18

condition will give theoretical lift for indefinitely long airfoils at a small angle of attack. is in this case given by

, where is the angle of attack. (Engineering Fluid Mechanics, 2010)

Drag force, , is given by the equation: . The equation has the same properties as the

equation for down force, however is usually found by experiment. The drag force of an airfoil (and

of a total wing package) is important to know for the main reason that one wants to gain down force

with the addition of as little drag as possible. Thus when designing a wing the lift/drag ( ) ratio

is used in order to measure its performance. (Engineering Fluid Mechanics, 2010)

There are some terminology concerning airfoils that is important to know in order to understand the

differences between airfoils;

Figure 8: Explanation of the key terms of an airfoil

The length of the airfoil is called span, the depth is called chord. Both of the measurements are from

the edges of the airfoil in question. The camber refers to the curvature of the airfoil, it can be

adjusted in order to gain a higher ; what can be used instead or in addition is to increase the angle

of attack However increasing the angle of attack will increase the drag . When the angle of

attack is increased over a certain level the wing will stall; what happens is that the flow separates

from the wing.

Thus in order to gain a good a combination of the correct camber and angle of attack is what

is being sought after.

The leading edge simply refers to the foremost edge of an airfoil section; the trailing edge is the rear

edge of the airfoil section, both are of great importance in order to gain a good and also in

general creating a good airfoil. The trailing edge is of the greatest importance, because you want the

flow to leave the foil smoothly. This can be referred to the Kutta condition and the concept of

circulation. (Engineering Fluid Mechanics, 2010)


by Mikael Sedlacek

2013-09-08

19

The endplates on racecar wings are used in order to contain the flow which without the addition of

endplates follows roughly this sketch;

Figure 9: A sketch of the flow on an airfoil without endplates

The flow in the middle of the wing is attached until the trailing edge, however the flow further out on

the sides will separate earlier. This will lead to a lower ratio if one does not use endplates.

However with the addition of endplates the phenomenon of horse shoe vortices can be seen; the

flow bonces on the end plate in a U-shape, this creates flow separation. Therefore one must consider

how to design the endplates in a good manner.

Regarding specifically front wings (because they are in most cases close to the ground) there is a

phenomenon called ground effect. Ground effect can be partially explained by Bernoulli’s equation; if

you bring an object close to the ground, the cross sectional area between the object and the ground

will shrink, this causes the air beneath it to accelerate, which in term leads to a pressure drop

underneath the object, but not on top. Which as earlier stated will give a force resultant; in this case

the object is drawn to the ground. The second part of ground effect has to do with Couette flow, and

is specific for the case where an object is at a certain velocity close to the ground. Further

explanation regarding this does not fit into this report.

Front and rear wing flaps

Flaps are used in order to lengthen the chord of the total wing, and retaining attached flow on the

wing. However the flaps must be carefully designed and placed in order to retain the flow.

(Competition Car Downforce, 1998)

Computational fluid dynamics

Or in short CFD is a branch of fluid mechanics that uses numerical methods and algorithms to solve

and analyze problems that involve fluid flows. It was used in order to analyze the different concepts

made by the aerodynamic subgroup.


by Mikael Sedlacek

2013-09-08

20

Computer-aided design

Also known as CAD, is the use of computers to visualize, analyze and optimize designs.

Race car aerodynamics in short; do not let the flow separate or as little as possible, and you will be

successful.

Team goal in reference

The team goal states;

In order to become outstanding Engineers with professional experience, we will, as a team, through

data driven decisions and efficient engineering, design and deliver a reliable yet lightweight Formula

Racing Solution to achieve 900 points at FS13.

The subgroup goal states;

In order to become outstanding engineers, we will, as a subgroup, through data driven decisions,

gain experience by designing and delivering an adjustable and reliable yet lightweight efficient

aerodynamic solution to achieve 900 points at FS13.


by Mikael Sedlacek

2013-09-08

21

Design targets

Specific design targets for the aerodynamic package were set to;

Down force: 500-600 N at 56 km/h

Down force ratio: Front/Back 40-60% (depends of

center of pressure)

Down force/Drag ratio: 2.75 (drag 200-220 N at 56 km/h)

Front Wing weight: 5 kg

Front Wing Height 75mm

Safety Factor wing mounting: 3

Time for assemble and disassemble the wings 2 persons/wing assembly 5 minutes

Minimize amount of fasteners types,

standardized system

Time to reach the cooler 30 seconds

Change the angle of the attack of the wings 5 minutes

Rear Wing weight 5 kg

Sidepod weight: 1.5 kg

Undertray +Diffuser weight: 3.80 kg

Min- max ground clearance 35 mm-50 mm

Mass flow for duct 0.4218 kg/s

Max weight of paint 1kg

Figure 10: A table with the design targets for the aerodynamic subgroup


by Mikael Sedlacek

2013-09-08

22

2.1 CAD assembly

Underneath a CAD rendering of the parts covered in this report can be found;

Figure 11: A CAD rendering of the parts current for this report


by Mikael Sedlacek

2013-09-08

23

2.2 Front wing

2.2.1 Design choice/ selection

The front wing is made up from: endplates, main elements, flaps and a middle segment. Underneath

a brief explanation of each sub part is given. The final total weight of the front wing is 2500 grams

without the mounts.

Airfoils

The main elements, flaps and middle segment are the airfoil; Selig S1223 high lift low Reynolds

number airfoil. In a comparison with other airfoils made in the report: High Downforce Aerodynamics

for Motorsports, 2011, it was found in an analysis of single elements airfoils that the S1223 operated

good and gave the most lift in comparison with three other airfoils under conditions assumed for

race car driving; low-speed natural laminar flow.

Figure 12: A picture of the flow field around the S1223 airfoil

The data for the airfoils where found in the UIUC airfoil coordinates database

(http://www.ae.illinois.edu/m-selig/ads/coord_database.html). The data was translated into an excel

document from which a macro-script was used in order to plot the airfoils into CATIA. The airfoils

were then scaled into appropriate size.

Size of the airfoils

The initial size of the airfoils were set to fulfill the current 2013 Formula SAE rules, Article 9: T 9.2;

which states that no aerodynamic device can be more forward than 762 mm from the front tires and

no wider than the outside of the front tires or rims. Also according to Article 2: T2.1; no part may

come closer than 68.6 mm radially from the tires. These rules therefore delimited the span and chord

length.

The final length of the spans and chord for the main elements and middle segments were

determined through data driven CFD analysis made by Eva Andersson and Athanasios Tzanakis. The

final lengths are; Chord 522 mm and Span 355 mm.

The chord length regarding the flaps follows the theories explained in: Competition Car Downforce,

1998; which state that on the flaps chord length should be 20-25 % of the main elements chord

length. The final chord length for the flaps therefore are; 123 mm.

Angle of attack

The angle of attack on the main element is set to 12.5 degrees through data driven results from CFD

analysis, which gave the ratio of 3.95. The angle of attack for the flaps is dependent on the


by Mikael Sedlacek

2013-09-08

24

angle of attack of the main element, the angle is set to 12.5 degrees in relation to the chord axle; it

can also later be adjusted on the car in order to fine tune the down force gained from the front wing

package. However neither the main element nor the middle segment can be adjusted later.

The middle segments angle of attack was set to 0 degrees because of the symbiosis between side

pods, diffuser and wings, explained in the discussion section below.

Ground clearance

The ground clearance of the wing package was set to 75 mm because of the 2013 Formula SAE rules

regarding jacking of the car: Article 6, T6.6.2 and the rules stating that no part of the car may touch

the ground during competition Article 6, T6.2. Part of the limitations is also the cars suspension

system, and specifically pitch; however the jacking rules was the most limiting.

End plates

The final size of the endplates was set to; length: 638 mm height 339 mm. The size is based partly on

data driven CFD analysis by Eva Andersson and Athanasios Tzanakis. It is also based on earlier stated

rules about both ground clearance and aerodynamic devices.

2.2.2 Discussion of design selection/ Limitations

Beneath a brief explanation of the most important concepts that lead to the final design.

Concept 1a: No middle segment

Early in the design process assumptions were made regarding how much down force the middle

segment really gave, as the air has nowhere to go on the top part of the wing; in this case it hits the

nose. Therefore one concept was based on that the front wing would be split up into two parts; one

of each side of the car. With the wings attached to the side of the frame (monocoque).

Figure 13: A CAD rendering of the concept front wing without a middle segment

CFD analysis later made by Eva Andersson and Athanasios Tzanakis showed that the ground effect

generated by the middle portion of the front wing contributes a lot to the wings ratio.

Therefore this concept was not designed any further. (Remark: The nose was later designed to fit the

wing and in essence removed the top part of the wing)


by Mikael Sedlacek

2013-09-08

25

Concept 1b: Neutral middle

This concept was made with the thought that since ground effect had an effect on the wing s

ratio; but nothing was to be gained on top of the wing (since the air was blocked by the nose) it

would be easy to manufacture a wing with a simple segment in the middle; also the fact that a bigger

area of the wing would be close to the ground (bigger ground effect) was part of the thought behind

this concept. Also part of the thought is that air needs to go in-between the endplates and chassis in

order to reach the side pod inlet; if you have an airfoil at a steep angle of attack in the middle

segment, it could possibly make the air flow over the inlet.

CFD analysis later made by Eva Andersson and Athanasios Tzanakis showed that turbulent flow was

created by the neutral middles shape and the gains from ground effect where not as big as expected.

Therefore this concept was not used as it was first intended;

Figure 14: A CAD rendering of the concept with a neutral middle segment

Because of this it was tested to use an airfoil with 0 degrees in angle of attack in the middle, and the

main segments at a different angle; this proved to be the best design. It can be seen in the final front

wing design.

Concept 2a: Different sized end plates

Because of the effects end plates can have on airfoils(earlier explained), the thought that small

endplates in the middle part of the wing would contribute to a better, or unchanged ratio.

Since the flow theoretically is attached in the middle part of the wing.


by Mikael Sedlacek

2013-09-08

26

Figure 15: A CAD rendering of the concept with small end plates

However CFD analysis later showed that the ratio decreased with smaller endplates.

Concept 2b: End plates at different distances from the chassis

As with the neutral middle concepts, this concept partly had to do with getting flow to the inlet of

the side pod. CFD analysis by Eva Andersson, Athanasios Tzanakis, with different iterations of the end

plates placed at different distances from the chassis, later gave a compromise in which the inlet

receives enough flow and the front wing has a good enough ratio.

Figure 16: A CAD rendering of the concept with endplates close to the chassis

2.2.3 Simulations/ Tests/ Experiments

The used software to realize sketches into CAD was Dassault Systems CATIA v5 r19. This CAD was

then cleaned and meshed in the program Ansa 13.2.3. To finally do the CFD analysis the program CD-

Adapco Star CCM + 7.4 was used.


by Mikael Sedlacek

2013-09-08

27

2.2.4 Front wing Drawing and CAD

Figure 17: A CAD rendering of the final front wing concept

2.3 Manufacturability/ Costs/ Sustainability

The analysis part will provide the reasoning behind the choice of material;

Carbon fiber reinforced plastic (CFRP) is lighter, cheaper and stiffer than magnesium alloys; therefore

it will be used for all applications. The main difference between the parts is the core material used in

et ee the a o fi e la e s. “i e the pa ts e ui e high stiff ess i all di e tio s You g’s modulus[E]) isotropic core material will be used. The core thickness is the biggest contributing factor

regarding stiffness, so adding more carbon fiber layers will not increase the stiffness in any big way.

High density core material will be used to stiffen up the main segments of the front wing.


by Mikael Sedlacek

2013-09-08

28

2.4 Rear wing

2.4.1 Design choice/ selection

The front wing is made up from: endplates, one main element, two flaps.

Underneath a brief explanation of each sub part is given. The final total weight of the rear wing is

2660 grams.

Airfoils and their size

The same airfoils and theory surrounding the same was used for the rear wing as with the front wing.

However two flaps were used instead of one; there are several reasons for the difference: there is

more room in the back of the car, the rear wing does not benefit from ground effect and there is no

side pod inlet that needs to be considered.

The initial size of the main segment chord size was based partly around the 2013 Formula SAE rules,

Article 9, T9.2, which states that no aerodynamic device may be further rearwards than 305 mm

from the rear wheels and partly on the rear sub frames dimensions. The span is based on the

wheelbase because of the same rules as with the front wing.

Later CFD analysis by Eva Andersson, Athanasios Tzanakis gave the final sizes of the main segments

chord. Main segments chord: 515 mm, span 1390 mm. The flaps have the same span as the main

segment, and a chord length of: 125 mm. This chord length follows the same theory as explained

with the front wing flaps (the chords are 24 % of the main segments chord).

Angle of attack

The angle of attack on the main element is set to 7.5 degrees through data driven results from CFD

analysis which gave a ratio of 3.47. The angle of attack can be adjusted for both flaps, the flap

closest to the main segment has an attack angle of 7.5 degrees in relation the main segments chord

axle and the second flap has the same relationship with the first flaps chord axle.

The angle of attack increased the from the initial 1.72 with 0 angle of attack to 3.47.

End plates

The final size of the endplates was set to; length: 700 mm height 450 mm. The size is based partly on

data driven CFD analysis by Eva Andersson, Athanasios Tzanakis. It is also based on earlier stated

rules about aerodynamic devices.

2.4.2 Discussion of design selection/ Limitations

Beneath a brief explanation of the most important concepts that lead to the final design can be

found.

Concept 1: Neutral middle

Early in the design process assumptions were made regarding how much down force the middle

segment really could give, since there was an assumption that the roll hoop would create turbulent

flow in the middle part of the wing; and thus lead to un-attached flow. Therefore concept one was

based on a wing with four end plates and a neutral middle;


by Mikael Sedlacek

2013-09-08

29

Figure 18: A CAD rendering of the rear wing with a neutral middle segment

CFD analysis made by Eva Andersson, Athanasios Tzanaki later showed that this was not the case, the

middle segment of the rear wing contributes a lot to the ratio.

The wing with a neutral middle gave a ratio of: 1.5 with the current angle of attack. In

comparison the final wing had a of 1.72 with the same angle of attack.

Concept 2: Plates in the middle of the wing

Because of the effects end plates can have on airfoils(earlier explained) and the thought that the flow

in the middle part of the wing would be turbulent another concept surrounding this thoughtworld

was made; the addition of two more plates, with the same size of the end plates; in the middle of the

wing.

Figure 19: A CAD rendering of the rear wing with plates in the middle


by Mikael Sedlacek

2013-09-08

30

However CFD analysis by Eva Andersson, Athanasios Tzanaki showed that the wing had a ratio

of 1.68, with the current angle of attack. Which is worse in comparison with the final wing at the

same angle of attack (1.72). Another factor affecting is that adding plates in the middle adds weight,

and at a bad place in the car dynamically (it is placed high up, far away from the center of the car).

2.4.3 Simulations/ Tests/ Experiments

The used software to realize sketches into CAD was Dassault Systems CATIA v5 r19. This CAD was

then cleaned and meshed in the program Ansa 13.2.3. To finally do the CFD analysis the program CD-

Adapco Star CCM + 7.4 was used.

2.4.4 Rear wing Drawing and CAD

Figure 20: A CAD rendering of the final rear wing concept

2.5 Manufacturability/ Costs/ Sustainability

The same motivation of material choice as with the front wing is used for the rear wing. Carbon fiber

reinforced plastic (CFRP) and a high density core material will be used.


by Mikael Sedlacek

2013-09-08

31

Analysis

Hereby the analysis part of the project can be found.

Material selection for the wings

Hereby a briefing on how the material for the wings where chosen can be found.

2.6 Software tools

Granata design, Cambridge Material Selector.

Learned through the course MTT075 Material och processval (Material and process selection).

2.7 Simulation stages/ steps and parameters

The following factors where used in order to delimit the materials to only the ones that fulfills the

primal needs for the wings:

1. Function

- Improve (decrease) drag coefficient

- Provide down force

- Be hit by small debris without cracking

2. Demands

- Be able to manufacture in the shape of current CAD model

- Total weight of one < 0.6 kg

- You g’s odulus > GPa

- Fracture toughness KIC 1 Mpa.m^0.5

- Be able to drop from 1 m

3. Goal function

Minimize weight (density), price,

Ma i ize ou g’s odulus/de sit E/δ

4. Free variables

Choice of material


by Mikael Sedlacek

2013-09-08

32

2.8 Results

Figure 21: A graph with aterials with you g’s odulus plotted agai st de sity

The g aph sho s You g’s odulus plotted agai st De sit fo all the ate ials fulfilling the earlier

stated factors. Two materials were found to fulfill these; Carbon fiber reinforced plastic (CFRP) and

magnesium alloys.

2.9 Recommendation

In order to use the program successfully one must first clearly define goal functions, which in all

cases will not be as simple as Ma i ize ou g’s odulus/de sit ; the goal function is most often

what one wants to display in the graph. Another important factor is to clearly define factual

de a ds; i this ase the de a ds he e so high ega di g ou g’s odulus and density that only

two material fit in; most often this will not be the case, especially if one looks for cheap plastics. In

the case that a lot of materials are found; the factors should be that for instance if one wants a

material with high young’s odulus a d lo de sit , the ou g’s odulus pa t of the plot should e i e ted. This a the ate ials ith the est ou g’s odulus/de sit ill e displa ed to the left of the graph. Any of these materials can be chosen for the application.


by Mikael Sedlacek

2013-09-08

33

CFD

Hereby a short briefing on the Computational fluid dynamics made by Eva Andersson and Athanasios

Tzanakis for the wings can be found.

2.10 Software tools

The software used for the CFD analysis was first Ansa 13.2.3 to clean the CAD up, create the mesh

and to create the wind tunnel. After this CD-Adapco Star CCM + 7.4 was used for the analysis itself.

The steps behind the process can be found in Eva Andersson and Athanasios Tzanakis reports.

2.11 Results

With all parts included in the car (diffuser, side pods and more) the final results from CFD were 455N

of down force and 255N of drag. This included lift which was created by the monocoque.

2.12 Recommendation

In order to work effectively with the transition from CATIA into Ansa it is best to create solids from

the surfaces made. This is because there always will be topological error in surface files; especially if

they are at a concept stage. These errors will not be found if one uses solids.


by Mikael Sedlacek

2013-09-08

34

3. Manufacturing

Following the earlier established data considering material properties the material chosen for front

and rear wing were carbon fiber reinforced plastic (CFRP). However there are first of all many

different types of Carbon fiber weaves, with different properties such as weight and stiffness in

different directions. Second of all to get a lightweight yet stiff CFRP part a core material had to be

used. Adding to this there are many types of CFRP manufacturing methods that could be used. All of

which were established through both availability of material and what gives the best results.

Underneath you will find which type of weave, manufacturing method and core material where used

for the parts and why they were chosen.

The parts are split up in; molds, front wing main, rear wing main, flaps and endplates.

3.1 Molds

One thing that were established, with only the prior knowledge that CFRP were to be used; molds

would have to be manufactured. Now as with CRFP, different types of material and methods for

creating a mold could be used. In short terms the higher the density of the material used, the higher

the finish of the final product would be. For the wings the finish is of upmost importance, since lower

skin friction means more attached flow. Considering the time constraints and high quality demands,

the method for creating the molds, Computer Numerically controlled (CNC) mill, combined with

limited manual work were chosen.

Thus the material Ureol were chosen with a density of 400g/l. The decision of using Ureol was in part

because of the availability, since Volvo Concept Centre was providing the material. There were also

concerns from the company providing the Computer Numerically controlled (CNC) mill, Cliff, because

they did not want to use their mills on any mold material, considering work environment factors.

In order for Cliff to mill the molds to specification the molds themselves were CAD:ed from the final

design set. The molds were made for front and rear wing main elements and flaps. These molds

consisted of a top part and bottom part and would later be glued together in order to form the total

airfoil. The mold is made by inverting the parts so that the outside meets the mold surface. This is so

that the surface on the outside gets the best finish and lowest skin friction. When the wing is

inverted a box was CAD:ed around it to determine how much mold material would be used, and how

it should be cut before putting it in the mill. In order to prepare the molds for Cliff the mold material

was cut and glued together in blocks at Cliff:s workshop.

Figure 22 A CAD of the top part of the front wing main element mold


by Mikael Sedlacek

2013-09-08

35

After the molds had been milled by Cliff they had to be prepared for a Carbon fiber layup, so that the

surface finish of the final parts could be as good as possible. This was done by first sanding the molds

and then waxing them with car wax for several layers. Now they were ready for layup!

3.2 Manufacturing method used

With the molds at Volvos concept lab (VCC) the layup could begin. As earlier mentioned there are

several ways to manufacture CFRP. The basics of manufacturing CFRP are that you need carbon fiber

cloth, epoxy and a vacuum bag. You can then choose to cure the part in room temperature, with an

oven or an autoclave(a pressurized oven). An autoclave or oven provides better quality and stiffness

of the parts however in the case of the wings it was chosen to cure in room temperature because the

stiffness needed was reached by this method. A vacuum bag is used to compress the cloth and epoxy

while curing so that the cloth does not move or expand.

The weave chosen was Oxeons Textreme which they call a spread tow weave. The reason for

choosing Textreme over other cloths was both because of availability, since Oxeon were a CFS

partner and also because the weave is very light compared to other weaves. In comparison twill

weave is the most commonly used weave for CFRP manufacturing, it provides a very stiff product,

however it must be handled with care at layup and it is also heavier than Textreme for this

application.

Figure 23 Twill weave Figure 24 Textreme weave

The method chosen was infusion molding which consists of laying up the carbon fiber cloth and

applying the epoxy using the vacuum created by the vacuum bag. So the epoxy is prepared in a

bucket and hooked up to a hose which is placed inside the vacuum bag and sealed. The method was

chosen because it is easier to control the distribution of epoxy in the cloth. Because of this the part

gets a better quality, since there are no heavy patches of epoxy.


by Mikael Sedlacek

2013-09-08

36

Figure 25 A picture of using vacuum infusion for the top part of the rear wing

As displayed in the picture you can see that a layer of textile is placed on top of the Carbon fiber

cloth. This is so that the vacuum bag does not stick to the cloth. The little green scraper seen in the

picture is used to press out any shrinks made by the vacuum bag so that no deformities are created

by the vacuum bag compressing the carbon fiber. All the wing parts were made using the same

method, however the endplates did not need CNC milled molds since they were flat.

3.3 Front wing airfoils

A brief on how the front wing airfoils were made can be found underneath.

3.3.1 Manufacturing

For the front wing main top element three (3) layers of 200g/m2

Textreme cloth were used. The top

layer(the one seen on the finished product) was placed at 90 degree angle and the two other placed

in 45 degrees compared to the first layer. The layers are placed in this way to get stiffness in several

directions. The front wing main bottom element was made with three (3) layers of 100 g/m2

Textreme cloth, placed in the same manner as for the top element.

To get stiffness in the wing high density core material was CNC milled at the Chalmers workshop. This

was done by using a two dimensional profile of the airfoil. Thirteen (13) ribs were made with a

thickness of 20 mm and then placed out on the top element of the wing using epoxy. To add stiffness


by Mikael Sedlacek

2013-09-08

37

in the width direction of the wing supports were hand trimmed in rectangular shapes and placed in

between the ribs.

Figure 26 A picture of the ribs placed out on the top part of the wing

When the core material had been placed the bottom part of the wing was glued together with the

top part of the wing. The flaps were made using the same exact same methods with two (2) layers of

100g/m2 Textreme cloth on both top and bottom elements.

3.3.2 Design changes

No specific design changes were made.


by Mikael Sedlacek

2013-09-08

38

3.4 Rear wing airfoils

A brief on how the rear wing airfoils were made can be found underneath.

3.4.1 Manufacturing

For the rear wing main top and bottom elements, three (3) layers of 100g/m2

Textreme cloth were

used. The top layer (the one seen on the finished product) was placed at 90 degree angle and the

two other placed in 45 degrees compared to the first layer. The same method as used with the front

wing with core material and gluing together the top and bottom parts were used for the rear wing.


No specific design changes were made.

3.5 Front and rear wing end plates

A brief on how the endplates were made can be found underneath.

3.5.1 Manufacturing

The endplates were made by placing two (2) layers of 100g/m2 carbon fiber cloth on each side of high

density core material in a rectangular shape seen in the picture below. Then 1:1 drawings of the

endplates were printed and glued with (very) small amounts of paper glue onto the CFRP. After this

they were cut out using an handheld electric saw.


by Mikael Sedlacek

2013-09-08

39


A lot of design changes were made to the endplates, mainly because the endplates from the

beginning were completely rectangular. This was not optimal from a weight saving point of view, and

looking back at the wing theory presented the flow at the beginning of the airfoil does not have to be

contained with endplates. Testing was done with endplates cut out in aluminum with two different

concepts, and no differences in down force could be seen.


by Mikael Sedlacek

2013-09-08

40

4. Manufacturing coordination

The writer of this report was manufacturing coordinator during the manufacturing phase of the

project. Since a lot was learned during this period, and the setup of the Bill of material (BOM) and

overall planning were important and time consuming parts it was figured that something had to be

written about it, so that the knowledge can be transferred to CFS 14. To motivate the improvements

proposed a short brief on how the BOM and planning was handled during CFS 13 will be found

underneath.

4.1.1 Bill of material and overall planning

Coming back from Christmas holiday two meetings were held in which a time schedule was set up

with each subgroup specifying when certain subsystems should be manufactured. From this the

subgroups then set up the BOM specific for their parts, and put a specific date to each part that was

going to match the time schedule set up for the subsystem. The Bill of material was set up by each

subgroup using an Excel template document, with each parameter set up prior by the manufacturing

coordinator.

Figure 27 Picture of a part of the BOM initially set up

(Considering the amount of parameters all of them are not mentioned in this report, templates can

be found in the manufacturing folder for CFS 13.)


by Mikael Sedlacek

2013-09-08

41

From the subgroups separate BOM:s a global BOM was set up with all the subgroups included. Now a

global BOM was established, however an overall schedule was also needed. This schedule was made

from the dates set up at the earlier two meetings with dates for when subsystems should be ready.

The overall planning also contained all the deliverables (processes), such as gluing endplate to

wing .

Figure 28 A picture of the overall planning document

The setup worked good for the first week, but after that changes were made. The changes were

made because the dates and split up between parts and subsystems in the overall planning and BOM

did not match up. The dates did not match because of the split up; One problem lead to another

problem. Because of this one big planning containing all the parts and deliverables was set up.


by Mikael Sedlacek

2013-09-08

42

Figure 29 A picture of the overall planning setup

The coloring is specific for each manufacturing subgroup or design subgroup (if a manufacturing

subgroup was not assigned). All the grey rows represent an assembly and the first visible columns in

the document gives the most vital information; deadline (the deadline setup by the design

subgroup), manufacturing deadline (the deadline set up by the manufacturing subgroup), current

deadline (which was set up because if the manufacturer had forgotten to set up a deadline the

designers deadline would be displayed, otherwise the manufacturing deadline was displayed),

subgroup, responsible, part and finished.

During this period people in the project were set up in different manufacturing subgroups, which did

not always match with the parts that they had designed. Each subgroup had a representative which

reported which parts had been made once a week, and changed dates for parts which had not been

made.

4.1.2 Discussion and improvements

There are several improvements that can be made in upcoming years of CFS, with the first one being

the setup of the BOM. The setup (what meta data do you want about each part) should be

established during the design period. This can be done by two people who work separately with this

part (these two people can then go on to work as manufacturing and materials coordinators).

If this is established beforehand, they can set up a PLM (product life cycle management) system that

you can import Catia asse l ’s into. In this system you then get prompted to fill in the specified

information. This system can also keep track of version naming and check in check out operations (so


by Mikael Sedlacek

2013-09-08

43

that you don’t screw up CAD files). All the KBE (knowledge based engineering) data can also be saved

within this system, such as simulations and Matlab scripts. In this case you would have all the

information at the same place. Adding to this you can create views within the system and add

users to it. A view means showing specific information to that specific user. Thus you only get the

information you need to know, avoiding information overflow. The manufacturer can then release

the file within the system and thus it is marked as done. Making the work of meeting each week to

establish which parts are done obsolete. This system already exists in the form of Dassault systems

Smarteam, which Chalmers has a license for.

One main problem with the setup used for CFS 13 was that it was hard to get an overview of the total

progress. This was due to information overflow in the overall document. It was not easy to see which

part lead to the next. But if the system mentioned above is setup a lot more time can be spent on

looking at the overall progress, and thus having an overall planning.

Another problem was that the designers did not manufacture their own parts, this lead to confusion

and loss of motivation. It was clear that if the designers had made their own parts they would have

been more motivated to finish their assembly. It would also simplify planning enormously, if one

designer has a set of parts that have to be done he or she can plan their own work accordingly. In the

setup used by CFS 13 the subgroup representative gave out responsibilities and planned the work for

the subgroup, which lead to that the parts were being made in a too random order. It would have

been beneficial to finish one assembly at a time.


by Mikael Sedlacek

2013-09-08

44

5. Costs

The selection of processes, design and manufacturing were considered for cost in the sense that first

of all the only really viable material for wings were CFRP, which was established in the material

selection process. Second of all top teams competing were using CFRP for their wings and thus it

would not affect CFS negatively compared to other teams.

Now of course using the motivation everybody uses it is never good, however as stated this was

considering competing against other teams in cost event only. In which it is a factor which material is

being used by other teams.

6. Testing/ Validation

Only dynamic testing was performed as no static tests were needed for the wings.

6.1 Dynamic testing

Dynamic testing was performed to evaluate which endplate design was going to be used and testing

different flap attack angles.

6.1.1 Motivation

The main reason for dynamic testing of the aerodynamic package was to get as good front to rear

down force distribution as possible. For the current car it was more important to think about the

dynamics of the car rather than gaining maximum amount of down force unevenly distributed.

6.1.2 Test setup

Both for testing which endplates were going to be used and setting up the angle of attack for the

flaps potentiometers which measured the damper travel were used. This is used in order to calculate

the down force on the front and rear wheels.

6.1.3 Results

As mentioned earlier two endplate concepts were tested, they had the same basic shape but one

version was smaller in total area. Testing proved that there was no difference between the two

versions and thus the smallest version was chosen considering weight saving.

For the flap settings the angle of attack proved a difference in weight distribution and the angle 12.5

degrees for the front flaps and 7.5 for the rear flaps was the best setup for good down force

distribution if you consider the endurance event. However since there are different events a neutral

angle of attack was used for acceleration, since you do not need down force and rather minimum

amounts of drag in that event (for this car).


by Mikael Sedlacek

2013-09-08

45

7. Improvements/ Conclusion/ Recommendation

Because of two members with a lot of prior knowledge about wings quit the project early on the

design of the wings was put on two aero members with little prior knowledge about wings

specifically (however with basic knowledge in fluid mechanics). Since this knowledge had to be read

up a lot of time was spent on this. This also gave less time to spend on designing only the wings since

the writer of this report also was involved with every single subsystem of the Aero subgroup. This in

combination with problems of setting up CFD simulations and CAD cleaning for the same led to a

very unplanned process.

Wings are not easy to design, and definitely not for a race car since the air is very turbulent and

ground effect is in use. Also considering there are no established ways to design wings for a race car,

since the wings differ depending how the car will be put together. Thus the recommendation is to set

one or two people responsible for making the front and rear wing. They should have some prior

knowledge about wings and also about mechanical simulations in Ansys. The problems with CFD and

CAD cleaning can be solved by putting one person responsible for CAD and CFD. This person does not

have to make the CAD for the wings, however should be responsible for the CAD within the

subgroup, so that everyone knows how to work and set up the parts so that they are prepared for

CAD cleaning.

A vital part of selling a product is aesthetics, and very specifically a race car. Aesthetics are one of the

key aspects of a race car that is to be sold to a consumer. CFS approach to aesthetics and branding is

very old fashioned, where the engineering is put before aesthetics. The best product is a combination

of both. Now of course for this specific application, where the car is raced in a competition and not

actually sold makes the engineering part more important.

However in the car industry the aesthetics are often what is made first. That is; industrial designers

makes the initial concept and the car is built to fit within those specifications. Thus it could be a good

idea to introduce another event at the competitions; aesthetical judgment (and branding). Since it is

such a vital part of the industry.


by Mikael Sedlacek

2013-09-08

46

8. References

Clayton T.Crowe , 2010, Engineering Fluid Mechanics 9th

ed. Wiley

McBeath, 1998, Competition Car Downforce

Pakkam, Sriram Saranathy, 2011, High Downforce Aerodynamics for Motorsports

9. Appendices

9.1 Appendix A: Material and Part list

Part Number Amount Material

Front wing main

element

1 3 layers 100g/m^2 Textreme spread tow

weave

Front wing flaps 4 2 layers of 100g/m^2 Textreme spread tow

weave

Rear wing main

element

1 3 layers of 100g/m^2

Textreme spread tow

weave

Rear wing flaps 2 2 layers of 100g/m^2

Textreme spread tow

weave

Front and rear wing

endplates

6 2 layers of 100g/m2

Textreme spread tow

weave


by Mikael Sedlacek

2013-09-08

47

9.2 Appendix B: Manufacturing Drawings


by Mikael Sedlacek

2013-09-08

48


by Mikael Sedlacek

2013-09-08

49


by Mikael Sedlacek

2013-09-08

50

aerodynamics-front & rear wings - final report · aerodynamics-front & rear wings - final...

Documents