Design and Manufacturing of a Real Scale Prototype of a Land Sailor

Luís Miguel André Monteiro [email protected]

Instituto Superior Técnico, Lisboa, Portugal June 2016

The present work documents the mechanical design and the manufacture of a prototype of a land sailor. At first step, the market solutions are studied in order to substantiate a new lighter, low cost, smaller solution that comply with the quality, safety and performance criteria. These criteria result from the analysis performed to the structure (chassis, seat, steering), evaluating diverse load cases (the sail model was approached as an EPPLER profile), designing the structural components according to a Design For Assembly philosophy. Additionally, mechanical design methodologies are applied to evaluate the bolted joints, bearings and welded joints (AWS method and AISC code). A brief cost analysis is performed using the formula SAE cost tables, which result in a production cost of the prototype of 564,32 €, 30 % below the retail price of the reference model (799,01 €). In conclusion, it is presented the built prototype of a land sailor capable of competing in the leisure market that fulfills the proposed goals.

Keywords: Land Sailor; Design For Assembly; Mechanical Design; Structural Design; Drawings; Cost Analysis

INTRODUCTION

Land sailors are wind powered vehicles that use sailors catches up to similar markets, such as a sail or wing as a propulsion system. In the last windsurf and cycling. To ensure the appeal of decades, the land sailors for recreation the prototype, the goals of the design are the purposes have been presented with different following: concepts and solutions.  Low cost;  Small dimensions; This type of vehicle relies on wind that,  Low weight; combined with an angle of attack, applies an  Simple manufacturing; aerodynamic load on the sail.  Small disassembled dimensions;  Ease of assembly. As there couldn’t be found a land sailor manufactured in Portugal, where land sailing is The main specifications for the designed still an undeveloped market, this paper presents prototype are presented in the Table 1. For a the design of a prototype of a land sailor as a more detailed description, see [4]. product with potential to be built and sold in Portugal. Spec Prototype Wheel base WB (m) 1.5 In order to stablish state of the art, a brief Width T (m) 1.2 literature search was conducted. In [1] is Height h (m) 5 documented the comparison between cloth Sail area A (m2) 5.1 sails and rigid wing. In [2] is documented the Weight m (kg) 21.5 design and analysis of a land sailor. Also, Table 1 – Main specifications [4]. Blokart has developed an electric motor applied to the wheel to improve the driving experience To ensure the quality and security of this of the land sailor [3]. prototype, it was established that the designed

vehicle has to fulfil the following requirements This work presents the methodology used and [4]: fundament choices made in the design of the proposed prototype.  Disassembled for transportation; The challenge of designing this vehicle is in the  All parts must resist corrosion; expectation that the market of recreation land  Include steering system;

1

 Include a sail control system;  Feet;  Three or more wheels; Controlled with  Hands.  The driver must be sat down;  Must be propelled by a sail or wing. Front Wheel  With offset; offset  Without offset. The main constrains that limit the development of this prototype are the following [4]:  Double arm;  Maximum driver’s weight 130 kg; Fork  Single arm.  Manufacturing processes limited to the ones available at the workshop; Table 3 - Steering solutions.  Material limited to steel, due to the constrain of the welding equipment.  With lumbar support;  Production cost limited to 799 €. Geometry  Without lumbar support.

METHODOLOGY  Steel frame with soft fabric; Type  Rigid (plastic or composite).

In the Figure 1 is presented the methodology Table 4 - Seat solutions. adopted for this work.

Requirements Load cases  Boat sail; and goals Type  Windsurf sail. Structural and mechanical design  Free; Benchmarking Boom  Rotates over the mast.

Drawings  Carbon Fibre; Mast Comparison  Aluminum. between material solutions Manufacturing Table 5 - Sail Solutions. Figure 1 – Methodology. PROTOTYPE OF THE CHOSEN CONCEPTS CONCEPT

In this section are presented the main concepts In the Figure 2 is shown the CAD model of the and solutions eligible for each of the prototype designed prototype. subsystems:  Chassis (Table 2);  Steering (Table 3);  Wheels (for hard ground or sand);  Seat (Table 4);  Sail (Table 5).

 Steel; Material  Aluminum;  Composite. Figure 2 – Perspective of the prototype without the sail.  Triangular frame;  Frame in T [4]; In the Table 6 are presented the solutions Geometry  Frame in Y [2]; adopted for the designed prototype.  Monocoque). Prototype Chassis Triangular, Steel (6.71 kg)  Rear wheels to Mast; Controlled with feet, double arm, Steering Reinforce  No reinforce. no offset (3.48 kg) Seat Kart bacquet (3.74 kg)  Bolts and nuts Sail WindSurf sail, free boom (5 kg) Connectors  Pins. Metallic rims with pneumatic tires Wheels (2.35 kg) Table 2 - Chassis solutions. Table 6 – Solutions and weights of the subsystems [4].

2

AERODYNAMIC LOADS Apparent wind speed

In the Figure 3 are represented the angles and In order to calculate the loads in the different the vectors of the velocities and forces directions, it is necessary to calculate the speed considered in the calculations of the maximum triangle. This triangle consists of the vehicle aerodynamic load. speed 푉푘, wind speed 푉푉 and the apparent wind speed 푉퐴. In the Table 7 it is presented the main dimensions and weight of the prototype and The wind speed is estimated, using the driver, used in the calculation of the loads. equation (1),

푎 푧2 (1) 푉푉2 = [ ] 푉푉1, 푧1

where 푉푉1 is the known wind speed at a certain height 푧1, 푧2 is the height corresponding to the vehicle and 푎 is a parameter discriminating the 1 type of terrain (푎 = for open terrain) [1]. 9

In order to calculate the apparent wind speed, it is presented the correlations based on the speed triangle, equations (2), (3) and (4) [5]. Figure 3 - Wind velocities, angles and forces (adapted from [5]). 푉 sin 휙 휋 훽 = arctg ( 푉 ) , 훽 ≤ (2) 푉푉 cos 휙 + 푉퐾 2 Data Value 휋 푉푉 sin (휙 − ) − 푉퐾 휋 휋 Total Weight (kg) 146.5 2 훽 = arctg ( 휋 ) + , 훽 > (3) Centre of gravity 푉 cos (휙 − ) 2 2 (467,0,304) 푉 2 coordinates Height of the pressure 푉 = √푉 2 + 푉 2 + 2푉 푉 cos 휙 (4) 2000 퐴 푉 퐾 푉 퐾 centre (mm)

Radius of the 휋 800 The maximum of 푉 (when 휙 = ) is calculated pressure centre (mm) 퐴 2 Width (mm) 1200 using the following equation (5) [4]. Wheel Base (mm) 1500 푉 Table 7 - Dimensions and Weight of the 푉 (5) 푉퐴 = prototype [4]. sin 훽

Methodology for load calculations Aerodynamic coefficients

To better explain the methodology used to In order to calculate the aerodynamic loads, the calculate the aerodynamic loads, the Figure 4 sail was approached as an EPPLER 472 airfoil illustrates the steps. [6].

Maximum aerodynamic load for each β To estimate the lift coefficient 퐶퐿 for the finite wing, using the equation (6), is used the lifting- line theory [7]. Lateral load of equilibrium Λ 퐶푙 푚푎푥 (6) 퐶퐿 = 훼, Λ + 2 훼푝푒푟푑푎 Aerodynamic load equivalent to where Λ = 푏/푐 = 6.27 is the aspect ratio, 푏 = Lateral load for each β 8 푚 is the lenght and 푐 = 1.275 푚 is the chord of the wing. 퐶푙 푚푎푥 = 1.4 is the maximum infinite Choose the smaller between the lift coefficient at an angle of attack 훼푝푒푟푑푎 = Aerodynamic equilibrium load with 15.5° [6]. the maximum aerodynamic load

Figure 4 - Methodology for the loads calculations.

3

The finite drag coefficient 퐶퐷 (7) results from the The equilibrium of momentum around 푄 defines adding of the infinite drag coefficient 퐶푑 and the 퐹푌′, i. e. 퐶 2 induced drag coefficient 퐶 = 퐿 [7], i. e. ∑ 푀 = 퐹′ × ℎ − 푃 × 푁 = 0, (12) 퐷푖 휋Λ 푄 푌 푁 (13) 퐹′ = 푃 × , 퐶퐷 = 퐶푑 + 퐶퐷푖 (7) 푌 ℎ

The equation (7) can be written as shown in the where 푁 = 383.6 푚푚 and 휆 = 21.8°. the lateral equation (8), load of equilibrium 퐹퐴 푒 is calculated using the equation (14). 퐶 2 (8) 퐶 = 푐 + 푐 훼2 + 퐿 , 퐷 1 2 휋Λ 퐹푌 푚á푥 (14) −5 퐹퐴 푒 = where 푐1 = 0.0096 and 푐2 = 8.99 × 10 [4]. cos(휔 − 90° + 훽)

Equations for aerodynamic loads Aerodynamic loads

The lift and drag equations [7]: Now, the aerodynamic load is limited by two conditions, the maximum aerodynamic load 1 (9) from the sail 퐹 (훼 = 훼 ) and the 퐹 = 휌푉 2퐶 퐴 퐴 푚푎푥 푝푒푟푑푎 퐿 2 퐴 퐿 aerodynamic load equivalent to the lateral 1 (10) 2 equilibrium load 퐹퐴 푒. Both of this conditions limit 퐹퐷 = 휌푉퐴 퐶퐷퐴 2 the magnitude of the aerodynamic load 퐹 for 3 퐴 where 휌 = 1.22 푘𝑔/푚 is the air density [8], and each 훽 (15). 2 퐴 = 5.1 푚 is the area of the sail.

퐹퐴(훽) = min(퐹퐴 푒, 퐹퐴 푚á푥) (15) From this, results the aerodynamic load (11). STRUCTURAL ANALISYS (11) 2 2 퐹퐴 = √퐹퐿 + 퐹퐷 To enforce the safety and quality of the prototype, it was required a factor of safety Lateral load at equilibrium (FOS) 푛 = 2.

The lateral load at equilibrium, 퐹푌, results from Chassis the momentum equilibrium around the axle 푄, that links the front wheel to one of the rear With the purpose of choosing a solution for this wheels depending on the direction of the force. work, different chassis geometries are analysed (Figure 6). For this analysis it was used the finite In the Figure 5 are presented the parameters element method, to run a static linear analysis necessary to calculate 퐹푌.

Figure 6 - Different chassis geometries.

The geometries are evaluated according to the results 휎푚푎푥/푚푎푠푠 and 푈푚푎푥/푚푎푠푠, as well as the design goals presented earlier. The material used was steel AISI 1045. Some of the material properties are presented in the Table 8 [9].

푬 𝝈풄풆풅 𝝈풖풍풕 흂 𝝆 (푮푷풂) (푴푷풂) (푴푷풂) (풌품/풎ퟑ)

Figure 5 - Parameters used in the calculation ퟐퟎퟔ 530 625 0.29 7.85 Table 8 - Some properties of the steel AISI of 푭풀 (adapted from [5]). 1045 [9].

4

It was used circular tube, the section is 1 2 3 4 illustrated in the Figure 7. 𝝈풎풂풙 (푴푷풂) 394.4 611.8 484.4 714.7 푼풎풂풙 (풎풎) 17.5 23.4 27.9 35.6 𝝈 풎풂풙 풎풂풔풔 70.4 218.5 110.1 264.7 (푴푷풂/풌품) 푼 풎풂풙 풎풂풔풔 3.13 8.26 6.34 13.19 (풎풎/풌품) 풎풂풔풔 (풌품) 5.6 2.8 4.4 2.7 Table 10 - Results of the different chassis geometries [4].

To better fulfil the design goals, the adopted Figure 7 - Tube sections for the chassis. geometry is the triangular, number 3, due to its advantage in assembly and disassembly. For this analysis, it was applied a moment load 푀푥 = 613.4 푁. 푚 and the total weight Steering fork 푃 = 1484.7 푁, see [4]. The 3 wheels were constrained (Figure 8). In this analysis are compared 4 different geometries for the steering fork (Figure 10). In the Table 9 is presented the finite element These geometries differ from each other in the size for each geometry. As an example, the type of arm (single or double) and the offset Figure 9 presents the displacement for different between the steering axle and the wheel axle elements size for the 3rd geometry. In the Figure (w/ offset or w/o offset). In the Figure 11 are 8 are presented the mesh, loads and constrains presented the section of the tubes used in this used in this analysis. analysis.

1 – 2 – T 3 - Triangle 4 – Y T reinforced ퟏퟎ 풎풎 5 푚푚 10 푚푚 7.5 푚푚 Table 9 - Element size for the different chassis geometries [4].

Figure 8 - Mesh and boundary conditions of the chassis. Figure 10 - Steering fork geometries.

Figure 9 - Displacement vs. element size for the 3rd chassis geometry.

Figure 11 - Tube section: a) double arm; b) In the Table 10 are presented the results of this single arm (mm). analysis for the 4 different geometry.

5

This static linear analysis was conducted using Based on the results 휎푚푎푥/푚푎푠푠, the chosen the finite element method. The material of the geometry is the 2nd (double arm without offset). models is the same used in the chassis analysis (Table 8). In the Figure 12 is presented the Analysis of the set chassis/seat/steering displacement for different finite element sizes for the 2nd steering fork geometry. In the Table In this section it is briefly analysed the static 11 are presented the results of this analysis, in behaviour of the set chassis/seat/steering. the conditions indicated at Figure 13. The material used is the steel AISI 1045 presented in the Table 8.

The aerodynamic loads were applied to the centre of the sail (Table 1). Two different load cases were applied. The Load Case 1 (LC1) is assuming that the 3 wheels are in contact with the ground, and using the maximum value of the aerodynamic loads. For the Load Case 2 (LC2) it is assumed that only the front wheel and rear (right) wheel are in contact with the ground, and that the wind speed considered is the double of Figure 12 - Displacement vs. element size for the wind speed considered for LC1. the 2nd steering fork geometry. The load cases are presented in the Table 12. In the Figure 14 are illustrated the boundary conditions for the LC1. The results are presented in the Table 13, including the factor 휎 of safety 푛 = 푐푒푑. 휎푉푀

In the Table 14 and Table 15 are presented the reaction forces for the LC1 and LC2, respectively.

LC Loads Constrains

 Front wheel, 푈푟푎푑 e 퐹퐿 = 326.2 푁 퐹 = 26.2 푁 푈푎푥푖푎푙 1 퐷 훽 = 25°  Rear wheels, 푈푟푎푑 e 푊푒𝑖𝑔ℎ푡 = 1275.3 푁 푈푎푥푖푎푙

 Front wheel, 푈푟푎푑 e 퐹퐿 = 416.3 푁 퐹 = 34.7 푁 푈푎푥푖푎푙 2 퐷 훽 = 50°  Right rear wheel,

푊푒𝑖𝑔ℎ푡 = 1275.3 푁 푈푟푎푑 e 푈푎푥푖푎푙 Figure 13 - Mesh and boundary conditions of Table 12 - Load cases for the set the steering fork. chassis/seat/steering.

Geometry nº 1 2 3 4 푼 풎á풙 0.772 0.624 1.363 1.463 (풎풎) 𝝈 풎풂풙 121.4 127.4 149.7 153.2 (푴푷풂) 𝝈 풎풂풙 풎풂풔풔 0.572 0.439 1.065 1.117 (푴푷풂/풌품) 푼 풎풂풙 풎풂풔풔 89.9 89.7 117.0 116.9 (풎풎/풌품) 풎풂풔풔 (풌품) 1.35 1.42 1.28 1.31 Table 11 - Results of the different steering Figure 14 - Boundary conditions for the set forks geometries [4]. chassis/seat/steering.

6

Load Case 1 2 So, when the shear load in the bolted 푼 connections is bigger than 퐹휇 = 5220 푁, the 풎á풙 0.778 1.50 (풎풎) connection is in failure. 𝝈 풎풂풙 258 276 (푴푷풂) The resulting von Mises stress 휎 = 115.11 푀푃푎 is lower than the yield stress 풏 2.05 1.92 푉푀 휎푐푒푑 = 530 푀푃푎 of the material AISI 1045, so Table 13 - Results of the set the pin connector has a better strength chassis/seat/steering [4]. compared with the bolt connector.

Right Rear Left Rear Front Although the pin connector has a better strength Wheel Wheel Wheel compared with the bolt connector, due to the 푹 (푵) 340.8 47.6 −535 level of tolerances needed to avoid free play 풙 and the fact that pins doesn’t resist axial loads, the type of connector used in this work was the 푹풚 (푵) 104.9 87.3 −23.5 bolted connectors. 푹풛 (푵) 248.7 149.3 692 Bolts strength Table 14 - Reactions for the LC1 [4]. The resulting stresses in the bolts are Right Rear Front calculated based on the resulting loads on the Wheel Wheel bolts (see detail in [4]). The bolt stress is 푹 (푵) 716.2 −916 calculated using equation (18) [10]. 풙 퐹 퐶퐹 + 퐹 푏 푖 (18) 푹풚 (푵) 400.2 60.9 휎푏 = = , 퐴푡 퐴푡 where 퐶 is the fraction of load 퐹 supported by 푹풛 (푵) 412.3 1220 the bolt (19). The bolts used in this work were Table 15 - Reactions for the LC2 [4]. M10x65 and M10x90, with respectively, 퐶 = 0.153 and 퐶 = 0.106. DETAILS ANALISYS The three factors of safety (FOS) analysed in Connectors this work were regarding the separation of the parts (19), the slip between the parts (20), and the bolt tension (21) [10]. In order to choose the type of connectors, a comparison between pins and bolt connectors 퐹푖 퐹푖 (19) is presented. 푛푠 = = 퐹푠 퐹(1 − 퐶) In this comparison the mechanical resistance 퐹휇 푝 휇 (퐹푖 − 퐹(1 − 퐶)) (20) 푛푒 = = and safety of the connection is analysed. The 퐹푒 퐹푒 Grade of the bolt connector is 8.8, which means 휎푝퐴푡 (21) 푛푏 = the Proof Strength is 휎푝 = 600 푀푃푎 [10]. 퐶퐹 + 퐹푖

The pre-load assumed on the bolt due to To summarize the results, in the Table 16 are tightening, for non-permanent connections is presented the minimum for each factor of safety calculated using equation (16) [10]. for the LC1.

퐹푖 = 0.75퐹푝, (16) FOS Value Bolt where the proof load is 퐹푝 = 퐴푡휎푝 = 34800 푁, Separation Rear seat support / 2 297.9 with the tensile stress area 퐴푡 = 58 푚푚 for 풏풔 chassis M10 bolts [10]. The pre-load applied in the M10 Rear seat support / Slip 풏풆 160.84 bolt is 퐹푖 = 26100 푁. chassis Bolt 풏풃 1.33 - Considering the friction coefficient between the Table 16 - Minimum FOS for the bolted parts is 휇 = 0.2 [10], the maximum friction load connection [4]. supported by the bolted connections is given by equation (17). Due to the pre-load applied to a tightened bolt 퐹휇 = 휇 퐹푖 = 5220 푁 (17) and the resultant forces are significantly smaller

7

than the pre-load, the bolt’s factor of safety in In this work, it was considered the more this work is always 푛푏 ≈ 1.33. conservative FOS of 푛 = 2.

Bearing selection There are 4 parts analysed with welded connections in this work. In the Table 19 are To select the bearing for each application, the presented the minimum values for each part following methodology was used [10]: and the respective welded joints.

1. Choose an initial 푌 from the table; 풏 Welded joint 2. Calculate 퐶10; Mast support 3.93 Upper steering 3. Choose a bearing and save the value of 퐶 ; Lateral Connection to Mast 0 2.70 4. From 퐹푎/퐶0; choose a new 푌; member support 5. Calculate 퐶10; Rear member 2.41 Insert 3 6. If equal, stop; Rear right connection Seat supports 2.35 7. If not, return to step 4. to chassis Table 19 - Minimum FOS for each part [4]. In the Table 17 are presented the reactions of the LC1 used to select the bearings. MANUFACTURING DETAILS

Based on the presented methodology and the In order to better control the dimensions and reaction loads, the chosen bearings are geometry of the prototype, a Jig was built to presented Table 18. place the components to weld (Figure 15).

푭풓 (푵) 푭풓 (푵) In the Figure 16 and Figure 17 are presented Upper steering 166.7 258.7 some welding details. The manufactured Lower steering 260.6 607.8 prototype is presented in the Figure 18. Right rear wheel 421.9 104.9 Left rear wheel 156.7 87.3 Front wheel 874.7 23.5 Table 17 – Loads on the bearings [4].

푪ퟏퟎ (풌푵) Bearing 푑 = 10 푚푚 Upper steering 3.45 퐷 = 30 푚푚 푑 = 12 푚푚 Lower steering 5.82 퐷 = 32 푚푚 푑 = 20 푚푚 Right rear wheel 9.71 퐷 = 47 푚푚 푑 = 10 푚푚 Left rear wheel 4.84 퐷 = 30 푚푚 푑 = 25 푚푚 Front wheel 13.42 퐷 = 52 푚푚 Figure 15 - Jig. Table 18 - Selected bearings [4].

Welded joints

To analyse the welded joints, the resulting von Mises stress from the FEM analyses are considered to calculate the factor of safety 푛. Using the AISC code for welded metals, the minimum FOS are established for each type of loads, tension (22) and shear (23) [10].

Figure 16 - Details: a) Insert; b) Lateral 휎푐푒푑 (22) 푛퐴 푚í푛푖푚표 = = 1.67 Member; c) Steering. 0.6 휎푐푒푑 휏/0.4 (23) 푛휏 푚í푛푖푚표 = = 1.44 √3휏

8

Regarding the surface finish, the chosen average roughness was 푅푎 = 3.2 μm corresponding to the characteristic roughness of lathing and milling [11].

COST ANALISYS

This analysis was conducted using the cost Figure 17 - Details: a) Lathing of an insert; b) tables from Formula SAE [12] [13]. These tables Hole drilling. are used to evaluate the unitary production cost of a series of 1000 formula type vehicles.

In the Figure 20 are presented the overall cost for each subsystem, excluding the sail. In the Table 20 are presented the total costs for the different resources (Materials, Processes, Fasteners and Tooling) and subsystems.

Figure 18 - Prototype.

DRAWINGS

Regulations and Norms Figure 20 - Overall cost of each subsystem.

In this work, the norm ISO 7200 was used on

the title block of technical drawings and the European type projections were used [11]. In the Figure 19 is presented the technical drawing

of the designed prototype.

Processes Fasteners Tooling Total Materials Chassis 41,56 € 114,42 € 3,99 € 12,63 € 172,59 € Steering 5,45 € 40,20 € 0,80 € 3,89 € 50,34 € Seat 128,49 € 15,67 € 4,88 € 4,90 € 153,93 € Wheels 30,00 € 4,50 € 2,89 € - € 37,39 € Sail 150,00 € - € - € - € 150,00 € Total 205,50 € 174,78 € 12,55 € 21,41 € 564,25 € Vehicle Table 20 – Estimate total costs for subsystems and resources using [12] and [13].

In the Figure 20 are presented the overall cost Figure 19 - Technical drawing of the prototype. for each subsystem, excluding the sail.

Tolerances and surface finish Note: This work follows a Design For Assembly (DFA) because the goal is to build a single For the fitting between holes and shafts, in this prototype. This results in a higher unitary work the class H8-f7 was chosen. This gives a vehicle cost for a production series of 1000 units rotational tight fit [11]. assumed in the procedure

The overall geometric and dimensional tolerance applied in this work complies with the norm ISO 2768-cL [11]. This norm gives a rough dimensional (c) and geometric (L) tolerance.

9

ACKNOWLEDGEMENTS [8] J. Katz, Race Car Aerodynamics: Designing for speed, Cambridge: First and foremost, I would like to thank Bentley Publishers, 1995. Professor Miguel Matos Neves and Professor [9] “AISI1045,” MatWeb, 1996. [Online]. Luís Reis for the guidance, knowledge, support Available: and the opportunity to develop this project, as http://www.matweb.com/search/DataSh well as the supply of means to acquire the parts eet.aspx?MatGUID=cbe4fd0a73cf4690 and materials necessary, and the access 853935f52d910784. [Accessed 30 9 granted to the workshop (Laboratório de 2015]. Técnicas Oficinais do DEM/IST). [10] Budynas-Nisbett, Shigley's Mechanical I would also like to thank André, Manuel, Pedro Engineering Design, Eight Edition, The and Ricardo for the availability, knowledge and McGraw-Gill Companies, 2008. review offered at some stages of this work. I thank the workshop technicians for the help [11] A. Silva, C. T. Ribeiro, J. Dias and L. and patience offered in the manufacturing of the Sousa, Desenho Técnico Moderno, components, and I specially thank Pedro for the Lisboa: Lidel, 2004. time dispended welding the components and [12] “FSAE Rules,” [Online]. Available: also to Mr. Frade for making the resources http://students.sae.org/cds/formulaserie necessary to weld available. s/rules/2015-16_fsae_rules.pdf. Lastly, a special thanks to my parents for [Accessed 21 9 2015]. providing the possibility to fulfill my academic [13] “Cost SAE,” Formula SAE, [Online]. goals, as well as the support given during this Available: journey. http://www.fsaeonline.com/page.aspx?p ageid=5ade9b01-8903-4ae1-89e1- 489a8a4f08d9. [Accessed 21 9 2015]. References

[1] F. Dias, “Metodologias de Implementação de uma Asa num Kart à Vela e Previsão de Velocidade,” MSc Dissertation (in portuguese), DEM, Instituto Superior Técnico, Lisboa, 2013. [2] V. Monteiro, “Desenvolvimento e Análise de um Kart à Vela,” MSc Dissertation (in portuguese), DEM, Instituto Superior Técnico, Lisboa, 2013. [3] “UKPPG,” Blokart electric motor, 2016. [Online]. Available: http://ukppgwebstore.com/blokart- electric-motor-1567-p.asp. [4] L. M. A. Monteiro, “Projeto e Fabrico de um Protótipo à Escala Real de um Kart à Vela,” MSc Dissertation (in portuguese), DEM, Instituto Superior Técnico, Lisboa, 2016. [5] M. Khayyat and M. Rad, “Comparison Final Velocity for Land Yacht With a Rigid Wing and Cloth Sail,” World Congress on Engineering, vol. II, p. 6, 2008. [6] “EPPLER 472 AIRFOIL,” Airfoil Tools, 2015. [Online]. Available: http://airfoiltools.com/airfoil/details?airfo il=e472-il#polars. [Accessed 27 9 2015]. [7] V. d. Brederode, Fundamentos de Aerodinâmica Incompressível, Lisboa: DEM IST UTL, 1997.

10