The College of New Jersey Solar Splash 2014 Technical Report

Transcription

1 The College of New Jersey Solar Splash 2014 Technical Report May 5 th, 2014 Boat # 6 Team Members Jeffrey Holman (M.E.) Jason Pfund (M.E.) Robert Ruff (M.E.) Faculty Advisors Dr. Karen Yan (Primary Advisor) Dr. Seung-yun Kim (Electrical Advisor) Dr. Norm Asper (Mechanical Advisor) Michael Schuhlein (M.E.) Joseph Maco (Comp. E. ) i

2 EXECUTIVE SUMMARY The IEEE Solar Splash competition is an annual intercollegiate international solar/electric boat regatta. Each entry boat powered though direct and stored solar energy will compete in a sprint, endurance and slalom race. The sprint competition demonstrates the boat s ability to traverse at high speeds while still having efficient use of the electrical power. The endurance competition tests the boat s ability to travel long distances using battery and solar power, thus demonstrating the efficiency of the boat s electrical system. During the slalom race the boat needs to show great maneuverability. To address these design challenges, this year s team identified four key areas for improvement, and the design objectives are reducing overall weight of the boat, increasing efficiency of the sprint propeller, a module design of drivetrain, and responsive steering. The team designed a new hull that takes its inspiration from a surfboard shape, in an effort to break away from the standard compromised monohull and gain an advantage in the competition. This surfboard shape design has features that enable great performance in both the sprint and endurance events. The design has a flat shaped hull in the back for greater planing abilities as well as a smooth bow stem in the front for wave shedding at low speeds. The design speed has been set for both the sprint and endurance races at 40 mph and 12 mph, respectively. These speeds were chosen based on winning times from previous year s competitions. Propeller design is another aspect that was focused on for this year s team, as the propeller is a key contributing factor to the overall performance and efficiency of the boat s drivetrain. The 2012 TCNJ team explored in-house propeller design and fabrication, an endurance propeller was designed that achieves ample efficiency and performance. Built upon previous success, a sprint propeller was designed and will be implemented for the competition this year. Software OpenProp version was used for the design and optimization of the propeller. By providing the input parameters such as thrust, number of blades, and RPM range the program would provide a propeller geometry that could then be used to generate a solid model for manufacturing in a 5-axis CNC. To keep the overall weight of the boat minimal while also accounting for the center of flotation shift to change the boat position in the water, a modular drivetrain was designed in which a separate set of motors and gearbox was designed for both sprint and endurance competitions, with the unused configuration to be used as ballast. This design was chosen after determining that the single motor used last year could not effectively provide the necessary performance in the sprint competition with the current electrical system. The new design added simplicity to the boat configurations by allowing for ballast to be used to optimize center of flotation positions. In addition, it kept the overall weight of the boat minimal by making use of the same powerhouse, transom, pintle, driveshaft, and lower unit. The comfort and maneuverability of the skipper needed to be addressed so a push/pull cable steering system was used, with the helm reused from 2013 s team, as it provided controls that offered familiarity to that of an automobile and would allow the driver to operate the vehicle with little to no learning curve. ii

3 This year s team is reusing previous year s electrical systems and reconfiguring it to meet the team s specifications. New batteries were selected to meet the new weight allowance for the endurance batteries (now 100 pounds). In addition the team will be adding a second motor controller to the electrical system to handle the dual motors in the sprint configuration. The telemetry system for this year s design includes sensors to monitor voltage, current, rpm and speed of the boat. The telemetry allows the on shore team to analyze data from the boat and make decisions for the driver to maximize performance during the competition. Currently the boat has been entirely designed and constructed. Design iterations were also carried out to address issues identified during the fabrication process. Static testing has been performed to determine weight management characteristics. The remaining tests for the boat are dynamic testing. Both the sprint and endurance configurations will be tested in a lake to ensure all sub systems are functioning properly and to determine optimal operating conditions. iii

4 TABLE OF CONTENTS EXECUTIVE SUMMARY... ii List of Figures... vi List of Tables... vi I. CURRENT DESIGN AND PROBLEM STATEMENT... 1 II. DESIGN PROCESS SUMMARY... 2 III. DESIGN CONCEPTS... 2 A. Hull ) Hull Design ) Hull Materials... 3 B. Steering... 4 C. Drivetrain... 4 D. Propeller... 4 E. Electrical... 5 F. Telemetry... 5 IV. DESIGN DESCRIPTION... 6 A. Hull ) Hull Design ) Hull Materials ) Hull Construction... 7 B. Steering... 9 C. Drivetrain... 9 D. Propeller... 9 E. Electrical F. Telemetry V. DESIGN EVALUATION A. Hull ) Hull Design ) Hull Materials B. Steering C. Drivetrain D. Propeller E. Telemetry VI. PROJECT MANAGEMENT iv

5 A. Team Organization and Responsibility B. Project Planning and Schedule C. Financial and fund-raising D. Strategy for Team Continuity and Sustainability VII. CONCLUSIONS AND RECOMMENDATIONS A. Strengths B. Weaknesses C. Future Development D. Goals Summary E. Recommendations REFERENCES Appendix A: Batteries Appendix B: Flotation Calculations Appendix C: Proof of Insurance Appendix D: Team Roster APPENDIX E: HULL ANALYSIS Appendix E Appendix F: Drivetrain F.1 Timing Belt/Pulley Specifications F.2 LEM-200 D126 Specifications F.3 Perm PMG-132 Specification F.4 Bearing Data F.5 ANSI Key Standards Appendix G: Propeller Appendix G.1: Stress Analysis Appendix G.2: Cavitation Analysis Appendix G.3: Manufacturing Appendix H: Eletrical Systems Appendix H.1: SCHOTT 240 W Solar Panel Data Sheet Appendix I: Telemetry Appendix I.1: XStream-PKG-R RF Module Appendix I.2: L01Z600S05 600A Hall Effect Current Sensor Appendix I.3: CSLA2CD 72A Hall Effect Sensor Data Sheet Appendix I.4: OPB715Z Optical Sensor Appendix I.5: EM-406A GPS Module Appendix I.6: Arduino Mega Datasheet Appendix I.7: Matrix Orbital LK WB Data Sheet v

6 Appendix J: Project Management Appendix J.1: Team Gantt Chart Appendix J.2: Sponsorship Brochure Appendix J.3: Materials and Travel Budget List of Figures Figure 1-80/20 Aluminum Rails... 3 Figure 2 Bracket designed to attach a pulley to the bottom of the helm... 3 Figure 3 - Endurance Power head (Left) Sprint Power head (Right)... 4 Figure 4 Proposed 2014 Hull Design for TCNJ (Solid Model in SolidWorks with Dimensions)... 6 Figure 5 - Foam & Wood laid out before construction... 7 Figure 6 - Rough bow stem shaping (left) versus finished bow stem (right)... 8 Figure 7 - Final sprint propeller design modeled in SolidWorks from Table 1 parameters Figure 8 - Endurance Electrical Configuration (Left) and Sprint Electrical Configuration (Right) Figure 9- Testing the Endurance Configuration to Try and Achieve Lifting the Transom Out of the Water Figure 10- Testing the Sprint Configuration to Achieve Neutral Trim Angle for Planing Capabilities Figure 11 - Drivetrain assembly Figure 12 Prototype g-code tested using Butterboard (left) and aluminum propeller after machining (right) Figure 13 - Comparison of the Full Hull versus Submerged Portion of Hull in the Water Figure 14 - Comparison Demonstrating the Reduced Drag Force and Vortex Shedding Between Transom In (Left) and Transom Out (Right) Figure 15 - Proposed Weight Management Configuration (Endurance Event) Figure 16 - Surface finish of the roughing pass by the CNC mill. A 1/2" end mill was used to quickly remove large amounts of material Figure 17 - FInishing pass by the CNC mill. Foam plugs were used to dampen blade vibrations caused by the mill. A water-soluble oil coolant was used Figure 18 - Machined surface finish resulted in small lateral ridges Figure 19 - Fine sand paper was used to smooth out the ridges to improve fluid flow characteristics Figure 20 Aft view of the final machined sprint propeller Figure 21 - View of the sprint propeller mounted on the lower unit. This will attach to the drive shaft of the drivetrain List of Tables Table 1 - Hullform Comparison Chart [1]... 2 Table 2 - Decision Matrix for Propeller Designs... 5 Table 3 - Specific Weight of Used TCNJ Core Hull Materials... 7 Table 4 - Sprint Propeller input and output parameters for final propeller design Table 5 - Results of Stress Analysis for Sprint Propeller Table 6 - Summary of the Flotation Requirement Calculations vi

7 Table 7 - Data Analysis for the Waterline Properties of the Hull Table 8 - Comparison of Drag Forces Between the Proposed Design and Past Years at TCNJ Table 9- Sprint Propeller Input Parameters for Cantilever Beam Stress Analysis Table 10 - Calculations for Cantilever Beam Stress Analysis Table 11 - Output of Cantilever Beam Stress Analysis vii

8 I. CURRENT DESIGN AND PROBLEM STATEMENT The Solar Splash competition is a five-day event in Dayton, Ohio, in which college teams from different parts of the world come together to compete with their solar/electric watercraft. Previous years designs were reviewed to make improvements and design changes where necessary. In the past, teams have been less effective in the sprint competition. This was due to the added weight of a catamaran design which prevents effective planing capabilities of the boat. In addition, past teams have experienced cavitation problems with the propeller. This caused a large loss of efficiency and prevented the boat from achieving its maximum theoretical speed. The steering system in the past used a sprocket that resulted in decoupling of the system during configuration changes. A great design in past years teams was the inclusion of 80/20 aluminum rails that allowed for the quick and easy weight configuration changes in between competitions. The 2014 team designed and manufactured a new, competitive boat to meet the following objectives: Hull Design o Design hull to be efficient in sprint and endurance competitions o Design for lightweight hull o Ensure easy configuration changes between events o Implement 80/20 rail system for weight changes Steering o Achieve 60 of rotation while avoiding derailment or locking points o Must be stable for the sprint race to ensure the safety of the driver o System must be able to accommodate any changes to the boat while configuring to different races Drivetrains o Design a modular drivetrain setup to maximize performance across all competitions o The endurance system must deliver a speed of 550 RPM at the propeller o The sprint system must deliver a propeller speed of 3400 RPM Propeller o Utilize available software to develop an optimized blade for the sprint race o Design to minimize the effects of cavitation o Design for manufacturability Electrical System o Design a motor controller system to maximize the efficiency in endurance race o Integrate the donated solar panels into the system to power the boat Telemetry o Provide real time data for the following Solar array voltage Battery voltage Battery current Solar array current Propeller RPM 1

9 II. DESIGN PROCESS SUMMARY The 2014 Solar Splash team divided up the design of a new solar boat amongst five interdisciplinary members. A variety of design options were considered and a variety of analyses were conducted to ensure the most optimal design was chosen. Each design was then compared to the team goals and objectives. During construction several design issues were encountered and solutions had to be found for each one. Overall, the boat was designed around a surfboard-style hull in an effort to produce a groundbreaking design. Drag was calculated on the hull, from which an appropriate propeller thrust was determined. The speed at which the propeller needed to rotate was then given to the drivetrain engineer, who created two power heads specialized for the endurance and sprint competitions, and provided the necessary RPMs through gear reduction. A push/pull steering system was then designed to provide the boat with the maneuverability required to compete across all events. Selection of batteries was then made, and motor controllers were selected to optimize drivetrain efficiency and performance. Telemetry was designed to record important parameters from the boat, including amp draw, battery life, and RPM of the propeller. These parameters could then be transmitted to an on-shore laptop to actively monitor the boat s performance. A. Hull III. DESIGN CONCEPTS 1) Hull Design Based on the competition events, each boat must be capable of performing at high and low speeds (in the sprint and endurance competition). This essentially goes against typical hull design techniques, in that hulls are typically designed for either high or low speed to maintain efficiency for the intended use. Table 1 shows some fundamental hull design characteristics. Table 1 - Hullform Comparison Chart [1] 2

10 Previous TCNJ hull designs include semi-displacement monohulls (hybrid monohull) and both displacement monohull & planing monohulls in the form of a catamaran. The hybrid monohull has competed well in the past because of the unique design, featuring a flat planing hull aft and a canoe shaped displacement hull towards the bow. The catamaran design of the 2013 team placed well in the endurance competition however lacked the necessary planing performance for the sprint event.. Taking a second look at the chart, the next design choice to push the envelope for competition performance would be a hydrofoil design because of its superior performance across the board. However, due to the limited resources of TCNJ teams, hydrofoil designs were ruled out. To be more competitive a complete redesign of the hull was determined to be necessary. The design goals included reducing the overall weight of the hull, while maintaining both displacement and planing hull characteristics and designing for ease of construction to minimize construction hours while maximizing testing time. The team came up with a new surfboard inspired hull design concept. The team decided to not reuse the hybrid monohull to explore lightweight materials and to reduce the overall weight of the hull. The hull was designed to have a flat planing section in the back for low drag at high speeds and gradual bow stem towards the front to induce wave shedding and to reduce drag at lower speeds. The hull also builds off the catamaran design in the form of the modular weight management system utilizing 80/20 aluminum rails, shown in Fig. 1, as attachment points for sub systems. This would allow the team to make major or minor weight management adjustments during static testing to achieve the proper center of flotation for each specialized event (bow heavy for endurance to lift the transom out of the water and neutralstern heavy in the sprint configuration to achieve planing quickly). Although a major portion of the hull is a flat planing Figure 1-80/20 Aluminum Rails hull, the team predicts with proper weight management this flat shape will be competitive in the endurance competition as well. 2) Hull Materials: To follow through with the team s goal of reducing the overall weight of the hull, material selection was taken into careful consideration. The 2009 TCNJ hull was built from a fiberglass epoxy sandwich with ¼ balsa wood core. This hull was relatively light, however, the nature of the balsa wood fabrication techniques meant another all wood hull would greatly increase the construction time, thus going against one of the team s set forth goals. Therefore, extruded polystyrene foam was chosen as the core material of the hull. In addition, white cedar stringer inserts would be provided as a source of rigidity for the hull as well as serving as the locations of mounting the 80/20 aluminum rails and keels. These lightweight materials are the core of the hull and wrapped in an epoxy resin fiberglass outer shell to further increase the rigidity and uniformity of the hull design. 3

11 B. Steering One of this year s team goals was to reduce the overall weight of the boat. The steering system was designed using a push-pull cable system. To use this design, a few modifications had to be made to the lower unit and last year s helm. A bracket was designed to allow a cable to attach to the steering column s sprocket and then extend out of both sides of the helm using a doublewide pulley; essentially running the cable down both sides of the boat. This bracket can be seen in Fig. 2, which will mount Figure 2 Bracket designed to attach a pulley to the bottom of the helm to the bottom of the helm and have a pulley attached to it. Also another bracket was designed to attach to the power head couple, allowing the cable to properly turn the boat. This design would also allow for any minor height adjustments when transitioning between events. Both of these modifications were designed to allow the skipper 60 degrees of steering and ease of transitioning configurations between events. C. Drivetrain For this year s competition, the team immediately considered continuing the compound drivetrain design of the 2013 TCNJ Solar Splash team. It was the goal of the team to design and manufacture a drivetrain that minimized weight, and facilitated configuration changes between each competition. The first design iteration made use of three motors attached to one gearbox, with a single belt used to change between configurations. Though an elegant design, it was found that three motors mounted to the gearbox rendered the center of flotation too far aft. To address this, the final design was to create two gearboxes, and to interchange them between competitions. Figure 3 - Endurance Power head (Left) Sprint Power head (Right) The endurance and sprint power heads can be seen in Fig. 3. The powerhouse, driveshaft, and lower unit would be shared in both configurations to reduce weight by not needing duplicates of these items. D. Propeller TCNJ teams have previously explored custom propeller designs for both the sprint and endurance events. The endurance propeller that has been designed and fabricated has performed well in previous years. This year s team is focusing on a propeller design for the sprint 4

12 competition. Three different propeller types were considered the advantages and disadvantages are shown in Table 2. Surface piercing propellers have been widely used by professional motorboat racing teams due to their extremely high efficiency. In its operation, the propeller is only partially submerged with the waterline slightly below the hub. The result of this is two-fold - there is a reduction of appendage drag and an elimination of cavitation, a phenomenon that causes a loss of efficiency and damage to the propeller. Contra-rotating propellers operate fully submerged with two coaxial propellers rotating in opposite directions. This configuration results in moderate gains in efficiency by recovering the induced rotational energy that would be lost from a single propeller. Conventional submerged propellers are used for a wide range of applications due to the lower complexity of design and operation. The conventional propeller was selected for this year due to the availability of software and empirical methods for the design of the blade geometry. Table 2 - Decision Matrix for Propeller Designs Propeller Type Advantages Disadvantages Surface Piercing High relative efficiency, no Complex design & analysis cavitation Contra Rotating Moderate relative efficiency Complex gearbox Conventional Submerged Simpler relative design & analysis Lower relative efficiency E. Electrical This year s electrical system is designed and reused after the previous year s electrical systems. Notable design changes for this year include battery selection and motor controller addition. The Solar Splash competition set new rules that allowed teams to have 100 pounds of batteries for the endurance competition. In addition, for the sprint completion this year s team intends to use two motors, thus a second motor controller will need to be worked into the existing system. F. Telemetry For the telemetry design, each data acquisition module was carefully selected. It is mandatory that data measurements have minimal impact on the electrical systems of the boat. Hall Effect sensors where chosen to measure battery and solar array current as they the magnetic field created by current flow minimizing the power draw on the electrical systems. Rail-to-rail operational amplifies were selected for voltage measurements to minimize current draw on the circuit. The speed of the boat is measured through the use of a global positioning system (GPS) receiver. The GPS module is able to provide accurate data for all conditions that the boat will experience. The rotations per minute (RPM) of the motor is measured using an optical sensor. All of this data is collected by a microcontroller unit (MCU). An embedded system was chosen due to their efficiency and size advantages. The MCU is programmed in the C programming language. Radio frequency (RF) modules were selected to transmit the collected to the on-shore subsystem. RF was chosen for its stability and cost effectiveness. The data on-shore is viewed using a laptop. 5

13 A. Hull IV. DESIGN DESCRIPTION 1) Hull Design Previous TCNJ hull designs have been designed and analyzed in a variety of commercially available software. The 2009 monohull was designed in SolidWorks using MaxSurf to analyze the hydrostatic and hydrodynamic characteristic of the hull. The 2013 team utilized the Orca 3D plug-in for Rhinoceros 4.0. The Orca 3D software worked well for the 2013 because their catamaran design consisted of true displacement and true planing hulls. Since the hull choice for this year was an uncommon hull shape, SolidWorks modeling was used instead. In addition, the hull was analyzed for hydrostatic and hydrodynamic performance within SolidWorks using mass property evaluation features and SolidWorks flow analysis. Design parameters were varied during the optimization process of the hull shape, including the overall hull length, hull width, hull thickness and bow stem transition placement. To make the process as efficient as possible, cross sections spaced one foot apart were utilized in the solid modeling program. This allowed the designer to sketch cross sections of the hull and change parameter dimensions more quickly. Each cross section was sketched as a half and then a loft function was used to generate a solid shape, which was then mirrored about the center to create the full hull. The final hull shape can be seen below in Fig. 4. Figure 4 Proposed 2014 Hull Design for TCNJ (Solid Model in SolidWorks with Dimensions) To analyze the new hull design hydrodynamic simulation was carried out using SolidWorks fluid flow software. Values of the previous year s hull were obtained and then an analysis was run for the proposed design. At our target speed of 12 mph in the endurance race (simulating the transom out of the water) it was found that the proposed design experienced lbs of drag, a reduction of 37% compared to the catamaran. The team felt this decrease in drag force deemed the new design a feasible design choice for this year s competition. 2) Hull Materials The choice of hull materials was based on the values of specific weights shown in Table 3. These materials were extensively tested for material properties during the 2009 year and each would be a valid design choice. The extruded polystyrene foam allowed the team to reduce weight while still maintaining high flotation characteristics. The white cedar stringers were chosen because of their relatively lightweight compared to okume plywood and it is relatively harder than balsa 6

14 wood providing both rigidity and serving as an anchor location for screws and bolts to hold on the subsystems. Table 3 - Specific Weight of Used TCNJ Core Hull Materials 3) Hull Construction: To construct the hull, female cross section plugs were made out of a hard cardboard material. This would allow the team to shave away at a foam and wood blank plug to meet the desired shape. Owen s Corning generously donated all the extruded polystyrene foam for this year s boat again in 4 x 8 x 2 sheets. These sheets were cut down to size, in halves, thirds and two thirds and glued together with epoxy and resin. The raw materials can be seen laid out in Fig. 5. The foam pieces were layered in such a way that no butt joints were directly above or below each other to make a more structurally sound hull. Once the foam pieces were all glued together the next step was to attach the foam pieces to the wooden inserts. This was done by laying down a sheet of fiberglass between the wood and foam and then using straps to ensure a uniform finish. Next full scale drawings (top view and side view) of the bow stem shape were printed and taped to the foam plug. Extensive bow stem shaping was conducted using saws, orbital sanders and hand held rasps. An example of the rough bow stem and fiber glassed bow stem with body filler can be seen in Fig. 6 below. A female plug was used to shape the sides to a nice rounded chine along the entire length. Before fiber glassing the hull, any high or low spots were taken care of by sanding and using lightweight automobile body filler. The keels were then attached to their desired positions. Then once the final desired shape was obtained the top was glassed using an 8 ounce grade fiberglass whereas the bottom was glassed using a 6 ounce sheet. This was done to reduce weight on the bottom where it was less likely for the hull to be stepped on and have components moved around. The last step was a final sanding ending with a primer coat and final coat of paint. 7

15 Figure 5 - Foam & Wood laid out before construction Figure 6 - Rough bow stem shaping (left) versus finished bow stem (right) 8

16 B. Steering To create an efficient and also ergonomic design, the bracket was fitted to the bottom of the helm allowing the pulley to guide the cable underneath the helm. The double pulley attached underneath the helm has the cable crossed so that the proper turn of the steering wheel corresponds to the proper turn direction of the boat. The cable runs down both sides of the boat along the 80/20 rails, keeping it protected and out of the skipper s way. The bracket attached to the power head couple was created using a shaft collar to allow for minor height adjustments with the outboard motor. This design, paired with the sprocket attached to the steering column, will allow the skipper to properly turn the boat a total of 60 degrees. Also, this overall design allows the skipper to only have to turn the steering wheel a minimal amount to turn. C. Drivetrain The 2014 team drivetrain makes use of two separate power heads dedicated for the sprint and endurance events, respectively. Through coordination with the propeller designer, an operating speed of 500RPM was decided for the endurance competition and a speed of 3400RPM was decided for the sprint configuration, to optimize the performance of the propeller. The endurance power head made use of a PMG132 motor, which applies a speed of 1080 RPM when run at 24V. The motor shaft has a 20 tooth pulley mounted, and this pulley drives a 40 tooth pulley on the driveshaft, producing a 1:2 ratio and stepping the RPM down to 540; through the 14:15 Konny Racing lower unit, the RPM is stepped down to a final speed of 504. [2] The sprint power head makes use of dual Lynch LEM200 D126 motors to run a single driveshaft. The motors run at a rated 3600RPM at the 36V power supply. The motors each have a 20-tooth pulley, which drives another 20-tooth pulley on the driveshaft to provide a 1:1 ratio. When combined with the lower unit, the final speed attained is 3360 RPM, which closely models the design RPM. Both power heads make use of a square couple. This square couple will allow for facilitated configuration changes. The Solar Splash rules specify that all components have to stay on board for all events within the competition. Through the modular design of the drivetrain, the unused power head will be used as ballast to effectively adjust the weight balance to accommodate the endurance and sprint boat configurations. D. Propeller For the optimization of the propeller geometry, OpenProp 3.3.3, an open-source software [3] was used. OpenProp allows for a parametric study based on user input specifications, such as required thrust, ship velocity, hub diameter, and water density. The parametric study was performed for a range of propeller diameters, angular velocities, and number of blades. A parametric study was performed for a RPM range of 2000 to 5000 RPM and a diameter range of 9 to 12 inches. As one of the team's goals was to ensure cavitation would not occur, a 4-bladed propeller was selected to increase the developed area. The optimized results of the parametric study were entered into a single-design analysis tool to iteratively modify the input parameters until the required propeller power was lower than the available shaft power, which was calculated to be 18 horsepower at the propeller. The inputs and outputs of the single design 9

17 analysis are shown in Table 4. The finalized was modeled in SolidWorks and can be viewed in Fig. 7. Table 4 - Sprint Propeller input and output parameters for final propeller design Input Parameter Input Value Number of blades 4 Rotation Speed (RPM) 3400 Diameter (inches) 10 Required Thrust (pound-force) 127 Ship Velocity (mph) 40 Hub Diameter (inches) 2 Output Parameter Output Value Torque (lb-ft) 27 Power (HP) 17.5 Pitch (in) 12.4 Efficiency 0.74 Figure 7 - Final sprint propeller design modeled in SolidWorks from Table 1 parameters A simplified stress analysis was performed by utilizing a cantilever beam method [4] to calculate the maximum stress of a particular cross section of a blade. This method calculates and sums the stresses due to the propeller thrust, propeller torque, and centrifugal force by using an iterative method - a more detailed analysis can be viewed in Appendix G.1. Assumptions were required for the application of the aforementioned forces as point loads on the propeller blade. The results of the stress analysis can be viewed in Table 5 there is a sufficient safety factor to compensate for the assumptions that were required. 10

18 Table 5 - Results of Stress Analysis for Sprint Propeller Stress Due to Propeller Thrust Stress due to Propeller Torque Stress due Centrifugal force TOTAL STRESS Aluminum 2024 Yield Strength MPa MPa MPa MPa 345 MPa Safety Factor 4.5 A cavitation analysis was performed by calculating the maximum allowable loading and actual blade loading. [5] The maximum allowable loading was psi, while the actual blade loading was calculated to be 4 psi, which meant cavitation would not occur during the sprint race. Specifications on the equations used for this cavitation analysis can be viewed in Appendix G.2. E. Electrical Figure 8 - Endurance Electrical Configuration (Left) and Sprint Electrical Configuration (Right) The endurance configuration consists of a two Sun Power solar panels each connected to a SunSaver Maximum Power Point Tracker. The MPPTs are then connected to a lead battery array with an output voltage of 24 V. There is a set of contactors used to bypass the batteries once they become too discharged to be effective. The battery array delivers power to the Alltrax SPM motor controller, which manages the power distributed to the Perm PMG motor. The PMG motor will be powered by 2 Interstate MPT 93 batteries. A full data sheet of the batteries can be seen in Appendix A. The motor controller is controlled by a throttle potentiometer that the skipper manually operates. The smart motor control calculates the efficiency of the motor by measuring the motor voltage, current, and speed, and estimating the speed using the current measurement and the motor torque constant. It then alerts the skipper whether to slow down or speed up to improve the efficiency of the boat. A non-contact LEM HASS 50-S Hall Effect sensor was used to measure the current without power loss. The datasheet is found in Appendix I.4. An Optek OPB716Z optical sensor, in combination with a black and white striped wheel in the drivetrain, was used to detect the angular speed of the motor. The output of the sensor drives an external interrupt on the Arduino, which tallies the number of edges over a set period and obtains the speed. The motor voltage is measured through a voltage divider and a voltage follower for isolation. 11

19 For the sprint configuration, two Alltrax SPM motor controller delivers power to the two Lynch motors. This time powered by six Odyssey PC 680, with two sets of three in parallel for an array voltage of 36 V. The potentiometer is used again as a throttle. A secondary contactor is added which can bypass the motor controllers and connect the motors directly to the batteries, as a last resort to gain extra speed. A comparison of the two electrical configurations can be seen in Fig. 8. F. Telemetry The telemetry system is composed of two subsystems; the on-board subsystem and the on-shore subsystem. The on-board subsystem s purpose is to process all of the data collected by the various sensors and display the relevant data to the skipper. Honeywell CSLA series current sensors are used to measure the current from the solar panel array, sprint battery array, and endurance battery array. The voltage across the battery array and solar panel array is measured using operational amplifiers in a differential attenuating configuration. The motor RPM is measured using a reflective object sensor by detecting the reflective wavelength of light from a painted wheel in a specified time and extrapolating based on this data. All of this data is collected by the ATmega2560 MCU running customized software. A subset of the collected data is displayed to the skipper using a Matrix Orbital LK204 LCD screen. As competition guidelines allow, all modules of the telemetry subsystem are powered using an auxiliary battery. Two MaxStream XStream-PKG-R 900MHz Stand-Alone Radio Modems are used to transmit data collected by the on-board subsystem to the on-shore subsystem. A laptop part of the on-shore subsystem collects all data from the on-board subsystem. It displays the data to the team using a LabVIEW Virtual Instrument and saves the data to an Excel spreadsheet for future reference. A. Hull V. DESIGN EVALUATION 1) Hull Design: The predicted weight of the surfboard hull from the SolidWorks model was about 55 pounds with the added estimation of the weight of fiberglass, primer and paint included. Due to different types of fiberglass needed during construction and the fiberglass that was added to the wooden inserts for added structural strength, the finalized hull weight is estimated to be about 70 pounds. The team still felt it achieved its goal of building the most lightweight hull at TCNJ s current disposal since the lightest hull in comparison was the 2009 monohybrid hull at 150 pounds. During construction, marine bow stem construction lines were obtained to correct for those generated in the model. This process involves using a long thin piece of wood to generate smooth curves. This was done under advisement because of potential stability issues with the curves generated in the CAD software. In addition during construction the bow stem was filled in rather than hollow as seen in the CAD model. This choice was made to reduce the chance of water building up in that area as well as simultaneously serving as a place to store sub system components for different center of flotation configurations. The thickness of the hull was changed from 5.75 inches to 6 inches because 3 layers of 2 thick foam were glued together. This design choice was used to ensure the hull had a uniform thickness along the entire length. Two smaller keels were added in addition to the larger center keel to increase stability. 12

20 Since construction has been completed, static testing has been completed in a lake on campus. Photos of this test can be found in Fig. 9 and 10. The test was deemed moderately successful. The original weight management analysis seen in Appendix E.1 shows the intended locations of the subsystems on board the hull. This configuration was thought to be sufficient to be able to shift the weight forward and lift the transom out of the water. Testing conditions proved that even with most of the subsystems pushed as far forward as possible behind the driver the transom still had about half an inch to three quarters of an inch to be able to lift out. The test was successful in that a proper sprint configuration trim angle was found without having to move the driver and helm positions between events. This added benefit allows for a simple steering system to be installed and not have to be reconfigured between events. At the time of writing this report the team is about a week away from hydro dynamically testing the hull in both the sprint and endurance configurations. Figure 9- Testing the Endurance Configuration to Try and Achieve Lifting the Transom Out of the Water 13

21 Figure 10- Testing the Sprint Configuration to Achieve Neutral Trim Angle for Planing Capabilities 2) Hull Materials The extruded polystyrene foam & white cedar fiber glassed hull was found to be apt in flotation requirements. The neutral waterline was close to that predicted in the analysis found in Appendix E.1. In addition, the hull was determined to be stable during the static testing. The skipper was able to stand and walk around the hull platform with little lateral instability. The use of the 80/20 rails proved to be efficient as well during the static testing. Weight configuration changeovers took only minutes to shift the center of flotation around. Slight modifications are going to be made to the dolly to ensure smoother transitions between unloading and loading of the hull. Overall the hull design to this point in time has been considered a success by the team. B. Steering After the design and dimensions were finalized for the helm s bracket, the bracket was fabricated using a ¼ thick aluminum plate. Once the plates were completed, they were spot welded before actually being welded to determine the necessary angle needed to allow the cable to pass underneath the helm. The bracket for the power head couple was fabricated using a shaft collar and an aluminum bar. The bar was cut to the proper length and then welded to the shaft collar. The cable then attaches to both sides of the bar, allowing the cable to pull the motor to the proper turning direction. Due to a late start fabricating the bracket, the team has yet to completely test the steering system and brackets. The team plans to test the system on the boat while out of the water ensuring that all of the parts work as a whole. Once the system is deemed reliable and safe for the skipper, the team will go out on the water and perform dynamic tests of the system. 14

22 C. Drivetrain Accuracy is one of the most important aspects of manufacturing the drivetrain; as a result, several steps were taken to ensure accuracy. All dimensions were kept to USCS units, to avoid possible error through conversions. The construction of the drivetrain components was facilitated through use of a 5-axis CNC machine. Because the accuracy of the hole locations on the power head plates was of utmost importance, the CNC machine was used, as it provides great accuracy through its programming. The CNC machine also allowed for the machining of pockets into the 40-tooth pulley to reduce weight. For the components where the CNC machine could not be used, care was taken to ensure tolerances of at least +/-.001 were maintained. An example of the completed drivetrain assembly can be seen in Fig. 11. The current design makes use of a modular gearbox setup in which the motors and gearbox are swapped between events. This presented a tradeoff; whereas the compound drivetrain facilitated gear reduction changes between events and reduced overall weight, the modular design allowed for easier center of flotation adjustment. By making use of two different gearboxes, the one not in use could be used as ballast. Because each individual power head is lower in weight than a compound power head, the resulting weight at the transom of the boat is reduced. This is especially true in the endurance configuration, where the power head is about 30lbs, as opposed to the estimated compound drivetrain weight of 90lbs. This reduction in weight at the transom, plus the advantage of the unused power head to further assist in moving the center of flotation, allows for improved boat position in the water during the endurance competition. When construction of the drivetrain is complete, a few different testing methods will be used to verify functionality and reliability of the drivetrain. First, a dry test will be conducted to ensure that the drivetrain Figure 11 - Drivetrain assembly runs, and that the propeller RPM produced matches the design RPM. Dynamic testing will also be performed before the competition to optimize a few key parameters, including propeller height, trim angle, and optimal motor speed for each configuration. D. Propeller Propellers are traditionally fabricated by a casting process and an additional CNC milling process to create a good surface finish. TCNJ facilities are not equipped with proper casting equipment for this process. It was desired to manufacture the propeller in-house to keep costs low, so it was decided that a CNC process would be used to machine out the propeller from a solid block of metal. The only practical metal to be machined was an aluminum alloy such as 6061 or 2024 aluminum, as stainless steel and nickel-bronze alloys have a low machinability T3 aluminum was selected because of a higher yield strength which would allow for thinner blade cross sections, while also having a good machinability. The College of New Jersey's Haas 5-axis CNC mill was used to machine the propeller out of a single block of 12"x12"x2" 2024 T3 aluminum. The extra material on the outside ring of the propeller was used as structural supports to provide rigidity and dampen vibrations during the 15

23 machining process. A propeller prototype was first machined in Butterboard to validate the g- code. The prototype highlighted two issues that were corrected for the final machined product - the blade thickness was globally increased by in. to improve rigidity and dampen machining vibrations, and the hub diameter was reduced to 1.5 in. A side-by-side comparison of the prototype and final propellers can be viewed in Fig. 12. More detailed steps on the machining processes can be viewed in Appendix G.3. Figure 12 Prototype g-code tested using Butterboard (left) and aluminum propeller after machining (right). The propeller has been integrated into the lower unit using a clevis pin and a nylock nut. It will be tested in open water during full system dynamic testing of the boat. The performance of the propeller will be optimized by fine-tuning the depth of immersion and trim angle at which the propeller operates. Several trial runs will be conducted to determine acceleration, velocity, and efficiency values for the propeller - these results will be compared with other available propellers to determine the best option for use in the competition. E. Telemetry The RF module, Hall Effect sensors, and voltage measurements have all been calibrated and tested to be properly working. Data can be collected and transmitted to the on-shore subsystem. The on-shore subsystem is able to display the transmitted data and record it for further use. However further calibration and testing still has to be done before the competition to ensure that the GPS module and optical sensor are working as intended. VI. PROJECT MANAGEMENT A. Team Organization and Responsibility The College of New Jersey s 2014 Solar/Electric Boat team is composed of five team members from two engineering disciplines, mechanical engineering and electrical and computer engineering. All of the team members worked together building one overall system for their Senior Project I and II capstone course, while also planning to compete at the 2014 Solar Splash competition. Two mechanical and one electrical and computer engineering faculty members 16

24 advise the team. Each member of the team is responsible for different subsystems of the boat, and is listed below: Jeff Holman o Project Manager, Steering System Joseph Maco o Telemetry Jason Pfund o Propeller Design Robert Ruff o Hull Design, Weight Management, Skipper Michael Schuhlein o Team Captain, Endurance and Sprint Drivetrain Designs B. Project Planning and Schedule The 2014 team decided that a key to developing a successful project would be to properly plan for it and to create a schedule. The team was first formed in the spring of 2013 and then the first official meeting was held in the beginning of the 2013 fall semester. During this meeting the team discussed each of the subsystem designs, initial discussion of integrating everything together, and the proper planning required to finish on time with a successful project. To help the team keep on schedule, a Gantt chart was created (Appendix J.1), which outlined schedules for each subsystem. The team met every Tuesday with the advisors to talk about their designs and any unforeseen complications. The team was on schedule throughout the fall, but unfortunately ran into delays starting the construction over the winter due to late material orders and necessary redesigning s of the hull s bow stem and drivetrain. They put in considerable time with the construction but due to the nature of building a new hull and two power heads, the testing schedule is pushed back until May. C. Financial and fund-raising To construct a successful boat, the project needed adequate funding. The project manager created a brochure (Appendix J.2) and letter, which highlighted this year s new designs, a breakdown of the budget, a summary of the Solar Splash competition, and a history of past TCNJ s Solar Boats and their success. This was sent out to private and corporate companies seeking for any support, discounts, or donations. This effort proved to be successful because the team received in full: Formular 250 foam from Owens Corning, Epoxy resin, hardener, primer, and paint from Interlux, PC680 batteries from Odyssey, and a motor controller from Alltrax Inc. Even after all these donations, the team still needed additional funds to complete their project. The team received a budget allocation increase by the TCNJ School of Engineering. The complete breakdown of the materials budget and travel budget can be seen in Appendix J.3. 17

25 D. Strategy for Team Continuity and Sustainability Every year, the TCNJ Solar Boat team is composed of senior students so it is important to pass on all resources used and any documentation collected to the future years teams. This year the team has included interested underclassmen during the design phase of the boat. The team has continued using a cloud-based service called Dropbox, which keeps future teams informed about the past projects successes and any recommendations. It is also fortunate that there is a 2015 team already formed and have helped out through the construction phase, allowing them to understand what needs to be done and to have a better understanding of the scope of the project. Two of these team members will be attending this year s competition to gain valuable experience. VII. CONCLUSIONS AND RECOMMENDATIONS A. Strengths Hull designed and optimized for minimal drag across all events Frame design allows for quick weight redistribution between races Optimized high-efficiency sprint propeller Modular drivetrain design allows for facilitated center of flotation adjustment. B. Weaknesses Limited time for boat testing and design changes. Compound drivetrain design did not work with weight management C. Future Development The College of New Jersey plans to continue its involvement in the Solar Splash competition, and next year s team has been selected. Important and relevant data and experiences regarding design, construction, and testing will be shared with the future team, so that they may improve upon the current team s shortcomings and the competitiveness of TCNJ s solar boat entry may be increased for the following competition. D. Goals Summary The team was able to design and construct a surfboard shape hull to effectively compete in the sprint and endurance configuration. A modular mounting system was implemented that allows for quick and easy reconfiguration of the center of flotation between races. The sprint propeller was machined out of a single block of aluminum using a 5-axis CNC milling machine. Additionally, a motor controller was implemented to run the endurance motor at maximum efficiency. Based on computer simulations and analysis, the team should be competitive with other top teams. E. Recommendations Research alternate propulsion methods, particularly contra-rotating propellers for increased endurance efficiency. Search for software that can incorporate both the propeller and hull analysis simultaneously Reduce weight of drivetrain components, and design for a compound configuration without sacrificing performance. 18

26 REFERENCES [1] Savitsky, Daniel. "On the Subject of High-Speed Monohulls." 02 OCT Society of Naval Architects and Marine Engineers. 28 Nov 2008 < [2] Juvinall, Robert C., and Kurt M. Marshek. Machine Component Design. Singapore: J. Wiley & Sons, Print. [3] B.P. Epps, "OpenProp v2.4 Theory Document," MIT Department of Mechanical Engineering. Technical Report, December [4] Carlton, John S. Marine Propellers and Propulsion. Oxford: Butterworth-Heinemann, Print. [5] Gerr, Dave. Propeller handbook: the complete reference for choosing, installing, and understanding boat propellers. Camden, Me.: International Marine Pub. Co., Print. 19

27 Appendix A: Batteries 20

28 21

29 Appendix B: Flotation Calculations The flotation requirement set forth by the Solar Splash competition ensures that the boats will not sink if completely filled with water. The equation below was used for calculating the flotation force provided. Where ρ2g is the specific weight of water and ρ1g is the specific weight of the flotation material, and V is the volume of the flotation material. Afterwards the 120% safety factor was added. Table 6 - Summary of the Flotation Requirement Calculations As evidenced by Table 3, the chosen size and shape of the hull far exceeds the required foam to achieve the ft 3 displacement requirement at a total of ft 3. Thus, the hull was deemed to satisfy the safety factor requirement. 22

30 Appendix C: Proof of Insurance 23

31 Appendix D: Team Roster Jeff Holman, Mechanical Engineer, Senior, Steering and Project Management Joseph Maco, Computer Engineer, Senior, Telemetry Jason Pfund, Mechanical Engineer, Senior, Propulsion Robert Ruff, Mechanical Engineer, Senior, Hull, Weight Management, and Skipper Michael Schuhlein, Mechanical Engineer, Senior, Drivetrain, Team Captain 24

32 Appendix E.1 APPENDIX E: HULL ANALYSIS Figure 13 - Comparison of the Full Hull versus Submerged Portion of Hull in the Water Table 7 - Data Analysis for the Waterline Properties of the Hull Figure 14 - Comparison Demonstrating the Reduced Drag Force and Vortex Shedding Between Transom In (Left) and Transom Out (Right) 25

33 Table 8 - Comparison of Drag Forces between the Proposed Design and Past Years at TCNJ Figure 15 - Proposed Weight Management Configuration (Endurance Event) 26

34 Appendix F: Drivetrain F.1 Timing Belt/Pulley Specifications 27

35 28

36 29

37 30

38 F.2 LEM-200 D126 Specifications 31

39 32

40 F.3 Perm PMG-132 Specification 33

41 F.4 Bearing Data 34

42 F.5 ANSI Key Standards 35

43 Appendix G: Propeller Appendix G.1: Stress Analysis The cantilever beam stress analysis was extracted from Marine Propellers and Propulsion textbook by John Carlton. The equations for the following iterative calculations can be found in that book. Table 9- Sprint Propeller Input Parameters for Cantilever Beam Stress Analysis Shaft power, Ps(W) RPM 3400 Ship speed (m/s) 17 Wake Taylor Fraction, wt wf D (mm) 250 Radial Position of Examined Stress, r/r Radial Position of Centroid rc/r, xc Pitch, p0 (mm) 315 Developed Area (mm^2) Ae/A0=4*Ad/pi*D^ Bending moment Arm, L (mm)* 7.93 Number of Blades, Z 4 Mechanical efficiency, ηm 0.95 Propeller Open Water Efficiency, ηo a=0.7r 0.7 b=0.66r 0.66 density of aluminum (kg/m^3) 2700 *If raked or skewed distance from center of hub (r/r) volume (mm^3) mass (kg)

44 Table 10 - Calculations for Cantilever Beam Stress Analysis Step (mm) Interpolated Ordinate x (m) yp (m) t (m) x (mm) yp (mm) t (mm) x (mm) yp (mm) t (mm)

45 Ordinate Simp Multi (SM) t*sm (2yp+t)t*SM [3yp(yp + t)+t^2]t*sm TOTAL

46 Table 11 - Output of Cantilever Beam Stress Analysis A Integral of(2yp+t)t Integral of[3yp(yp + t)+t^2]t Zm mm^ mm^ mm^ mm^3 Centrigual Force (N) Section Pitch angle (degrees) Propeller Speed of Advance, Va (m/s) Stress Due to Propeller Thrust Stress due to Propeller Torque Stress due Centrifugal force TOTAL STRESS Mpa Mpa Mpa Mpa Appendix G.2: Cavitation Analysis Cavitation calculations were completed with the use of David Gerr's Propeller Handbook. where, Va = Speed of water at propeller, in knots Ft = depth of immersion of the propeller shaft, in feet where, SHP = shaft horsepower at the propeller e = propeller efficiency in open water Ad = developed area of propeller blades, in square inches 39

47 Appendix G.3: Manufacturing Figure 16 - Surface finish of the roughing pass by the CNC mill. A 1/2" end mill was used to quickly remove large amounts of material. Figure 17 - FInishing pass by the CNC mill. Foam plugs were used to dampen blade vibrations caused by the mill. A water-soluble oil coolant was used. 40

48 Figure 18 - Machined surface finish resulted in small lateral ridges. Figure 19 - Fine sand paper was used to smooth out the ridges to improve fluid flow characteristics. 41

49 Figure 20 Aft view of the final machined sprint propeller. Figure 21 - View of the sprint propeller mounted on the lower unit. This will attach to the drive shaft of the drivetrain. 42

50 Appendix H: Eletrical Systems Appendix H.1: SCHOTT 240 W Solar Panel Data Sheet 43

51 44

52 Appendix H.2: Morningstar SunSaver MPPT 45

53 46

54 Appendix I: Telemetry Appendix I.1: XStream-PKG-R RF Module 47

55 48

56 49

57 50

58 51

59 52

60 Appendix I.2: L01Z600S05 600A Hall Effect Current Sensor 53

61 54

62 Appendix I.3: CSLA2CD 72A Hall Effect Sensor Data Sheet 55

63 56

64 Appendix I.4: OPB715Z Optical Sensor 57

65 Appendix I.5: EM-406A GPS Module 58

66 59

67 60

68 61

69 Appendix I.6: Arduino Mega Datasheet 62

70 Power The Arduino Mega can be powered via the USB connection or with an external power supply. The power source is selected automatically. External (non USB) power can come either from an AC to DC adapter (wall wart) or battery. The adapter can be connected by plugging a 2.1mm center positive plug into the board's power jack. Leads from a battery can be inserted in the Gnd and Vin pin headers of the POWER connector. The board can operate on an external supply of 6 to 20 volts. If supplied with less than 7V, however, the sv pin may supply less than five volts and the board may be unstable.!fusing more than 12V, the voltage regulator may overheat and damage the board. The recommended range is 7 to 12volts. The Mega2s6o differs from all preceding boards in that it does not use the FTDI USB to serial driver chip. Instead, it features the ATmega16U2 (ATmega8U2 in the revision 1and revision 2 boards) programmed as a USB to serial converter. Revision 2 of the Mega2s6o board has a resistor pulling the 8U2 HWB line to ground, making it easier to put into DFU mode. Revision 3of the board has the following new features: + 1.0pinout: added SDA and SCL pins that are near to the AREF pin and two other new pins placed near to the RESET pin, the IOREF that allow the shields to adapt to the voltage provided from the board. In future, shields will be compatible both with the board that use the AVR, which operate with sv and with the Arduino Due that operate with 3.3V. The second one is a not connected pin, that is reserved for future purposes. + Stronger RESET circuit. + Atmega 16U2replace the 8U2. The power pins are as follows: + VIN. The input voltage to the Arduino board when it's using an external power source (as opposed to s volts from the USB connection or other regulated power source). You can supply voltage through this pin, or, if supplying voltage via the power jack, access it through this pin. + sv. The regulated power supply used to power the microcontroller and other components on the board. This can come either from VIN via an on board regulator, or be supplied by USB or another regulated sv supply. 63

71 + 3V3. A 3 3 volt supply generated by the on board regulator. Maximum current draw is soma. + GND. Ground pins. Memory The ATmega2s6o has 256 KB of flash memory for storing code (of which 8KB is used for the bootloader), 8KB ofsram and 4 KB of EEPROM (which can be read and written with the EEPROM library). 64

72 65

73 Appendix I.7: Matrix Orbital LK WB Data Sheet 66

74 67

75 Appendix J.1: Team Gantt Chart Appendix J: Project Management 68

76 Appendix J.2: Sponsorship Brochure 69

77 Appendix J.3: Materials and Travel Budget 70

78 71