Thunniform Marine Propulsion Vehicle Final Report

7/29/2019 Thunniform Marine Propulsion Vehicle Final Report

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Conducted at the University of Illinois atUrbana-Champaign by six first-year

engineering students; Fall 2011.

Thunniform

MarinePropulsion

VehicleA project by Team Nature Thing

Casey Fee

Chris Nobre

Davis Born

Geordan Chapman

Shawn Williams

Zong He Chua

An IEFX Engineering Projects

investigation of natural methods of

water propulsion and their potential

applications for human use through

biomimetic engineering.


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Project Description

Problem Statement:Current methods of marine propulsion (i.e. propellers) are very dangerous to wildlife andswimmers. Animals get caught in the blades and can be severely injured or killed. Team NatureThing is proposing a more natural and safer method of marine propulsion: a fish fin. In replacinga spinning propeller with an oscillating fish fin, dangerous sharp edges that are responsible fordamage to marine life are eliminated.

The team drew its inspiration from the tuna fishs method of thunniform swimming. The tunafish swims with high efficiency and minimal back-and-forth motion in the body. This is idealbecause a boat that constantly rocks from side to side would be essentially useless to the likelyconsumers of this product. Furthermore, the projects main goal is a proof of concept. In otherwords, the team will attempt to demonstrate that propelling boats, submarines, and the like withfish-like methods is plausible so that further work on the subject may be justified. There are noplans for commercialization at this stage.

Deliverables for this project include: A functioning boat propelled by a fish fin A summary (including visual aids) of the teams work Early test results A final report on the project

Note: In this report, pictured below and any such phrases will refer to the first pictureembedded in the report which follows unless stated otherwise.

Description of Work

1. Research Phase:During this phase, the team conducted research on biomimetic adaptations that reduceddrag and conserved energy during movement through a fluid. Through this exercise, themechanics of fish locomotion, the special shape of humpback whale fins, and theaerodynamics of bird feathers were explored. The most promising biological adaptationswere those of the tuna fish, which use the thunniform method of swimming to conserveenergy, and the flippers of the humpback whale, which have special bumps calledtubercles along the edge to reduce drag.

The team also conducted research on existing biomimetic propulsion technologies. Itwas found that researchers at MIT had successfully created the Robofish, which hadan electronic motor and a circuit board encased in a flexible polymer shell that acted asa skin, the fish had potential applications in underwater autonomous vehicles. Also, thecompany BioPower Systems had created a prototype tidal energy generator based onthunniform swimming. In the field of manned watercrafts, Pacific Tailboats designed apedal operated watercraft based on thunniform swimming action. The team also foundthat the tubercles of the humpback whale had been successfully adapted to improvewind turbine performance by a company called WhalePower Corporation.

2. Design and Build PhaseThe team compiled its findings and explored the potential of the various ideas foradaptation and implementation in the final product. It was decided that the thunniformswimming mechanics would be adapted based on the Pacific Tailboat watercraft design


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and that the adaptations of the humpback whale could potentially be added in at a laterdate. Obviously, though, this was not in the initial scope of the project.

a. Airfoil Caudal FinThe Pacific Tailboat watercraft did not have a scientifically designed fin. Hencethe team used research on tail fin (caudal fin) shape to find the characteristics

that would give it maximum propulsion capability. According to Sfakiotakis(1999), this propulsion effectiveness was determined by frequency of the tailmovement and the aspect ratio of the fin. It was also noted that thunniformswimmers usually have a fin of aspect ratio ranging between four and seven(aspect ratio given by surface area divided by vertical span, shown below). Theefficient movement of these swimmers was due to the lateral lift generated asthe tail, which is an airfoil, cut through the water.

The team then proceeded to model a fin based on the airfoil profile of a Boeing737 wing that was obtained from the UIUC Airfoil Data Site. The aspect ratio wasthen optimized based on the size constraints of the boat which was ultimatelylimited by hull size. Based on these design constraints the team designed acaudal fin that had an aspect ratio of seven. This foil was modeled inpro/ENGINEER and rapid prototyped out of ABS plastic at Professor Leakeslaboratory in the Transportation Building (see below, next two pictures).

Figure 1: Thunniform Swimming Efficiency DiagramTaken from Sfakiotakis research papers.

Figure 2: The Initial Failed Fin Design in Both 3D Modeland Prototyped Part


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As can be seen on the previous page, the resulting foil was too thin for themachine to print accurately, so the team remodeled the fin to increase itsthickness. Based on the changes, the aspect ratio was reduced to four. The teamfelt that this would produce negligible loss in effectiveness of the tail todemonstrate the proof of concept given the small scale and early stage of theproject. The fin was also modified to include a hole to house a ball bearing that

would be part of the transmission mechanism (see below, next two pictures).

b. TransmissionThe transmission consisted of 3 main parts:

1. Servo to transmission connection

The servo was connected to the struts using a 2 piece wooden block withthe lower piece being screwed directly on to the rotating axle of the servo(pictured on the next page). A single half cylinder was drilled into each ofthe 2 pieces. When the two pieces were joined together they created ahole into which the strut could be fitted. The method of adhesion wasepoxy resin.

Figure 3: The Final Fin Design


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2. StrutsThe struts were created using 3/16 inch dowel rods. Slots were filed outof each piece corresponding to the required angles for proper interface.The overall layout of the struts is shown in the picture below. The overallheight of the strut system was calculated based on the required depth thetail fin would need to be submerged to. The length was calculated basedon the value of the servo motors angular velocity and the period ofoscillation that was programmed into the ARDUINO. For this test, theteam restricted the chord of the arc the fin would sweep out to be exactlythe width of the boat. The equation relating the angular velocity (), withthe strut length (), is given by:

()

Where is the width of the boat and is half the period (it makes moresense to write it in this way because of the way the ARDUINO isprogrammed). This works out to the dimensions given in the image below.Method of adhesion was epoxy resin.

Figure 4: Servo to Transmission Connection

Figure 5: Diagram of Strut System with Calculations


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3. Strut to fin interfaceThe strut system was connected to the fin via a bearing that would allowthe fin to rotate around the dowel. The inner ring was joined to the rodusing epoxy resin and the outer ring was joined to the fin by a press fit.The initial circumference of the hole on the fin was too small and had tobe sanded to achieve this fit. The fin, if unrestricted, could rotate

continuously about the bearing in either direction. Its movement wasconstrained by a thin metal strip made of aluminum connected to both thestrut and the top of the fin. The purpose of this strip was to allow the fin tonaturally reorient itself, resulting in a more effective push against thewater as it oscillated.

Figure 7: Complete Transmission Mechanism

Figure 7: Strut to Fin Interface


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c. Power SourceBased on a recommendation by ELA Jack Tu, the team decided to power thewatercraft using the ARDUINO system with a high torque servo motor. The code,shown below, was written with assistance from Tu and ELA Neil Christanto. Thecode allowed the programmer to modify the period of oscillation of the motor;however it did not allow one to modify the angular velocity of the motor. This was

the limiting factor that dictated the dimensions of the strut system. The ARDUINOchipset (the board containing the programs and electrical connections) wasdirectly connected to the servo motor without a breadboard. Connections were

joined using the provided connectors and secured using electrical tape. Since thecraft was to be mobile, it would not be powered by a USB power source. It wouldinstead draw power from a nine-volt battery that would be stored on-board.

Figure 8: The ARDUINO Chipset and9V Battery

Figure 9: ARDUINO Final Code


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d. Hull and KeelTo reduce cost and save time the team opted to buy off-the-shelf toy boats anduse the pre-fabricated hulls that came along with them. The toys also includedstands that could be used to raise the boat up. These were, with somemodifications, ideal for display use. The dimensions of the boat were: 355.6mm x109.2mm x 91.4mm and when fully loaded sunk down by a depth of

approximately 21.3mm. To house the ARDUINO chipset, servo motor, andbattery, a thin wooden platform was carved out of balsa wood and attached tothe bottom of the hull using epoxy. This provided a flat surface that would betterallow mounting of the aforementioned components. The motor and the chipsetwere attached to this platform with screws and the battery was caged with nailswhich could be removed if it needed to be replaced

To stabilize the boat as it moves through the water, the team opted to use a keel.This is similar to the stabilization mechanisms found on sailboats. The teampredicted that it would provide resistance against the boats natural tendencies toroll. This keel was developed based on existing keel designs and modeled inpro/ENGINEER. Like the fin, it was then rapid prototyped out of ABS at Professor

Leakes laboratory (see below, next two pictures). The keel was both lighter andsmaller in size than anticipated, but due to unforeseen errors within thelaboratory, there was not time to make any modifications outside of attachingsome extra weights to the bottom of the keel. Fishing weights were used for thispurpose. The keel was adhered to the hull using epoxy resin. This keel modeland prototyped part with weights attached can be seen at the top of the nextpage.

Figure 10: Inside of Boat with Battery, Servo, and ARDUINO Chipset


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3. Test PhaseThe first phase of testing was to place the boat in water to ascertain if there wasadequate buoyancy. This test was done in the sink in the ELS laboratory, and itconfirmed that the boat was able to float with its center of mass located towards theback, creating a nice angle of attack against the water.

During the next phase of testing, which involved the testing of the fin mechanism whilethe boat was in water, water was being scooped into the boat at its stern. This wascaused by the boats tendency to roll, which was not sufficiently counteracted by thekeel. Had there been more time and fewer delays, a modified keel may have improvedperformance in this area. The boat also had unacceptably large side-to-side motion. Thisis a direct result of the boat not having a sufficiently greater mass than the finmechanism, so the law of conservation of rotational momentum has a significant effect.Furthermore, the amplitude of oscillation was much larger than would be ideal of a truethunniform swimmer. The implementation of a more precise motor and programmingsystem may lead to a decrease in this amplitude.

The team then made some modifications to the boat by weighting the keel with fishingweights and placing a fiberglass plate over the exposed part of the stern in order toprevent water from being collected during operation. These modifications were enoughto shield the electronic components from water.

The final stage of testing was done in a swimming pool. The boat was allowed to propelitself through the water for brief windows of time, and it was found that it no longer tookon water and its rolling was marginally decreased by the additional weight on the keel.

Figure 11: Keel Modeling and Prototyping(Shown with Fishing Weights)


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Statement of Budget

Table of Expenditures:

Item Vendor DateRequested

Quantity UnitPrice

Total

Toy Boat. 12 inches ASIN:B0056B8TES

Amazon.com 10.5.11 2 7.95 15.90

High Torque Servo Motor College ofEngineering

10.12.11 1 14.00 14.00

9 Volt Batteries Walmart 10.5.11 1 6.00 6.00

ARDUINO College ofEngineering

10.5.11 1 30.00 30.00

Ball Bearings, 5x11x4mm Amazon.com

Ball Bearings,5x11x4mm

10.17.11 2 3.83 7.66

Dowel Rods 36"-3/16" Hobby Lobby 10.17.11 7 .2970% off

1.42

Total: 74.98

Under/Over Budget:The original projection of about $80 was quite accurate, and luckily Team Nature Thing came inunder this self-imposed budget and far under the allocated $120 budget limit.

In terms of time allocation, the team roughly followed this Gant Chart to reach our goals. Attimes, progress got a bit behind or ahead, but they always managed to even out by the end.

Tasks 9/28 10/3 10/5 10/10 10/12 10/17 10/19 10/24 10/26 10/31 11/2 11/7 11/9 11/14 11/16 11/28 11/30 12/5 12/7

Submission of

Proposal

Research

Initial design

planning

Drawing up of

Sketches/ CAD

models

Sourcing for

materials and

costing

Review of Design

Mid-semesterReview

Revision Approvals

Start work on

prototyping

Testing of

Prototype

Revising of Design

Prepare for Demo

Day

Demo Day

Fall Break

Figure 12: Gant Chart


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Justification:The project was under budget because the team overestimated the price of many of thecomponents that were required. For example, the dowel rods, ARDUINO and servo motor wereall bought at a discounted or subsidised price. The team also opted to go with simplemechanisms and materials that were easy to work with. This resulted in reduced costs. It is alsoimportant to note that the team utilized rapid prototyping to fabricate two key parts and that this

service was provided free of charge. If this cost were to be taken into account the team wouldhave gone over the 120 dollar budget.

Hull: From a survey of the available boats on Amazon.com the team opted to purchase twoplastic boats with built in motors. While these were more expensive than boats without motors,the team operated with the original intention of testing a propeller-run boat to compareperformance with. Therefore, one boat would be stripped of its propeller and retrofitted with thefin while the other would serve as a control. However due to time constraints, the team did notrun these tests.

High Torque Servo: While the ARDUINO kit provided a stock servo motor, its torque output wasdeemed insufficient to power a fin immersed in water as resistance would be very high. Hence,

with input from ELA Jack Tu, the team decided to purchase a high torque motor.

9V Batteries: The ARDUINO can be powered by battery or by USB. However, the boat requiredthe freedom to move uninhibited on the water, and thus it was not practical to power the

ARDUINO via USB. Therefore the team decided to purchase 9V batteries as an on board poweroption.

ARDUINO: The primary reason for purchasing the ARDUINO was its capacity for programming.The team needed the motor to oscillate across a fairly precise range, and while this could havebeen accomplished with a less ideal oscillating motor and gears, it was determined that thiswould become too cumbersome and impractical. Also, the team was operating well under-budget otherwise and decided they could definitely afford to buy this higher quality device.

Apart from material costs, the ARDUINO also required about 4 class periods to fully understandand program, and thus the total time invested in this task was approximately 8 hours from startto finish. This is longer than originally planned because of the initial desire to program two codesfor the two different modes of propulsion. This represented significant time expenditure;however, it was ultimately time well-spent as it was a critical component of the project.


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Ball Bearings: For obvious operational purposes, it was important to minimize the frictionbetween the fin and the transmission connected to it. Ball bearings were the obvious solution tothis problem. The team was able to find inexpensive ball bearings that were the size needed, sothey were easily implemented into the design.

Dowel Rods: Team Nature Thing utilized dowel rods for the transmission from the motor to thefin. The team originally explored using metal, but decided it would be too difficult to work with,too heavy for the motor to spin effectively, and not rigid enough to keep from flexing so much sothat it would affect performance. Considering the short-term scope of the project, it was finallydecided that wood would be light and rigid enough to suit the mechanisms function; its inherentweaknesses in water (i.e. swelling and softening) would not have time to take effect.

Reflection/ Discussion

What was learned:Working as a team: The team developed high-level collaboration and cooperation skills duringthe time spent working on this project. The project was very large and comprehensive; the timeand resources required for its completion were beyond the scope of any other project members

had undertaken individually in the past. Under such circumstances, it was not only important toevenly distribute responsibilities, but it wasnecessary. Otherwise, the project would not havebeen completed on time and at the standardsrequired of the team. For these reasons, groupmembers teamwork skills have improvedsignificantly.

Time management: Given the scope of theproject (conception to prototype) over a singlesemester, time management was an importantskill to possess. On top of the short long -term

time frame, each class period was only two hourslong, and class only met twice a week. As a resultof conflicting schedules, these allotted meetingtimes ended up being the only times the entireteam could meet together. The team needed toeffectively use the four hours a week that weregiven, and this would have been impossiblewithout a sense of direction and self-imposeddeadlines. Thus, time management was a criticalskill that was required of each individual. Theteam managed to stay on schedule in spite of set-backs that were beyond internal control. This,

however, highlights the importance of givinggreater allowance for tasks outsourced to external parties, such as Professor Leakes team thatwas behind the rapid prototyping, as these resources also have other commitments. Parts thatwere only scheduled to take twenty to thirty minutes were often only ready the next day or twodays later and the machines used were not the most reliable, leading to reprints beingnecessary at times.


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Insights (on the project and the course):More than anything else, the time spent working on this project showed the team how importanteffective management is with respect to resources, responsibilities, and time. While TeamNature Thing maintained a healthy level of effectiveness throughout the semester (i.e. did notexceed budget and finished on time), the team also had experiences with other parties whodemonstrated poor management, and it hindered the project. This was most prevalent when

working with the staff at the rapid prototyping laboratory in the Transportation Building. Staffeither failed to produce or misplaced the keel three times before successfully getting it into theteams hand. Had this not occurred, time could have allowed for modification of the keel to bemore effective in reducing rocking.

That being said, planning for such delays is imperative. Even if a team is lucky enough tocomplete a project with no outside problems, they would only finish ahead of schedule in thiscase. If an unavoidable delay puts a project irreparably behind schedule, it can severely impactthe quality of the final product. These built-in delays also fall out of effective management.

As far as the class goes, the team members mutuallyagree that the project has prepared them very well for

many of the obstacles that can be expected whenworking on similar problems in the real world. It hasexposed them to unavoidable third-party issues,discrepancies between the theoretical and theexperimental, and all sorts of people that they mayneed to cooperate with somewhere down the line.

The peer reviews were beneficial in many ways.Primarily, it allowed the team to see how its project might be received by the general public.This was beneficial as it let the team identify areas of improvement and paths it should continueto pursue. The reviews were also beneficial in that they provided insightful feedback from peerswith a different perspective. It is always good to receive new opinions. While the team never

faced any major creative difficulties once the project was underway, the resource was usefulnonetheless. Possibly the most helpful aspect of the peer reviews was that they kept the groupon schedule. When the team was showing signs of falling behind schedule, the criticism fromthe peer reviews highlighted this key issue and the team worked diligently to get back on track.

However, the team felt that the presentations were often not very organized. Verbalpresentations lacked structure and it was hard to follow the direction of the presentation evenwith the handouts provided. The team feels that the facility should be equipped with mini-projectors and screens to allow teams to effectively present their information throughPowerPoint. Through this, more panelists will be engaged and provide more insights. This willincrease the utility of these panel reviews.

Future Work

What could be done better?There are many aspects of this project that could be improved in the future. In terms of projectmanagement, there could be more even distribution of tasks across the team. This would allowquicker progress to be made as there is concurrent work being done. It will also foster greaterengagement with the project and this would provide greater incentive for team members to havea more complete understanding of all aspects of the project.


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In terms of design, stability was a big issue. With regards to this, the team felt that the size andweight of the keel could have been greater to provide larger damping of the z axis rotation. Thiswould require the use of or adding on of heavier materials such as steel and lead. Anotheroption that the team felt that could possibly work is the use of two fins operating in tandem tocancel out the moments generated by each one.

To provide greater stability, outriggers could also be added to each side of the boat to createresistance against the z-axis rotation (side-to-side) and rolling. This would also create greater

buoyancy to offset the increased weight of the keel.

What are the next steps if you or someone else wanted to continue the project?:Were this project to be picked up by another group the next logical step would be to comparethe performance of the fin propelled boat to a boat using a conventional propeller, keeping theamount of variables between the boats as small as possible. This would mean modeling apropeller of about the same volume as the fin, while keeping the dimensions of the propellertrue to an existing model. The propeller would ideally be powered by an ARDUINO systemutilizing a high torque motor and would be mounted in the same position on the same size andshape boat hull as the experimental boat. The projects original goal was to create a control boatin this manner for comparison, but due to time constraints and the difficulty of modeling apropeller forced them to abandon this aspect of the final product and simply determine if the testboat would perform at a reasonable level, if at all. Aspects to be compared would includeacceleration, maximum speed, stability, and wake generation. Another step to be taken in thisproject would be giving the boat the capability of steering and accelerating, ideally throughremote control. Maneuverability could then be tested between the boats.

Specific modifications that should be made to the boat include: Implementation of a more precise motor to allow for a smaller amplitude of oscillation Increase in the weight of the boat relative to that of the fin mechanism Increase in the weight and vertical span of the keel Re-distribution of weight in the boat (i.e. more towards the bow)


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ReferencesBioPower Systems. (20011). bioSTREAM. Retrieved December 15, 2011,

http://www.biopowersystems.com/biostream.html

Pacific Tailboats. (2004). Technology. Retrieved December 15, 2011,

http://www.tailboats.com/propulsion_technology.html

Sfakiotakis, M. , Lane , D.M, & Davies ,J.B.C. (1999). Review of Fish Swimming Modes for

Aquatic Locomotion. IEEE Journal of Oceanic Engineering, Vol. 24, No. , April 1999, 237-252.

Retrieved from :

http://www.societyofrobots.com/robottheory/Review_of_Fish_Swimming_Modes.pdf

Trafton, M. (2009, August 24). Fish and Chips. MIT News. Retrieved from:

http://web.mit.edu/newsoffice/2009/robo-fish-0824.html

Villano, M. (2010, November 23). A Whale of an Idea. Entrepreneur. Retrieved from:

http://www.entrepreneur.com/article/217520
http://www.biopowersystems.com/biostream.htmlhttp://www.biopowersystems.com/biostream.htmlhttp://www.tailboats.com/propulsion_technology.htmlhttp://www.tailboats.com/propulsion_technology.htmlhttp://www.societyofrobots.com/robottheory/Review_of_Fish_Swimming_Modes.pdfhttp://www.societyofrobots.com/robottheory/Review_of_Fish_Swimming_Modes.pdfhttp://web.mit.edu/newsoffice/2009/robo-fish-0824.htmlhttp://web.mit.edu/newsoffice/2009/robo-fish-0824.htmlhttp://www.entrepreneur.com/article/217520http://www.entrepreneur.com/article/217520http://www.entrepreneur.com/article/217520http://web.mit.edu/newsoffice/2009/robo-fish-0824.htmlhttp://www.societyofrobots.com/robottheory/Review_of_Fish_Swimming_Modes.pdfhttp://www.tailboats.com/propulsion_technology.htmlhttp://www.biopowersystems.com/biostream.html

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Thunniform Marine Propulsion Vehicle Final Report