The Powered AUV-Glider 2007 Senior Design Project

Submitted to: Dr. Stephen Wood, PE Department of Marine and Environmental Systems

Florida Institute of Technology Submitted by: Sam Arden

Jason Borman Christian Flemming Jean Valcin

July 25, 2007

July 25, 2007

Dr. Stephen Wood, PE Florida Institute of Technology Department of Marine and Environmental Systems 150 W. University Blvd. Melbourne, FL 32901 Dr. Wood: Subject: Final report for the AUV-Glider team, MantAUV The MantAUV, powered AUV glider team would like to submit to you this report, detailing the progress that we made this summer towards the Powered AUV Glider project here at Florida Tech. We have included all information and data collected throughout the term, and submit it for your review. Sincerely, Sam Arden, Jason Borman, Christian Flemming, Jean Valcin MantAUV Team

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Acknowledgements

This project would not be possible without the support and assistance provided by the following people, companies, and donors. Thank You.

� Dr. Stephen Wood – Academic Project Advisor

� Department of Marine and Environmental Systems

� The Florida Tech Machine Shop

� The Following Sponsors:

� Arcom, A Member Of Eurotech Group

� General Plastics Manufacturing Co.

� Hitec

� Syntech Technology, Inc

� Vectorworks Marine, Inc

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Table of Contents

1. Front Matter 1.1 List of Figures…………………………………………………….. IV 1.2 List of Tables……………………………………………………....IV 1.3 List of Abbreviations…………………………………………….....V 1.4 Executive Summary……………………………………………….VI

2. Introduction ...……………………………………………………………...1

2.1 Scope Statement……….….…………………………………………1

3. Background………………….…………….………………………………2 3.1 Introduction ………………….……………………………………. 2 3.2 Powered AUV……….……………….……………………………...2 3.3 AUV Gliders ………..………………………………………………3 3.4 2006 AUV Glider, Florida Tech…….……………………………...5

4. Product Design……………………………………………………………..6

4.1 Technical Specifications………….…………………………………..6 4.2 Part Decomposition…………………………………………………...7

4.2.1 Main Structures Construction………..…………………………7 4.2.1.1 Main Foil…………………………………………………...7 4.2.1.2 Foil Extension………………………………………………9 4.2.1.3 Glass Spheres……………………………………………...11 4.2.1.4 Aluminum Frame………………………………………….13

4.2.2 Rear control Surfaces……………………………………………14 4.2.2.1 Rear Foil…………………………………………………..14 4.2.2.2 Main thrusters……………………………………………..18 4.2.2.3 Kort Nozzles………………………………………………20 4.2.2.4 Control Servos…………………………………………….23

4.2.3 Recovery System………………………………………………..26 4.2.4 Bow Thrusters…………………………………………………...28 4.2.5 Electronics……………………………………………………….30

4.2.5.1 Remote Control System…………………………………...30

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5. Testing and Analysis……………………………………………………...32 5.1 Fluid Mechanics Testing…………………………………………….32 5.2 Materials Testing…………………………………………………….39

6. Safety Risks and Hazards………………………………………………...40

7. Conclusion…………………………………………………………………41

8. References…………………………………………………………………42

9. Appendix A………………………………………………………………..43

10. Appendix B………………………………………………………………...44

11. Appendix C………………………………………………………………..45

12. Appendix D………………………………………………………………..47

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1.1 List of Figures 3.1 MIT’s Cetus ……………...……………………………….……………..2 3.2 MIT’s Xanthos …………………...……………………………………...3 3.3 Webb’s Pelagia ………………………………………………………….3 3.4 Scripps’ Spray …………………………………………………………...3 3.5 Revision Points……………………………………….….……...………..5 3.6 Present Control Surface Servos………………………………..................6 4.1 Finished Vehicle Concept Design………………………………………..7 4.2 Bottom of Shell Mounted to Frame……………………………………...8 4.3 Main Shell with Extension Connected…………………………………...9 4.4 Foil Extension Trimmed and Painted…………………………………...10 4.5 Half of Glass Sphere with Cable Attached……………………………..12 4.6 Aluminum Beam………………………………………………………..13 4.7 Polishing Rear Beam……………………………………………………14 4.8 Rear Foil Mounted……………………………………………………...15 4.9 Rear Aileron…………………………………………………………….16 4.10 Main Thruster…………………………………………………………...19 4.11 Kort Nozzle Design……………………………………………………..21 4.12 Nozzle Attached to Motor………………………………………………22 4.13 Mounted Rear Servos…………………………………………………...23 4.14 Assembled Servo/Aileron………………………………………………24 4.15 Milled Front/Rear Recovery Handles…………………………………..26 4.16 Front Handles Holding Foil Extensions…………………………….......27 4.17 Bow Thruster/Bracket Assembly……………………………………….29 4.18 Bow Thruster Mounted to Vehicle……………………………………...29 4.19 Radio Control System for Testing………………………………………31 5.1 “C” Grid Mesh………………………………………………………….33 5.2 Standard Mesh Grid for Airfoils……………………………………......34 5.3 Residuals for Turbulent Flow…………………………………………...36 5.4 Pressure Distribution around Rear Foil………..………………………..37 5.5 Vector Map of Fluid Velocity near Rear Foil….……………………….37

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1.2 List of Tables

4.1 Dimensional Specifications………………………………………………6 4.2 Main Foil Specifications…………………………………………………6 4.3 Propulsion Specifications………………………………………………...6 5.1 Net Force on Foils………………………………………………………38

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1.3 List of Abbreviations

AUV Autonomous Underwater Vehicle

CTD Current, Temperature, Depth (Sensor)

DMES Department of Marine and Environmental Systems (Florida Tech)

GPS Global Positioning System

MIT Massachusetts Institute of Technology

NOAA National Oceanic and Atmospheric Administration

SONAR Sound Navigation and Ranging

R/C Radio Controlled

CNC Computerized Numerical Control

CFD Computational Fluid Dynamics

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1.4 Executive Summary

Providing oceanographic researchers with a cheap yet reliable submersible data collection

platform is vital to the understanding of the world’s oceans. The 2007 AUV (autonomous

underwater vehicle) glider team, MantAUV, is dedicated to the production of a versatile

autonomous underwater glider that will provide this platform for oceanographic research

programs. The AUV, when complete, will be capable of autonomously traversing large

distances on minimal power, allowing researchers to collect an array of oceanographic data from

all over the ocean. With a target maximum depth of 4000 meters and an estimated range of 200

km on one charge, the glider will be able to economically cover large distances, both

horizontally and vertically. With such a great potential for long range data collection, the AUV

will be able to perform a variety of data acquisition operations. Along with being a general

platform for small instruments of the researcher’s choice, the glider will include devices for the

collection and photographing of physical specimens as well as sensors to record environmental

data such as water density, water salinity, and bathymetry.

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2. Introduction

Team Goal: To provide a strong and functional glider platform to allow for future teams to focus

on other important areas of development.

As the 2007 AUV Glider team, we knew coming into this project that we were the second

team to work on the project and certainly not the last. The previous team had done a tremendous

job in both design and construction, but with such an extensive project (originally estimated to

take at least five years to complete), they had naturally run out of time. We began where they

left off, continuing some of their designs and modifying others, making the project uniquely ours

while at the same time working towards the same common objective of building an autonomous

underwater glider.

When we inherited the project, a lot of progress had been made on the construction of the

glider itself. The following main components had been acquired and/or constructed:

• Two main aluminum beams

• Main foil fiber-glassed, painted and mounted

• Six syntactic foam blocks acquired and machined (both through generous donations)

• Two main thrusters modified and mounted

• Two glass instrumentation spheres acquired

• Two kort nozzles constructed

• Main rear control surfaces constructed and mounted

This list does not include the extensive list of designs that the 2006 team had conceived for

future development. Needless to say, we weren’t starting with a “blank slate.”

With the ultimate goal of this entire project being a completely autonomous, long range

underwater glider, we made our goals realistic in that we knew we were not going to have a

finished product when our time was up. To completely finish the AUV project, extensive work

needs to be done on the structural components, running equipment, control systems, navigation

equipment, and various data acquisition instruments. Each of these areas could be a project in

itself. Knowing this, we decided to focus our attention on mostly the structural design and

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construction of the glider, with the intention of providing a solid, functional foundation on which

future teams could add to.

The following report explains what we have accomplished in the past two semesters. We

have created our own computer models, added to and modified the existing construction of the

craft, and gained important flow characteristics of the glider through computer analysis.

3. Background

3.1 Introduction

Autonomous underwater vehicles (AUV) are computer controlled machines that can be

programmed to perform various underwater missions. Currently, they are being used for

oceanographic, military, and commercial purposes. They range in size from a few feet to several

yards. Their missions vary from recording the bathymetry of water basins, to searching for

mines in the path of naval submarines.

3.2 Powered AUV

Powered AUV rely solely on thrusters to move about. They are short range vehicles, but

very maneuverable and can get from point to point quickly. They are usually required to

complete rigorous tasks over a short time span. The CETUS (Composite Endoskeleton Testbed

Untethered Underwater Vehicle System) for example, is a prototype created by MIT to detect

underwater mines [1]. It only has a range for 20 to 40 km, but is capable of moving at 5 knots

when needed.

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The titanium model of the CETUS is capable

of diving 4000 m. It uses brushless DC thrusters

powered by lead acid batteries. The hull is made

from a rotary molded, high impact plastic. The

CETUS has a curb weight of 100 kg, and weighs

150 kg when the various sensors are added.

Fig. 3.1 – MIT’s CETUS

Fig. 3.2 – MIT’s Xanthos

Another example of a powered AUV is

Xanthos [2]. This was also designed by MIT.

Its shape is more torpedo-like which results in

less drag. It has a range of 44 km and is capable

of 3 knots. It can reach 3000 m, and weighs 200

kg. It utilizes a drop weight system for recovery.

3.3 AUV Gliders

AUV Gliders do not need thrusters to move about. They are long range, but move very

slowly. All though the method employed may differ, they all move by changing their buoyancy.

In this way they are able to seesaw forward. Pelagia is a Slocum-glass glider developed by

Webb Research Corporation [3]. Unlike powered AUV, Pelagia can go for hours without

resurfacing.

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Pelagia is able to travel between 4 and 24 hours

before resurfacing to communicate via antenna [4].

It has a 1000 km range, and can dive to 200 m. It is

meant to go on month long missions, but at a very

slow pace (about 0.4 m/s). Pelagia weighs a mere 54

kg, but it is not meant to carry many instruments.

The true downside of any AUV glider is the

limitation of payload size.

Fig. 3.3 – Webb’s Pelagia

Fig. 3.4 – Scripps’ Spray

Spray is a very long range glider

designed by Scripps Institute of

Oceanography [5]. It has a 6,000 km

range. It moves at .5 mph and can reach a

depth of 1000m. It weighs 112 lb and yet

can only carry a payload of no more than

4-5 pounds. Like the Pelagia, this

contributes to its limited abilities as a

research tool.

3.4 2006 AUV Glider, Florida Tech

The powered AUV glider project began here at Florida Tech as a 2006 design team

project headed by a student, Todd Allen, under the supervision of his academic advisor Dr.

Stephen Wood. The 2006 team made great strides in the project, providing our team with a great

base upon which to build off of. The vehicle would consist of a main foil, attached between a

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frame made of aluminum beams, and be powered by two main thrusters. Although most of the

parts and design concept have been maintained, our team decided that it would be in the best

interest of the project to make a few revisions to the vehicle and its control surfaces in order to

enhance the maneuverability and structural integrity when launched, navigated, and recovered

from the ocean or any other service location. [6]

Fig. 3.5: Revision Points Fig. 3.6: Previous Control Surfaces and Servos

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4. Product Design

4.1 Technical Specifications

VEHICLE

HEIGHT (in.) 20

LOA (in.) 78.5

WIDTH (in.) 62

WEIGHT, DRY (lbs )

*Varying Payloads

650 – 750*

Table 4.1: Dimensional Specifications

MAIN FOIL

LENGTH (in.) 43.5

WIDTH (in.) 54

MATERIAL FIBERGLASS/EXPOXY

COMPOSITE, SYNTACTIC

FOAM CORE

Table 4.2: Main Foil Specifications

PROPULSION

MAIN THRUSTERS (MINN KOTA BRAND) 55 LB. THRUST

11.0625 INCH PROPELLER

PRESSURE COMPENSATED

BOW THRUSTERS DC BRUSHLESS MOTOR, 4 INCH PROPELLER

KORT NOZZLE (MAIN TH RUSTER) MARIN’S Nozzle No. 37

Table 4.3: Propulsion Specifications

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4.2 Part Decomposition

4.2.1 Main Structures Construction

Fig 4.1 Finished Vehicle Concept Design

4.2.1.1 Main Foil

The main foil was constructed by the previous team. It is made out of fiberglass and

houses the glass spheres and syntactic foam. The glass spheres are rated to a depth of 6700

meters, and the syntactic foam is rated to a depth of 4000 meters. The main foil also has an L-

beam glassed into the bottom foil for lateral support between the beams.

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Fig 4. 2 Bottom of Shell Mounted to Frame

The syntactic foam inside of the main foil is a high density foam made out of small glass

particles suspended in a high density resin. The foam is capable of going to depths of up to 4000

meters, and has a density of 38 lb/ft³. The foam in the main foil is composed of 6 main pieces,

three on top and three on bottom. There is a funnel down the middle for future sample analysis

and photography, and there are fittings in the four outside blocks to fit the glass spheres. There

are also foam blocks inside of the aluminum beams, for further buoyancy.

The only modification that we had to make to the main foil was trimming the foam

blocks. There were two main problems with the foam blocks when we started the project. The

first was an incorrect alignment of the cutouts for the glass spheres. When the blocks were

originally cut, the top housings were about two inches out of alignment with the bottom

housings. This problem was remedied by shifting the housings to meet in the middle. This was

done on the CNC machine, and had an ultimate beneficial side effect in that it gave clearance for

the input/output plugs on the glass spheres. The second main problem was that the foam blocks

did not fit properly inside of the fiberglass shells. This problem was remedied by significant

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sanding of the blocks, along with an aluminum strip that fills the approximately 1 inch gap

between the top and bottom shells.

Fig 4. 3 Main Shell with Extensions Connected

4.2.1.2 Foil Extension

When we inherited this project, we noticed two zones of very high drag at the front of the

glider. The two main aluminum spars that the main foil was mounted to were also mounting

points for two relatively obtrusive specimen collection devices. They were also completely flat

at their leading edge, a design that went against the whole streamline flow idea of a highly

efficient glider. To fix this minor design flaw, we created detachable foil extensions. The

extensions have the same profile as the main foil, and extend over the specimen collection

devices. They are not sealed so as not to be an issue with pressure, but they eliminate the

previous points of high drag at the outside leading edges of the glider. They also have

indentations for the streamline accommodation of the recovery system handles, another

component of the glider that will be discussed further later in the report.

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Fig 4. 4 Foil Extension Trimmed and Painted

The extensions were constructed out of fiberglass, using the same molds that were used

for the main foil. They were constructed in four pieces, a top and bottom for each side of the

glider. Because the extensions only needed to be as wide as the 4 inch aluminum spars, they

were made to be 5 inches wide from the sides of the molds to ensure uniform glassing of the

inside edges of the extensions. To accommodate the integration of the handles in the streamline

construction, “plants” were installed onto the bare mold. The “plants” were constructed to be the

same size/shape as the part of the handle that would be attached and then secured to the mold

before finishing layers of aluminum foil

A layer of aluminum foil was then applied to the mold and a petroleum based mold

release (like car wax, but better) as the last layer. The mold release was applied 5 times over, as

to ensure a smooth release of the finished glass. Strips of 6 oz. fiberglass cloth were then cut and

the extensions were glassed using epoxy resin. Ultimately, 6 layers of cloth were used, with two

layers at a 45 degree angle to the other two layers. After the extensions had cured, they were

“popped” from the mold carefully and trimmed to the appropriate width and each top was grafted

to its respective bottom.

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To join the two pieces together, more 6oz. cloth was used in conjunction with an e-glass

matting. The e-glass matting was a 12 oz. cross weave cloth, consisting of multiple layers of

glass with a matting of meshed glass strands on the back. The layers consisted of a 2-inch strip

of 6oz. cloth, then a layer of matting, 3 strips of 2-inch glass at 45 degrees, and finally an 8 inch

layer of the 6oz. cloth. This combination/formation ensured a very secure binding of the top and

bottom pieces, resulting in one solid extension piece.

Although not completed, the theoretical connection of the extension to the craft is

through the forward handles of the recovery system. That is why proper placement of the

“plants” on the mold becomes a critical part of construction. It is suggested that if further

manufacturing were to take place, then a single mold should be created to form one solid

extension rather than two pieces that must be grafted together. This would ensure uniformity and

a solid structure.

***Note on Fiberglass Manufacturing: It is of greater ease to apply the resin to the cloth prior to

placing it in the mold. Extra resin can be placed into the cloth after application, but when

glassing around intricate structures such as “plants”, this method works best.

4.2.1.3 Glass Spheres

The glass spheres are the pressure resistant housings for the onboard instrumentation of

the glider. Currently, for preliminary testing purposes, they will be housing the receiver, receiver

battery, and speed controllers for the remote control system. Ultimately, they will house the

onboard computer systems and control boards.

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Fig 4. 5 Half of Glass Sphere with Cable Attached

The glass spheres are manufactured by different companies but each have an outside

diameter of 17 inches. They each have pressure release valves for opening them after they have

been pressurized, as well as multiple I/O ports. The first sphere is made by Benthos Inc. and is

model number 2040-17H. It weighs 39 lbs. and has been tested at depths up to 6700 meters, and

has two I/O ports. The second sphere is made by Victrovex and is the 17”/14 (standard) model.

It weighs 38.14 lbs and has also been tested at depths up to 6700 meters. The Victrovex sphere

has 3 I/O ports.

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4.2.1.4 Aluminum Frame

The aluminum frame on the glider is made up of two very strong aluminum beams. The

beams are ¼” thick and 4” square on the outside. Their main purpose is to serve as a strong

mounting point for almost all of the major components on the glider. Each beam is split into two

sections to make mounting the components easier and to make transporting the craft easier. The

front sections, on which the main foil is mounted, measure 43 inches in length. The rear

sections, on which the thrusters, kort nozzles, and rear foils are mounted, measure 32 inches in

length. Each beam is also filled with blocks of syntactic foam to add to the overall buoyancy of

the glider.

Fig 4. 6 Aluminum Beam

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Fig 4. 7 Polishing Rear Beam

4.2.2 Rear Control Surfaces

4.2.2.1 Rear Foil

The rear foil that we created serves two main purposes. First, it provides directional

control through the use of dual action flaps, and second, it provides a much needed lateral

support in the rear of the glider through an L-beam that runs the width of the foil. The foil, as it

is constructed now, is meant to be temporary in the sense that it cannot withstand the same

pressure as the rest of the craft. This is due to the use of a different foam than in the main foil,

which has the syntactic foam that is rated to a depth of 4000 meters. It will be able to go at least

30 meters in depth and will allow actual underwater performance testing of the glider. It will

also serve as a prototype design that can be easily swapped out for a foil of the same design but

of different materials that will be able to reach the targeted depths.

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Fig. 4.8 Rear Foil Mounted

The foil consists of a fiberglass shell surrounding a skeleton of 1/8 inch thick aluminum

ribs mounted to a 1 inch by 1/8 inch thick aluminum L-beam. The L-beam is welded to two

outside plates, also of 1/8 inch thick aluminum, which will serve as the mounting points of the

foil onto the main spars of the glider. The servos are secured onto the two inner aluminum ribs,

and they control the two flaps. The shafts that the flaps are mounted to are made of layered PVC

pipe and aluminum pipe, and are filled with the same foam that fills the rest of the foil.

The foam is a two part pourable urethane resin that expands to almost 4 times its original,

liquid volume. The foam adds buoyancy to the foil, provides extra rigidity, and allows the foil to

withstand higher compressive pressure forces. The foam was chosen for this particular

application because it will conform to the shape of the foil, has moderate pressure resistance, and

is relatively inexpensive.

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Fig.4.9 Rear Aileron

The construction of the foil started with the machining of a mold using modeling foam.

The mold would allow us to form the fiberglass into the foil profile that we wanted. The foil was

done in two halves, an upper and a lower, each from the same mold. The foil is just a generic

profile that was created on Pro Engineer and transferred to the CNC machine. After the mold

was completed, we covered it with aluminum tape to seal it and give it a smooth surface. We

then put down a layer of regular aluminum foil so that the fiberglass shell would not stick to the

mold. We used a petroleum based mold release wax on the aluminum foil so it could be easily

pealed from the final shell.

Once the mold was prepped, we cut pieces of fiberglass cloth for the shell halves. We

used a 7.5 oz cloth for the bottom half and a 6 oz cloth for the upper half. Each shell half was

made using 6 layers of cloth: 4 straight and 2 at a 45 degree angle. After glassing each foil half

with epoxy resin, the edges were trimmed so that the halves fit flush against each other.

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The next step was to weld the outside mounting plates to the L-beam. Once that was

completed, it was mounted to the bottom shell at the point of maximum thickness on the foil

profile, approximately 1/3 of the length back from the leading edge. The mounting was done by

first creating a bed of resin and cloth strips for the L-beam to rest on, and glassing strips of

fiberglass over the top of the beam. The beam and foil were then clamped together and left to

cure.

After the L-beam was mounted to the bottom shell, the 4 aluminum ribs were mounted in

place. The ribs served as a mounting point for the flaps. They were glued in using Gorilla Glue

and clamped tightly into place.

Once the inside framework was assembled, the two halves were fiberglassed together

using three layers each at the leading and trailing edge of the foil. Once cured, the flaps were cut

out as well as a hatch on the top of the foil to access the servos.

There are two flaps on the rear foil that serve the purpose of ailerons and elevators at the

same time through a simple mixing function on the controller. They are each 21 inches by 5

inches. Their construction consisted of cutting them out of the foil and mounting them onto the

shafts that were connected to the servos. They were mounted using roofing nails and Gorilla

Glue. Roofing nails were used because they have a very flat top, which allowed a very flush and

aerodynamic fit against the flap. Once the fiberglass flaps were mounted to the shafts, some

trimming of the flaps and their housings on the main foil was necessary to allow for adequate

control throw. The flaps were then filled with the pour foam and mounted.

After the basic construction of the rear foil was completed and the flaps were tested to

ensure proper functioning, the foil was painted to match the computer generated model. It was

mounted to the rear aluminum beam sections using two 6” by ½” bolts and two 5.5” by 3/8”

bolts. The ½” bolts screw into the rear foil at the point of maximum thickness on the foil profile,

and the 3/8” bolts screw into the rear foil four inches behind that. Each bolt goes through both

vertical walls of its adjacent aluminum beam, with a cap nut on each bolt on the outside of the

beam.

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As previously stated, the flaps function as elevators and ailerons through a simple mixing

function on the controller. Each flap has just under 45 degrees of throw in each direction (up and

down) about its respective neutral setting. The servos are currently running off of a 6V 1100

mAh receiver battery, which is a larger capacity pack than the standard 4.8V 600 mAh pack.

The larger battery pack was chosen because of the high torque servos and long servo extensions

that run from the receiver (housed in the glass sphere) to the servos in the rear foil. The higher

voltage is necessary because the unusually long servo extensions used (~4’) inherently have

higher resistances than just the shorter stock servo leads, which causes a larger drop in voltage

between the receiver and the servos than if the servo leads were just plugged straight into the

receiver. The higher current rating of the new pack is necessary because the high torque servos

require more power than a standard servo, and because the voltage is constant in this case the

current must be raised to meet the higher power requirements (Power = Current*Voltage).

Everything on the rear foil is watertight and ready for underwater tests to ensure proper function

while submerged.

4.2.2.2 Main Thrusters

The main thrusters on the glider are two Minn Kota 55 lb thrust trolling motors. They

provide slow speed maneuverability as well as short range propulsion.

The trolling motors were made to fit the glider by cutting the graphite mounting shaft

about 10 inches away from the lower unit and cutting the wires that ran down the shaft.

Originally, there were three wires; one for power, one for ground, and one for throttle control.

The stock throttle control wire was disconnected so that just the power and ground (red and

black) wires remained, and the shaft was sealed off with epoxy resin.

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Fig. 4.10 Main Thruster

The thrusters are mounted to the aluminum beams via an aluminum shaft that has been

welded to the beams about 30 inches forward from the rear. The shafts (one on either side) are

welded to the inside wall of the beam and extend through the width of the beams to the outside

wall. They protrude 4 inches from the inside of the beam. They have an inner diameter that fits

flush with the graphite shafts of the trolling motors, so that the graphite shafts fit snugly inside of

the firmly mounted aluminum shafts. The two are then held together via a bolt in each mounting

shaft.

Other than trimming the mounting shafts of the thrusters, two significant changes had to

be made to their design and operation. The first modification was to make the thrusters more

pressure resistant. Stock, the lower units of the thrusters (the parts that we were using) were

sealed but filled with air, which is a very compressible fluid. Under normal design, any

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compressive forces experienced by the thrusters would act directly on their hard plastic casings.

To increase their resistance to pressure, the air (compressible) was replaced with mineral oil,

which is non-reactive and virtually incompressible when compared with air. A flexible vinyl

tube was also mounted to each thruster. Now, instead of the compressive pressure force acting

on the rigid casings, it works to compress the liquid, and any compression that does take place is

absorbed by the flexible tube.

Although the oil filled method is effective in increasing a sealed housing’s pressure

resistance, it still has its limits. It is therefore important to realize that the current construction of

the main thrusters, like the rear foil, is strictly temporary and for testing purposes only.

The second significant change that had to be made to the main thrusters was

modifying their throttle control mechanisms. Stock, the thrusters have a mechanical speed

controller. This however is very inefficient, gets very hot, and is too bulky. To control the

throttle, we opted for two DuraTrax Intellispeed 8T electronic speed controllers. The controllers

operate on 7.2-8.4 volts at a continuous 420 amps, and are rated to a maximum peak current of

1410 amps. They are also small enough to be easily mounted onboard.

4.2.2.3 Kort Nozzles

The Kort nozzles are another component that was designed but never manufactured.

They were designed based on the MARIN No.37 nozzle profile. This profile allows the

encompassed propeller to work approximately 50% more efficient in both forward and

reverse[7], perfect for our vehicle and the maneuverability that we want to build into it. They

would also serve as protection to the user from being subjected to exposed propeller blades when

handling the vehicle. A mesh or grating can be applied to the front and rear of the nozzle to

ensure no injury to fingers or limbs caught by the moving propeller.

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Fig.4.11 Kort Nozzle Design

The Nozzle itself will be made of syntactic foam, much like the rest of the vehicle. This

way they can not only provide buoyancy characteristics, but be quite strong as well. A layer of

fiberglass could be applied as a shell, or a simple epoxy marine grade paint could be used

alternatively.

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Fig.4.12 Nozzle Attached to Motor

The Nozzles would be attached to the Motor Housing via four lateral supports that are

clamped or welded to the housing itself. A clamped system would be preferred due to its

accessibility and a non-permanent structure that would have to be replaced if the motor housing

were damaged, or vis-a-versa. The supports would be made of aluminum, and would be ¼”

thick, and ¾” wide. They would each have an aluminum base that would match the diameter of

the motor housing, serving as a mounting point that can either be screwed to, or clamped around

the motor.

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4.2.2.4 Control Servos

The servos that control the flaps on the rear stabilizing foil needed to be modified for

underwater usage. In their original form, the servos are water resistant, but not properly sealed

for underwater operation. To seal the servos and make them more pressure resistant, they

needed to be completely filled with a nonconductive liquid (mineral oil) and sealed with some

type of adhesive or sealant at each seam. By replacing the air (compressible) with a liquid

(almost incompressible), the compressive load is taken off of the plastic casing for the servo and

applied to the liquid. To account for the slight compressibility of a liquid, a vinyl hose is

attached to the outside of the servo casing, allowing for slight compressibility without cracking

the rigid servo casings.

Fig.4.13 Mounted Rear Servos

24

Fig.4.14 Assembled Servo/Aileron

Before anything could be sealed or filled with mineral oil, the vinyl hose had to be

attached to the outside of the servo casing and the main shaft had to be greased with a sealing

lubricant. The first was done using pieces of vinyl hose 3 inches in length and ¾ inch in

diameter. To attach the hoses to the servo cases, we first drilled a ¼ inch hole in the bottom of

each servo and mounted the hoses with Marine Tex. We then plugged the end of the hose with a

standard brass plug. To seal the main servo shaft, “White Lightning” lithium grease was used.

To make sure that the grease would stand up to the mineral oil and not dissolve, it was left to

soak in a cup of the oil for several days. Once convinced that it would seal the shaft properly, it

was applied to the shaft itself, the outlet on the top casing, and the rubber O-ring that would be

mounted between the servo horn and the upper casing to further seal the servo. The servos were

then ready to be filled with mineral oil.

25

Two methods were used for the servo modifications. After trying the first method on one

servo and encountering several tedious obstacles, a second method was used for the second

servo. The first method consisted of disassembling the servo into its four main parts (bottom

casing, main body, top casing and servo horn) and reassembling the parts while they were fully

submerged in a tub of mineral oil. Theoretically, assembling in the oil would get rid of all the air

bubbles, which in turn would make the oil as efficient as possible in absorbing all of the

compressive forces. The idea was to assemble in the oil, take out the finished servo, wipe the

casing with acetone, and seal the joints with some type of adhesive. However, once assembled

and removed from the mineral oil, the “water resistant” seals proved to be just that, slowly

leaking oil and making it nearly impossible to remove enough oil from the surface to get the

sealant (super glue) to adhere to the servo casing. After finally sealing the servo, about half of

the oil content was lost.

Knowing that the ideal was not possible, we devised a method that would at least seal the

servo and still give us a little more compressibility than a regular servo. First, the plugs were

removed from the ends of the vinyl hoses. We then assembled the second servo (the first was

already assembled) and proceeded to seal each servo with a generous amount of Marine Tex,

making sure that every joint was as watertight as possible. With each servo sealed, we then used

a turkey baster to fill the servos with oil through the open end of the hoses. The turkey baster,

along with the flexible hoses, allowed us to get rid of most of the air bubbles, as we were able to

make a temporary seal of the hose around the baster and actually mildly pressurize the servo as

we were filling it. After the servos were filled, we used brass caps and more marine tex to seal

them completely.

After several days, we noticed that there was a slow leak of mineral oil out of the servos

where the three wires exited the case. We cleaned the problem spots as best we could and

applied a generous portion of epoxy resin, which worked its way in between the wires better than

the Marine Tex could and gave us our final seal.

26

The final product turned out to be less than ideal, but it is still watertight and will allow

us to at least perform some shallow water testing. The process also pointed out some methods to

be avoided, such as assembling servos in a tub of mineral oil. In the future, for more permanent

applications, it would be much better to manufacture a servo box with two ports, one for the

shaft and one for the three wires. The box itself could be made much stronger than the actual

servo casing, absorbing the brunt of the extreme compressive forces experienced while

underwater.

4.2.3 Recovery System

The recovery system is very important in that it makes deployment possible. It provides

strong lifting points at each of the four corners of the glider for easy and safe lifting of the craft.

Having a four point connection system allows for secure lifting while on a boat/ship that may be

rocking and pitching in rough seas. In most cases, the glider will probably be launched by means

of a crane or lifting arm over the side or stern of a large vessel. The current design was chosen

because of ease of attachment and stability. The large area that the handles afford will create a

larger target area for any hook device that will have to be attached via crane operator/deckhand.

Fig.4.15 Milled Front/Rear Recovery Handles

27

Fig.4.16 Front Handles Holding Foil Extensions

The recovery system is very important in that it makes deployment possible. It provides

strong lifting points at each of the four corners of the glider for easy and safe lifting of the craft.

Having a four point connection system allows for secure lifting while on a boat/ship that may be

rocking and pitching in rough seas. In most cases, the glider will probably be launched by means

of a crane or lifting arm over the side or stern of a large vessel. The current design was chosen

because of ease of attachment and stability. The large area that the handles afford will create a

greater target area for any hook device that will have to be attached via crane operator/deckhand.

28

The recovery system consists of four large aluminum handles, one placed at each corner

of the glider. The front two handles were CNC machined out of 5/8” thick 6061 T6 aluminum

plating, while the rear two handles were machined out of 3/8” thick 6061 T6 aluminum plating.

6061-T6 aluminum has tensile strength and corrosion-resistance properties that allowed for

construction of pieces that are light-weight but strong, and capable of standing up to the harsh

environment of the ocean[8]. The handles are mounted to the frame rails by 3/8” countersunk

cap screws and secured with 5/8” square nuts that are slotted into the interior foam block on the

inside of the beam. The forward handles also create a location at which the foil extensions can be

attached to the craft.

4.2.4 Bow Thrusters

We have made plans to install bow thrusters at the front of each main aluminum beam.

This was an initial design concept brought forth by last year’s design team, but now a practical

solution has been found. The thrusters would be mounted inside of the foil extensions to keep

the both the motors from being damaged along with keeping the vehicle as efficiently

hydrodynamic, with cutouts for their operational flow. Bow thrusters would allow for greater

slow speed maneuverability as well as give the glider landing capabilities. If the glider were to

land, it would be very hard if not impossible for the rear thrusters to push the vehicle out of the

sand or other substance encountered. With these forward thrusters, the bow would lift and allow

a proper pitch at which the main thrusters propel the vehicle off of the ground.

29

Fig.4.17 Bow Thruster/Bracket Assembly

Fig.4.18 Bow Thruster Mounted to Vehicle

30

Ideally, the thruster motors will be of the DC-Brushless variety to operate in such aquatic

environments. They will be mounted to an aluminum bracket that is then welded or fastened to

the aluminum frame on each side of the vehicle. The location of the thruster on the bracket will

play an important part in how efficient it is. If it is too far a stern, there will be too much of a

moment for the thruster to lift, so being as far forward as possible is ideal. A propeller that

creates as much force as possible will also be an important part of the design. It must be small

but powerful as to be contained within the restricted area inside of the extension.

4.2.5 Electronics

Due to the underwater environment in which the AUV will be operating, certain

accommodations had to be made to some electronic components, mainly the servos. Because the

remote control system that we are using for our preliminary testing is merely temporary, its

components do not need to be able to withstand the extremely high hydrostatic pressure forces

that the AUV will ultimately be experiencing. For our preliminary tests, we are not planning on

traveling deeper than about 3 meters, so the main goals for the temporary control system

components, particularly the servos, are to make them watertight and marginally pressure

resistant. The rest of the control system components will be mounted inside of the glass spheres.

4.2.5.1 Remote Control System

Using a temporary remote control system allowed us to focus our time and budget on

more important aspects of the glider. The system that we chose consists of a Tower Hobbies 6

channel transmitter, 6 channel receiver, two Hitec high torque servos, and two DuraTrax

Intellispeed 8T electronic speed controllers. Although we are currently only running a 3 channel

system (elevator, aileron, main thrusters), the 6 channel system was chosen for possible future

testing of bow thrusters, specimen collection devices, and individually controlled main thrusters.

31

Fig.4.19 Radio Control System for Testing

Other than the servos, all of the onboard components will be mounted inside the glass

spheres to protect them from the water and pressure. The vehicle will be powered via a tether to

the surface, eliminating the need for batteries that are capable of being submerged for this short

amount of time. The antenna will be a wire connected to a float, much like a fishing bobbin, that

is on the surface of the water. This will allow for transmission of functions given through the

radio controller that will be in the hands of the user on the surface.

32

3. Testing and Analysis

5.1 Fluid Mechanics Testing

One of the most important parts in designing a submersible is fluid mechanics testing.

The idea is to get some idea of the forces the submersible will be exposed to while operating in

the environment it was designed for. This way the submersible can be made to withstand these

forces.

There are two ways to test the fluid mechanics forces on an object immersed in a fluid.

One way is to perform similitude tests, and the other is to run computer generated simulations.

For our AUV glider, similitude tests meant creating a scaled model and seeing how it acts in a

wind tunnel. The wind tunnel must have a free stream Reynolds number equal to that which the

glider would be exposed to in the water. In our case, this meant having a wind tunnel which

could run at 150 mph to 300 mph. Unfortunately, we did not have a wind tunnel this powerful at

our disposal. So, we were left with computer simulations.

Computational Fluid Dynamics (CFD) is the process through which computer

simulations are preformed for fluid mechanics testing. CFD uses the initial properties of a fluid

in motion and the geometry that the fluid moves through to solve for the fluid mechanic and even

thermodynamic properties of that fluid at various points within that geometry. It does this by

using by dividing the geometry into discrete cells – a process called meshing – and finds an

approximate solution to the governing fluid mechanic equations at each cell. Figure 5.1.1 is an

example of a meshed grid. In our case, we are mainly interested in the lift and drag of the fluid

on the foils of the AUV. With this information is required for calculating things such as the

thrust required by the motors, the range of the glider, the glide ratio, and maneuverability of the

AUV.

33

Fig.5.1 “C” Grid Mesh

Three programs were used for the CFD calculations on our glider: ProEngineer,

GAMBIT, and Fluent. ProEngineer is the 3D modeling program used to create many of the

pictures illustrated in this report. After making a model of what needs to be examined an IGS

file is created and imported to GAMBIT which creates the geometry and mesh which will be

analyzed with the CFD program.

34

Figure 5.1.1 is an example of a mesh ready to undergo CFD calculations. The outside

edge of the mesh represents an area where the fluid flow is not affected by the foil. At this point

the fluid would still be in free stream conditions. The inside curve represents the object under

examination, in this case the main foil of the AUV. Geometry is a large factor in how accurate

the CFD program will be able to calculate the properties of the fluid. In a good mesh the

individual cells can be different sizes and shape, but there should be a sense of continuity

between adjacent cells. Also, along the foil the cells would ideally be nearly normal to its

surface.

There are a few things that influence how precise the CFD solutions will be. One of them

is the number of cells in the mesh. However, the more cells one puts in the mesh the longer it

will take for the solutions to be processed. So, a good mesh will have larger cells near the

outside boundary where the foil will not have a large affect on the fluid flow, but much smaller

and compact cells near the foil. Figure 5.1.2 is a mesh of a different geometry. Like the

previous mesh, the cells are large near the outside boundary and gradually become much smaller

as they approach the foil.

Fig.5.2 Standard Mesh Grid for Airfoils

35

Finally, conditions are defined at the boundaries of the mesh. In figure 5.1.2, the curved,

top, and bottom boundaries are defined as a velocity inlet. So, the CFD program will ask for the

speed and direction of the flow at this boundary. The right boundary is defined as a pressure

outlet. Finally, the foil in the middle is defined as a wall, which makes the CFD program apply

the no slip condition. Boundaries in GAMBIT can be defined in several other ways, and can

even be time dependent. It can also do three dimensional geometries and meshes. However, for

our 2D steady flow calculations these three boundary types are suffice.

After this is done the mesh is complete it is exported to Fluent which does all the CFD

calculations. Since these calculations can take a long time to process, fluent allows you to

choose from a number of different solvers. The solvers are different forms of the governing

equations, some more powerful but more complex than others. If for instance the flow is known

to be laminar, it can be defined as such which will cut down on the time it takes for the program

to reach an accurate solution. In our case, we have a turbulent flow regime. Many more factors

can be included into Fluent such as heat exchange, radiation, mixed fluid, and multiple phases of

a fluid.

After all the significant properties of the fluid are defined the program can begin to

process the information. CFD programs us iteration to solve for values to the various flow

properties at different points within the defined boundary. This means it tests different values to

enter into the governing equations and attempts to get the answers to converge to some point. In

a two dimensional analysis at the very least Fluent will check to make sure that continuity, the x

velocity, and y velocity are converging. Fluent can be set up to plot the residuals of these values

which a measure of the difference in answers with each iteration. Figure 5.1.3 shows an

illustration of these plots. More variables will appear on the plots depending on what solvers

were chosen for the calculations.

36

Fig.5.3 Residuals for Turbulent Flow

After the residuals reach a level of convergence defined by the user fluent can map the

values of many different properties within the boundaries of the calculations. For example,

figure 5.1.4 is a contour map of the pressure distribution around the rear foil of our AUV. It can

also be used to make graphs of the value of a property along the defined walls, and vector maps

such as figure 5.1.5. Finally, fluent can calculate the net forces acting along a wall (in our case

the airfoil) in different directions.

37

Fig.5.4 Pressure Distribution Around Rear Foil

Fig.5.5 Vector Map of Fluid Velocity Near Rear Foil

38

The meshes are complete for our AUV, and we have started getting data on the main and

rear foil. We still have to perform test with the free stream velocity set at different magnitudes

and angles. After this we have to perform some calculations to see what the data means in terms

of range, power requirement, maneuverability, stability, and glide ratio of our AUV. These

calculations are not just important for our glider, but for future versions of the AUV glider.

Below is a summary of the preliminary results we have for our main and rear foil. This is the net

force is the horizontal and vertical direction when there is a 2 m/s flow of water at a 0° angle of

attack. This is the force per unit length (meter) of the specified cross section. (NOTE: the net

vertical force for the rear foil at 0° appears greater than zero due to the mesh made for the gap

between the frame and the flaps. However, this is a relatively small force given the size of the

flap and the speed of the water moving across it.)

Member Orientation Net Horizontal

Force

Net Vertical

Force

Main Foil N/A 18.3N 0N

Rear Foil

Frame N/A 14.18N 0N

Rear Foil 0° 97.36N 8.97N

30° 277.50N 883.49N

60° 566.26N 1050.72N

Table.5.1: Net Force on Foils

39

5.2 Material Testing

Our AUV is being designed with the intent to reach depths of 4000 m. At such depths

there will be a tremendous amount of pressure on the glider. Even though our prototype is not

expected to reach this limit, we must determine how the material we are using will respond to

these compressive forces. Specifically, we want to know how our fiberglass composite will

handle these pressures; it is known that the glass ball housing and structural foam can handle

such depths.

We can use a universal tester to determine ultimate strength of our composite. The

universal tester on our campus can reach loads of 60,000 lb. However, the load cells available

will only function up to 30,000 lb; normally a 10,000 lb load cell is used. A load cell is a device

that converts strain into electrical signals, which is how a computer reads the force universal

tester is exerting.

For our test we would take small samples of the fiberglass composites we made, and put

them in the universal tester under compression until they fail. Failure would probably be in the

form of a crack in the fiberglass. If this happens in the environment that the AUV is designed to

operate it might meant parts of the shell for the main and rear foil breaking off. The glider would

probably still be able to function, but it would create more drag, and one crack may cause more

cracks to form. This test will have to be done by the next team that will work on completing the

AUV.

40

4. Safety Risks and Hazards

During the manufacturing process of this project, we had to take certain safety

precautions on several occasions. We dealt with heavy machinery and hazardous materials on

several occasions.

Several components of the AUV were machined on the CNC machine and the bandsaw.

For these two machines, eye protection was worn at all times. The CNC was used for the cutting

of the blue modeling foam blocks for the mold of the rear foil, the re-cutting of the syntactic

foam blocks, and the cutting of the recovery system handles. For each of these pieces there was

a possibility of loose debris getting thrown around, so eye protection was worn at all times.

We also had to do a considerable amount of sanding of the 6 syntactic foam blocks to

make them fit into the main foil shell. When sanded, the blocks gave off a very fine, abrasive

dust (glass particles) that would have been hazardous to our health if inhaled. For the sanding of

the syntactic foam blocks, we respirators with organic filters for extra protection.

When working with the blue modeling foam, it was also necessary to wear the organic

filters because of possible gases the foam could have given off. We wore the filters when the

foam was being cut by the CNC.

We also used the organic filters when we fiber-glassed the rear foil and the foil

extensions. Because the epoxy we were using gave off considerable fumes, we used the masks

and made sure the work areas were properly ventilated. We also wore latex gloves so as not to

get any resin on our skin.

The last material that we had to be cautious about was the urethane pour foam that we

used for the rear foil. The foam was mixed as a two part resin which when combined, began to

expand and give off toxic gases. For this process, we used latex gloves and the organic filters

and worked in a well ventilated area.

41

5. Conclusion

Our main goal of providing a strong foundation for future teams to build on was

accomplished in many ways, but there is still much that can be done. The parts of the project

that were effectively completed were:

• creating functional foil extensions

• creating a strong and practical recovery system

• creating a structurally strong and functional rear foil

• designing an optimally efficient main kort nozzle

• obtaining useful flow characteristics of the foils used (main and rear)

There is still much work to be done, including improvements on the parts we created.

For instance, the surfaces of the foil extensions and the rear foil are unfinished and need to be

smoothed to increase flow efficiency, and the kort nozzles still need to be constructed. But, as

stated in the introduction, we knew that the project was not going to be completed upon our

teams ending.

We would like to have tested the glider in a pool or shallow water environment to test the

functionality of the rear foil and the effectiveness of the recovery system handles, along with the

general response of all of the individual parts of the glider to water submersion, but we ran out of

time. One main obstacle that we faced was the lack of a crane or similar structure for

deployment. As the glider sits, it is almost ready for its initial submersion. Assuming a capable

deployment method is devised, all that would need to be completed for an initial submersion test

is:

• Proper fitting of the glass spheres

• Wiring of the main thrusters and servos to the receiver and power source located in the

glass spheres

42

• Supplying of a power source, be it onboard batteries or external power tether, to power

the main thrusters

• Proper securing of the syntactic foam blocks and upper main foil shell to the glider

body (lower main foil shell/aluminum beams)

6. References

[1] MIT Sea Grant College Program, “AUV Laboratory at MIT Sea Grant: CETUS,” 2007. <http://auvlab.mit.edu/vehicles/vehiclespecCETUS.html>

[2] MIT Sea Grant College Program, “AUV Laboratory at MIT Sea Grant: CETUS,” 2007. <http://auvlab.mit.edu/vehicles/vehiclespec2x.html>

[3] University of North Carolina Wilmington, “NURC’s Autonomous Underwater Vehicles,” 2007. <http://www.uncw.edu/nurc/auv/pelagia/>

[4] University of North Carolina Wilmington, “NURC/SEGM CAPABILITIES: Webb Slocum Glider AUV,” 2007. <www.uncw.edu/nurc/auv/glider/glider_one_pager.pdf>

[5] SCRIPPS Institute of Oceanography, “Underwater Robot Makes History Crossing Gulf Stream,” 2006. <http://scrippsnews.ucsd.edu/Releases/?releaseID=655>

[6] “Autonomous Underwater Vehicle: Powered Glider,” Senior Design Project, Internal Florida Tech Document, 2006.

[7] E. V. Lewis, Ed., Principles of Naval Architecture. Jersey City: Society of Naval Architects And Marine Engineers, c1988-c1989, 3v., pp 217-220

[8] M. S. Mamlouk and J. P. Zaniewski, Materials for Civil and Construction Engineers. Upper Saddle River: Pearson Education Inc., 2006, pp. 142-145

43

Appendix A

Donors

Vectorworks Marine, Inc – Titusville, Florida (321) 269-8444

General Plastics Manufacturing Co. – Tacoma, Washington (253) 473-5000

Syntech Technology Inc. - Pavilion, New York (485) 768-2513

Arcom – A Member of Eurotech Group – Overland Park, Kansas (888) 947-2224

44

Appendix B

Budget for Spring ‘07

Date Vendor Part # Description QTY Unit Price Total

4/25 Metal Express a1p.625 5/8 6061-t651 Aluminum Plate 2 $51.32 $102.64 L = 14" W = 8"

a1p.375 3/8 6061-t651 Aluminum Plate 2 $20.67 $41.34 L = 8" W = 8"

4/25 McMaster Carr 90585A628 3/8"-16 SS Flat Sockethead capscrew 16 $2.04 $32.64 L = 1-1/2" Shipping 1 $4.75 $4.75

4/25 Tower Hobbies Charge Leads Hitec/AirZ 1 $8.99 $8.99 Hobbico Multi-Charger 1 $29.99 $29.99 Shipping 1 $8.99 $8.99

4/10 Tower Hobbies LC705248 6 - Channel Radio 1 $119.99 $119.99 LC7509 Hobbico HD Switch 1 $10.99 $10.99 LC7624 Hitec 12" HD Ext. 2 $10.99 $21.98 LC7625 Hitec 24" HD Ext. 8 $9.69 $77.52 LC7626 Hitec 36" HD Ext. 6 $10.59 $63.54 LC7633 Hitec 6" Y Harness 3 $7.59 $22.77 LC7694 Sanyo 6V 1100mAH 1 $22.99 $22.99

Shipping 1 $8.99 $8.99 Promotional Discount 1 -$30.00 -$30.00

4/12 Joann Fabric 8596959 Lint Roller Twin Pac 1 $7.99 $7.99 3005980 Black Alpine Solids 8 $3.99 $31.92

Tax 1 $2.39 $2.39

4/25 Teledyne Benthos B-204-86 204-VPT: Ti Vacuum Port 1 $172.00 $172.00

PC/104/IDE Peripheral Module 1 $135.00 $135.00

Miscellaneous Fasteners 1 $14.60 $14.60

Total $912.01

45

Appendix C

Budget for Summer ‘07

Date Vendor Part # Description QTY Unit Price Total

5/15 Home Depot 2.8878E+10 Hi-Performance Masonry Blade 1 $17.47 $17.47 Subtotal $17.47

5/17 Fiberglass Florida 3RE7512 Qt. Vinyl Ester Resin 1 $16.79 $16.79

8MEKP 2oz. MEKP Catalyst 1 $2.75 $2.75 7TR102 14oz. TR-102 Regular Paste Wax 1 $11.64 $11.64

E5220E 1/2" x 3" Aluminum Economy Roller 1 $5.44 $5.44

Subtotal $36.62

5/22 Home Depot Angle Aluminum Beam 1 $20.48 $20.48 Contact Cement 1 $6.47 $6.47 2" Foam Brush 1 $0.56 $0.56 1/2" 2x4 Plywood 1 $9.33 $9.33

Subtotal $36.84

5/22 Home Depot Gorilla Glue 1 $12.97 $12.97 Subtotal $12.97

5/23 Plastic Depots SBP-374 A&B Urethane Pour Foam 10lns 1 $36.00 $36.00

Shipping 1 $7.21 $7.21 Subtotal $43.21

5/29 Ace Hardware 87211 White Lithium Grease 1.25oz 1 $2.29 $2.29 13273 Plastic Dip 14.5oz Red 1 $9.49 $9.49 56 Fasteners (O-Rings) 3 $0.49 $1.47 94 Vinyl Tube 1 $0.29 $0.29 41207 Flared Cap 3/8" Brass 2 $2.29 $4.58 56 Fasteners 1 $0.49 $0.49 10238 Glue Super All Purpose 2GM 1 $1.29 $1.29

Subtotal $16.63

5/30 Tower Hobbies DTXM1075 DuraTrax IntelliSpeed 8T Rcing Rev ESC 2 $74.99 $149.98 Promotional Discount 1 -$25.00 -$25.00 Shipping 1 $3.99 $3.99

Subtotal $128.97

6/1 Fiberglass Florida 7.5oz. Cloth (yds) 6 $5.83 $34.98

46

6/20 Fiberglass Florida 1CY630/11+ CUT YDG(11+) 60Z-30" FABRIC 25 $3.63 $90.75

13PLMU1PT 1PT MULTI-MEASURE MIXING CONT. 6 $0.50 $3.00

10-K-SMALLS EA. 4" SMALL SPREADER 1 $0.29 $0.29 10-K-LARGES EA. 6" LARGE SPREADER 1 $0.47 $0.47

Subtotal $94.51

7/1 McMaster-Carr 94855-A278 Machine Screw Square Nut 1pk $5.50 $5.50 Zinc-Plated Stl, 3/8"-16, 5/8"H,1/4"W 50ea/pk

Shipping $4.75 Subtotal $10.25

7/3 Online Metals.Com 4358 Aluminum 6061 T6 Bare Tube 1 $21.90 $21.90

1.375" x 0.125" x 1.125" x 36" Shipping $8.34 SubTotal $30.24

7/9 Ace Hardware 43771 PVC Pipe 1.25" x 10' 3 $0.75 $2.25 5118534 Aluminum Tube 1 $10.99 $10.99 44877 PVC Pipe 1.00" x 10' 4 $0.60 $2.40

SubTotal $15.64

7/16 Ace Hardware Lock Nut 2 $1.30 $2.60 Hinge 1 $3.29 $3.29 Spray paint 1 $3.49 $3.49

Subtotal $9.38

Total $490.98

47

Appendix D

Gantt Chart

48

49

50

51