1998 – 99 NCDA
Final Design Report
Team 1:
Hovercraft
May 11, 1999
Brandon Fichera
B. Sean Gallagher
Gregory Pease
David Rabeno
Sponsor: Dr. Stephanie Wright
Delaware Aerospace Academy
Advisor:
Dr. Michael Keefe
Table of Contents
Pg. #
I.
SUMMARY
2
II.
INTRODUCTION
3
III.
CUSTOMERS/WANTS/CONSTRAINTS
4
IV.
BENCHMARKING
6
V.
METRICS
8
VI.
CONCEPT GENERATION
10
VII. CONCEPT SELECTION
14
VIII. FABRICATION AND ASSEMBLY
17
IX.
TESTING
20
X.
RE-DESIGN/SUGGESTED MODIFICATIONS
23
XI.
CONCLUSION
24
XII. BUDGET
25
XIII. APPENDICES
26
A. Shapes of Footprint and Sample Calculation
B. Educational Poster
C. Laboratory Experiment
D. Theoretical Work and Graphs
E. Hovercraft Safety and Operations Manual
F. Engineering Drawings
1
SUMMARY:
The purpose of this report is to present a detailed explanation of the work and thought
processes that went into our senior design project. Presented here is the final design concept
including a background of the project and its complete history.
In defining the project, it was important to determine the identities of the people that
would have an interest in our design. Once the customers were established, we had to take into
account their role in the project and to determine their specific wants. Once this list of customers
and wants was developed, the wants were evaluated with respect to customer importance. This
was done so that we would be better able to prioritize our efforts.
Benchmarking was performed to learn more about the system and its operation.
Benchmarking was also used to develop yardsticks for measuring the quality of our design
concepts. These yardsticks became metrics, which are what we used to compare our many
concept ideas.
Before intelligent discussion of ideas could be undertaken, further research was needed.
This research consisted of the derivation of relevant equations, discussion with experts and trips
to libraries. This deepened the understanding of the mechanics behind the problem.
After benchmarking and research, brainstorming sessions were held to generate concepts
that met the problem criteria. During these brainstorming sessions, all ideas were considered to
be valid, no matter how absurd they might seem. All possibilities were taken in to account.
Once the ideas were developed, they were compared to wants and constraints via the
metrics. After which, some concept ideas were discarded, some were kept, and some were
combined to produce a cohesive design concept that we believe to be the best solution according
to the specific problem. The selected concept presents a complete idea for our solution to the
problem.
2
INTRODUCTION:
Dr. Stephanie Wright, president of the Delaware Aerospace Academy (DAA), has
sponsored senior design projects for the past few years. The DAA specializes in educating
children about the technology involved in the space program. In teaching, they hope to raise an
interest in the United States Space Program by presenting relatively new and interesting
technology that has yet to be widely distributed. This year, Dr. Wright desires a hovercraft to be
used at the DAA technical camps by students of grades 7 – 9. The hovercraft is to float on a
cushion of air and will be used to simulate exploration of a new planet and will also teach certain
scientific principles to the students. After discussing the scope of the project with Dr. Wright
and other customers, we formed a mission statement, which included our own goals for the
design. The statement reads as follows:
To design a two person hovercraft for the DAA that will demonstrate the relevant
scientific principles involved, simulate planetary exploration, interest children in
the space program, and provide a fun, safe and educational environment for
everyone involved.
The craft will be used as an educational tool to teach scientific principles to children in
high school and junior high demonstrations. By utilizing a two-pilot operating system, it teaches
teamwork and cooperation. Since hovercrafts are not very widespread, a vehicle that actually
floats on a cushion of air should especially intrigue the children. Allowing the children to pilot
the craft will make the experience fun.
3
CUSTOMERS/WANTS/CONSTRAINTS:
A customer is anyone that would have a substantial interest in the final prototype or
design. After talking with our sponsor and considering all of the people who could possibly play
a role in the design and final product, we came up with a ranked list of customers. The list is as
follows (in order of importance):
1)
2)
3)
4)
5)
6)
7)
8)
Dr. Stephanie Wright – DAA
Eric Rabeno – Junior High Student (8th grade)
Bethany Fichera - High School Student (9th grade)
Martin Rabeno – High School Teacher
Selina DiCiccio – Junior High Teacher
Ron Perkins – Educational Innovations
Dr. Robert Bloom – Aerospace Engineer (DAA)
Dr. Mark Elison - Principal of Junior High and High School
Dr. Wright was the most important customer because her organization sponsored the
project, provided the funds and will be the primary user of the hovercraft for demonstrations.
Students were the next most important customers because they are the people that should
benefit the most from the project. The students’ input was needed to understand how to let them
have fun while being educated.
In addition to students, other members of the educational community that were our
customers are their teachers. After we designed our concept, we had to make sure that high
school and junior high school teachers understood what we were trying to accomplish. Since
they are professional educators, their input as to how to make the design educational was
essential to the success of the project.
Educational Innovations supplies lab and science equipment to schools which teachers
use to explain certain scientific principles to children. Mr. Perkins, a company representative, is a
customer because of the insight he can provide as to what works well and what doesn’t work
well as an educational tool. In addition, he provides help with the educational aspect of the
mission.
The school system superintendents and principals were included as customers because
they are concerned with the education of their students. As well as education, their knowledge of
what safety considerations were needed for the craft to be considered safe in a school
environment proved invaluable.
4
Each of the customers had their own list of functions they wanted the hovercraft to be
able to perform. After talking with these customers and discussing each of their wants for the
project, it was realized that, for the most part, the customers had many of the same wants on their
lists. The ranked wants are listed below. All of the customers wanted the hovercraft to
demonstrate scientific principles, to be fun to use, to look like it could be used in outer space,
and to be easily maneuverable. Based on the fact that these wants were on all of the customers’
lists, these became our top four wants and are all of relatively equal importance. The last five
wants below these on the list (5-9), were only on Dr. Wright’s list of wants and are only about
half as important as the top four.
1)
2)
3)
4)
5)
6)
7)
8)
9)
Demonstrate scientific principles
Make it fun
Have it look ‘cool’
Maneuverability
Reliability
Transportability
Reproducibility
Durability
Affordability
We were fortunate in the design process to be able to meet the customers’ wants without
having to make many trade-offs. The trade-offs we made were slight. For example, to make the
craft cool looking would cost more money, decreasing the craft’s affordability.
There were certain things that absolutely could not be sacrificed at any cost. Those items
that are not negotiable are constraints. The constraints imposed by the customers and the
working area, are listed as follows:
1)
2)
3)
4)
Operation (The hovercraft must hover)
Allowable Funds ($2000)
Size of door in Room 109 Spencer Lab (4.5’ X 6.3’)
Number of pilots (must be able to fit two)
5
BENCHMARKING (System and Functional):
Benchmarking, a process that continued throughout the duration of the project has proven
to be very valuable in the design of the hovercraft. Initial benchmarking was done on a variety of
overall hovercraft systems as well as components in order to determine best practices.
Initial benchmarking determined that there was not a complete system on the market that
satisfied the wants of the specific design problem. The system closest to what was desired is the
Triflyer Hovercraft from Robert Q. Riley Enterprises. The Triflyer was able to handle a
maximum payload of 800 lbs. (3 people), traveled 75 mph and was 12' x 6'. This design is close
to what we were looking for. The size of 12’ x 6’ is roughly about the size we were interested in.
75 mph, however, is significantly faster than what is considered safe as a top speed, according to
the customers. In addition, two children in high school or junior high would weigh on the
average of 200 lbs. (not the 800 lbs. that the Triflyer was built for). Also, the construction of this
model was fairly complicated and would have taken too long to build for the time given. This
benchmark is close to what is needed but is overpowered and has slightly too complicated of a
shape. Regardless, it still proved to be useful in certain ways. We studied how it was constructed
and applied some of its rib structure design to our own craft. Since this system was very close to
the desired goal, plans for the Triflyer were ordered and studied for concept and component
design. This gave insight as to industry standards for such components as steering, skirt design
and typical mounting points for engines and fans. Other benchmarks are shown in the table
below.
Table1: Benchmarking
Company
Robert Q. Riley Enterprises (Triflyer)
What they offered
Complete plans for hovercraft.
Robert Q. Riley Enterprises (Pegasus)
Round hovercraft plans, max weight 150 lbs.
Design has no viable propulsion method.
Universal Hovercraft (Kits and components)
Costs were well above our budget.
They offer fans for lift and thrust. Staff was very
helpful.
Hoverclub of America
Published a variety of articles describing principles
of hovercraft such as lift, thrust, and design tips.
Hovertech
Levitation using electromagnets
6
Universal hovercraft supplies hovercraft kits and components such as fans for personal
hovercrafts. Our fan and hub assemblies for lift and thrust company, as well as material for the
skirt (neoprene coated nylon) were purchased from this
Functional Benchmarking was done on a variety of systems and ideas in order to generate
concepts and determine components for the design. Also, functional benchmarking became
important in the educational and recreational aspect of the project. We performed searches that
would help us become familiar with different teaching methods. Six Flags Amusement Parks and
the Smithsonian Air and Space Museum were studied in order to come up with a way to satisfy
the wants of educational and fun. Six Flags uses velocity, acceleration, jerk, sounds, and colors
in order to make their rides fun for children and adults of all ages. The Air and Space museum
takes a more reserved approach towards fun and learning. They use videos, descriptive posters
and/or exhibitions, and rely on some hands on demonstrations to facilitate learning and fun.
As far as the operational aspect of the hovercraft is concerned, we looked into the
different requirements for the hovercraft. These requirements being the lift, thrust, and power
requirements for the craft. We looked into engine/fan systems, magnetic levitation systems, and
suspension systems as means for providing lift. Different forms of power such as electric, liquid
fuel (gas engines), and fuel cells were researched. As far as engines for thrust and lift are
concerned, Briggs and Stratton, Tecumseh, and Honda were researched and priced from a variety
of distributors, such as Grainger and Northern Tool Supply. In addition to researching different
kinds of lift, thrust, and power systems, components such as fans, skirt material, wood and other
building materials were also investigated. This was done to get a better idea of the quantity that
would need to be ordered. Also, their costs and the lead-time associated with each were
important so that we could properly schedule the construction of the hovercraft.
7
METRICS:
During the benchmarking process, notes were taken with regard to operation on some of
the important items that are normally measured in order to estimate the quality of a hovercraft
design. The design can not be compared to competitor’s best practices unless a common
yardstick is developed upon which to base the evaluation. By observing what items the
competitors measured to determine quality as well as conversing with the customers, a list of
metrics for our wants was developed. Once the metrics were established, target values were
assigned to them based on the customers wants and the competitor’s values. The list of metrics
and their corresponding target values is shown below.
Metric
1
Object Clearance (from bottom of
Target Value
Wants
6 inches
3, 5
Importance
Medium
craft to ground)
2
Angle of Hover
0 degrees
4
Low
3
Start Time
2 seconds
2, 5
Low
4
Settling Time
1 second
Safety
Low
5
Height of Oscillations
0 inches
2, 4, 5, Safety
6
Drift velocity
0 feet/second
4
Low
7
Skirt Maintenance hours per use
0 hours per use
7, 8
Low
8
Number of Principles Taught
3
1
High
9
Performance on a lab experiment
average score = 80%
1
High
Medium
Medium
(to be explained)
10
Skirt to Ground Clearance
0.5 inches
4
11
Speed of vehicle
5 - 10 mph
2, 4, Safety
High
12
Acceleration of vehicle
1 mph/s
2, 4, Safety
High
13
Directions of Travel
360 degrees (all
2, 4
High
2, 4
Medium
2, 4
Medium
horizontal directions)
14
Travel Range
unlimited (limited by
fuel capacity alone)
15
Turning Radius
15 meters
8
16
Fuel Efficiency/Capacity
3.5 continuous hours.
5
Low
17
Cost
$2000
7, 9
High
18
Weight
1000 lbs.
4, 6, 7
High
The importance of a metric is determined by how well it quantifies a want and by how
important that want is.
9
CONCEPT GENERATION:
This specific design project is unique in that there are more goals involved in the project
than simply designing a functional piece of equipment. In addition to using our engineering skills
to design a working hovercraft, the wants of our customers require that the design be built in
such a manner that teachers will be able to teach the students using the scientific principles
involved (lift, thrust and drag). Our customers also want learning these principles to be fun.
Therefore, the hovercraft must function in such a manner that will hold the children’s’ interest.
As a result of brainstorming and benchmarking, concept ideas were generated that would
satisfy the top four wants of education, fun, cool looking, and maneuverability individually.
Once concept ideas for each want were obtained, the next stage was to try and combine the most
feasible ideas corresponding to each want into a total, cohesive design concept based on the
metrics and some calculations. This combining of ideas into one complete design would satisfy
the top wants of the problem best according to the metrics and result in a well-balanced final
design. It was determined that if the top four wants were satisfied through concept generation,
wants 5-9 could be easily satisfied regardless of how we combined the different concept ideas for
the top four wants.
Since demonstrating scientific principles to children turned out to be one of the four most
important wants, we began our concept generation ideas with this want. Because this project is
geared towards children, we looked to proven leaders in the field of education during our
functional benchmarking. The museums of the Smithsonian Institute are excellent in educating
children about all aspects of science. We especially took note of the Air and Space Museum as it
is closely related to our project. As a result of the benchmarking done for education, we
generated two specific concept ideas for satisfying the wants of teaching scientific principles.
The “Smithsonian Approach” is our concept generation for satisfying the first of our three most
important wants. Two possible concepts consist of showing either an informative video that
describes the scientific principles of lift, thrust, and drag or creating a descriptive poster that
explains what hovercrafts are, why they would be useful in the space program, and how they
work.
To deal with the second and third of our four important wants, making it fun for children,
we based our concept generation ideas on the results of our functional benchmarking for fun.
Practically all children enjoy going to amusement parks. They love to go on the rides. Therefore,
10
we should attempt to make this hovercraft feel like a “ride” to the children using it. The
“Amusement Park Approach” is our concept generation for satisfying this want. Rides at these
parks are fun for children because of their colors, shapes, and sounds. By making the hovercraft
look like a machine that would be used in outer space, and by using the proper colors and shapes,
kids will be intrigued and interested in knowing how it works and what they could do with it.
Therefore, the idea is to use the right colors and shapes to make the children feel like they’re on a
ride.
Our fourth important want, maneuverability, deals with the physical functioning of the
hovercraft itself. This is the part of our project, the design of the actual prototype hovercraft,
which will best utilize the engineering tools we’ve acquired over the past four years. Concept
generation for this portion of our project deals with the overall functioning and construction of
the craft itself and its concepts will be used to satisfy wants 4-9. In designing the actual
hovercraft for good maneuverability, durability, transportability, and reliability, concepts have to
be generated in a number of areas. These areas are lift system, thrust system, means of providing
power, skirt type, shape of the craft, steering system, and pilot positioning.
As far as the lift system is concerned, fans, magnets, and suspension systems were
researched and discussed briefly in the functional benchmarking section. One concept was to
have magnets on the ground along with opposing ones on the craft. The magnets would repel
each other and lift the craft. Suspension systems could be used to provide “lift” by suspending
the craft above the ground by means of a cable attached to the frame. One concept studied, and
engine/fan system, turned out to be the most common, cheapest, and simplest method for
providing the lift forces.
Thrust is another area where we had to generate concepts. Benchmarking showed that
like the lift system, an engine/fan system used for thrust seemed to be the best practice. Other
possible thrust methods would be to have the craft pulled/pushed by another person, or use some
sort of jet propulsion. Jet propulsion is dangerous and expensive and human power for thrust
would not do as well as a fan in demonstrating the principle of thrust.
As far as power generation is concerned, concepts using liquid fuel, batteries, and fuel
cells were studied. It turns out that fuel cells are costly but provide a great deal of clean energy.
Batteries are inexpensive but are heavy and might be detrimental to our lifting capabilities.
Liquid fuels are abundant, lightweight and inexpensive and seem to be a good choice.
11
Another area that affects the overall maneuverability of the craft, and one that goes along
with the lift system is the type of skirt to be used around the bottom to keep air trapped under the
craft. Two concept ideas were generated for the skirt design. The first is a bag skirt, which is a
lot like an inflated inner tube under the craft. The second is a C skirt, which is a piece of
material draped along the craft much like a tablecloth. Bag skirts allow for a more complex
shape. The C skirt has a few drawbacks. It is a more unstable system because it has the tendency
to flap out, releasing air and lowering the craft. In addition, objects passing under the craft have a
tendency to be picked up by the skirt. This increases the possibility of ripping the skirt and, if the
object is heavy enough, the possibility that the craft will abruptly stop.
Shape is another important consideration in concept generation with regard to
maneuverability and function. An important aspect that is inherent in the shape picked is the
perimeter surface area under the craft. This quantity comes into play in determining the air
pressure under the craft. The pressure multiplied by the bottom perimeter surface area limits the
lifting weight. A number of shapes were looked at when considering the design of the footprint.
The main concern with shape would be in obtaining one so that the area under the craft allowed
for a relatively small air pressure required. Also, an overall perimeter shape has to be chosen that
can be constructed in such a manner as to provide good durability for the craft. Several shapes
considered are included in Appendix A along with a sample pressure calculation.
When one thinks of maneuverability, one of the first things that come to mind should be
steering. Steering could be done a number of ways. It could be done with a rudder system, by
having multiple fans that rotate to change the direction of airflow, or by having multiple fans that
12
use different thrust configurations to turn the craft. The second and third options would be more
expensive and also would be difficult to construct so that a high school student would be able to
control the hovercraft.
Pilot positioning was also a concern. The pilots could be positioned one behind the other
or side by side. The craft needs to hover almost exactly horizontal so that a level gap height from
craft to ground is achieved. In addition to making it harder to balance the craft, positioning the
pilots front and back would make it so that one pilot would probably have to control the lift,
steering and thrust exclusively since all controls will be on a dashboard in the front of the craft.
Positioning the pilots side by side would allow both pilots to easily access the controls. It would
also allow for the best weight distribution needed to balance the hovercraft.
The craft needs to be level if we are to satisfy the maneuverability want. The air rushing
out from under the craft in the second drawing below would detract from the overall hovering
capability of the craft. In order for the craft to hover at a constant height (h), the air pushed
underneath by the lift fan must remain trapped under the craft. Once air begins to rush out from
under the craft unevenly, equilibrium is disrupted and the craft will no longer function as
designed.
13
CONCEPT SELECTION:
With all of the concept ideas just described as possible means of satisfying each of wants,
it became a matter of studying our metrics and constraints to determine the best way to combine
all concepts into one cohesive solution. The idea is to choose one concept for satisfying each
want based on the metrics and then combine each of the concepts into one complete design for a
fun, cool looking, educational, and maneuverable hovercraft.
Arriving at a complete design concept that would satisfy each of the four most important
wants proved to be easy to accomplish. Our final design concept consists of three parts. The first
part of our final concept is an educational poster that will be displayed near the hovercraft
demonstration area so that students can look at it. It discusses what hovercrafts can be used for,
how they relate to the space program, and also the scientific principles our prototype relies on for
successful operation (slides are located in Appendix B). Also included is a laboratory experiment
to be performed on the concept of lift (located in Appendix C) which will give the children hands
on experience that the Smithsonian Institute does so well. These two portions of our final
concept will demonstrate to the children the relative scientific principles involved. Finally,
piloting the actual hovercraft will allow the children to see everything the first two items has
taught them and, in addition, will satisfy wants 2 and 4-9. They will be able to take the
information from the poster and experiment and apply it to a working hovercraft that will
provide plenty of excitement.
The teachers on our customer list, Dr. Wright, and our design team feel that students will
learn the most by reading the poster and performing the lab before operating the hovercraft. The
poster itself explains two scientific principles: lift and thrust. In addition to studying the poster,
the students will build a simple hovercraft themselves in the short laboratory experiment. The lab
is designed to show how lifting force, air pressure, and footprint sizes are related. The students
can get a sense of the drag force by pushing the model hovercraft along different surfaces and
see how far it travels before coming to a stop. With these three scientific principles explained
(thrust, lift, and drag), our metric dealing with the want of education has been satisfied and the
proper number of principles taught according to our target value of three. Another metric to
measure the educational value of our project is performance on the laboratory experiment. We
had a target value of 80% as an average grade for a class of students. It turns out that this metric
14
was satisfied by the final laboratory experiment submitted as Appendix C and is a good means
for measuring understanding. The average grade on the lab was approximately 85%.
After studying the poster and performing the experiment, students will be allowed to ride
the prototype hovercraft with a better understanding of its working principles. The prototype
hovercraft is the third part of our complete design concept. The prototype is a 10-ft long, 6-ft
wide and 2-ft deep box. A semi-complete picture of what the prototype looks like is the picture
on the title page of this report. Assembly and component drawings are shown in Appendix F.
This shape was picked because of the footprint. It optimized the area underneath the craft for the
lift system. By optimizing this area and perimeter, we were able to get the maximum lift for our
craft. This lift allowed the craft to hover a full 5.5” off the ground. Height of hovering (object
clearance) was listed as one of our metrics and this footprint shape would allow us to maximize
the height of hovering.
The lifting is done with a single fan and vertical shaft engine located in the front of
hovercraft. A fan system was chosen over a magnetic system due to the cost restriction on the
project as indicated in the metrics. In addition, the magnetic system did not allow unlimited
planar range. It also might limit the directions of travel, as the magnets would already have to be
placed on the ground in direction to be explored. Suspension systems were eliminated for one
major reason: the craft would not be hovering. Since hovering is one of our constraints, this idea
had to be discarded. Thus, we chose the engine/fan system as the best of our options based on the
wants and metrics of cost, directions of travel, object clearance, planar range, and the “hovering”
constraint. Calculations for the lift system are located in Appendix D.
We determined the lift fan diameter, after consulting with Universal Hovercraft.
According to their calculations, the fan needed to lift the estimated weight of our craft with an 8
HP motor is 26" in diameter and has four blades. The lift engine is mounted in the front of the
craft above the fan. The location for the engine was determined by examining competitors best
practices. By positioning the lift system in the front, the angle of hover (metric #2) was best
satisfied by providing maximum balance.
For the thrust system, another fan and a 3.5 HP horizontal shaft motor on the back of the
hovercraft will accomplish the thrust for the craft according to our theoretical calculations
(Appendix D). This is not only industry standard, but it is also the best practice for what we seek.
15
According to our calculations, a 3.5 HP motor will satisfy the metrics and target values for top
speed and acceleration.
Concept selection for means of power led us to choose gas power over electric power or
fuel cells due to the high cost of the latter two. An engine/fan system would be the lightest
system and was chosen to maximize our metric of hovering height. An 8 HP gas engine costs
about $400 and weighs about 60 lbs. The batteries to operate an equivalent electric motor weigh
twice as much and replacement batteries are expensive. Fuel cells were eliminated on cost alone.
A fuel cell to power an electric motor costs in the tens of thousands of dollars.
As far as skirts are concerned, a bag skirt had fewer drawbacks than the C skirt. It was
chosen based on the balance (angle of hover) metric, object clearance metric, and the
maintenance hours metric.
In the final design, we decided to position the pilots side by side. If the pilots were
positioned front to back, the pilot’s compartment would have to be longer. With a design longer
than the current one, the prototype would not be able to leave the Senior Design Room.
Therefore, the pilot positioning was determined partly by our size constraint. Balancing any
difference in weight between the pilots can be compensated with weights under the seat and a
better angle of hover is achieved with side by side seating.
Maneuvering of the craft is done by a rudder system attached to the rear of the thrust fan
assembly. The two rudders will be coupled and the steering system for the rudders is assembled
so that the steering “column” will be on the dashboard and accessible by either pilot. It appears
to be the best way to satisfy the turning radius metric of 15 ft. with a top speed of 10 mph. This
will also allow for teamwork as both the steering and the lift throttle will be placed on the
“dashboard” allowing each pilot to operate one of the two systems.
Each concept selected for building the prototype was done by taking our metrics into
account and comparing the different ideas. Based on the metrics and target values, we believe
that the prototype constructed is the best solution to the wants on our list dealing with the
operation of the hovercraft (wants 2, and 4-9).
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FABRICATION AND ASSEMBLY:
The final development and fabrication times



Engineering Concept Development
110 hours
Fabrication
610 hours
Redesign and Modification
20 hours
TOTAL: 740 hours
The frame of the hovercraft is a rib structure designed to be lightweight and strong at the
same time. The ribs were constructed with 1” x 2” pine. A template was laid out on a piece of
plywood and the pine was cut and made into kits for each rib. The template was then used to
construct the ribs (drawing No. 2) and ensure all ribs came out to be the same dimensions. The
template was then modified to allow for the construction of the second type of rib used
(drawing No. 3) in the driver compartment and also the third type used at both ends (drawing No.
1).
Once all the ribs were constructed, the next step was to hang the ribs on two 2” x 4” x 10’
stringers (see drawing No. 5). The ribs were spaced out according to the drawings and attached
to these stringers.
Next, the 10’ x 1” x 2” stringers were put in to place.
This was followed by the installment of the rest of the members used for support around
the lift and thrust fans.
The craft was then turned so the bottom was face up and ¼” plywood was used to cover
the entire bottom. One piece contained a 30” diameter hole, cut on a CNC router for accuracy, to
accommodate the lift duct. Bondo was then applied at the seams to help make the bottom
airtight. Once this was done the wood was sealed with a polyester resin and the skids were
installed.
Upon the completion of the bottom, the craft was turned right side up. The crew
compartment’s bottom was covered with ¼” plywood and 1/8” Luan applied over the rest of the
craft. Bodywork was done with joint compound and Bondo to even out the body and give it a
more professional appearance.
17
The skirt was fabricated using the material obtained from Universal Hovercraft. The
material was cut (drawing No.10) and then sewn together using Kevlar thread and super-glue to
create the corners. Sheet metal screws were used to attach the skirt to the craft. A small flap of
material was placed over a portion of the lift duct to direct some air from the lift fan into the bag
skirt.
The lift duct was created using a roll of aluminum flashing. The aluminum was wrapped
four times and machine screws were used to help it keep its shape. This duct was then placed in
the two 30” holes and ran through the entire craft.
The lift engine was mounted to a composite plate made of vinyl-ester resin, 3 layers of
24oz woven roving E-glass, a ¼” balsa core and then 3 more layers of E-glass. This was then
mounted to two pieces of angle iron used to span the lift duct. The fan was mounted to the engine
shaft using the hub provided by Universal Hovercraft and a 1in. diameter split taper bushing. At
this point the first lift test was successfully conducted with one person in the craft.
A windshield was constructed next using pultruded fiberglass box beams and a piece of
polycarbonate. This was attached with four bolts keeping in mind it would need to be removed
in order to remove the craft from the room. Two boat seats were installed side by side in the
crew compartment for the pilots. Also, the controls for the lift and thrust fans and the steering
system were mounted on a “dashboard” so that the two pilots could work together to operate the
three systems.
In order to allow the craft to be removed from the building, the thrust housing was
required to be removable. The box to contain the fan was made with 1” x 6” pine. A ¼” x ¼”
protective screen was placed over the outer opening. All of this was attached to a piece of ¼”
plywood. This assembly is bolted to the craft to allow the assembly to be removable (see
drawing No.8-9). The thrust motor was placed above the back of the hovercraft on a box 8” high
to allow the fan to be centered in the housing. The two rudders were made from 1” Styrofoam.
The steering is done by sliding the handle in the “dashboard” from right to left depending on the
desired direction of travel. This is attached to the rudders using ¼” nylon cord.
The entire craft was next painted with a semi-gloss black paint. After this was complete,
yellow caution labeling was applied to areas that were dangerous. The construction was
completed with the mounting of a fire extinguisher. After the hovercraft is removed from the
senior design room and before the craft is delivered, safety screens will be placed over the front
18
lift fan and also the remaining portion of the thrust assembly.
19
TESTING/RESULTS:
1) Hovering Capability
Weight Craft bottom to ground clearance
Just Craft Trial 1 Trial 2 Trial 3
Average
50 lbs.
6"
6"
6"
6"
100 lbs. 6"
6"
6"
6"
150 lbs. 5.8"
5.5"
5.75"
5.68
200 lbs. 5.75" 5.6"
5.5"
5.62
250 lbs. 5"
5.25" 5"
5.08
300 lbs. 4.25" 4.33" 4.2"
4.26
2) Approx. angle of hover
We found that getting the craft to hover flat is just a matter
of balancing it. With two pilots of relatively equal weight,
the craft hovers almost exactly horizontal.
4) Time it takes craft to settle after
shutting engine off
Time
Trial #
1 pilot
2 pilots
1
1 sec.
1 sec.
2
1 sec.
1 sec.
3
1 sec.
1 sec.
4
1 sec.
1 sec.
5
1 sec.
1 sec.
* We found that as soon as the engine
is cut, the craft settles down on its
skids pretty quickly. It is not so sudden
as to deter from the safety of the craft
5) Stability
Height of Oscillations
Small to nothing. With the throttle in one position,
3) Amount of time from when the engine
starts until it is hovering
6) Does the craft hover in place or does
it tend to go in a certain direction?
Time
Trial #
1
2
3
4
5
1 pilot
2 sec.
3.5 sec.
4 sec.
2.5 sec.
2.5 sec.
the craft will hover at a constant height
2 pilots
3 sec.
3.5 sec.
2.5 sec.
2 sec.
3 sec.
This depends on two factors: wind and terrain.
On perfectly flat ground with no wind, the craft
hovers in place. With hills and wind, the craft
tends to move.
* Basically, the time it takes the craft fully rise
depends on how the pilot operates the throttle.
7) Do we have to adjust the skirt each time
we start it or will it hover by simply starting
the fan?
The hovercraft will rest on the skids so that
the skirt does not have to be adjusted each
Metric
Test
Results
Explanation
8) Number Principles
Grade School
1- lift
See paragraph below
Taught
Demo
2 – lift, thrust
See paragraph below
University
Demo
9) Performance on Lab
Grade School
experiment
Demonstration
Children performed laboratory
85% Average
and quiz
experiment and were graded by
team to determine understanding
20
10) Skirt to Ground
Tested
0.5”
While hovering, clearance was
Clearance
measured manually with a scale
on all sides of the craft. Values
were averaged. It was found that
the weight of passengers did not
affect the clearance significantly.
11) Speed of Vehicle
Not Tested
See paragraph below for
explanation of missing test results
12) Acceleration of Vehicle
Not Tested
See paragraph below for
explanation of missing test results
13) Directions of Travel
Not Tested
See paragraph below for
explanation of missing test results
14) Travel Range
Tested
Range limited by
During testing, no unexplained
only physical
engine shutoffs, skirt failures.
obstacles and fuel
15) Turning Radius
Not Tested
See paragraph below for
explanation of missing test results
16) Fuel Efficiency
Lift Engine –
5 hours
Tested
Thrust Engine
with fuel, burned them for a
25 hours
Lift Engine –
1 gallon
fuel needed to fill it up again.
This gave us a value of gallons
Tested
Thrust Engine
prescribed amount of time, and
then took note of the amount of
- Tested
Fuel Capacity
We filled both engines to capacity
½ gallon
per hour
- Tested
17) Cost
N/A
$1779.36
See part XII, Budget
18) Weight
Empty Craft
425 lbs.
Empty weight of craft measured
Weight
with scale
21
Education and Fun:
To determine the final result and overall effectiveness of the lab and poster in providing a
means of learning, we have gone through several iterations of each. The poster and laboratory
model were brought into a classroom where verbal feedback and reactions from the students
helped us to make the necessary changes to both items. When we first showed the students our
working model from the lab, all of them crowded around it and wanted to touch it and push it.
Several students asked how to build it and wanted to try making a miniature model on their own
time. In addition to the model, the students told us they liked the poster and that it explained the
lift and thrust principles to them in a manner they could understand. Based on the results of
talking to several students and their teacher, the presentation of important concepts has been
altered until optimal understanding was obtained. An average score on the lab experiment
determined optimal understanding. This was one of our metrics. The average score we obtained
from the students was 85% and our target value was 80%. This means that the metric of
measuring understanding of the lab and hovercraft principles was satisfied as well as our metric
for demonstrating three scientific principles.
Thrust:
Since the thrust fan was not the proper kind, the thrust force needed to move the craft was
tested using a scale to measure the force required to get it moving. It was found that the
calculations for the thrust (in Appendix D) were indeed accurate. With 300lbs in addition to the
empty weight of the craft (roughly the weight of two pilots), 60lbs of force was required to move
forward and only 15lbs of force was required to turn. These values were obtained empirically by
pushing on the craft with a scale and noting the amount of force on the scale when the craft
began to move. It is our engineering estimation that when we receive a thrust fan pitched in the
right direction that our craft would satisfy the thrust metrics of top speed, acceleration, turning
radius, directions of travel, and planar range.
22
RE-DESIGN/SUGGESTED MODIFICATIONS:
During the testing of the lift system it was noticed that the lift fan had risen up the shaft
and was rubbing against the engine support plate. To prevent this from happening again a 1”
bronze collar was placed on the shaft above the hub for the fan. This will prevent the hub from
hitting the engine plate again. A new engine plate was also fabricated to replace the damaged
plate.
The thrust fan, which had been donated to the project, turned out to be pitched wrong for
the motor set-up. The fan needed to push air when turned clockwise, but instead the fan pulled
air. To rectify this, a new fan was ordered with the correct pitch that would work based mainly
upon our theoretical calculations (Appendix D) and also on our testing results using the scale.
Depending on the weight of the pilots, ballast must be added to compensate. This can be
changed during operation to allow the craft to float level. Water jugs can be placed in the front
of the craft to allow for extra weight.
A complete operation and safety manual is to be submitted to the sponsor as part
complete design. This manual is located in Appendix E and will be delivered to the primary
customer with the hovercraft.
23
CONCLUSION:
The task of constructing a prototype hovercraft according to Dr. Stephanie Wright’s
wants that satisfied our mission statement has proven to be a successful one. With only one
minor setback, we satisfied all of our wants according to the problem definition. The first three
wants, demonstrate scientific principles, fun, and cool looking, were satisfied well according to
the feedback received from our sponsor, the students, and teachers. The most significant
accomplishment of the project was being able to theoretically design a mechanism for lifting the
hovercraft to a desired height according to our desired weight and then having the assembly
work almost exactly how we designed it. The desired height of hovering with two children (from
base of craft to ground) was listed in the metrics as 6”. Upon testing of the lift system, it was
found that with the equivalent weight of two students, the craft hovered at a height of 5.25”. This
is very close to our target value.
The only setback came with the discovery that the fan we were going to use for thrust
force was pitched the wrong way. This combined with the fact that the thrust engine did not work
initially and had to be repaired did not leave enough time before the final presentation to have a
new fan delivered and the thrust system tested using the fan/motor combination. However, to
compensate for this, we used scales to test the amount of actual thrust force needed to move the
craft and to turn the craft. We discovered during these tests that our theoretical calculations for
thrust force were accurate and also found out that it would only take 15 lbs. of force to turn the
craft. This number also coincides well with the theoretical calculations, which can be found in
Appendix D. With these test results, we were able to order a new thrust fan that will satisfy the
thrust requirements and finalize the project. With the completion of the thrust system, we will
have satisfied all the wants given to us by the customers.
The one concern when starting the project was the relatively small budget of $2,000
dollars. After careful benchmarking and research, we were able to come up with and construct a
complete solution for $1779.36, which is under budget.
Before we began working on the project, we all thought it sounded pretty interesting.
Only now that it is complete can we fathom how important and educational the whole process
has been. We can now look back on all our initial expectations and worries and take pride in the
fact that we were able to design a complete solution to the problem assigned.
24
BUDGET:
The final budget report for the project is as follows:





Materials (Wood, Hardware) Lift fan, Skirt, Hub 8hp Lift Engine Thrust Fan 3.5hp Thrust Engine TOTAL:
$ 734.45
$ 361.22
$ 358.70
$ 157.00
$ 167.99
$1779.36
The estimated cost for production of a similar craft is the Projected Production Cost and is as
follows:

Total Material Costs:
- $1779.36

Estimated Production Hours:
- 200 hours
- $25/hr

Projected Cost = $5000 + $1779.36 = $6779.36
25
Appendix A: Shapes of Footprint and Sample Calculation
Sample Calculation for rectangle:
Area = length x width = 10 x 6 = 60 ft2 = 8640 in2
Weight = 2000 lbs.
(Weight from metrics with a factor of safety of 2)
Cushion Pressure = Weight/Area = 2000 lbs./8640 in2 = 0.231 lbs./in2
26
Appendix B: Slides for Educational Poster
27

B a ck g ro u n d :
–
A h over craf t is a vehicle tha t is rais ed off th e
gr oun d by a sm all cus hio n of air an d can b e
dr iven a rou nd lik e a c ar. T he lif t, sp eed , an d
direction of a ho ver craf t c an be co ntr olled in
m any w ays. On e of the se way s is by th e use of
po wer ful fa ns and m oto rs
–
EXPLORATION
In the future, it may
be possible for
people to land on
another planet in
our solar system.
View of Venus
The hovercraft is a
prototype of a
vehicle that could
be used to explore
and study the
surface of planets
other than our own.

The advantage of a
hovercraft is that it
floats. Since we do
not yet completely
know what the
surfaces of some
planets are like, the
cushion of air will
help avoid small
obstacles and allow
for easier
maneuvering.
Surface of Mars
28
H ow It W orks...
L if t:
T h e li ft fa n b lo w s a ir th ro u gh a n op e n in g a n d u n de r th e
c ra ft w he r e it is m o s tly e nc l o se d by a s k irt . Th e tra p p ed a ir
p ro d uc e s p re s s u re on t h e s u rfa c e l ift in g th e c ra ft a nd
c a u s in g it to flo a t. T h e p re s s ur e n e e de d t o li ft th e c r af t is
o b ta in e d fr om th e e q u a ti on P = F /A . T h e P = a ir p re s s u re
u n de r th e c ra f t. T he F = w e ig h t of th e cr a ft pl u s p il ot s a n d
A = a re a o f th e c ra f t. It is its le n g th ti m e s i ts w id th .
Lifting of Hovercraft
Air Flow
Direction
of Travel
T hru st & S tee ring:
N ew ton’ s L aws of Ph ysi cs -
E v e r y fo r ce i s o p p o s ed b y a n
eq u a l an d o p p o si t e re a cti on f o rc e
The th ru st f an and en g ine f orce a ir b ackw ards . Thi s
caus es an e qual an d op posi te force on the h ov ercraft
push ing it fo rw ard. A ls o, the rudder s t urn t o push the air in
one direc tio n causi ng the ho verc raft to go in the oppo sit e
directio n
29
Appendix C: Lab
Demonstration of Lift System for AntiGravity Vehicles
Purpose:
It is important to understand the scientific principle of lift in any vehicle that is freefloating or built specifically to defy gravity. The purpose of this experiment is to learn about how
a free floating vehicle actually “defies” gravity. It will be important to understand the
relationship between surface area of the vehicle, the weight of the vehicle and the air pressure
developed between the vehicle and the ground. This experiment will provide the information
necessary to understand the concept of lift.
Theory and Background:
Anti-gravity vehicles have become an area of great interest recently. Some people build
them at home as a hobby much like go-carts. There are also important scientific uses for
hovercrafts and other free-floating vehicles. The present level of scientific technology is so
advanced that NASA and separate state space programs and space camps would have very
important uses for an anti-gravity hovercraft. One of the uses is to use a hovercraft to explore
unknown places on a planet. Astronauts that land on a planet for the first time would not be able
to completely know what the terrain is like before they land. Because of this fact, a vehicle that
hovers off of the ground may be a better way to explore that planet in case it is difficult to drive a
vehicle with wheels. The Delaware Aerospace Academy will demonstrate a life size hovercraft
that was designed for the purpose of showing how planetary exploration would take place. By
performing this experiment before viewing the demonstration, you will better understand how
the hovercraft actually lifts off the ground and how it works. The equation that is important in
figuring out if a hovercraft will actually hover is F = (P) X (A). In this equation, F = weight of
the hovercraft plus passengers (the force needed to lift the hovercraft). A = the surface area on
the bottom of the hovercraft (in this experiment the hovercraft is a rectangle and its A = length X
width. And the P = air pressure between the hovercraft and the ground. Its units are force per unit
area. You will construct hovercrafts of different weight (F) and area (A) and find the air pressure
needed to cause lift.
30
Necessary Equipment:
- Two standard 3” computer cooling fans (12VDC, .13Amps, 1.60Watts)
- One 12 Volt DC battery
- Two pieces of polystyrene poster-board 9” X 16”
- Eight strips of pre-cut plastic (trash bag material)
- Four 16” strips, two 9” strips, and two 18” strips
- Masking Tape
- A set of small weights totaling about 4 lbs.
Procedure:
1) Using the piece of poster-board with the computer fans attached (holes will be precut
in the poster-board with computer fans taped into them), tape one 9” piece of plastic
to each shorter edge of the poster-board. Then, use the two 16” strips of plastic and
tape those to the longer edges of the poster-board. Turn the poster-board over and use
one piece of tape at each corner to attach the plastic strips as shown in figure 1 on the
next page.
2) Before you turn the fans on, you must make sure the hovercraft is right-side up and
all the loose ends of plastic are tucked under the craft. Then, hook the red wires on
the fans to the positive (+) terminal of the battery. Then hook the black wires to the
negative (-) terminal. Observe what happens. Does the hovercraft lift off the table? If
it lifts, try putting some small weights on the poster-board away from the fans. If it
lifts, write down the largest amount of weight it can hold up (and add this value to the
weight of the hovercraft which is 1 lb.). The area A = 16” X 9” = 144 inches squared.
With this weight (F) and area (A), use the equation F = P X A to calculate the air
pressure. If it does not lift at all, move on to the next part.
3) Take the pieces of plastic off and tape the other piece of poster board onto the first
one. Now use the two 18” pieces of plastic on the edges you used the 9” pieces on
before and put the two 16” pieces on the other two edges as in figure 2. Then tape the
corners as before and use the fans to try and lift the new set up. Again, add different
weights to the hovercraft away from the fans. Does this one lift? Does this hovercraft
lift better than the first one? Write down the largest amount of weight it can lift this
time (remember to add the weight of this craft which is 1.25 lbs.). The area for this
craft is A = 288 inches squared. Calculate the value of air pressure for this hovercraft.
4) Based on what you saw for the two hovercrafts, which one seemed to work better?
Which one had a lower value of air pressure (P)? What can you say about the
relationship between the value of P and how well the hovercraft works?
31
FIGURE 1
Top View
Bottom View
FIGURE 2
Top View
32
Appendix D: Theoretical Work and Graphs
Equations Used And Derivation of Power Equation:
Conservation of Energy and Conservation of Mass from the fluid mechanics perspective
is used throughout.
P3 V 23
V 22

 gz 2 

 gz3

2

2
V 21
P 2 V 22

 gz1

 gz 2 ws
 2

2
P2
P1
Steady-Flow Energy Equation 1 – 2
Bernoulli’s Equation 2 – 3
The principle of lift of a hovercraft is fairly straight forward. Using a fan, air (from area
1) is put into the plennum chamber under the craft (denoted as area 2 ). This chamber acts as a
pressure vessel. When the pressure inside is high enough, the craft will lift off the ground. With
the craft off the ground, air now has a chance to escape around the perimeter (shown as area 3 ).
We needed a way to model this problem. After consulting woth Dr. Ajay Prasad, we
found that we only need to use one equation: the Steady-Flow Energy Equation. This equation
reduces to the Bernoulli Equation when there is no work being done.
To use this equation, we made several assumptions. First, we assumed that there would
be no losses due to friction on the air intake. We believe that this is a valid assumption because
the surface roughness to the intake diameter is very small. Second, we ignored gravitational
effects on the air. This assumption was used because the height from the top of the craft is twothirds of a meter. This contribution is dwarfed by the other factors. The third assumption we
made was that we could approximate the velocity of the air in the plennum chamber to be zero.
33
We know that its velocity is indeed not zero, but Dr. Prasad assured us that it is still a valid
assumption. Fourthlt, The hovercraft manufacturers we talked to told us that hovercrafts typically
have a half of an inch(about 1.5cm) gap between the perimeter of the skirt and the ground. We
assumed this height. Finally, we used gague pressure in all of our derivations. This is not an
assumption, per se, but it allowed simplification in our derivation.
After some manipulation of the Steady-Flow Energy Equation and using the equations
under the heading ‘Other Useful Equations’, we derived the three relevant equations. The
equations are for pressure, volumetric flow rate and power. Pressure and flow rate were
absolutely necessary for fan selection. The power equation allowed us to specify a power
plant/engine. The graphs that follow were created from these equations combined into a single
equation.
The graphs plot power versus length and width for a given gap height and gap height
versus length and width for a given power. These graphs allowed us to get a better ‘feel’ of how
the equations work together. We wanted the smallest engine that could lift the craft and not
violate our size metrics.
The equation used for finding the thrust required could not be easier. The equation is
simply Newton’s Second Law: F=ma. We had a weight from the metrics. It needed to be
converted to mass. Then, this mass is multiplied by the acceleration, also from the metrics. The
result is shown below.
weight
ws 
From Energy Equation:
A
From Bernoulli’s Equation: V3 
2P2


A  lw
m  Q
Other useful Equations:
Aperimeter  h(l  w)
Final Relevant Equations:
P
Wweight
A

Wweight
lw
Q  V3 Aperimeter  2(l  w)
2Wweight
lw
3

Wweight
 
W   w s m  2(l  w)
 (lw)3


Thrust Equations & Calculations:
F  Ma
W
M
go
W = 1000lbs. (from Metrics)
a = 1.5 ft/s2 (from Metrics)
34
go = 32.2 ft/s2
Thrust Force Required = 60lbs.
35
Figure 1 : Gap Height = 1.0cm
Figure 2 : Gap Height = 1.5cm
Figure 3 : HP = 8
Figure 5 : HP = 6
Figure 4 : HP = 7
36
APPENDIX E:
Hovercraft Safety and
Operations Manual
37
Safety Suggestions:
Please use caution when operating or standing close to the hovercraft. It is
suggested that safety glasses and hearing protection be worn during operation for all
pilots and adult spotters. Please use in a flat open area with adult supervision at all
times. A fire extinguisher is located at the back right corner of the craft in the case of
an emergency.
The hovercraft’s direction can change depending on terrain, for this reason an
adult must stay close to the hovercraft and act as a spotter. Because of the little force
required to move the craft, an adult near the hovercraft can simply hold the side of the
hovercraft to steady its position and allow the pilots to recover. All stopping
mechanisms are located near the sides of the craft to allow the engines to be shut
down easily in the event of a problem.
Operation:
The craft is designed to hold two pilots: one to control the lift and throttle and
one to control the direction. These two pilots should be close to the same weight and
the total weight should be less than 300 lbs. for optimal performance.
Starting the hovercraft:
1) Enter the craft from the sides, stepping only on the panels labeled ‘step’.
2) Make sure both pilots are seated and familiar with the operation of the craft.
3) Do an inspection check of the craft including:
a) Both engines and fans
b) All screens. To be sure they are in place and secure.
c) The wiring to be sure all wires are connected.
d) The skirt for tears and holes.
4) Starting the thrust engine: Set the bottom lever to choke and the top lever to fast.
Pull the cord to start the engine, once started move the bottom lever to run and the
top to slow.
38
5) Starting the lift engine: Pull the throttle one half inch from its base; then, turn the
key to the right. Once the engine starts to run, pull the throttle level up slightly.
Then adjust until you can here the engine run at its highest speed. Caution.
Pushing the throttle all the way forward will shut the engine off. Note: Turning the
key to the off position will always shut the engine off.
6) Once hovering set the thrust engine to desired speed (top lever).
7) Steering is accomplished through the moving of the rudder stick located in the
dash. Remember: Moving the rudder to the left will make the craft’s rear travel to
the right. Centering the controls will then move the craft it the desired direction.
This it also true for the reverse direction.
Shutting down the hovercraft:
1) Shut down thrust engine by moving the top lever to the stop position. Do not
move the lever to choke to shut the engine off.
2) Shut down the lift engine by turning the key to the off position (turning to the
left).
3) Once both the lift and thrust fans have stopped it is safe to exit the craft.
4) Exit the craft be standing and then stepping on the panel labeled “step”.
Gas and Oil:
Both the lift and thrust engines can be filled with regular unleaded gas.
Both the lift and thrust engines run on SAE 30 motor oil, which is available at most
auto-part stores and gas stations. Both gas and oil levels should be checked
frequently. Both engines should have their oil changed after the first 5hrs. of use.
Thereafter, follow the maintenance suggested in the manuals located at the end of this
document.
Maintenance:
A)
Tools possibly needed:
½" open ended wrench
½" socket drive
39
Flat head screwdriver
Phillips head screwdriver
Staple Gun with staples
B)
Both the lift and thrust engine manuals are located at the end of this manual.
These contain the maintenance schedules and also a trouble-shooting guide for each
engine. If there are any problems with the engine that can not be solved by consulting
these manuals, contact Charlie’s Equipment Service at the below address.
Charlie’s Equipment Service
14-B2 Albe Drive
Newark DE 19702
(302) 738-5664
C)
The battery for the electric start is located at the front of the craft just inside
the access panels. Wiring diagrams are provided at the end of this manual.
D)
All bolts used on the hovercraft are 5/16" in diameter. The length varies with
location, however all are equipped with two washers, a single lock washer and one
nut. Should one be lost or broken any hardware store will carry replacements.
E)
Frequently check all protective screens to ensure they are properly secured. If
any area is unsecured re-staple the screen in place. If it becomes necessary to replace
a screen the grid spacing is ¼" x ¼".
F)
If the body of the hovercraft is damaged in anyway it can be repaired with
joint compound or Bondo. Simply fill the damaged area, and once dry sand smooth.
Clean the area prior to painting with a semi-gloss black paint.
G)
Should the skirt become torn or damaged it can be repaired with an inner tube
patch kit in most cases. If the tear is large, take extra skirt material and sew and glue
a patch in place. This may require the removal of a portion of the skirt. Remove the
screws that hold the skirt in place to do this. After the repair is made replace the
40
screws and skirt as close to the original position as possible, this will ensure the skirt
remains efficient. Extra skirt material can be obtained from:
Universal Hovercraft
Box 281
Cordova, IL 61242
Phone: (309) 654 – 2588
H)
Periodically check the location of the lift and thrust fans. For the lift make
sure the ductwork is in place and no parts have worked loose. Check the attachment
of the fan hub to the shaft, make sure that no parts are rubbing or in danger of binding.
For the thrust fan, check to make sure the fan is not hitting the protective screens.
41
APPENDIX F: Engineering Drawings
42
43
44
45
46
47
48
49
50
51
52
53
54