1. Propulsion Team The University of Alabama
Andrew Treadway, Kelli Harding, Ryan Miller,
Daniel Stucki, Timothy Nash
10/27/2014

2. Engine Mount Fan Calculations
Lift Engine
Engine Mount Fan Calculations
Briggs & Stratton Vertical Engine
Same as last year-Works well
RPM
Vertical shaft
Weight: 24.3 lbs (w/o fuel and oil)
Ready start system
1.0 quart fuel tank w/ Fuel Pump
Muffler included

3. Engine Mount Fan Calculations
Lift Engine
Engine Mount Fan Calculations
Modify previous year’s design
Works well, minor issues

4. Engine Mount Fan Calculations
Lift Engine
Engine Mount Fan Calculations
24 inch fan diameter
5 blades
Pitch angle adjustable to 45°
Weight: 7.5 lb

5. Engine Mount Fan Calculations
Lift Engine
Engine Mount Fan Calculations
Hovercraft parameters:
Length: in
Width: 68.3 in
Footprint area: 9544 in2
Weight: 500 lb
𝑃 𝑐 𝑐𝑢𝑠ℎ𝑖𝑜𝑛 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 = 𝑊𝑒𝑖𝑔ℎ𝑡 𝐴𝑟𝑒𝑎 =0.052 𝑝𝑠𝑖
𝑉 𝑒𝑥𝑖𝑡 = 𝛽 𝑑𝑖𝑠𝑐ℎ𝑎𝑟𝑔𝑒 2 𝑃 𝑐 𝜌 = ∗ 𝑥 10 −3 =42.07 𝑓𝑡 𝑠
𝐴 ℎ𝑜𝑣𝑒𝑟𝑔𝑎𝑝 = 𝐻 𝑔𝑎𝑝 ∗𝑃𝑒𝑟𝑖𝑚𝑒𝑡𝑒𝑟=0.5∗405.7=202.9 𝑖 𝑛 2
𝑃 𝑏𝑎𝑔 𝑏𝑎𝑔 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 =1.2∗ 𝑃 𝑐 = 𝑝𝑠𝑖
𝐿𝑖𝑓𝑡= 𝑃 𝑏𝑎𝑔 ∗𝐴= 𝑙𝑏

6. Engine Mount Fan/Prop Calculations
Thrust Engine
Engine Mount Fan/Prop Calculations
Kholer PAE-CH
Improved over last year’s design
Lighter Weight
More Horsepower
Electronic Fuel Injection
Brand
Kholer
Type CH
CH (old)
CH (new)
Power [hp] 27 25
Compression Ratio
9.1:1
9.0:1
Weight [lb]
108
115 94
Displacement [cc]
725
Power-to-Weight [hp/lb]
0.2500
0.2347
0.2660

7. Engine Mount Fan/Prop Calculations
Thrust Engine
Engine Mount Fan/Prop Calculations
Modify last year’s mount design
Reduce vibration
May do preliminary design to dampen vibrations on current craft

8. Engine Mount Fan/Prop Calculations
Thrust Engine
Engine Mount Fan/Prop Calculations
Decided on fan
Adjustable pitch and blades
Easily replaceable blades (also cheaper)
Same dimensions as old craft (propulsive screws are interchangeable)
Re-order wooden prop for 2014 craft
Ensure correct parameters
Vs.

9. Engine Mount Fan/Prop Calculations
Thrust Engine
Engine Mount Fan/Prop Calculations
Regulations
Max Engine Speed: 3600 RPM
Max Tip Speed: 330 ft/s
Max Fan Speed (4 ft diameter)
𝑀𝐹𝑆= 𝑉 𝑡𝑖𝑝 𝑟 = = 𝑅𝑃𝑀
Gear Reduction: 𝐺𝑅= 𝐹𝑎𝑛 𝐻𝑢𝑏 𝐸𝑛𝑔𝑖𝑛𝑒 𝐻𝑢𝑏 = =2.28

10. Engine Mount Fan/Prop Calculations
Thrust Engine
Engine Mount Fan/Prop Calculations
Diameter (ft)
A (ft2)
mass flow Ue T
Tstatic
3.50
9.621
0.8911
183.21
137.16
163.27
3.66
10.55
0.9780
175.10
142.60
171.26
3.83
11.54
1.0690
167.71
147.95
179.2
4.00
12.56
1.1639
160.94
153.22
187.33
4.16
13.63
1.2630
154.72
158.39
195.41 U0
29.308 U1
39.1 ρ Ps
14575

11. Ducts Lift Thrust Same design as last year 24 inch duct Weight: ~5lb
Will be strengthened with fiberglass and sheet metal for protection
Both ducts will be built with better techniques to ensure constant diameter

12. Skirt Skirt material left over from last year
Will use same design, slightly modify dimensions
Last year forced to add holes
Will build a better balanced craft to alleviate issues

13. Questions?

14. Structures Team The University of Alabama
Amber Deja, Victoria Reasoner, Clay Lemley
10/27/2014

15. Hull Design Based on Chris Sorgatz’s design
Similar to Hoverteam design
160.3 inches long (Approx ft.)
68.3 inches wide (Approx. 5.7 ft.)

16. Hull Structure Fiberglass Resin Other
Materials
Hull Structure Fiberglass Resin Other
Polypropylene honeycomb material
1” thickness – 3 sheets
0.5” thickness – 9 sheets
Total of 384 ft2 will be ordered
Light (total of 35 lbs. to construct hovercraft)
Aids in flotation
Cost effective
$55 per 1” sheet
$35.75 per 0.5” sheet
Ease of use
Cuts smoothly

17. Hull Structure Fiberglass Resin Other
Materials
Hull Structure Fiberglass Resin Other

18. Hull Structure Fiberglass Resin Other
Materials
Hull Structure Fiberglass Resin Other
Inquired about other types of honeycomb
Polycarbonate
Aramid fiber
Contact at Plascore stated polypropylene is the type of honeycomb most widely used for laying up with fiberglass

19. Hull Structure Fiberglass Resin Other
Materials
Hull Structure Fiberglass Resin Other
Both carbon fiber and fiberglass were considered
Carbon fiber costs 4-6 times as much
Want to keep the craft light but strong
Previous team used 4 oz. E-Glass woven cloth
This year, 4 oz. S-Glass woven cloth will be used

20. Hull Structure Fiberglass Resin Other
Materials
Hull Structure Fiberglass Resin Other
S-Glass is used when extra strength is needed and extra weight is not desired
40% higher tensile strength
20% higher modulus
Greater abrasion resistance
Same working qualities as standard E-Glass
Considered using a heavier E-Glass cloth instead
More resin required
Increased weight of craft

21. Hull Structure Fiberglass Resin Other
Materials
Hull Structure Fiberglass Resin Other
Four brands of epoxy resin were compared
West Systems 105 was chosen
Most widely used, reliable brand
Competitively priced with other resins of the same quality
4.35 gallon pail will be ordered

22. Hull Structure Fiberglass Resin Other
Materials
Hull Structure Fiberglass Resin Other
West Systems 205 Fast Hardener
9-12 minute working time
6-8 hour drying time
West Systems 206 Slow Hardener
20-25 minute working time
9-12 hour drying time
Slow hardener will be used
Both have same cost
Increased working time is a plus
Increased drying time will not be an issue

23. Hull Structure Fiberglass Resin Other
Materials
Hull Structure Fiberglass Resin Other

24. Hull Structure Fiberglass Resin Other
Materials
Hull Structure Fiberglass Resin Other
Fiberglass Shears
Plywood
Create molds to piece together plenum chamber
Heavy Duty Adhesive
Piece together plenum chamber before fiberglass is applied
Paintbrushes

25. Hull Structure Fiberglass Resin Other
Materials
Hull Structure Fiberglass Resin Other
Epoxy Pumps
Ensures correct ratio of resin to hardener
Disposable Gloves
Disposable Cups
For mixing resin and hardener
Sandpaper

26. Costs Item Cost Plascore $617.00
Fiberglass (500 sq. feet 4 oz. S-Glass)
$415.00
Epoxy Resin/Hardener (4.35 gal/1 gal)
$453.00
Resin Pumps
$12.00
Heavy Duty Adhesive (Three 28 fl. oz. bottles)
$25.00
Plywood (Three 4’x8’ sheets)
Fiberglass Shears
$35.00
Other (gloves, cups, etc)
$100.00
Total Estimated Cost
$1,682.00

27. Balance Structural Weaknesses Measure Twice, Cut Once
Improvements
Balance Structural Weaknesses Measure Twice, Cut Once
2014 racecraft is very back heavy
CG is not at optimum location
Driver had to lean forward to attempt to balance the craft while racing
Lift duct was moved further toward back of craft than was originally designed
Contributed to CG being too far aft
2015 racecraft lift duct will be moved back to original designed location
Front
Hovercraft Hull
160.3 in
80.15 in
Actual CG at 93 in
Side View of 2014 Racecraft

28. Balance Structural Weaknesses Measure Twice, Cut Once
Improvements
Balance Structural Weaknesses Measure Twice, Cut Once
Addition of fiberglassed honeycomb lip to add more support for the deck
Fiberglass both sides of plenum chamber stiffener

29. Balance Structural Weaknesses Measure Twice, Cut Once
Improvements
Balance Structural Weaknesses Measure Twice, Cut Once
2014 Racecraft
Jigsaw used to cut all pieces of honeycomb
Cuts were not necessarily straight
Angles were not properly cut
Pieces didn’t fit together properly – gap fill used as a remedy
2015 Racecraft
Measure TWICE, cut ONCE
Tablesaw will be used, especially for larger pieces and to cut angles properly
Avoid using gap fill

30. Questions?

31. Controls and Electronics Team
The University of Alabama
Jacob Wilroy, Ashely Reasoner, Liang Zhu
Ethan Slusher, Sara Guiley
10/27/2014

32. Theory Applications Construction
Stator Vanes
Theory Applications Construction
Spinning motion of fan/propeller imparts swirling motion to the air moving through the duct. Fans tend to induce more swirling motion than propellers.
Using stator vanes, we can translate the rotational momentum of the air into backwards momentum (thrust)
Stator vanes also serve a structural purpose, adding rigidity to the duct, especially near he rudders.
Trying to achieve better aerodynamics within the duct.
Region of separation = increased drag x 4 x 2

33. Stator Vanes Theory Construction
Blade twist leads to change in velocity vector direction
Linear blade twist = linear cut along curved portion of stator

34. Stator Vanes Theory Construction
Stators can be created using a mold and vacuum bagging technique.
Mold can be created from sheet metal bent at the appropriate angle and given the correct curvature.
Multiple stator vanes can be created from a single mold.
Vanes will be attached to the duct by fiberglass
Center piece will be created from Styrofoam covered with fiberglass. All vanes will attach here.

35. Stator Vanes Theory Construction Make stator from plastic fan blade
Twist blade to get the correct pitch
Smooth leading edge of fan blade will be better than sharp edge of fiberglass “plate”.
Use fan blade = use hub in the center
Make stator blades optional/removable

36. Stator Vanes Theory Construction
Vacuum Bagging: (
Basic kit - $161.50
1 VentVac Plus Venturi Vacuum Generator
2 Yds of Peel Ply
1 Yd of Bleeder Breather Cloth
1 Yd of Vacuum Bag
1 Roll of Sealant Tape (25ft.)
2 Yds of Vacuum Tubing
Vacuum Bagging Benefits:
Needed for molding of parts
Can acquire the shape you need
Can be used year after year
Helps to remove trapped air and distribute resin/hardener

37. Control Surface - Rudders
Previous Design New Design
Last year’s design
5 rudders of the same dimensions
Utilize 70 % of flow area
Evenly spaced across diameter
Rudder size: 24 in x 7 in
Rudder shape: triangle
Rudder weight: lb

38. Control Surface - Rudders
Previous Design New Design

39. Control Surface - Rudders
Previous Design New Design
Rudder shape
Rudders bend and deform easily
Consider a stiffer shape or material

40. Control Surface - Rudders
Previous Design New Design

41. Control Surface - Rudders
Previous Design New Design
Option 1 Design
Four control surfaces
Evenly spaced across diameter
Utilize entire duct flow area
Two panels: 47 in x 10 in
Two panels: 38.4 in x 10 in
Constraint: 48 in diameter duct
Top View
Front View
Side View

42. Control Surface - Rudders
Previous Design New Design
Four Rudders – (width of inches)
Material: Aluminum
Density: 169 lb/ft3 or lb/in3
Rudder shape: Triangle
Rudder volume(long): in3
Rudder volume(short): 48 in3
Total weight: lb

43. Control Surface - Rudders
Previous Design New Design
Option 2 Design
Three control surfaces
Evenly spaced across diameter
Utilize entire duct flow area
One panel: 48 in x 10 in
Two panels: 41.5 in x 10 in
Constraint: 48 in diameter duct
Top View
Front View
Side View

44. Control Surface - Rudders
Previous Design New Design
Three Rudders – (width of inches)
Material: Aluminum
Density: 169 lb/ft3 or lb/in3
Rudder shape: Triangle
Rudder volume(long): 60 in3
Rudder volume(short): in3
Total weight: lb

45. Control Surface - Rudders
Previous Design New Design
Turning angle is mostly based on the push-pull cable actuation length. In order to give ourselves a fighting chance, we will purchase the longest cable possible.
Upon installation of the first set of rudders, we will find a turning angle that produces the largest turning force. From there the maximum turning angle can be set.

46. Discussion Calculations
Cockpit
Discussion Calculations
Reduce quantity of fuel
Move fuel to a different location
Creates more problems
Shift cockpit forward
Shift rear components (P-duct, P-engine, rudders) forward to achieve correct CG

47. Discussion Calculations
Cockpit
Discussion Calculations
Best option is to shift engine, rudder, and propulsion duct forward
Component
Weight [lb]
Local CG Refernce Distance [in]
Moment [in-lb]
Lift Engine 30 32
960
Lift Engine Mount 15
480
Lift Duct 37
1184
Driver
170 74
12580
Fuel Tank fully loaded 39 77
3003
Battery 6 46
276
Propulsion Engine
125
111
13875
Propulsion Engine Mount
118
3540
Propulsion Duct 90
129
11610
Upper Pulley
1770
Fan and Hub 10
1290
Rudders 50
142
7100
Plascore Hull 35 86
3010
Fiberglass Hull
172
14753
CG Location: 92 inches
Move everything up 4 inches with lift duct :88 inches!
Move propulsion engine, mount, duct and rudder up another 7 inches: 84 inches!

48. Questions?