ME 441 Senior Design CUA Hovercraft – Class of Joe Cochrane, Aldo Glean, James McMahon, Omar Monterrubio, Kalin Petersen ME 441 Semester Summary 12/4/08

Project purpose System requirements Hull and deck Lift calculations Skirt construction Lift engine modifications/mount Lift fan justification Thruster justification/testing Thruster housing design 36 V Power system/alternator testing Goals for next semester Presentation Outline

Purpose To develop an autonomous hovercraft for carrying landmine detection hardware for the facilitation of humanitarian efforts to de-arm post conflict mine fields.

System Requirements Sufficient deck space to accommodate components Cushion pressure less than 8 psi (pressure required to trigger a landmine) Remote maneuverability Minimum payload capacity: ~562 lb -Does not include weight of hull or possible counter- balance weight

Hull and Deck 6’x10’ Deck Size* 7’x10’ Deck Size* Equipment requirements: Minimum area: ~50 ft 2 Does not include obscure equipment footprints or additional equipment Radar antenna spacing Modeled deck layout Proposed size: 7’x10’ *configurations are tentative

Hull and Deck Hull is ~3x bigger than last year’s, but conceptual design was retained Proven design Simplicity Time and money invested Took approximately 6 weeks to complete construction Next semester: Waterproofing: drain holes and polyurethane

Hull and Deck

Hull: I-beam Testing Conducted “pullout test” on sections of base to I- beam and deck to I-beam connections Test shows connections can withstand over 15 psi Connections must be able to withstand at least 7.7 psi Factor of safety of at least 1.94 Calculations

Hull: I-beam Testing

Lift Calculations Fluid dynamics reexamined for the lift system Cushion pressure: psi Required flow rate: cfm Inside hull pressure: ~0.72 psi Calculations

Skirt Maintained previous skirt design Used same material (ballistic nylon) Went to Cambridge Canvas & Sail Loft in Cambridge, MD to have skirt professionally sewn

Skirt

Hull and Skirt Assembly

Zenoa G50 Fan Cooled Engine – rpm – 2 stroke, Twin Cylinder, Horizontal Opposed Engine reorientation required intake manifold modifications Intake manifold modifications are complete Engine fully functional in new orientation Next semester: – Exhaust modifications – Engine shaft-lift fan-alternator connection – Engine mount Lift Engine

Modification Original

Conceptual Engine Mount Design Top views Side view

Previous lift fan model and size determined sufficient for project requirements Lift Fan

During the summer, gas engine was tested extensively Decision was made to switch to electric motors due to difficulty with tuning and inconsistency of gas engine Researched electric model airplane motors, went with largest model Thrusters

Electrifly Rimfire 63mm Out-Runner Brushless Motor – Weight: 22.4 oz. (635 g) – Suggested prop size: 18x6W - 20x8E – Input Voltage: V Thrusters

Wooden 20x8 (diameter x pitch) and plastic 20x8 propellers tested Concluded that the wooden and plastic props produced the same amount of thrust force Plastic props were chosen: less expensive Thruster Testing

Electric motor is lighter and smaller Thruster housing design modified for space conservation Decision to use 0.01” thick galvanized steel for thruster shroud in place of bending wood Next semester: – Motor mount strength testing – Thrust reduction testing Thruster Housing

250 Amp externally regulated alternators 36V system using alternators to power electric motors Basic testing completed 36 V Power System

28.9 V produced on unloaded alternator at approximately 3300 rpm Tested electric motor powered by single alternator Motor was run successfully, but only produced maximum of 12.6 lb of thrust Alternator Testing

Final engine mount design and construction Working hovercraft Functioning 36 V power system Thruster controls Employment of radar, GPS and other system components Goals for Next Semester

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