AIRCRAFT
CARRIER
DRAFT
MEASUREMENT
Introduction
• Newport News Shipbuilding partnered with Old Dominion
University to develop a draft measuring system for use on
naval aircraft carriers
Draft Overview
• Shift Draft:
• Ship draft is the vertical distance between the keel and the waterline.
• Draft is used to estimate the weight of cargo on board, by calculating
the total displacement of water and applying Archimedes’ Principle.
• The current method of draft measurement is to visually inspect the
waterline markings on the ship. This process is accurate up to 1”
• By improving draft measurement, the ship weight can be more
accurately determined.
• Design Specifications:
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1/8th inch accuracy
Economical
Portable
Wireless
Reduce risk to personnel
Non-permanent mounting
Ultrasonic Overview
Our system utilizes a sonic range
finder:
• The ultrasonic range sensor
sends a high frequency
(42kHz) sound wave toward
the water surface. The wave is
then reflected back to the
sensor.
• The distance from the sensor to
the water surface is calculated
based on the time of flight of
the sound wave.
Electronics System
MaxBotix Ultra-Sonic High Performance Rangefinder:
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42kHz frequency
195 inches maximum range
32-149 ºF temperature range
Real-time calibration voltage, humidity, ambient noise
Arduino Micro Controller Board
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32kB flash memory and 2kB SRAM
16mHz clock speed
Provides USB connection
14 digital input and output pins
6 analog input pins
Adafruit Bluefruit EZ Link Bluetooth
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Bluetooth serial link and Arduino programmer
10m range and 9600 Baud rate
LabVIEW Display
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LabVIEW is a graphical user
interface and instrument control
tool used to acquire and analyze
measurement data
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Professional engineering
platform that allows access to
any networked user.
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Allows remote activation
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Utilized to generate data plots
Mounting Assembly
Designed and created the following components using AutoDesk Inventor, and
Stratsys and MakerBot Z18 3D Printers:
Magnetic L-mount
Block Adapter
Angle Adapter
Purchased and installed the following components:
• Easy On/Off Magnetic Switch (150lb pull strength)
• Zinc plated steel in-line ball joint linkage
• Steel Push Pins
Electronics enclosure
Configurations
Assembly
configurations
allow for multiple
mounting angles
on ship hull
FE Analysis
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40lb force applied at the
end of a 24 inch aluminum
4043 hollow rod
0.125 inch wall thickness
Minimal deformation
20lb force applied designated
point of the L-shaped bracket
ABS plastic construction
Minimal deformation
Testing
Multiple tests were performed to verify the device specifications:
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Blue Tooth Signal Range
Temperature
Waves
Precipitation
Blue Tooth Signal Range:
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Blue tooth signal was
successfully transmitted
up to 33ft from a PC
Temperature Range:
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The sonar system was
operational between
32 – 76 F
Wave Height Testing
Wave Height (inches)
1.969
3.937
5.910
7.874
Manual “Draft” Measurement (inches)
48.70
48.70
48.70
48.70
Average value from sonar readings (inches)
48.75
48.72
48.68
48.58
+ 0.05
+ 0.02
- 0.02
- 0.12
Difference (inches)
Precipitation Testing
Condition #1
• Water spray was directed through
the sonar beam
• 3.937 inch waves were introduced
Condition #2
• Water spray was directed at the target
zone.
• No waves were introduced
Condition #1
Condition #2
Manual “Draft” Measurement (inches)
50.00
50.00
Average value from sonar readings (inches)
49.93
50.54
Difference (inches)
- 0.07
+ 0.54
Conclusions
• The following design specifications were met:
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1/8th inch accuracy: Desired accuracy was achieved in calm water
conditions and in wave heights ranging between 2-8 inches. However, the
system is not recommended in rain conditions.
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Economical: Rapid prototyping utilizing 3D printing reduced costs over
traditional machine shop labor, and using readily available off the shelf
components reduced hardware costs.
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Portable: Components are made of light weight ABS plastic and are
modular, which allows easy assembly and transport.
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Wireless: Bluetooth technology provides sufficient range for testing the
concept.
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Reduce risk to personnel: System will automate draft measurement
process, eliminating the need for technicians to be in small crafts to
manually take measurements.
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Non-permanent mounting: Using a magnetic mounting system, the
device can be easily mounted and removed without damage to the
carrier’s protective hull coating.
Gantt Chart
Acknowledgements
 Faculty Advisor
 Dr. Miltiadis Kotinis
 Shipyard Liaison
 Butch Brenton – Manager Engineering 3
 Department of Mechanical and Aerospace Eng.
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David Mooney – Team Manager
Sam Harpin
David Mann
Philip Stickle
Devin Samples-Wright
Thomas Wheeless
 Department of Electrical and Computer Eng.
 Ashley Smith
 Department of Engineering Tech.
 Ashley Wilson – EET
Additional Assistance:
 Dr. Navid Tahvildari – Wave tank training
 Dr. Gangfeng Ma – Wave tank training
 Michael Polanco – 3D Printing and Poster Assistance
Questions?