JEE335 Assignment 4 PDF

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Structural design assignment...

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National Centre for Maritime Engineering & Hydrodynamics Australian Maritime College OFFICE USE ONLY Assignment Received:

ASSIGNMENT COVER SHEET

For attention of: Dr Thomas Mitchell Ferguson..................................…………………………………………… (Lecturer or Tutor’s name – whichever is applicable)

Student ID Number: 401887………………………… Student’s Family Name/ Surname:Toh................................................................................................................. Student’s First Name: Nicholas......................................................................................................................

Unit Code: JEE335……………………………. Unit Name: Applied Ship Design..................................................................................................... Assignment Title: Structural Design Assessment....……………………………. ............................................... ………………….…………………………………………………………………………………………...……………. Assignment No:……4…….. (as per unit outline) Due Date: 28 September 2018.................................. Date Submitted: 28 September 2018.......................... [Late submission of assignments may incur a penalty]

I declare that all material in this assignment is my own work except where there is clear acknowledgement or reference to the work of others and I have complied and agreed to the University of Tasmania statement on Plagiarism and Academic Integrity on the University website at www.utas.edu.au/plagiarism*

Signed. NIC……………………………………. Date ……28……/……9……/……2018……… *By submitting this assignment and cover sheet electronically, in whatever form, you are deemed to have made the declaration set out above.

Table of Contents Table of Contents ........................................................................................................................ i List of Figures ............................................................................................................................ii List of Tables .............................................................................................................................ii 1.

Introduction ........................................................................................................................ 1

2.

Spade rudder ...................................................................................................................... 1 2.1.

Advantages .................................................................................................................. 2

2.2.

Disadvantages.............................................................................................................. 2

3.

Design process ................................................................................................................... 2

4.

Justification ........................................................................................................................ 2 4.1. Rudder dimensions ...................................................................................................... 2 4.2.

5.

Rudder profile ............................................................................................................. 3

Structural calculations performed ...................................................................................... 4

6.

Conclusion ......................................................................................................................... 5

7.

References .......................................................................................................................... 6

8.

Appendix ............................................................................................................................ 7 8.1. Structural drawings ..................................................................................................... 7

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List of Figures Figure 1: Spade and semi spade rudders as adapted from (Det Norske Veritas, 2000)............. 1 Figure 2: Rudder dimensions as adapted from (DNVGL, 2018) ............................................... 3 Figure 3: NACA 0024 airfoil profile as adapted from (Airfoiltools, 2018) .............................. 4 Figure 4: Bending moment and shear force as adapted from (DNVGL, 2018)......................... 4

List of Tables Table 1: Vessel parameters as adapted from (Ferguson, 2018) ................................................. 1 Table 2: Design constraints as adapted from (Ferguson, 2018)................................................. 3

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1. Introduction Rudders is an essential component as it acts as the primary control surface for steering through a fluid medium. This report focuses on the design process of a spade rudder and stock for a vessel with the parameters as listed in Table 1. Besides that, the designed model has to comply the several criteria as stated in the design brief which will be mentioned in the design process section of this report. From this, a spreadsheet containing the various calculations regarding the rudder and the rudder stock have been completed to obtain the minimum dimensions for the designed structure.

Table 1: Vessel parameters as adapted from (Ferguson, 2018) Parameter

Symbol

Value

Unit

Rule length

L

62.6

m

Rule draft

T

2.3

m

Rule beam

B

9.8

m

Displacement

Δ

650.8

tonnes

Max speed

V

32

kts

2. Spade rudder Spade rudders which are also known as balanced rudders as seen in Figure 1 are categorized by obtaining the ratio percentage of the forward portion area of the rudder and the total area. This structure consists of a rudder plate that is constrained at the top of the rudder by a rudder stock. The rudder post extends out of the hull into the rudder to allow the structure to rotate to either side of the vessel.

Figure 1: Spade and semi spade rudders as adapted from (Det Norske Veritas, 2000)

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2.1. Advantages There are several advantages of utilizing a spade rudder. Firstly, the rudder is a selfstanding structure whereby it can operate without the requirement of other structural supports or a skeg for mounting. Secondly, the vessel can be easily steered due to the equaled forces acting on the helm. This is due to the rudder stock being positioned slightly aft from the front of the rudder thus causing the leading edge to rotate to the side of the vessel while the trailing edge rotating to the other side. Besides that, when the rudder area is at 20% to 37%, the rudder stock does not experience any torque. (Lochhaas, 2017)

2.2. Disadvantages On the other hand, the usage of such rudder can contribute to several disadvantages. This includes the rudder being vulnerable to external objects in the water. When these objects contact the rudder plate, the rudder stock experiences additional forces which may attribute to difficulty when steering. Besides that, another factor of damaging stress can be caused due to the slamming motion of the vessel. (MarineEngineeringOnline, 2015)

3. Design process There were various software utilized in designing the rudder and the stock. Firstly, the rudder design was drawn on the AutoCAD Mechanical 2017 Software. Then the calculations was done by utilizing the equations on the Det Norske Veritas (DNV) documents and listed on the Microsoft Excel Spreadsheet Software. These dimensions are to comply with the minimum total required area calculated as 1.83m2. From this, the rudder stock dimensions are obtained from the aforementioned calculations and drawn onto the AutoCAD software. Lastly, the remaining dimensions of the rudder and stock are to comply with the DNV documents as mentioned previously. These dimensions will be discussed upon in the justification section of the report.

4. Justification 4.1. Rudder dimensions Once the minimum dimensions of the rudder and stock were carried out, the dimensions of the structure was set due to various specifications. These specifications must comply with the constraints as listed in Table 2. Firstly, the height of the model was set to 1.5m with a large breadth of 1.5m and small breadth of 1.3m which results in a mean breadth of 1.4m. From this, the area was calculated to be 2.1m2 which complies with the minimum area required for the design. Furthermore, the forward section area (Af) of the rudder plate as seen in Figure 2, was calculated to be 0.75m2. This generated a ratio of approximately 35.7m2 which concludes that this rudder is categorized as a balanced rudder as mentioned previously. Besides that, the clearance distance was set to 0.3m. This value was set to be relatively small to prevent a large bending moment and forces on acting on the rudder while reducing the stiffener thickness and the diameters of the rudder stock and shaft. Moreover, the rudder post was extended 0.75m inside the hull to comply with the design criteria as listed in Table 2. By doing so, the minimum top diameter and the bottom diameter of the rudder stock was obtained at approximately 0.112m and 0.331m respectively. These values were rounded off to 0.115m and 0.335m as the dimensions must be above the minimum calculated dimensions. From this, the stiffener thickness were obtained to be approximately 0.0168m and 0.00967m for the horizontal and vertical stiffeners respectively. Similarly, these values were rounded up as 0.017m and 0.01m. In addition to that, the spacing between both the vertical and horizontal stiffeners were also a factor when determining the stiffener 2

thickness. Therefore, to obtain an optimum thickness, the horizontal stiffener spacing were set to 0.25m while the vertical spacing were set to 0.3m. It should be noted that the minimum thickness of the stiffeners were obtained by utilizing the larger value obtained from the calculations of the stiffeners. Table 2: Design constraints as adapted from (Ferguson, 2018)

Maximum breadth Draft at the rudder post Rudder stock extension inside the hull Rudder position Construction specifications Bearings and couples Condition

1.5m 0.75m 0.75m Behind the propeller According to DNV-GL from DNV Grade VLA Steel Not required to be designed Ahead condition only

Figure 2: Rudder dimensions as adapted from (DNVGL, 2018)

4.2. Rudder profile The chosen rudder profile was set to NACA 0024 as depicted in Figure 3 due to several justifications. This profile specifications includes a maximum thickness of 24% at 30% of its chord length thus generating a maximum profile width of 0.360m when at the rudder large breadth value of 1.5m. This allowed the profile to accommodate the larger diameter of the rudder stock at 0.335m. This will be illustrated in the structural drawings as displayed in the Appendix section of this report.

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Figure 3: NACA 0024 airfoil profile as adapted from (Airfoiltools, 2018)

5. Structural calculations performed This section discusses of the various sections utilized in the calculations performed on the Excel Spreadsheet. Firstly, the minimum area of the rudder as mentioned previously was obtained by utilizing the DNV Part 3 Chapter 3. Then, the remaining calculations were conducted by utilizing the equations as listed in the DNVGL Part 3 Hull Chapter 14 Rudders and steering document. It should be noted that these calculations involved sections 1, 2, 4 and 5 while neglecting section 3 due to the exclusion of bearings and couplings in the scope of the assignment. Besides that, it should be noted that the minimum service speed and astern speed were obtained but were not utilized in any sections of the calculations. In addition to that, the rudder shaft scantlings were also not utilized in any of the aforementioned calculations. Furthermore, by utilizing the calculations in the Appendix section and Figure 4 of the DNVGL document, the rudder’s bending moment and shear forces were obtained.

Figure 4: Bending moment and shear force as adapted from (DNVGL, 2018)

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6. Conclusion In conclusion, the advantages of utilizing a spade rudder includes easier steering capabilities as well as being a self-standing structure. However, the model structure experiences various disadvantages such as external forces generated by debris when in contact with the rudder plate as well as the damaging stresses generated from the slamming motion of the vessel. Besides that, the structure was designed on the AutoCAD software and the calculations were listed on the Excel Spreadsheet by utilizing the equations from the DNV documents. Furthermore, the design was to comply with various constraints which includes the design constraints as listed in the task brief as well as the minimum calculated dimensions obtained through the calculations from the Excel Spreadsheet. Moreover, NACA 0024 profile was utilized due to the profile specification accommodating the larger section of the rudder stock.

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7. References Airfoiltools. (2018). Airfoiltools. Retrieved from NACA 0024 (naca0024-il): http://airfoiltools.com/airfoil/details?airfoil=naca0024-il Det Norske Veritas. (2000). DNV Part 3 Chapter 3. Retrieved from Mylo: https://mylo.utas.edu.au/d2l/le/content/241809/viewContent/2816806/View DNVGL. (2018). DNVGL-RU-SHIP-Pt3Ch14. Retrieved from Mylo: https://mylo.utas.edu.au/d2l/le/content/241809/viewContent/2816808/View Ferguson, T. (2018). Structural design. Retrieved from Mylo: https://mylo.utas.edu.au/d2l/le/content/241809/viewContent/2816807/View Lochhaas, T. (2017). The Types of Sailboat Rudders. Retrieved 9 28, 2018, from https://www.thoughtco.com/sailboat-rudder-types-2915591 MarineEngineeringOnline. (2015). Construction and Types of Rudder on Ships. Retrieved 9 27, 2018, from Marine Engineering Online: https://marineengineeringonline.com/construction-and-types-of-bearing-on-ships/

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8. Appendix 8.1. Structural drawings

7

1

2

3

4

5

A

335 115

749.96

B

335 115

360

300

450

C

Rudder plate thickness of 10mm

Top View 300

1500

D

E

250

1300 1500

Side View TOLERANCES +/- 0.1 EXCEPT AS STATED

F

SURFACE FINISH:

DIMENSIONS IN MILLIMETERS 1

2

DRAWN TO AS 1100

DO NOT SCALE 3

DRAWN BY: DATE DRAWN: CHECKED BY: APPROVED BY:

Nicholas Toh

Rudder and

28 09 2018 4

CODE INDENT No.: CODE SCALE:

1:15 5

DR NU

SH

1

2

3

4

5

A

B2 792.21

750

B

l30 MB

300

390.58

C

l20

1500

D

l10 PR

180.96

E

Load

1300

M

C1 1500

C2

F

TOLERANCES +/- 0.1 EXCEPT AS STATED SURFACE FINISH:

DIMENSIONS IN MILLIMETERS 1

2

DRAWN TO AS 1100

DO NOT SCALE 3

DRAWN BY: DATE DRAWN: CHECKED BY: APPROVED BY:

Nicholas Toh 28 09 2018 4

Rudder Load, Mom CODE INDENT No.: CODE SCALE:

1:15 5

DR NU

SH...