Study of the stability and the hull integration with the propulsion system of a riverine support vessel, in order to optimize the efficiency of the propulsion plant and improve its maneuverability in its operations area

1. Computational optimization of stability, propulsion
and maneuverability of a riverine vessel
Lieutenant Commander Luis Javier Serrano Tamayo
Colombian Navy
University of the Andes - Naval Academy “Admiral Padilla”
COLOMBIA

2. Contents
1. Introduction
2. Hull and Stability
3. Resistance and Propulsion System
4. Maneuverability
5. Conclusions
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

3. 1. Introduction
Riverine importance of Colombia
Caribbean Sea 2nd country in biodiversity
Coasts and
Andean Region:
55% Territory
95% Population
Pacific Ocean
Amazon Jungle:
45% Territory
05% Population
Highways
Rivers
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

4. 1. Introduction
Problem
The 1rst generation of RPV’s (Riverine Patrol Vessels) are very useful
ships, but the armor is very heavy, the motors were racing just 1500
of the 1800 RPM, the propellers were present cavitation and the
ships should improve their maneuverability due to the narrow rivers.
¼”
20 mm Arena
Polyurethane
¼”
20 mm Arena
Polyurethane
¼”
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

5. 1. Introduction
General goal
The study of the integration between the hull
and the propulsion system of the RPVs in
order recommend improvements to optimize
its propulsion system and reduce the tactical
diameter in their operational area.
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

6. 2. Hull and Stability
Hull geometry construction in field
half width height
Station 4; x=1,75 m
(axis "y") (axis "z")
Point 1 0 1.7
Point 2 1.7 1.65
Point 3 2.7 1.58
Point 4 2.7 1.295
Point 5 1.62 1.115
Point 6 1.18 0.575
Point 7 0.89 0.37
Point 8 0.78 0.31
Point 9 0 0
Is only necessary to write a half width, the software GHS
(General Hydrostatics) completes the shape
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

7. 2. Hull and Stability
1st edition results
Reference point 0,0,0
The bow has to be refined
Astern reached soft
curves and it was ready
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

8. 2. Hull and Stability
Refining process (fairing)
The control points were used to
accomodate the geometry
properly, as well as other
Rhinoceros software commands.
It was possible to obtain a faired
surface of the hull and to model
3D the hull of the RPVs.
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

9. 2. Hull and Stability
Tanks construction
The tanks were constructed utilizing different GHS commands
which permit fill in or fill out the tnaks in order to evaluate
different loading conditions.
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

10. 2. Hull and Stability
Coefficients of form
The curves show the full forms of the ship (above 0.8), as
well as the variation of the form coeffcients below 0.5 m of
depth, due to the semi-tunnels in the astern (propellers).
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

11. 2. Hull and Stability
Hyidrostatics curves
metacentric radius
long. moment I
H. Curves indicate different values to evaluate the intact stability
of the ship (no trim) for different loading conditions.
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

12. 2. Hull and Stability
Weight previous studies (Methods by main characteristics)
Method Result
Method of Benford Used for bigger ships displacements
Method of Danckwardt L/D is too little
Method of Lamb Lenght is too little
Method of Mandel Non logical value
Method of Murray Non logical value
Method of Osorio Could be useful as a reference
Method of J.L. García G. Too little value
The main characteristics methods evaluate the weight of any ship according
formulas related to other ships of the same type, but as conclusion, none
method satisfied the weight of the RPV precisely.
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

13. 2. Hull and Stability
Weights study. Ship Work Breakdown Structure (SWBS)
GRUPO CONCEPTO
100 Hull Strcuture
200 Propulsion plant
300 Electrical plant
400 Communications and Command
500 Auxiliary services
600 Equipment and Furniture
700 Weapons
M Margins
F Deadweight
The SWBS has subgroups and elements which describe precisely all the ship
components. Every one has a weight and a position in the 3D model and all
the weights were inserted to model the ship with its components.
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

14. 2. Hull and Stability
Summary of calculated loads according SWBS
When every weight is calculated and its 3D position is related to the
reference point, the final result is the CG of the ship.
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

15. 2. Hull and Stability
Example of weight distribution in the different stations
The example shows the longitudinal
distribution of some elements of the 100
SWBS group in the stations used to divide
the lenght of the ship.
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

16. 2. Hull and Stability
Curves of Loads
There are three main loading conditions:
Light ship. The weight of the ship without
any deadweight. Equitative distribution of
loads. Main weights are astern.
Minimal operational condition. The ship
has the minimum deadweight to
navigate. Water tanks 2/3 of load and
fuel 1/3 of load.
Full load. The ship has the 100% of
deadweight. Liquid cargo create punctual
weights in some stations.
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

17. 2. Hull and Stability
Stability criterion DDS-079 USN
Protection of vital spaces and main wall spacing
1. Spacing between transversal bulkheads = 10’ + 0.03 LBP
2. Collision bulkhead must be maximum at 5% de LBP
3. Crossed connections must be prevented
The ship passed the spacing criterion
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

18. 2. Hull and Stability
DDS-079 USN. Stability Threats
1. Beam wind combined with rolling
2. Heavy lifting over one side
3. Towing forces
4. People crowding over one side
5. High speed turning
6. Top icing
The first and the last two pose no threat to the vessel
considering its characteristics and surroundings.
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

19. 2. Hull and Stability
Stability Criterion. 46CFR Part 170. USCG
Minimal metacentric permitted height
PAH
GM ≥ P = 0.028 + ( L 1309 ) 2
W tan(T )
Factor for shallow waters maneuvering
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

20. 2. Hull and Stability
Results for the minimal operational condition
The ship shows good intact stability, because passed the criteria
established and is confirmed the prediction that if a ship have high
Width/Depth ratio will have a good intact stability. 7.2 m / 1.2 m = 6
• General cargo ship, 40 m/ 20 m = 2
• Container ship, 60 m/ 30 m = 2
• Oiler ship, 80 m/ 35 m = 2.3
• USN Aircrat carrier, 112 m/ 45 m = 2.5
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

21. 2. Hull and Stability
Critical points
The critical points are those that permit a progressive flooding
in the ship, for example, the ventilation of machinery room.
Critical point intersection
at 24° of heeling
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

22. 3. Resistance and Propulsion System
Analysis of NAVCAD sistematic series
Method Result
Basic Formula Value spectrum too widht
Holtrop Method BWL/T ratio too short
Oortmerssen Method BWL/T ratio too short
Denmark Univ. Method OK, LWL/BWL quite short
USNA YP Series Characteristics matched
60 Series Only for round bilge keel ships
Nordstrom y YP 81-1 Series High dead keel
64, SSPA, NPL y Dutch Series Planning hulls
The ship characteristics must match properply to use the sistematic
series of NAVCAD, otherwise is not possible to use.
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

23. 3. Resistance and Propulsion System
Hull characteristics
In the hull data, the main influence factor is the wetted surface for resistance prediction
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

24. 3. Resistance and Propulsion System
Environmental characteristics
In the environment data, the main influence factor is the depth of
the channel (river) for resistance prediction.
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

25. 3. Resistance and Propulsion System
The “Squat” effect
Is the change in the draft and trim of a ship, as result of
variations in the hydrodinamic pressure over the hull.
In this critical zone, if the
ship in navigating in shallow
waters, eventually can touch
the bottom.
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

26. 3. Resistance and Propulsion System
0.8
PREDICCIÓN MANACACÍAS-1m.nc4
Squat variation at 0.7
PREDICCIÓN MANACACÍAS-3m.nc4
PREDICCIÓN MANACACÍAS-6m.nc4
PREDICCIÓN MANACACÍAS-9m.nc4
different depths 0.6
The squat curve for 1 m depth
0.5
shows the three cirtical regions.
Squat m
0.4
The other are always in the
subcritical region. 0.3
0.2
What is the minimum depth for
secure navigation, without 0.1
squat effect?
0
0 2 4 6 8 10 12 14
Vel kts
The ship is in full load condition. Subcritical
región Critical
región crítica Supercritical
región
subcrítica
region region region
supercrítica
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

27. 3. Resistance and Propulsion System
Squat effect in resistance
4000 N difference between 3-6 m
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

28. 3. Resistance and Propulsion System
Minimal secure depth = 3 meters
There are other
problems associated:
Vibrations
Cavitation of propellers
due to reverse trim
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

29. 3. Resistance and Propulsion System
Resistance and motor performance
• 02 DD671L motors, 180 BHP
@ 1800 rpm
• 02 Twin Disc gearings, 2.45:1
• 02 FP propellers, 3B, 36”X32”
Previous performance
area of the motors
Detalles of eroded blade
due to cavitation 1800
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

30. 3. Resistance and Propulsion System
Optimal pitch selection
0.50
BS-3: 0.914x0.813x0.450
BS-3: 0.914x0.555x0.450
BS-4: 0.914x0.530x0.610
0.48
PropEff
0.46
0.44
2 3 4 5 6 7 8 9 10
Vel kts
The 3 blade propellers show better performance in efficiency evaluation
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

31. 3. Resistance and Propulsion System
Optimal expanded area of the blade
0.50
BS-3: 0.914x0.555x0.450
BS-3: 0.914x0.546x0.800
GA-3: 0.914x0.503x0.800
0.48
0.46
PropEff
0.44
0.42
0.40
1 2 3 4 5 6 7 8 9
Vel kts
The comparison between B-Series and Gawn propellers was more favourable to
B-Series. In the other hand, not always more blade area means more efficiency.

32. 3. Resistance and Propulsion System
Optimal performance
• Optimal P/D ratio
• More speed
Optimal P/D
• More power Previous P/D
• Less carbon in cylinders
• Less manteinance
• Less emissions
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

33. 3. Resistance and Propulsion System
Fuel consumption and range
8,0
Fuel consumption 7,0
Fuel consumption (gph)
6,0
Half gallon per hour 5,0
less since 12 kph 4,0
3,0
2,0
Range
1,0
3 more days of range 0,0
8,00 9,00 10,00 11,00 12,00 13,00 14,00 15,00 16,00 17,00
Ship speed (kph)
Previous propeller Optimal propeller
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

34. 4. Maneuverability
Field visit and rudder geoemtry
• Before to be a mother vessel for the soldiers, the ship was a river
tug, used for push 3 barges with cargo.
• The rudder area oversized, considering the barges lenght.
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

35. 4. Maneuverability
Shape ratios. Aspect and balance
• Very low aspect ratio:
Lift coefficient
b / c = 0.43
Rudder angle, degrees
• Low balance ratio
A1 A2
A / A2
1 = 0.12 < 0.265
Mínimum for CB = 0.81
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

36. 4. Maneuverability
Sizing the rudder
The calculated rudder shouldn’t touch the semmi tunnel of the hull in
its maximum angle of steering (35˚), procuring the maximum height.
1. Minimum distance propeller – rudder. (0.30 m, facilitation of remove the propeller)
2. Size the rest of the distance till the mirror (last nulkhead, 0.75 m)
3. The distance of the balance ratio should be discounted (0.2 m)
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

37. 4. Maneuverability
Rudder shape innovation. Schilling rudder
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

38. 4. Maneuverability
Characteristics and improvements of Schilling rudder
1. One-piece construcition. No additional maintenance
2. Important control improvement at low speed
3. CL is 1.3 times higher, which reduces tactical diameter
4. Maximum force at bigger stall angle (40 - 45˚)
5. High lift coeffcient going astern
6. Excellent course control (fuel save), even without dead keel
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

39. 4. Maneuverability
Lift coefficient comparative curves
Source: Schilling Rudder Monovec
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

40. Conclusions
1. Instead of the heavy armor, the intact stability of the
RPVs is excellent. However, the heavy armor reduces
cargo capacity.
2. The optimal propeller increased efficiency and range as
well as reduced fuel consumption and cavitation.
3. The Schilling rudder increased significantly the lift and
reduced the tactical diameter since 4 to 2 lenghts.
Additionally the improvement in course control reduced
fuel consumption of the RPV.
Computational optimization of stability, propulsion and maneuverability of a
riverine vessel. Lt Cdr Javier Serrano Tamayo

41. Gracias!
Thank you!
Computational optimization of stability, propulsion
and maneuverability of a riverine vessel
Lieutenant Commander Luis Javier Serrano Tamayo
Colombian Navy
University of the Andes - Naval Academy “Admiral Padilla”
COLOMBIA