specialist committee on surface treatment€¦ · representation of surface roughness (continued)...

Specialist Committee on Surface Treatment

Committee Members

Richard Anzböck (Chairman), Vienna Model Basin

Michael Leer-Anderssen (Secretary), SSPA

(Dazheng Wang replaced by

Mehmet Atlar, University of Newcastle (Sept, 2010)

Eloy Carillo, CEHIPAR

Hishashi Kai, Yokohama National University

J.H. Jang, Samsung Heavy Industries

M. Donnelly, NSWCCD (left, 2009)

2

Specialist Committee on Surface Treatment

Committee meetings were held in:

Vienna in November 2008,

Madrid in May 2009,

Daejon in February 2010

Gothenburg in October 2010

3 Specialist Committee on Surface

Treatment

Tasks given to the Committee

TASK 1 - Review the-state-of-the-art different surface treatment methods.

TASK 2 - Review the possible impact on ship performance in the following areas in the light of the recent rapid development of coating systems:

Resistance (friction line)

Propeller characteristics

Cavitation behaviour

Comfort (propeller induced noise)

Acoustic signature

4

TASK 3 - Review the existing measurement methods for surface roughness at model scale and at full scale.

TASK 4 - Propose methods that take into account surface roughness and other relevant characteristics of coating systems in model testing.

Check the need for changes to the existing extrapolation laws.

Study the roughness allowance for high speed and conventional ships (hull, appendages and propellers).

Tasks given to the Comitte (continued)

5

STC concentrated only on coating systems for hull &

propellers,

No practical support from paint manufacturers to the

request of the committee, except, available poduct briefs:

Claims fuel consumption upto 10%

No serious scientific evidence and proof

Examples from major stake holding company product

briefs are in the Committee report

TASK 1 - Review the state-of-the-art different

surface treatment methods

6

Example advertisements by some Paint Manufacturers

7

Example Advertisments by some Paint Manufacturers

Foul Release coating compared to self polishing coating

8

Example advertisments by some Paint Manufacturers

9

Example advertisements by some paint manufacturers

10

Example advertisements by some Paint Manufacturers

11

Example advertisements by some Paint Manufacturers

12

Example advertisements by some Paint Manufacturers

13

Examples of Advertisements by Paint Manufacturers

14

Example advertisement by some Paint Manufacturers

15

Several thousands of species of marine organisms can

foul a ship

Most will release when ship is running above 4- 5 Kn,

except slime!!

Each organism can attach is affected by many factors

including, e.g.

pH

Temperature

Salinity

Dissolved salts

Oxygen concentration

Types of Fouling

16

17

Microalgae

(slime)

Animal Plant

Macroalgae

(weeds) Soft Bodied Hard Shelled

Red Brown Green Unlimited Limited Barnacles Mussels Tube Worms

Specialist Committee on Surface

Treatment

Marine fouling classification

Antifouling technology is under further scrutiny due to

environmental concerns and current financial climate

Although currently in small proportion (~ 10%) the application of

completely environmentally friendly Foul Release coatings are

increasing worldwide requiring further attention and investigation.

Credible evidence comparing the drag characteritics between

majority of coatings is non-existent. Different application, evaluation

and measuring techniques make it very difficult to come up with

reliable performance comparisons.

TASK 1 - Conclusions

18

TASK 2 - Review the possible impact on ship performance in the following areas in the light of the recent rapid development of coating systems

Task 2.1 - Resistance (friction line)

Task 2.2 - Propeller characteristics

Task 2.3 - Cavitation behavior

Task 2.4 - Comfort (propeller induced noise)

19

Task 2.1 - Resistance (Friction Line)

Committee report includes review on:

Ship resistance (Data Published)

Ship resistance (Data Not Published)

Resistance of Flat Plates (Data published)

Resistance of Circular Cylindrical surfaces

Interaction Ship – Propeller

Further Papers of Possible Interest

Paints

Marine creatures

20 Specialist Committee on

Surface Treatment

Ship resistance (data published)

Schultz, MP (2007) – Effect of coating roughness and biofouling on ship

resistance (*)

Munk, T (2006) – Effect of drydocking and propeller polishing using

performance monitoring system

Yokoi ( 2004) – Effect of fouling on trial performance

Leer-Andersen, M and Larsson, L (2003) – Full-scale skin friction

estimations using CFD and roughened pipe experiments

Lars-Erik, J(1984) – Full-scale skin friction estimation of two hulls using

measured floating element friction data and 3D BL theory

21

Ship resistance (data are not published)

Yano, Y and Wakabayashi, N. (2008) – Effect of fouling with different coatings by trials

Townsin, RL (2003) – A good review on coating penalty and economies based on vast experience (*)

Willsher, J ( 2001) – Discusses benefits of FR coatings

Doi, H. and Kikuchi, O (1984) – Five rough plates as replicates of real ship hull surfaces were tested in flow channels and speed penalties were predicted.

Yamazaki, H. et al (1983) – Experimental study with sand roughened pipes to establish roughness-drag correlations

Yamazaki, H et al (1984) – Investigated difference between sand roughened surfaces and painted surfaces using wavy roughened surfaces

Tokunaga, K. and Baba, E. (1982) – 2D turbulent BL theory and 3D potential flow for full-scale prediction of resistance increase due to roughness

Sone, M. (1981) – Power penalty estimations based on 10yrs ship abstract log-book data

Orido, H. and Kakinuma, M. (1980) – Some practical analysis of surface roughness penalties based on full scale ship in-service data 22

Drag of flat plates (Data published)

Candries, M and Atlar, M (2005) – BL, Roughness and drag

comparisons of FR and SPC coatings using LDA and drag tests (*)

Schultz, MP (2004) – Frictional drag data for different ship hull coatings

Schultz, MP (2002) – Very useful rough wall friction data with 7 different

grades

Candries, M and Atlar, M (2001) – Relative drag data on FR and SPC

coatings using a large flat plate in a large towing tank

Candries, M, Atlar, M and Anderson, M (2001) – Relative drag data on

FR and SPC data using a medium flat plate in a small tank.

Schultz, M (2000) – Investigated the effect of macro algae on skin

friction using LDV in a water channel

Schultz, M and Swain, G W(1999) – Effect of marine biofilms on flat

coated surfaces investigated using LDA 23

Resistance of circular cylindrical surfaces

Mirabedini, SM et al (2006) – Drag and roughness characteristics of

different coatings on aluminium circular cylinders by using rotor drums

Weinell CE et al, T (2003) – Comparative effects of paint roughness and

large scale irregularities of different paint systems were investigated

Tanaka, H. et al ( 2003) – Effect of surface characteristics of paints on

their drag including the influence of aging was demonstrated using a

specially built rotating drum

Candries, M et al (2003) – Effect of different coatings and application

methods (spraying and rollering) were investigated on a rotating drum (*)

24

Interaction ship and propeller

Miyamoto, M (2007) – An approximate method exploited to estimate the

effect of fouling, aging of paint and sea conditions and compared based

on abstract log-book data (*)

Matsuyama, A et al (2001) – Marine fouling effect on a ship hull and

propeller was investigated based on 8 years abstract log data

Nagamoto, K et al (1993) – Bottom and propeller fouling of a real ship

was investigated over a year data including special protection to bow

thruster

Sato K et al (1987) – Comparative performance of coatings on flat

plates and actual ships in sea water were investigated

Nishikawa, E and Uchida, M (1985) – Effect of marine fouling on hull

and two different type propulsors (CPP and FPP) were investigated

Nakai , N and Suzuki S (1984, 1983, 1983) – Effect of bottom and

propeller fouling on a full-scale ship were investigated 25

Further studies of possible interest (on Paint)

Almeida, E, Diamantino, TC and de Sousa O (2007) – An overall review of marine paints is given

Chambers LD et al (2006) – Review paper on the development of marine coatings

Casse, F and Swain, GW (2006) – Effect of microfouling on three different type of coatings under static and dynamic immersion were investigated

Tetsuya, S (2006) – Environmental risk evaluation methods of different coatings were presented

Anderson et al (2004) – A state-of-the-art review of new generation marine coatings with a good balance on their chemistry, biofouling and hydrodynamics including effect of hull and propeller performance is presented. (*)

Ogawa, K (1996, 1996) – Early generation silicon paint was investigated on FRP plane in sea water and physics of the foul release were discussed

Hirota, N (1985) – Early generation non-toxic “bioclean” coatings were investigated on large ships and propellers 26

27

TASK 2 - Review the impact of coating

systems on

Task 2.2 - Propeller characteristics

Task 2.3 - Cavitation behavior

Task 2.4 - Comfort (propeller induced noise)

There has always been an interest to propeller coatings to control biofouling growth

to reduce galvanic corrosion

to prevent cavitation erosion

Propeller coating applications are growing since the introduction of

Foul Release (FR) coatings

FR applications currently about 5% but increasing (e.g. 250 ships)

Smoother; may reduce drag; durable; non-biocidal

Promoted by paint companies

Control fouling

Further anectodal claims (fuel saving, reduced cavitation/vibration)

Reality is that frictional losses in a propeller’s efficiency can be

as high as a 15% compared to potential (axial & rotational) losses

So keeping the propeller smooth and free of fouling is saves energy

Rest needs to be proven

Introduction

Measurements of propeller surface condition Roughness comparator (e.g. Rubert roughness scale)

Portable stylus instrument

Taking replicas and measure in the laboratory

They all have their own problems

Representation of surface roughness Townsin’s approach for APR using Musker’s characteristic

roughness parameter (h’)

i Region Weight

1 0.2 - 0.5 0.07

2 0.5 - 0.7 0.22

3 0.7 - 0.8 0.21

4 0.8 - 0.9 0.27

5 0.9 - tip 0.23

35

1

31

)'(

ii hWAPR

Ca PRh )5.2(0147.0' 2

Representation of surface roughness (continued) In case of FR coated propellers, use of fully turbulent (ks) – as in the

ITTC’78 method- is not valid because:

- Actual propeller roughness are different than sand roughness

- FR surfaces do not correlate only based on a single roughness

parameter, texture parameters are also important

Review of propeller coatings

As old as Holzaphel (1904) – Preventing fouling and G/corrosion

Kan et al (1958) – Fouling prevention simulated by rubber sheets

Dashnaw (1980) – To protect scarced (cheap) alloys for economy

Heatcock et al (19790; Angell et al (1979); Akhtar (1982) –

Ceramic coating research to prevent cavitation damage

Foster (1989) – Full scale reports with vinyl coating for positive

fouling and G/corrosion prevention

Coldron & Conde (1990) – Positive report on full-scale ceramic

coating applications but not so on TBT-SPC application.

Matsushita et al (1993) – First application of FR coating on

FS propellers and positive impact on fouling and cathodic protection

Anderson et al (2003) – Positive report on reduced ICCP current

output due to coating

Atlar (2004) – Opinion on complex corrosion issue and economy

trade-off between coating and surface finish

Newcastle University research (2003 – present) – to report later

Propeller coating applications are growing since the introduction of

Foul Release (FR) coatings

FR applications currently about 5% but increasing (e.g. 250 ships)

Smoother; may reduce drag; durable; non-biocidal

Promoted by paint companies

Control fouling

Further anectodal claims (fuel saving, reduced cavitation/vibration)

Reality is that frictional losses in a propeller’s efficiency can be

as high as a 15% compared to potential (axial & rotational) losses

So keeping the propeller smooth and free of fouling is saves energy

Rest needs to be proven

Review of Foul Release coatings

Non-biocidal; Fouling is released by weak hydrodynamic shear

forces over “low surface energy” silicon based coated surfaces

Bio-adhesion is strongly correlated with , Brady & Singer (2000)

Silicon (and other PDMS) materials have an order of magnitude

lower , Singer et al (2000)

Candries (2001) demonstrated reduced drag properties

of FR coatings as opposed to TBT free –SPC coatings

Candries & Atlar (2003) indicated the importance of texture

parameters in correlations with drag for FR coatings

EC

,

EC

Foul Release coatings R&D as applied to propellers

Effect on propeller efficiency:

- Atlar et al (2002, 2003) used Musker’s equivalent roughness parameter

based on the measured surface parameters of newly painted FR surfaces

- The equivalent roughness value was related to Rubert scales and they

were used to represent various surface finishes

- The equivalent roughness was also related to the blade sectional drag

coefficients and hence to the propeller performance in a lifting surface

analysis code

- Simulations for a typical merchant propeller after 2 years of service

indicated a 5-6% gain due to coating - High speed propellers can take advantage of the foul release coatings further due to their relatively large blade surface area and higher shaft speeds

,

,

0.4 0.5 0.6 0.7 0.8 0.9J

0

0.1

0.2

0.3

0.4

0.5

0.6

KT,

10K

Q,

O

KT

10KQ

O

Design

Rubert D

Rubert E

Rubert F

Rubert F

Design

DesignRubert F

Figure 1. Propeller Open Water Characteristics

Ship type Medium Tanker

Deadweight 96920 tonnes

Length Overall 243.28 m

Max Draught 13.616 m

Speed 14.86 knots

Shaft RPM 139.5

Power (installed) 9893kW

Built 1992

Full-Scale Propeller Dimensions:

Diameter 6.85m

Mean Face Pitch 4.789m

Expanded Blade Area Ratio 0.524

Design Advance Coefficient, J 0.48

- Model tests in Emerson Cavitation

Tunnel with freshly applied F/R

coatings on a commercial tanker

propeller showed no conclusive

evidence of any undesirable effect

on efficiency (including damage to

paint),

Effect on propeller efficiency

The Effect of Coating Damage upon the Propeller Open Water Characteristics

(Confidence Limits 95%)

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8

Advance Coefficient, J

KT, 10K

Q, E

ffic

ien

cy

Intact Coating KT

Intact Coating 10KQ

Intact Coating Efficiency

Damage Scenario 1 KT

Damage Scenario 1 10KQ

Damage Scenario 1 Efficiency

Damage Scenario 2 KT

Damage Scenario 2 10KQ

Damage Scenario 2 Efficiency

Damage Scenario 3 KT

Damage Scenario 3 10KQ

Damage Scenario 3 Efficiency

Effect on Cavitation Inception

LOADED CONDITION (J) -

Uncoated Coated % Change

Inception Inception Inception

0.517 0.505 -2.32 (Delayed)

Dissidence Dissidence Dissidence

0.513 0.510 -0.58

BALLAST CONDITION (J)

Uncoated Coated % Change

Inception Inception Inception

0.542 0.590 8.86 (Earlier)

Dissidence Dissidence Dissidence

0.540 0.557 3.15

LOADED CONDITION BALLAST

Cavitation number,

= 0.50

0.320

Propeller Immersion,

H = 10.0m

4.66m

RPM = 100 104

Advance Coefficient,

J = 0.48

J = 0.486

Loaded

J= 0.5

Coated uncoated

• Some evidence of

coating altering the

inception /

dissidence of tip

vortex cavitation

• But trend in

delaying or earlier

inception is mixed

Effect on fully developed cavitation

uncoated Coated Coated uncoated

J= 0.45

J= 0.40

Loaded, = 0.50 Ballast, = 0.48

UNCOATED PROPELLER:

Well defined (thicker) tip

vortex , more stable (&

slightly larger extent) sheet

cavitation patterns.

COATED PROPELLER:

Less well defined tip

vortex and less stable

sheet & hence more misty

cavitation patterns

• Depending upon the advance coefficient (J) some beneficial effect of

coating (waterborne noise reduction), mainly in non-cavitating condition (at

high J’s) is observed

SPL

(dB) uncoated coated

Cf (Hz)

J=0.7 J=0.6 J=0.4

Loaded condition, = 0.50 10 100 1000 10000

60

100

140

140

SPL

(dB)

Cf (Hz)

uncoated

coated

J=0.6 J=0.4 J=0.7

Ballast condition, = 0.48

SPL

(dB)

100

60

10 100 1000 10000

Effect on noise

Final Power Curve ComparisonErrors estimated at 10%

0.00

20000.00

40000.00

60000.00

80000.00

100000.00

120000.00

140000.00

6.00 6.50 7.00 7.50 8.00 8.50 9.00 9.50

Tide Corrected Speed over Ground (knots)

Co

rre

cte

d S

ha

ft P

ow

er

(Wa

tts

)

Uncoated Trial

Coated Trial

Coated

Uncoated

• Despite the weather

effecting the coated

trials, the results

showed little

difference between the

performance of the

coated and uncoated

propellers

Full scale trials with uncoated vs coated propeller

Full-scale observations

Application of F/R coatings on propeller

keeps the propeller free from major fouling

as clearly observed in full- scale and

prevents the increase in roughness over

the time (next slide)

14 months uncoated

Newly coated

After 24 months

After 12 months

After 36 months

• Roughness and texture

characteristics of coated

propeller are similar after

2 years in-service

Roughness in service

Full scale observation shows that FR

coatings can prevent major biofouling

but not slime which attaches more

strongly to FR coatings than other

fouling mechanisms

Modelling of roughness in the presence

of biofouling is a complex issue

requiring further research with

experimental data. One such research

study by Schultz (2007) using

Granville’s approach (1958, 1987)

presents interesting findings that may

be exploited for propeller applications.

However it requires further data on

roughness-drag correlations

Interaction with biofouling

Newly applied

37 months

later

CONCLUSIONS – Propeller coating (TASK 2.2 – 2.4)

Propeller coating has always been attractive and FR coating applications

are increasing

There is no credible evidence that propeller coating demonstrates gain/loss

in efficiency. But there is limited evidence that coating keeps the roughness

and texture levels similar as newly applied as well as preventing macro fouling

Limited model tests (Newcastle University) on efficiency, cavitation and

noise do not display any major favourable or unfavourable effect of coating.

Model test requires care for the coating thickness effect

Semi-empirical expressions used for blade section drag coefficient requires

modification to take into account the coating effects properly

There is a need for standard measurement tools and procedures for surface

measurements and model testing with coated propellers

There is a need for dedicated full-scale trials and observations with coated

propellers

TASK 3 - Review the existing measurement

methods for surface roughness at model

scale and at full scale

Surface roughness parameters:

Amplitude parameters (Rt, Rz; Ra, Rq; Rsk, Rku, etc)

Texture parameters (Sm; Sa)

Spectral parameters (ACF; PSDF)

Fractal parameters (FD)

44

Surface measurement techniques & equipment

In full scale Direct measurement using portable

Stylus (contact) type equipment

Optical (non-contact) sensor equipment

Indirect measurement by taking

Representative impression (print) of old applications

Sample plates during coating for new applications

& measuring them using non-portable or portable devices

In model scale Direct measurement using portable

Stylus (contact) type equipment

Optical (non-contact) sensor equipment

Other sophisticated photogrammetry techniques

45

46

BMT Hull Roughness

Analyser (HRA)

47 Typical output from BMT HRA

48

Lab based non-portable

laser profilometer

(OSP 100 – UNISCAN)

Sample coated

surfaces

49

Foul Release Roughness profile:

Ra = 1.10

Rq = 1.21

Rt = 4.50

Sk = -0.87

Ku = 5.04

Sa = 0.23

-15

-10

-5

0

5

10

15

20

0 5 10 15 20 25 30 35 40 45 50

mm

mic

ron

SPC Roughness profile:

Ra = 3.26

Rq = 4.04

Rt = 19.98

Sk = 0.01

Ku = 3.29

Sa = 1.90

-15

-10

-5

0

5

10

15

20

0 5 10 15 20 25 30 35 40 45 50

mm

mic

ron

Typical output from lab based laser profilometer (OSP 100 – UNISCAN)

50

Surtronic3+

Portable

stylus device

Typical output from SURTRONIC3+ on a propeller blade

51 New prototype BMT-HRA using a laser sensor developed by BMT - Newcastle University

Laser sensor based

prototype BMT – HRA

52

New BMT- HRA device Non-portable Laser profilometer

TASK 3 – Conclusions

Ship hull and propellers coated with new generation coatings, especially with the FR types, cannot be reliably measured by current mechanical contact devices at drydocks. There is a need for non-contact, portable, robust device.

New generation coatings need more surface parameters to be known than just AHR and hence such devices need to be more sophisticated to provide such ability

A new portable non-contact prototype device has just been developed requiring to be proven by marine industry

Roughness measurements on ship models are carried out but the results of the measurements are used for quality assurance and not for further investigation.

Most of the model basins do not measure the roughness of the model hull and propellers.

53

TASK 4 - Propose methods that take into

account surface roughness and other

relevant characteristics of coating systems;

check the need for changes to the existing

extrapolation laws.

Measurement Equipment

Test Procedure Recommendations

ITTC Rough Skin Friction Database

54

Flat plate in towing tank (still the best)

Flat plate in cavitation tunnels (in atmospheric)

Flat plate in open water channel

Pipe friction device

Flow cell

Couette cell (two coaxial cylinders)

Other shapes than flat plate in towing tank or the like

(such as axysymmetric body or model ship)

Full scale tests

Friction Measurement Equipment

55

Best combination of accuracy and complexity

Direct measurement of flat plate drag (majority of cases) or

a floating small cell (edge effects!)

Longer and thinner the better

Towing speed is limited (usually 5 m/s)

Re-rigging for each new surface test requires care

Orientation and time between the tows are important

Flat plate in towing tank

56

Mostly boundary layer measurements using LDV to

estimate measure wall velocity, velocity shift (roughness

function) and hence friction coefficient

In some cases direct measurement of friction drag of the

plate or even a floating cell in the flat plane (edge effect!)

are used

Overall expensive but accurate method

Flat plate in cavitation tunnel

57

Cost effective, practical and also well suited for bifouling effect

investigations

It is an indirect method, average values based on pressure drop and

hence lower accuracy for less rough surfaces. BL is not free confined

in pipe radius and hence correction will require for flat plate skin

friction

Couette cell, rotor apparatus Simple, practical and cost economical but experience non-uniform BL

development as well as temperature issues. Some complexities in

calculating skin friction based on torque measurements

Friction pipe

58

Flow cell

High aspect ratio channel provides fully developed shear and hence turbulent flow on very small testing surfaces using micro slides They are mainly used for biofouling adhesion tests using seawater but can be exploited for friction tests though complex.

59

Other shapes

Using other shapes than flat plates will bring further complexities introducing much higher residual and wave making, hence are recommended.

However some simple shapes without free surface for convenience and higher Re number (e.g. Axy-symmetric body in high speed channels) may be preferred

60

Friction test procedures – recommendations

High Re-numbers should be preferred (Lower the Re no higher the risk of surface being hydraulically smooth). At least 2m/s above

It is imperative that all measurements should be completed with reference to a hydraulically smooth (practically polished) surface, y+ ~ 5 (i.e. h ~ 5-50m)

Reproducibility is essential without and with re-rigging during coating changes. Strict uncertainty procedures should be followed

Representative coating applications should follow the same procedure as in the real world application (in shipyards)

Roughness measurements should be taken as precise as possible using appropriate devices and as many as possible roughness parameters

61

ITTC Rough (wall) Skin Friction Database (RSFD)

STC proposes to start an International database for skin friction measurements including coated surfaces with/without biofilms by following a harmonised procedure

Submission:

SSPA and Newcastle University will maintain a website for submission of data that will be publicly available

Submitted data will be evaluated to meet required confidence level to be included in RSFD

Cf, DU+, h will be made public compared to Cf,ITTC

62

63

Velocity shift (roughness) function can be used for each friction line with

more than one roughness parameter

will be replaced by

RSFD Analysis and comparison procedure

Efficiency parameter C will be defined by LSM for each surface and

fairly constant values of C can be devised for different surfaces to be

used for full scale predictions

All measurements will be referred to a reference “Hydraulically Smooth”

surface for comparisons

and velocity function can be evaluated using a known smooth skin friction line

e.g. Cf, ITTC

64

ITTC Skin Friction Data Submission Form

Company/institution Phone

Contact person Adress

e-mail Submission date

Appended material (raw data, analysed data, reports, papers)

File name (description) Public (Yes/no)

1.

2.

3.

Test description

1. Equipment (see document XXX, section 1.1, 1-8). If other please specify

2. Reynolds number range

3. Flow speed range

4. Roughness height measurement type (device and parameter)

Short description of test equipment if not standard

Surfaces tested

Deliverables Description Roughness height Other parameters

1. (name or description)

2.

3.

Additional information

RSFD Submission Form

Extrapolation Methods:

Conclusion: No changes to Powering Performance

Prediction regarding the use of the Townsin roughness

allowance due to lack of data.

Recommendation: It will not be possible to generate a

new formulation without an extensive database of skin

friction measurements: ITTC Rough Skin Friction

Database (RSFD) initiative is proposed

Conclusions and Recommendations

65

Model test procedures:

Conclusions: Most accurate method for skin friction

measurements probably is the flat plate in tow tanks but

others can be used by paying attention to high Re no,

and reproducibility. There is a need for accurate

measurements of roughness characteristics with

more parameters.

Recommendation: Establishment of comparative

skin friction database development following

coherent test procedures

66

Propeller Coatings

Conclusions: No credible evidence from full-scale

measurements to prove any gain or loss from a vessel

fitted with a coated propeller compared to a newly

polished uncoated propeller.

There is evidence that these coatings can maintain the

blade surface free from major fouling for long time

without any maintenance

Propeller model tests with coated blades suffer from

appropriate paint thickness in model scale due to

application methods with commercial coatings.

67

Propeller Coatings

Recommendations: More dedicated model tests, full-scale trials and progressive docking observations to accurately assess the effect of coatings on the propeller efficiency, cavitation and noise performance should be conducted

As a generic problem of the foul release type coatings, investigations on the application and measurement of coatings on model and full-scale propeller should continue

As a generic problem of any coating the investigation on the effect of slime on propeller coatings should continue.

68

69

State-of-the-art-coatings Coatings

Conclusions:The applications of Foul Release (non-

biocidal) type antifoulings are increasing worldwide and

require further attention and hence further investigation.

Different model evaluation, application and measuring

techniques make it difficult to compare measurements for

which reason most of the measurements are only able to

state that this coating is xx% better than another coating

Recommendation: Methods measuring FR coating

surface characteristics in drydocks should be developed

based non-contact technology. Investigations on the drag

performance of these coatings should continue.

70

THANK YOU

Q & A

mehmet.atlar@ncl.ac.uk