Page 542 - Practical Design Ships and Floating Structures

Practical Design of Ships and Other Floating Structures 517
You-Sheng Wu, Wei-Cheng Cui and Guo-Jun Zhou (Eds)
0 200 I Elsevier Science Ltd. All rights reserved

LOWER FRICTIONAL RESISTANCE CHARACTERISTICS OF
FOUL RELEASE SYSTEMS

M. Candries', M.Atlar', A. Guerrero' and C.D. Anderson3

'Department of Marine Technology, University of Newcastle-upon-Tyne,
Newcastle-upon-Tyne, NE1 7RU, UK
'Canal de Experiencias Hidrodinamicas (CEHIPAR),
El Pardo, 28048 Madrid. Spain
31nternational Coatings Ltd.
Stoneygate Lane, Felling, Tyne and Wear, NE10 OJY, UK.

ABSTRACT

The roughness and drag characteristics of two antifouling paint systems are investigated; a state-of-the-
art (Tributy1)tin-free Self-Polishing Co-Polymer (SPC) and a non-toxic Foul Release system. Towing
tank experiments have confirmed that the total resistance of a 6.3m long plate coated with the Foul
Release coating system was on average 1.4% lower than when it was coated with the tin-free Self-
Polishing Co-polymer. The roughness characteristics were measured with both a stylus instrument and
an optical measurement systcm. Correlation with the measured drag has shown that the roughness of
the Foul Release cannot be characterised solely by a height parameter, such as the parameter Rt50. The
texture of the Foul Release surface is significantly different from SPC systems as is evident from
parameters such as the average absolute slope Sa and the correlation length r of the roughness profile.
Roughness and drag seem to correlate well when the parameter h, which takes the slope and curvature
of the surface into account, is used to characterise the roughness.

KEYWORDS

Foul Release, Roughness. Resistance, Antifouling, Roughness function, Friction, Coatings

1 INTRODUCTION
The intended worldwide ban on the application of TBT Self-Polishing Co-Polymers from 2003 and
the complete prohibition of their presence on ships from 2008 will have profound consequences for the
marine industry. While much attention has been spent on the antifouling efficacy and ecological
repercussions of the proposed alternatives to TBT-SPCs, no study has paid attention to the roughness
and drag charactcristics of these new paint systems, to the authors' knowledge. A research project set
up at the University of Newcastle-upon-Tyne has compared these characteristics, for a tin-free SPC.