Deep sea moorings fishbite handbook

The purpose of this handbook is to bring awareness and a degree of expertise to the very real problem of fish attacks on mooring lines and cables deployed in the open seas. Over the years the authors have carefully examined a large sample of damaged, sometimes entirely severed ropes retrieved from the sea. Often direct evidence and/or biological observations showed that the ropes were the victims of fish attacks. In many cases however the cause of rope failure remained difficult to ascertain. Techniques and rationales therefore had to be devised to elucidate the more thorny cases. Understanding a problem, the saying goes, is half of the solution. The other half, as far as this handbook is concerned, is of course to make known the ways which, at the moment, could help prevent fishbite attacks or at least abate its effects. Thus the handbook will follow a natural progression. A short introduction retraces the early suspicions which soon translated into confirmed fish attacks. The next two chapters cover the recognition and the extent of the fishbite problem in great depth. Chapter 2 presents in meticulous details the techniques which can be used to determine how a rope was damaged while in service, either by fishbite or any other plausible cause. The analysis of a data base which spans over twenty years and encompasses close to a thousand moorings is presented in Chapter 3: Dimensions of the fishbite problem. This chapter provides valuable information for use in estimating fishbite hazard. Who are the culprits and why they do it is reviewed in Chapter 4: Biting organisms and predisposing factors. This chapter identifies the marine organisms which have significant biting capabilities and outlines some of the environmental factors and processes which incite and result in fishbite damage. The last chapter: Prevention and control of fishbite damage, reviews the preventive methods used to reduce the incidence or the severity of fish attacks and the curative methods - including up to date techniques for jacketing metallic and non-metallic ropes and cables - which hopefully will protect mooring lines from the mechanical damage inflicted by fish teeth.Prepared for the Office of Naval Research under contract No. N00014-84-C-0134, N R 083-400

Design of a stable floating platform for air-sea interaction measurements

The design of an oceanographic platform can be defined as the rational specification of the platform dimensions and geometry. This specification is usually the result of an iterative process which compares the platform performance with the objectives to be reached and the logistic constraints to be met. This report describes such an exercise. The scientific objectives - measurements of heat flux at the ocean surface - are first outlined. The limits of heave and roll motion compatible with the desired measurement accuracy are then established. Given the stochastic nature of platform response, these limits are stipulated in terms of expected means. A review is then made, in some detail, of the analytical approach followed and of the computer programs used to compute the statistical expectations of buoy heave and roll response to random sea excitation. The next section of the report describes the comprehensive parametric study performed on some twenty different buoy configurations. The purpose of this study was first to investigate the dynamic response of a plausible base line design and of modified versions of the base line. A comparison of the dynamic response of these configurations could then"be made, and the good features that this comparison would reveal could be used to design the buoy prototype. Following this approach a final configuration was specified which would meet the rather severe motion requirements (0. 2 feet RMS in heave and 5. 0 degrees RMS in roll in sea state 3). The final section describes the techniques recommended to deploy and recover the 60 feet long buoy prototype.Prepared for the Johns Hopkins University, Applied Physics Laboratory under Subcontract 600651

Analysis & experimental evaluation of single point moored buoy systems

Originally issued as Reference No. 69-36, series later renamed WHOI-This report reviews the analysis and the evaluation of surface buoy systems performed in the Engineering Department of the Woods Hole Oceanographic Institution in 1968. The buoy systems considered are single point moored, taut and compound consisting of wire and synthetic ropes, The first part of the report describes the forcing functions and the system response as measured in situ during and after launching, The second part presents the results of the mooring line components testing and evaluation programs performed at sea or in laboratories. The third part briefly outlines the present development in telemetry transmission of scientific and engineering information, It is believed that this systematic engineering effort is an important factor in the continuous improvement of the reliability and performance of the deep sea buoy systems used in scientific measurements programs.Submitted to the Office of Naval Research under Contract N00014-66-C0241, NR 083-00

CTD electromechanical termination users manual

This report desribes a new, easy to install, reliable electromechanical cable termination to mechanically attach and electrically connect cable lowered instrument packages to their lowering cable.Funding was provided by the National Science Foundation through Grant No. OCE 8821977

Self deployable deep sea moorings

As part of a development effort in the field of moored arrays sponsored by the Office of Naval Technology, the Ocean Structures and Moorings Laboratory (OSM&L), Applied Ocean Physics and Engineering Department (AOP&E), Woods Hole Oceanographic Institution (WHOI) conducted a study in 1991 to assess the feasibility and the merits of several self-deployable mooring designs. This study included a brief review of the state of the art, the performance of lab tests to evaluate different mooring line payout concepts, and the preliminary design of a typical candidate mooring. The results of this study are presented in this report. The report first reviews three types of single point moored arrays which are amenable to self-deployment: subsurface, subsurface with surface expression, and surface with bottom inverted catenary. It then describes the features common to all self-deploying moorings: techniques for line and instrument storage, means for controlled payout, bottom finders and lock up mechanisms, and it also outlines desirable specifications for sensor sizes, cables and connectors. Next the report reviews typical deployment scenarios from the bottom up or from the surface down as they apply to the three types of moorings retained. In its final section, the report presents the conceptual design of a 6000 meters depth capability, bottom up deployment, candidate mooring. This configuration should be of strong interest when contemplating the deployment of a large number of identical subsurface moorings, interconnected by a bottom cable, and in "close" proximity to one another. The case study outlines the design objectives and the current profiles, specifies the main components, evaluates their performance with the help of a standard computer program, and presents packaging and payout control details. Finally, a plan is proposed for the controlled, in-situ evaluation of a prototype.Funding was provided by the Office of Naval Technology under Contract No. N00014-90-C-0098

ESOM I and II final report

An Engineering Surface Oceanographic Mooring (ESOM) program was initiated in 1989 by the Woods Hole Oceanographic Institution for the purpose of evaluating the long term, in situ performance of new moored array materials and sensors. For logistic and practical reasons, a site 12 miles southwest of Bermuda, with a water depth of 3000m was selected to deploy the mooring. Following well established design practice the upper part of the mooring down to a depth of 1900m was made of plastic jacketed, steel armored wire ropes and cables. Groups of test samples were attached at different depths to the main mooring line. The lower part of the mooring was made of compliant, plaited nylon rope. The mooring was deployed in March 1989. It was recovered and reset, with a vertical acoustic telemetry prototype system, in April 1990. The at-sea phase of the program ended in November 1990 when the termination of a test cable failed and the mooring broke loose. The entire mooring was recovered and all of its samples and components were carefully inspected and tested. In addition to the novel acoustic link, mooring components tested included new wire ropes, new electromechanical cables and their terminations, low drag fairings, fishbite resistant jackets, and a new type of surface buoy.Funding was provided by the Office of Naval Research under Contract No. N00014-90-J-1719

Testing and evaluation of SURLYN foam and SPECTRA fiber ropes for buoy systems applications

Funding was provided by the Office of Naval Research through contract Number N00014-84-C-0134

In situ measurements of the dynamics of a full scale bottom moored mine model

Under the sponsorship of the Naval Surface Warfare Center (NSWC), Dalgren Division, White Oak, Marland, the Ocean Systems & Mooring Laboratory of the Woods Hole Oceanographic Institution devised (1991) and conducted (1992) an experiment to measure the dynamic response of a full scale model of the CAPTOR mine, submerged and moored in strong tidal currents near Woods Hole, MA. Specifically, the purpose of this sophisticated engineering experiment was to obtain long term, high frequency measurements of the spatial position of the CAPTOR body, of the tension at both ends of the mooring line, and of the mooring line strumming, as a function of the currents prevailing at the site. This report first describes the main components and the method of deployment of the complex CAPTOR Dynamics Experiment (CAPTORDYN) set up. It then presents the mechanical and electrical designs of the entire system. Finally a review of the results obtained concludes the report.Funding was provided by the Naval Surface Warfare Center under Contract No. N60921-91-C-0216

Experimental evaluation of CTD package hydrodynamic behavior and recommendations for improved lowering techniques

This report is the last of a series of three reports on a comprehensive study of CTD instrument lowering mechanics. The first report, WHOI 79-81, "A Study of CTD Cables and Lowering Systems", examines the causes and modes of lowering cable failures, both mechanical and electrical, and makes recommendations to improve existing instrument packages and lowering procedures. The second report, WHOI 81-76, "Hydrodynamics of CTD Instrument Packages", is a theoretical study of instrument package stability when cable lowered or free falling. The model is used to predict the hydrodynamic response of CTD packages in their present or improved configuration. This report, WHOI 83-21, is more factual. It describes the tests performed on scale models and actual CTD packages to actually observe and/or measure their hydrodynamic behavior. Analytical results and experimental data obtained in this study are used to draw recommendations for CTD package improvement and future lowering procedures.Prepared for the Office of Naval Research under Contract N00014-72-C-0019

A study of CTD cables and lowering systems

This study first reviews both the electrical and mechanical modes and causes of failure of electromechanical (E/M) cables used to lower deep sea sensors, such as CTD instruments, from oceanographic ships. It then outlines measures or steps that could be taken to correct some of the deficiencies observed and improve the systems presently used. These measures include quality control, tests, operational limits, improved handling and maintenance, improved machinery. The study then surveys alternative cables for lowering the sensors and convey the information from the sensors back to the ship. These alternatives include strength members other than steel (Kevlar)and signal carriers other than conventional copper conductors (fiber optics). The final section - Conclusions - summarizes the recommendations, based on this study, for improving the reliability of present and future CTD lowering systems.Prepared for the Office of Naval Research under Contract N00014-7l6-C-0197; NR 083-400