INVESTIGATION OF LEEWAY AND DRIFT FOR OVATEK LIFE RAFTS PROJECT FINAL REPORT

Transcription

1 INVESTIGATION OF LEEWAY AND DRIFT FOR OVATEK LIFE RAFTS PROJECT FINAL REPORT Submitted to: Canadian Coast Guard Newfoundland Region St. John s, Newfoundland Prepared by: 85 Lemarchant Road St. John s, Newfoundland A1C 2H1 Telephone: Facsimile: March 2006

2 The contents of this document reflect the views of OCEANS Ltd. and are not necessarily the official view, opinion or policy of the Canadian Coast Guard. OCEANS LTD. PROJECT TEAM: R. Fitzgerald Project Manager D. Finlayson Project Analyst A. Cook Project Engineer and others ii

3 ACKNOWLEDGEMENTS It is a pleasure to acknowledge the interest and support of the National SAR Program, National SAR Secretariat, Canadian Coast Guard, and United States Coast Guard. We thank the Canadian Coast Guard, Newfoundland Region, for making available the CCGS "Harp" and Ann Harvey for use during field trials. There were a number of individuals and groups at the CCG base in St. John s that helped us to complete this project. In particular we would like to thank Brian Stone, Regional Superintendent, Maritime Search and Rescue for his interest, cooperation and support during all phases of the project. Grant Ivey proved to be an integral part of this project and we appreciate his day-to-day help and logistical support throughout the project. As well we appreciate the interest and assistance of Neil Peet, Peter Fontaine, and Dan Frampton. Also, Steve Sheppard and Kevin Lawless provided us with a great deal of help around the CCG Base. Thanks also go to the Ship s Electronic Workshop group from the CCG base for helping with the installation of equipment onboard the Ann Harvey. The Marine Rescue Sub-Centre also assisted us during our field trials and we would like to thank them for their co-operation. Finally, we would like to thank Janice Brasier of the Canadian Coast Guard in Ottawa for her help and support during the project. We gratefully acknowledge the continued advice and support given by Dr. Arthur Allan of the United States Coast Guard Research and Development Center, Groton, Connecticut. As well, we thank Chris Turner of the USCG R&D center for his support during the field program. We also worked closely with the personnel from the USCG contractor SAIC during the 2005 field trials. We appreciate their interest in our work and hope their stay in Newfoundland was enjoyable. Special thanks go to SAIC s field crew: John Morris, Tom Waddington, Pamela Leuy, Kate Montgomery, and Jim Singer. We wish to acknowledge and emphasize the individuals who contributed to the safe and successful completion of our field programs. In particular, we would like to thank Captain Mike O Brien, Chief Officer John Matchum, and the remaining officers and crew of the CCGS Harp for their work during the Phase I field trials. As well, we thank Captain Jim Gurney, Captain Guy Durnford, First Officer Guy Vanderwaeren, First Officer Wayne Rice, and the remaining officers and crew of the CCGS Ann Harvey for their work during the Phase II field trials. Their dedication, interest and total cooperation was invaluable in making the field programs a success. iii

4 EXECUTIVE SUMMARY This document is the final report on a two-phase project that was conducted by OCEANS Ltd. during fiscal years 2004/2005 and 2005/2006 to investigate the Leeway and Drift of Ovatek Life Rafts on behalf of the Canadian Coast Guard. Primary funding for the project was provided by the National SAR Secretariat. In-kind support was provided by OCEANS Ltd., the Canadian Coast Guard and the United States Coast Guard. Background In recent years Ovatek Inc., based in New Brunswick, has developed and marketed a new type of life raft, the 4-person and 7-person Ovatek rigid life raft. These life rafts have been approved by SOLAS, the Canadian Coast Guard and the United States Coast Guard. These life rafts have become a popular alternative to the inflatable life raft on board fishing vessels in Atlantic Canada and the west coast of North America. An incident involving an Ovatek life raft precipitated the need for leeway data for these life rafts. In the spring of 2003 a SAR operation was conducted for a 7-person Ovatek life raft in the Gulf of St. Lawrence. The life raft belonged to the MV Caboteur that sank on April 4, 2003 at 1215 EST. Fortunately, in this case, a vessel was standing close by when the ship sank and the 6-man crew was recovered from the life raft within an hour with no injuries. The life raft and the Caboteur s EPIRB were recovered 2 days later on April 6, However, the incident report noted that the position of the search objects was very different than the positions calculated by CANSARP. Further, it stated that upon examination of the incident it is evident that the Ovatek life raft did not have the same rhythm of drift as a conventional life raft. In an effort to improve the accuracy of CANSARP predictions, a leeway study was proposed and conducted on 4-person and 7-person Ovatek life rafts. Details of this work are discussed in body of this report. The National SAR Manual (DFO, 1998) defines leeway as the movement of the search object through water caused by the action of wind on the exposed surfaces of the object. In this investigation, consistent with other recent leeway studies (Fitzgerald et al., 1994; Allen and Plourde, 1999), leeway is defined as: Leeway is the velocity vector of the SAR object relative to the downwind direction at the search object as it moves relative to the surface current as iv

5 measured between 0.3 and 1.0 m depth caused by the winds (adjusted to a reference height of 10 m) and waves. In the late 1980 s to mid 1990 s OCEANS Ltd. personnel, with support from the Canadian Coast Guard, the Transportation Development Centre and the United States Coast Guard conducted a number of leeway experiments for common SAR objects in environmental conditions typically encountered on the east coast of Canada. The objects tested in these earlier studies included: - 4, 6, and 20-person inflatable life rafts - small open plank boats - 22-person SOLAS approved fibreglass life capsule - 46-person L1011 passenger slide / life raft - an air deployable Sea Rescue Kit consisting of three 6-person life rafts and two survival packs The results of these studies have been incorporated in the National SAR Manual and into CANSARP. Overall Project Objectives There was a primary and secondary objective identified for this project with each phase of the project having specific objectives. The primary objective of this project was to determine a functional relationship between wind velocity and leeway speed and angle for 4-person and 7-person Ovatek rigid life rafts in operationally limiting configurations (1 person on board without a sea anchor deployed and 4 or 7 persons onboard with a sea anchor deployed) for inclusion in the National SAR Manual (DFO, 1998) and CANSARP. The secondary objective of this project was to investigate improved analysis methodologies for obtaining SAR object leeway angles off the downwind direction with the goal of increasing the precision of leeway angle divergence and, ultimately, reducing search area, search time, and SAR resource requirements v

6 Phase I Objectives There were two main objectives for Phase I and these included: 1. Collect and analyze preliminary field data for determining the leeway for the 4- and 7-person Ovatek life rafts in wind speeds up to 25 knots. 2. In preparation for the Phase II trials, Phase I was to serve as a test of equipment, deployment/recovery procedures, scientific instrumentation, and communications. Phase II Objectives The main objective of Phase II was to: 1. Collect and analyze field data for determining the leeway for the 4- and 7-person Ovatek life rafts in wind speeds up to 50 knots Conclusions The conclusions in this report are based on a total of hours of leeway and drift data that was collected for the 4- and 7- person Ovatek life rafts during this two-phase project. The results of the leeway analyses to determine the leeway characteristics of the Ovatek life rafts have been presented in two forms in this report (see section 4). In the first form linear regression models have been developed for leeway speed while descriptive statistics are provided for leeway angle divergence. This is the form currently used by the Canadian Coast Guard. The leeway characteristics of SAR objects may also be presented in the form of downwind and crosswind leeway components. This method is presently employed by the USCG and has the advantage that the downwind and crosswind statistical models used in combination provide complete information about the SAR object leeway vector, and include a measure of the scatter about the regression models in the form of standard error statistics. In summary, there is sufficient confidence in the results to state the following general conclusions about the leeway characteristics of the Ovatek life rafts. vi

7 For lightly-loaded Ovatek life rafts deployed without a drogue: 1. Leeway rates and downwind leeway rates are sufficiently similar, at approximately 3.9 percent of the 10 m wind speed, that the data can been combined to provide linear models that are representative for the two life raft sizes. 2. Leeway angle divergence characteristics of the 4- and 7-person life rafts are markedly different; as a consequence, leeway angle statistics and crosswind leeway components models have been developed for each size of life raft. For fully-loaded Ovatek life rafts deployed with a drogue: 1. The controlling influence of the drogue is sufficiently strong that the leeway data may be combined to generate leeway speed models, leeway angle statistics, and downwind and crosswind leeway velocity component models, that are representative for both sizes of life raft. 2. For this configuration, leeway rates are approximately 1.0 percent of the 10 m wind speed. Full details of the leeway models and statistics are given in Table 4-1 through Table 4-6 in this report. The models are expected to be valid for 10 m wind speeds up to storm force winds of 50 knots Recommendations The following are recommendation stemming from the findings of the Ovatek leeway and drift project. 1. Leeway Speeds and Angles It is recommended that the Canadian Coast Guard, when planning SAR missions in wind speeds up to 50 knots for 4- and/or 7-person Ovatek life rafts, use the leeway models shown in Table 4-1 through Table 4-6. vii

8 2. Leeway Model Validation It is recommended as a follow up to the collection of leeway data for the 4- and 7- person Ovatek life rafts that a validation of the derived leeway models be carried out. The purpose of the validation would be (1) to confirm the reliability of the leeway models recommended in this report and (2) demonstrate, by using reliable leeway models based on field research, the improvement that can be obtained in SAR performance as it relates to finding a SAR object faster and thus increasing the chances of saving lives which is the real goal of this research. 3. Conduct Probability of Detection (POD) Trials for Ovatek Life Rafts It is recommended that a Probability of Detection Exercise be carried for 4- and 7-person Ovatek life rafts. This work would be a logical extension in completing the collection of SAR data for the 4- and 7-person Ovatek life raft. It is recommended that the data be collected by an all weather SAR vessel during poor weather which is the more common scenario when there is a marine emergency on Canada s East Coast. Note: Recommendations 2 and 3 could be carried out in parallel. 4. Modify the Rode for Sea Anchor on the Ovatek Life Raft It is recommended that the rode for the sea anchors presently being used with the Ovatek 4- and 7-person Ovatek life raft be modified to reduce the effects of the dynamic loading on the rode. Observations made during the Phase I and II field trials first of all showed that this sea anchor is very efficient. However, it was noticed that the rode of the sea anchor after only a 24 hour period, in relatively light sea conditions, had begun to fray. It was felt that the constant tugging of the rode against the rigid hull of the Ovatek life rafts would eventually lead to rode failure. 5. Determine the Leeway of Fully Loaded Ovatek Life Rafts without a Sea Anchor It is recommended that a short project be carried out to determine the leeway characteristics of fully loaded 4- and 7-person life rafts without a sea anchor deployed. The sea anchor has to be attached and deployed by the persons in the life raft. Depending on the evacuation circumstances this may or may not take place. Coupled with the discussion raised in viii

9 recommendation 4, there is a reasonable probability that during a SAR mission for an Ovatek life raft that the configuration could well be a full life raft drifting without a sea anchor. ix

10 TABLE OF CONTENTS ACKNOWLEDGEMENTS... III EXECUTIVE SUMMARY... IV TABLE OF CONTENTS...X LIST OF FIGURES...XII LIST OF TABLES... XIV LIST OF ACRONYMS...XV 1.0 INTRODUCTION BACKGROUND PROJECT OBJECTIVES PHASE I OVATEK LEEWAY PHASE II OVATEK LEEWAY USCG OBJECTIVES RELATED DOCUMENTS PROJECT METHODOLOGY PROJECT TASKS SAR OBJECTS Instrumentation SAR Object Configurations Data Collection Parameters FIELD TRIALS LOCATION AND TIME FRAME COAST GUARD SUPPORT VESSELS TYPICAL DRIFT RUN SCENARIO Deployment and Recovery Planning Transit and Deployment Tracking Recovery LEEWAY DETERMINATION DATA REDUCTION AND ANALYSIS METHODOLOGY DATA REDUCTION SUMMARY OF THE OVATEK LIFE RAFT LEEWAY DATASET ANALYSIS METHODOLOGY Definition of Leeway and Measurement Reference Levels Leeway Vectors Regression Models RESULTS AND DISCUSSION LIGHTLY-LOADED OVATEK LIFE RAFTS WITHOUT DROGUE Leeway Speed Leeway Angle Divergence Progressive Leeway Displacement Plots Downwind and Crosswind Leeway Components FULLY-LOADED OVATEK LIFE RAFTS WITH DROGUE...60 x

11 4.2.1 Leeway Speed Leeway Angle Divergence Downwind and Crosswind Leeway Components CONCLUSIONS RECOMENDATIONS REFERENCES...79 xi

12 LIST OF FIGURES FIGURE PERSON OVATEK LIFE RAFT...2 FIGURE 1-2 OVATEK LIFE RAFTS IN ST. JOHN'S...2 FIGURE 2-1 OVATEK 4-PERSON LIFE RAFT...9 FIGURE 2-2 OVATEK 7-PERSON LIFE RAFT...9 FIGURE 2-3 SUBMARINE EMERGENCY INDICATING RADIO BEACON (SEPIRB)...10 FIGURE 2-4 SUBMARINE ESCAPE AND IMMERSION EQUIPMENT (SEIE) LIFE RAFT...10 FIGURE 2-5 SIMULATED COCAINE BALE...10 FIGURE 2-6 METOCEAN SLDMB...11 FIGURE 2-7 SEIMAC SELF LOCATING DATA MARKER BUOY...11 FIGURE 2-8 OVATEK DATA LOGGER SETUP...12 FIGURE 2-9 INSIDE OF OVATEK LIFE RAFT...13 FIGURE 2-10 INSTRUMENTED AND OUTFITTED 4-PERSON OVATEK LIFE RAFT...14 FIGURE 2-11 INSTRUMENTED 4-PERSON LIFE RAFT AT SEA...14 FIGURE 2-12 INSTRUMENTED AND OUTFITTED 7-PERSON OVATEK LIFE RAFT...15 FIGURE 2-13 INSTRUMENTED 7-PERSON LIFE RAFT AT SEA...15 FIGURE 2-14 DATAWELL MKII DIRECTIONAL WAVEBUOY...16 FIGURE 2-15 OVATEK 4-PERSON LIFE RAFT DEPLOYED WITH DROGUE...17 FIGURE 2-16 OVATEK 4-PERSON LIFE RAFT DEPLOYED WITHOUT DROGUE...17 FIGURE 2-17 OVATEK 7-PERSON LIFE RAFT DEPLOYED WITH DROGUE...18 FIGURE 2-18 OVATEK 7-PERSON LIFE RAFT DEPLOYED WITHOUT DROGUE...18 FIGURE 2-19 PHASE I OPERATIONS AREA...20 FIGURE 2-20 PHASE II OPERATIONS AREA...21 FIGURE 2-21 CCGS HARP...22 FIGURE 2-22 PHASE I OVATEK RECOVERY...22 FIGURE 2-23 CCGS "ANN HARVEY"...23 FIGURE 2-24 PHASE II OVATEK DEPLOYMENT...23 FIGURE 2-25 INTEROCEAN S4 CURRENT METER IN TOW FRAME...27 FIGURE 3-1 PHASE I DRIFT TRACKS...32 FIGURE 3-2 PHASE II DRIFT TRACKS...33 FIGURE 3-3 RELATIONSHIPS BETWEEN LEEWAY SPEED AND ANGLE AND THE DOWNWIND AND CROSSWIND LEEWAY COMPONENTS...36 FIGURE 4-1 LEEWAY SPEED AGAINST 10 M WIND SPEED - OVATEK 4-PERSON LIFE RAFT, LIGHTLY-LOADED WITHOUT DROGUE...40 FIGURE 4-2 LEEWAY SPEED AGAINST 10 M WIND SPEED - OVATEK 7-PERSON LIFE RAFT, LIGHTLY-LOADED WITHOUT DROGUE...41 FIGURE 4-3 LEEWAY SPEED AGAINST 10 M WIND SPEED - OVATEK 4- AND 7-PERSON LIFE RAFTS, LIGHTLY-LOADED WITHOUT DROGUE...43 FIGURE 4-4 PROGRESSIVE LEEWAY DISPLACEMENTS: OVATEK 4- AND 7-PERSON RIGID LIFE RAFTS,...45 FIGURE 4-5 PROGRESSIVE LEEWAY DISPLACEMENTS ENLARGED SCALE...46 FIGURE 4-6 SAMPLE TIME-SERIES PLOT DURING LEEWAY DRIFT RUN FIGURE 4-7 TIME-SERIES PLOT AT THE START OF DRIFT RUN FIGURE 4-8 LEEWAY ANGLE AND WIND SPEED, OVATEK 4- PERSON LIFE RAFT, LIGHTLY-LOADED WITHOUT DROGUE...50 FIGURE 4-9 LEEWAY ANGLE AND WIND SPEED, OVATEK 7-PERSON LIFE RAFTS, LIGHTLY-LOADED WITHOUT DROGUE...51 FIGURE 4-10 DOWNWIND LEEWAY - OVATEK 4-PERSON RIGID LIFE RAFT, LIGHTLY-LOADED WITHOUT DROGUE...53 FIGURE 4-11 CROSSWIND LEEWAY - OVATEK 4-PERSON LIFE RAFT, LIGHTLY-LOADED WITHOUT DROGUE...54 FIGURE 4-12 DOWNWIND LEEWAY - OVATEK 7-PERSON RIGID LIFE RAFT, LIGHTLY-LOADED WITHOUT DROGUE...55 FIGURE 4-13 CROSSWIND LEEWAY - OVATEK 7-PERSON RIGID LIFE RAFT, LIGHTLY-LOADED WITHOUT DROGUE...56 FIGURE 4-14 DOWNWIND LEEWAY - OVATEK 4- AND 7-PERSON RIGID LIFE RAFTS, LIGHTLY-LOADED WITHOUT DROGUE...57 xii

13 FIGURE 4-15 CROSSWIND LEEWAY- OVATEK 4- AND 7-PERSON RIGID LIFE RAFT, LIGHTLY-LOADED WITHOUT DROGUE...58 FIGURE 4-16 LEEWAY SPEED AGAINST 10 M WIND SPEED OVATEK 4-PERSON RIGID LIFE RAFT, FULLY-LOADED WITH DROGUE...61 FIGURE 4-17 LEEWAY SPEED AGAINST 10 M WIND SPEED OVATEK 7-PERSON RIGID LIFE RAFT, FULLY-LOADED WITH DROGUE...62 FIGURE 4-18 LEEWAY SPEED AGAINST 10 M WIND SPEED OVATEK 4- AND 7-PERSON RIGID LIFE RAFT, FULLY- LOADED WITH DROGUE...63 FIGURE 4-19 PROGRESSIVE LEEWAY DISPLACEMENTS: OVATEK 4-AND 7-PERSON RIGID LIFE RAFTS, FULLY-LOADED WITH DROGUE...65 FIGURE 4-20 LEEWAY ANGLE SCATTER PLOT - OVATEK 4- AND 7-PERSON LIFE RAFTS, FULLY-LOADED WITH DROGUE...66 FIGURE 4-21 DOWNWIND LEEWAY - OVATEK 4-PERSON RIGID LIFE RAFT, FULLY-LOADED WITH DROGUE...68 FIGURE 4-22 CROSSWIND LEEWAY - OVATEK 4-PERSON RIGID LIFE RAFT, FULLY-LOADED WITH DROGUE...69 FIGURE 4-23 DOWNWIND LEEWAY - OVATEK 7-PERSON RIGID LIFE RAFT, FULLY-LOADED WITH DROGUE...70 FIGURE 4-24 CROSSWIND LEEWAY - OVATEK 7-PERSON RIGID LIFE RAFT, FULLY-LOADED WITH DROGUE...71 FIGURE 4-25 DOWNWIND LEEWAY - OVATEK 4- AND 7-PERSON RIGID LIFE RAFTS, FULLY-LOADED WITH DROGUE..72 FIGURE 4-26 CROSSWIND LEEWAY - OVATEK 4- AND 7-PERSON RIGID LIFE RAFTS, FULLY-LOADED WITH DROGUE..73 xiii

14 LIST OF TABLES TABLE 1-1 PROJECT RELATED DOCUMENTS...6 TABLE 3-1 DRIFT RUN DATA COLLECTION SUMMARY...31 TABLE 3-2 OVATEK LIFE RAFT CONFIGURATION DATA SUMMARY...34 TABLE 4-1 LINEAR REGRESSION MODELS OF LEEWAY SPEED ON 10 M WIND SPEED FOR OVATEK 4- AND 7-PERSON RIGID LIFE RAFTS, LIGHTLY-LOADED WITHOUT DROGUE...42 TABLE 4-2 LEEWAY ANGLE STATISTICS - OVATEK 4- AND 7-PERSON RIGID LIFE RAFTS LIGHTLY-LOADED WITHOUT DROGUE...49 TABLE 4-3 DOWNWIND AND CROSSWIND REGRESSION MODELS FOR LIGHTLY-LOADED OVATEK 4- AND 7-PERSON LIFE RAFTS WITHOUT DROGUE...59 TABLE 4-4 LINEAR REGRESSION MODELS OF LEEWAY SPEED ON 10 M WIND SPEED FOR OVATEK 4-AND 7-PERSON RIGID LIFE RAFTS, FULLY-LOADED WITH DROGUE...60 TABLE 4-5 LEEWAY ANGLE STATISTICS - OVATEK 4- AND 7-PERSON LIFE RAFTS, FULLY-LOADED WITH DROGUE...64 TABLE 4-6 DOWNWIND AND CROSSWIND REGRESSION MODELS - OVATEK 4- AND 7-PERSON LIFE RAFTS, FULLY- LOADED WITH DROGUE...74 xiv

15 LIST OF ACRONYMS APLwaves ARGOS CANSARP CCG CCGS DFO DGPS EPIRB GPS NIF NSS PTT S4 SAIC SAR SEIE SEPIRB SLDMB SOLAS TDC USCG John Hopkins Applied Physics Laboratory Waves Analysis Software A Satellite-based Location and Data Collection System Canadian Search and Rescue Planning Canadian Coast Guard Canadian Coast Guard Ship Department of Fisheries and Oceans Differential Global Positioning System Emergency Position Indicating Radio Beacon Global Positioning System New Initiatives Fund National SAR Secretariat Platform Transmitter Terminal InterOcean S4 current meter Science Applications International Corporation Search and Rescue Submarine Escape and Immersion Equipment Submarine Emergency Position Indicating Radio Beacon Self Locating Data Marker Buoy Safety of Life at Sea Transportation Development Centre United States Coast Guard xv

16 1.0 INTRODUCTION A two-phase project was conducted by OCEANS Ltd. during fiscal years 2004/2005 and 2005/2006 to investigate the Leeway and Drift of Ovatek Life Rafts on behalf of the Canadian Coast Guard (CCG). Primary funding for the project was provided by the National SAR Secretariat (NSS). In-kind support was provided by OCEANS Ltd., CCG, and the United States Coast Guard (USCG). Phase I of the project was completed during the 04/05 fiscal year and Phase II completed during the 05/06 fiscal year. This document constitutes the OCEANS Ltd. Final Report for the project (NIF ID , DFO 2/04). Included in the report will be the following: - background information on the project - overall project objectives - project methodology - project objectives - data reduction and analysis - preliminary results and discussion - recommendations for future projects 1.1 BACKGROUND In the late 1980 s to mid 1990 s OCEANS Ltd. personnel, with support from CCG, Transportation Development Centre (TDC), and USCG conducted a number of leeway experiments for common SAR objects in environmental conditions typically encountered on the east coast of Canada. The National SAR Manual (DFO, 1998) defines leeway as the movement of the search object through water caused by the action of wind on the exposed surfaces of the object. The objects tested in these earlier studies included: - 4, 6, and 20-person inflatable life rafts - small open plank boats - 22-person SOLAS approved fibreglass life capsule - 46-person L1011 passenger slide / life raft - an air deployable Sea Rescue Kit consisting of three 6-person life rafts and two survival packs The results of these studies have been incorporated in the National SAR Manual and into the Canadian Search and Rescue Planning (CANSARP) tool. CANSARP is a computer tool used to 1

17 plan search operations. It uses the target s leeway characteristics, visual characteristics, and environmental factors such as ocean currents and winds to determine probable target drift trajectories. In recent years Ovatek Inc., based in New Brunswick, has developed and marketed a new type of SAR object, the 4-person and 7-person Ovatek rigid life raft. Figure Person Ovatek Life Raft Ovatek life rafts have been approved by SOLAS, CCG, and the USCG. In recent years they have become a popular alternative to the inflatable life raft on board fishing vessels in Atlantic Canada and the west coast of North America. Figure 1-2 Ovatek Life Rafts in St. John's An incident involving an Ovatek life raft highlighted the need for leeway data for these SAR targets. In the spring of 2003 a SAR operation (Incident L Quebec Region) was conducted for a 7-person Ovatek life raft in the Gulf of St. Lawrence. The life raft belonged to 2

18 the MV Caboteur that sank on April 4, 2003 at 1215 EST. Fortunately in this case a vessel was standing close by when the ship sank and the 6-man crew was recovered from the life raft within an hour with no injuries. The life raft and the Caboteur s EPIRB were recovered 2 days later on April 6, However, the incident report noted that the position of the search objects was very different than the positions calculated by CANSARP. Further, it stated that upon examination of the incident it is evident that the Ovatek life raft did not have the same rhythm of drift as a conventional life raft. In an effort to improve the accuracy of CANSARP predictions, a leeway study was proposed and conducted on 4-person and 7-person Ovatek life rafts. The field trials and analysis followed a general approach used successfully by OCEANS Ltd. in previous leeway work. The details of this work are discussed in the remainder of this report. As well, at the outset of this project the USCG was invited to participate. Dating back to the late 1980s OCEANS Ltd. personnel, on behalf of the Canadian Coast Guard, have successfully carried out several leeway and drift experiments off Newfoundland in partnership with the USCG. During the Phase I field trials the USCG supported this project through the supply of various instrumentation and equipment. During the Phase II field trials the USCG and their contractor, Science Applications International Corp. (SAIC) took part in field operations and collected leeway data on three targets of interest to the USCG. The targets included Submarine Escape and Immersion Equipment (SEIE) life rafts, Submarine Emergency Position Indicating Radio Beacons (SEPIRB) and simulated cocaine bales. Further information on USCG targets, objectives and participation is provided throughout this document. 1.2 PROJECT OBJECTIVES The primary Ovatek leeway project objective was to: determine a functional relationship between wind velocity and leeway speed and angle for the 4-person and 7-person Ovatek rigid life rafts in operationally limiting configurations for inclusion in the National SAR Manual (DFO, 1998) and CANSARP. A secondary project objective was to: to investigate improved analysis methodologies for obtaining SAR object leeway angles off the downwind direction with the goal of increasing the precision of 3

19 leeway angle divergence and, ultimately, reducing search area, search time, and SAR resource requirements. Interim objectives were established for each phase of the project to satisfy the above goals. As well, the USCG conducted a field program in cooperation with the Phase II Ovatek field study. The objectives of their research as well as a discussion of the Phase I and II interim objectives follows below PHASE I OVATEK LEEWAY Primary Objectives 1. Collect and analyze preliminary field data for determining the leeway for the 4- and 7- person Ovatek life rafts in wind speeds up to 25 knots. Life rafts were to be configured as follows: - light loading (1 person on board) without sea anchor deployed - maximum loading (4- or 7-person on board) with sea anchor deployed 2. In preparation for the Phase II trials planned for the Fall of 2005 the work in Phase I was to serve as a test of equipment, deployment/recovery procedures, scientific instrumentation, and communications. Secondary Objectives 1. Collect field data for determining the leeway for the research sailboat Tigger PHASE II OVATEK LEEWAY Primary Objectives 3. Collect and analyze field data for determining the leeway for the 4- and 7-person Ovatek life rafts in wind speeds up to 50 knots. Life rafts were to be configured as follows: - light loading (1 person on board) without sea anchor deployed - maximum loading (4- or 7-person on board) with sea anchor deployed 4

20 4. Determine a functional relationship between wind velocity and leeway speed and angle for the 4-person and 7-person Ovatek rigid life rafts in operationally limiting configurations for inclusion in the National SAR Manual (DFO, 1998) and CANSARP. 5. Investigate improved analysis methodologies for obtaining SAR leeway angles off the downwind direction with the goal of increasing the precision of leeway angle divergence and, ultimately, reducing the search area, search time, and SAR resource requirements. Secondary Objectives 1. Carry out a drift characteristics comparison of the MetOcean SLDMB versus the Seimac SLDMB USCG OBJECTIVES 1. Collect field data for determining the leeway of a SEPIRB. 2. Collect field data for determining the leeway of a SEIE life raft configured with and without a sea anchor. 3. Collect field data for determining the leeway of simulated cocaine bales. Leeway data was acquired by deploying SLDMBs in the vicinity of the above leeway targets. Environmental data was collected using an Aanderra Coastal Monitoring Buoy and wave data from a Datawell Directional Waverider buoy. In the case of the SEIE life rafts, a single life raft was outfitted with an RDI Sentinel Acoustic Doppler Current Profiler current meter to collect leeway speed directly. 1.3 Related Documents The following documents were also prepared as part of this project and will be submitted on CD with the final of this report. 5

21 Table 1-1 Project Related Documents Document Number Document Title Project Proposal 11340_PWP_P1 Phase I Project Work Plan 11340_FP_P1 Phase I Field Plan 11340_FR_P1 Phase I Field Report 11340_SR_P1 Phase I Summary Report 11340_PWP_P2 Phase II Project Work Plan 11340_FP_P2 Phase II Field Plan 11340_FR_P2 Phase II Field Report 6

22 2.0 PROJECT METHODOLOGY The following sections provide details on the leeway targets, equipment and methods used to perform the Ovatek field experiment. These sections also give a brief overview of the USCG targets and their involvement in the field trials. 2.1 Project Tasks This section provides an overview of the Phase I and II project tasks. Much of the preparatory work performed during Phase I and II was carried out simultaneously in order to meet project schedules. The following is a list of the tasks and subtasks performed in each phase. 1. Phase I activities 1.1. Preparation and mobilization for phase I field trials Preparation of the phase I work plan Research, source and procure project instrumentation and equipment Prepare, test and mobilize project instrumentation and equipment Prepare a field trial plan 1.2. Conduct phase I field trials Identification of support vessel and field trial time frame Logistics and personnel Meeting with support vessel crew Transport of project instrumentation and equipment to coast guard base Mobilization of project instrumentation and equipment on support vessel Weather forecast support Target tracking and communications Directional wave data collection Daily drift run scenario De-mobilization of project instrumentation and equipment from support vessel 1.3. Phase I data analysis and interim report preparation Preparation of phase I field report Field data consolidation and preliminary quality control Submission and presentation of field trial report Data reduction and analysis of Phase I leeway data Preparation of Phase I summary report Presentation of Phase I summary report 7

23 Finalization of Phase I report 1.4. Phase I NIF sponsor project management NIF sponsor project management activities 2. Phase II activities 2.1. Preparation and mobilization for Phase II field trials Review recommendations of Phase I final report Evaluate equipment and instrumentation performance from Phase I Preparation of the phase II work plan Procure required project instrumentation and equipment Prepare, test and mobilize project instrumentation and equipment Prepare a field trial plan 2.2. Conduct Phase II field trials Identification of field trial operations area and time frame Identification of support vessel Logistics and personnel Meeting with support vessel crew Transport of project instrumentation and equipment to coast guard base Mobilization of project instrumentation and equipment on support vessel Weather forecast support Target tracking and communications Directional wave data collection Daily drift run scenario De-mobilization of project instrumentation and equipment from support vessel 2.3. Phase II data analysis and final report preparation Preparation of Phase II field report Field data consolidation and preliminary quality control Submission and presentation of field trial report Data reduction and analysis of phase ii leeway data Preparation of final project draft report Presentation of final project draft report Finalization of final project report French Translation and submission of final project report 2.4. Phase II NIF sponsor project management NIF sponsor project management activities Preparation and implementation of project communications plan 8

24 2.2 SAR Objects The primary leeway objects for project were the 4- and 7-person Ovatek Life Rafts. The life rafts are seen in Figure 2-1 and Figure 2-2. Figure 2-1 Ovatek 4-Person Life Raft The general specifications of the 4-person life raft are: Length 2.1 m Width 1.3 m Height 1.1 m ` Weight 115kg/250 lb Full Load 430kg/950 lb Ballast External Figure 2-2 Ovatek 7-Person Life Raft The general specifications of the 7-person life raft are: Length 2.8 m Width 1.3 m Height 1.4 m Weight 182kg/400 lb Full Load 740kg/1600 lb Ballast 100 litre internal 9

25 The USCG leeway targets include a SEPIRB, SEIE life raft and simulated cocaine bales. The targets are shown in Figure 2-3 through Figure 2-5 respectively. Figure 2-3 Submarine Emergency Indicating Radio Beacon (SEPIRB) Figure 2-4 Submarine Escape and Immersion Equipment (SEIE) Life Raft Figure 2-5 Simulated Cocaine Bale Figure 2-6 and Figure 2-7 respectively show the MetOcean and Seimac SLDMBs. 10

26 Figure 2-6 MetOcean SLDMB Figure 2-7 Seimac Self Locating Data Marker Buoy Instrumentation During the 2004 and 2005 field programs, data were collected from a set of sensors attached to each Ovatek life raft. This equipment logged meteorological parameters, life raft position, and heading. The S4 current meter frame was tethered to the life raft via a 20m line. As well, an ORBCOMM satellite communications system was installed to transmit the life raft s position and various status indicators back to shore at regular intervals. As a backup, an ARGOS PTT was installed inside the life raft to transmit position for recovery purposes. The data logger and sensors were powered with two 12V sealed lead acid batteries which provided enough power for 11

27 approximately 7 days of operation. The following is a complete listing of equipment installed onboard the Ovatek life rafts: - R.M. Young anemometer system - Campbell Scientific 107B air/water temperature sensors - Honeywell HMR axis compass system (Phase I) - KVH AutoComp 1000S tilt-tompensated flux gate compass (Phase II) - Campbell Scientific CR10X data logger - Two 12V 26AHr sealed lead acid batteries - InterOcean S4 current meter - Garmin 16 GPS receiver - Garmin GBR21 DGPS beacon receiver / CSI Wireless SBA-1 DGPS beacon receiver - Orbcomm satellite communications system c/w Stellar Satellite ST2500 transceiver with service from ROM Communications - Seimac SmartCat ARGOS PTT - Novatech VHF beacon - Mobri S-2 radar reflector The data logger, satellite communications transceiver, and batteries were installed inside a watertight Pelican case. The case and electronics are shown in Figure 2-8. Figure 2-8 Ovatek Data Logger Setup The case was secured inside the life rafts and the sensors were connected via waterproof connectors. Figure 2-9 shows the complete system mounted inside of a life raft. 12

28 Compass Plywood Floor & Bracing Sandbag ARGOS PTT Pelican Case Figure 2-9 Inside of Ovatek Life Raft Figure 2-10 through Figure 2-13 illustrate the external configuration for the 4-person and 7- person life rafts respectively. 13

29 Figure 2-10 Instrumented and Outfitted 4-Person Ovatek Life Raft Figure 2-11 Instrumented 4-Person Life Raft at Sea 14

30 Anemometer Guywire Air Temperature Sensor Mast 3-Point Lifting Strap Satellite Communications Antenna GPS Floor & Floor Supports Water Temperature Sensor Datalogger & Communications Package Belly Strap Compass Waterline Figure 2-12 Instrumented and Outfitted 7-Person Ovatek Life Raft Figure 2-13 Instrumented 7-Person Life Raft at Sea 15

31 A Datawell Directional waverider buoy, shown in Figure 2-14, was deployed in the operations area. This buoy was primarily used as an operational tool during field trials to determine appropriate deployment schedules. The Datawell buoy transmits data to a receiving station via a high frequency radio Figure 2-14 Datawell MKII Directional Wavebuoy link. During Phase I, the receiving station was set up in a Canadian Coast Guard building at Cape Spear. For Phase II, the receiving station was set up at OCEANS Ltd. s office in St. John s SAR Object Configurations Both life rafts were deployed in two configurations during the trials. The configurations included 1-person loading without a drogue and full loading with a drogue deployed. The drogue, SOLAS approved and manufactured by Ovatek, was a nylon cone with swivel and nylon rode. The drogue, with a rode of 30.5 m, has a cone 0.64 m in length with the wide opening being 0.6 m and the narrow opening being.08 m. Approximately 22 kg sand bags were used for ballast. The weight of one person was considered to be 79.5 kg. The life rafts were outfitted with plywood floors and aluminum support bracing to accommodate the mounting of equipment and ballast inside the life rafts. A 3-point lifting bridle was used deploy and recover the life raft. The bridle was made from 2-ply x 2 nylon strapping and had a safe working load of º from vertical. In the lightly-loaded configuration a belly strap, swivel and stiff rope arrangement was used to attach the S4 tether to the life raft. This ensured the life raft s orientation was not influenced by the S4 current meter assembly. 16

32 Figure 2-15 and Figure 2-16 show the 4-person life raft in its deployed configuration with and without a drogue deployed respectively. Figure 2-17 and Figure 2-18 show the 7-person life raft in its deployed configuration with and without a drogue deployed respectively. Figure 2-15 Ovatek 4-Person Life Raft Deployed With Drogue Figure 2-16 Ovatek 4-Person Life Raft Deployed Without Drogue 17

33 Figure 2-17 Ovatek 7-Person Life Raft Deployed With Drogue Figure 2-18 Ovatek 7-Person Life Raft Deployed Without Drogue 18

34 2.2.3 Data Collection Parameters Positional information on the SAR objects was obtained through GPS, ARGOS PTT's and VHF beacons. GPS positions were logged every five minutes using the CR10X data logger and ed to OCEANS Ltd. hourly via the ORBCOMM system. The GPS data was subsequently used to derive true wind at the SAR objects and to obtain total drift displacement. ARGOS positions were updated every 2 to 3 hours and were obtained on a routine basis from the ARGOS website via the USCG International Ice Patrol. The VHF beacons provided SAR object direction when the vessel was within VHF range (approximately 10 nm) of the SAR object. SAR object headings were determined using a 3-axis compass system. In Phase I a Honeywell HMR3300 tilt-compensated compass was used to determine heading. These units also provided pitch and roll information. Due to communication problems, they were replaced with KVH Autocomp 1000s compasses in Phase II. The KVH units are internally gimbaled and did not provide pitch and roll information. Wind direction was computed from a 10-minute unit vector average using a sampling interval of one second. The standard deviation of wind direction was computed following the algorithm described by Yamartimo (1984). Average wind speed recorded was simply the scalar mean apparent wind speed over the sampling period. Ten-minute maximum 1-second apparent wind speed was also recorded. For all drift runs the S4 current meters were programmed to provide 10-minute vector averages of the half-second velocity component samples. Data collection times for the instrumentation packages on board the SAR objects were synchronized with the S4 data collection program. Air and sea temperature was recorded every 10 minutes. These data were used in the adjustment of the true wind to the 10 m reference height. The following wave data was recorded by the Datawell waverider system hourly: wave direction significant wave height maximum wave height mean zero crossing period peak period spectral data statistics data 19

35 raw data sea temperature 2.3 FIELD TRIALS LOCATION AND TIME FRAME The Phase I field trials were conducted off Cape Spear, Newfoundland. The general operations area was approximately 20 nm X 20 nm (400 square nautical miles). The centre of the operations area was approximately 15 nautical miles east of Cape Spear. A Datawell directional waverider buoy was deployed within the operations area. The Phase I field trials were conducted during the period September 1 17, The field trial location is shown in Figure The deployment position for the rafts was planned so that the Ovatek life rafts would likely stay within the operations area during their drift run. 40' 47 40'N 52 30'W Phase I General Operating Area 47 40'N 52 01'W 35' St. John s 47 o N 30.00' Cape Spear Wavebuoy 'N 'W 25' 20' 47 20'N 52 30'W 47 20'N 52 01'W 40' 30' 20' 10' 52 o W Figure 2-19 Phase I Operations Area For the second phase of the leeway project it was intended that the Ovatek life rafts would be deployed for 3-4 day periods. Therefore, the general operations area was enlarged to approximately 90 nm X 90 nm (8100 square nautical miles). The field trial area is shown in Figure As with Phase I, the deployment position for the life rafts was planned so that the 20

36 Ovatek life rafts would likely stay within the operations area. The smaller USCG targets (SEPIRBs, SEIE life rafts, cocaine bales and SLDMBs) were deployed for 1-2 day periods before recovery was attempted. Essentially, these smaller targets were deployed upwind of the moored wave and meteorological buoy with the intent that their drift tracks would pass in close proximity to the moored buoys. Therefore, the directional wave data and meteorological data reflected the conditions being experienced by the leeway targets as closely as possible. 30' 48 o N 48 00'N 52 30'W Phase II General Operating Area 48 00'N 50 18'W Metbuoy 'N 'W 30' Wavebuoy 'N 'W 47 o N 30' 46 30'N 52 30'W 46 30'N 50 18'W 46 o N 53 o W 30' 52 o W 30' 51 o W 30' 50 o W Figure 2-20 Phase II Operations Area 2.4 COAST GUARD SUPPORT VESSELS The primary support vessel for the Phase I Field Trials was the CCGS Harp. The CCGS "Harp", shown in Figure 2-21 and Figure 2-22, is a small multi-task ice strengthened cutter. The 21

37 overall length is 24.5 m with a beam of 7.6 m and a draft of 2.5 m. Deck space is minimal but was adequate for the stowage and management of project equipment including the 4- and 7- person Ovatek life rafts. The after deck is equipped with a PM Autogru crane and an inflatable runabout. The crane, with a safe working load of 1400 kg at 7.5 m reach was adequate for handling both life rafts within trial operational limits for deployment and recovery of the Ovatek life rafts. After some experience was gained, the operating limits were deemed to be less than 1.8 m significant wave height. The low freeboard facilitated the handling of SAR objects and equipment over the side. Figure 2-21 CCGS HARP Figure 2-22 Phase I Ovatek Recovery 22

38 The primary support vessel for the Phase II Field Trials was the CCGS Ann Harvey. The CCGS "Ann Harvey", shown in Figure 2-23 and Figure 2-24, is a light icebreaker/major navaids tender. The overall length is 83 m with a beam of 16.2 m and a draft of 6.2 m. Space on the forward deck was more than adequate for the stowage and management of project equipment including the 4- and 7-person Ovatek life rafts. The main hold was also used as an area to perform life raft maintenance and was used for equipment stowage. The forward crane s reach and capacity easily accommodated the deployment and recovery of the Ovatek life rafts and the USCG targets. The higher freeboard made recovery operations slightly more difficult than the previous year. However, the vessel s stability was an asset. After some experience was gained, the operating limits were deemed to be on the order of 3 m significant wave height. Figure 2-23 CCGS "Ann Harvey" Figure 2-24 Phase II Ovatek Deployment 23

39 Equipment was required onboard both support vessels for tracking the SAR objects at sea. Both the CCGS Harp and Ann Harvey had VHF direction finders previously installed. As well, a GONIO 400 ARGOS direction finder unit was temporarily installed on both vessels to assist with target tracking. Also, a connection was provided to the Ann Harvey s GlobalStar Satellite system to allow for collection of position data from the internet. 2.5 Typical Drift Run Scenario As stated in the project objectives, the Phase I field trials were used as an opportunity to collect data in light wind conditions. This also served as a test of equipment, deployment/recovery procedures, instrumentation, and communications systems in preparation for the Phase II trials. For Phase II the goal was to obtain data for wind speeds up to 50 knots. A typical drift run was completed in 4 stages: deployment location planning, transit and deployment, target tracking, and recovery. The details of these stages are discussed in the following sections Deployment and Recovery Planning Prior to leaving port, actual and predicted weather and sea conditions were assessed and discussed with the Captain. This was normally done in the evening prior to sailing and again in the morning before a sailing time was finalized. To assist in the go or no-go decision-making, certain tools were utilized. These decision-making tools included the following: 1. A 5-day marine site-specific forecast provided to the project from the OCEANS Ltd. Weather Office. These forecasts were issued daily. 2. An Oceanogram for the operations area provided by OCEANS Ltd. that was accessed at the OCEANS Ltd. website. The Oceanogram provided a 7-day forecast of winds and waves for selected points within the operations area. 3. Wave parameters from the directional waverider buoy deployed in the operations area were checked. For the Phase I trials drifts were expected to last between 12 and 24 hours. This limited the total drift distance in case of equipment failure. Generally the life rafts were deployed in the late morning and retrieved in the early afternoon of the following day. During Phase II the Ovatek 24

40 life rafts were deployed in reasonably good weather ahead of an impending weather system. The life rafts remained at sea while the weather system passed through the region and tracked from shore. They were then recovered in good weather conditions after the system had passed through the area. It was hoped to limit the duration of a drift run to less than seven (7) days. The life rafts were always deployed and recovered within the operating limits of the vessel. Once it was decided that conditions looked suitable for the deployment of SAR objects, based on the above criteria, a deployment plan was finalized. The deployment plan usually included deciding a deployment location and setting a sailing time. Every effort was made to deploy the life rafts in a location that would keep them within the operating area and in the general area of the directional waverider buoy, particularly in Phase I. Deployment locations were generally upwind of the wave buoy. Therefore the wave data being collected by the wave buoy was relevant to what was being experienced by the life rafts Transit and Deployment OCEANS Ltd. personnel prepared the Ovatek life rafts for deployment. Usually the life rafts were prepared for deployment the day before sailing with final preparations being made on the departure day prior to leaving port for the deployment location. The actual deployment of the life rafts was carried out by the ship's crew with OCEANS Ltd. personnel assisting. General preparation of the Ovatek life rafts involved charging and changing out batteries as required for the data loggers, lights and beacons. As well, life raft configurations were changed as necessary. Wind speed and direction sensors were checked routinely and their correct operation confirmed. Prior to departing for the deployment location the CR10X data loggers in the 4- and 7-person life rafts were turned on to collect wind, temperature, GPS and life raft heading data while the Orbcomm satellite communications systems were set up to communicate positional information back to OCEANS Ltd. via . As well, the InterOcean S4 current meters were set up and their operation confirmed as were the ARGOS PTTs in each life raft. VHF beacons for each life raft were turned on and their operation confirmed through the vessel s VHF direction finder. The final tasks prior to leaving port were securing the instrumentation and ballast inside the life rafts and then locking down the hatches. Life rafts remained secured in their cradles until it came time to deploy them. 25

41 Once at location, life raft deployment operations began. The life rafts were lifted over the side using the ship's crane. Once the life raft was in the water, it was allowed to drift away from the vessel while the S4 tether and drogue were payed out. Once deployed, a positional fix was taken. The ship then moved away from the life raft in such a fashion so as not to disturb the natural drift of the life raft. The vessel would then proceed to the next deployment location. The life rafts were generally deployed between 0.25 and 0.50 nautical miles apart. The time required to deploy each life raft was generally in the order of 10 minutes Tracking After the life rafts were deployed the vessel returned to St. John's or stayed in the vicinity of the life rafts overnight depending on the operational plan. While in St. John's the life raft positions were monitored through the Orbcomm system and ARGOS network. If the support vessel remained onsite the life rafts were visually and electronically monitored. Visual monitoring was normally limited to checking the general condition of the life raft. Visual checks included such things as the trim of the life raft, fouling of the S4 tether, confirmation that the S4 was attached, the lights were working and so forth. Electronic monitoring of the life rafts included tracking on the vessel s radar and the use of direction finding equipment. Onboard the CCGS Ann Harvey, personnel were also able to check the Orbcomm and ARGOS messages via a Globalstar Satellite connection Recovery Prior to departing from St. John s for recovery operations the latest positions were obtained from the Orbcomm system and ARGOS. When the vessel departed St. John s it proceeded to the general location of the last known position. Normally, when the vessel arrived at this location the VHF direction finder would be receiving the signal from the VHF beacon. Once the VHF beacon signal was received it was simply a matter of steaming up to the life raft. An ARGOS PTT direction finder was used as back up to the VHF beacon/direction finder system. During recovery operations the life raft was normally approached from down wind. The first item to be retrieved was the S4 tether. Once this was on board it was used to bring the life raft alongside the rail while the S4 and drogue (if attached) were brought on board. Once alongside, the tag lines of the life raft were grappled and brought on board and used to stabilize the load during recovery. Once the life raft was stabilized the lifting hook of the crane was attached to the eye of the life raft lifting harness. The life raft was then lifted onboard by the crane while control was maintained by the tag lines. When lifted onboard the life rafts were lowered into their cradles where they were 26

42 lashed and secured. Ancillary equipment including the InterOcean S4, floats, beacons and tethers were all stowed and secured while heading for the next life raft or prior to departing the site for St. John s. Downloading of data was carried out once the vessel tied up in St. John s. All data collected were downloaded to laptop computers with backups stored on CDROM discs. From there certain plots of the data were generated and reviewed. 2.6 Leeway Determination Ovatek leeway speeds and angles were determined directly using the InterOcean S4 current meter during the Phase I and Phase II trials. Using the principle of an electromagnetic ship's log, the current meter was tethered to the SAR object to measure velocity relative to the water. Tenminute vector averages based on half second sampling rates were logged. An internal electronic Figure 2-25 InterOcean S4 Current Meter in Tow Frame tilt-compensated compass provided direction reference. Leeway direction was given by the reciprocal of the logged direction and the difference between the downwind and leeway directions provided leeway angle. The S4 current meter was selected because of its stable hydrodynamic characteristics and its ability to provide accurate current data in the wave zone. The water drag of the current meter and tow frame was at least partially offset by the wind drag on a 0.65 m float to which the frame was secured. The float size was determined from calculations and tests conducted during previous leeway work (Fitzgerald et al., 1993). The center of the current meter was 0.75 m below the sea surface. 27