Observations

Personal Views by David Dillingham, Dillingham & Associates

The Observations column voices the ‘personal views’ of guest contributors, offering them the opportunity to express their opinions – or vent their spleens – on a single hydrographic issue or a range of topics.

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Inshore Survey Boats - Size Really Matters

Using the right inshore boat for a hydrographic survey with regard to size, draught, type, stability, effective support of survey staff and spread, survey duration, location and expected sea conditions, is very important. Consequently attention is now drawn to survey contractors’ increasingly frequent and unsatisfactory use of small, 6-8m, road towable, rigid inflatable, GRP mono-hull or catamaran type vessels for open sea survey work.

No criticism is made of the safety of these boats. However, despite claims to the contrary from the survey contractors who operate them, for effective 10- or 12-hour day open sea survey work using a range of survey equipment in varied wind and sea conditions, these boats have proved very unsatisfactory.

Because of their light, planing, shallow draught hull forms, the boats are extremely prone to wave, wind and tidal stream action, particularly in short seas, gusting winds, tidal stream boils or overfalls. This results in unacceptably low upper limits on the wind and sea conditions in which they can operate in order to obtain reliable survey data. In winds above force three or four, the boats have been found to be extremely uncomfortable for prolonged survey work.

The limited working weather window of such vessels often results in surveys taking much longer than planned, with clients consequently having to pay excessive bad weather down-time in both marginal and poor survey conditions when a larger, more suitable displacement boat would have completed the job in a wider range of sea conditions and a shorter time.

Wheelhouse space in small boats is generally limited to no more than 3 persons, who not only find themselves unable to move around in the cramped conditions, but also having to share the limited space with survey equipment. One of these persons will be the helmsman, the other two the surveyor and assistant surveyor or engineer. All others, including the client’s representative, crew and any geophysical staff have to remain outside on a small deck in all weathers, or swap places, at intervals, with those in the wheelhouse. In general, small boats have inadequate domestic facilities to support typical 10- or 12-hour day operations.

  On board a small vessel there is only limited deck space for sidescan sonar cables and fish, towed hydrophones or survey equipment. Such space as there is has to be shared with the personnel who cannot get into the wheelhouse. Stowage space for spares and replacement equipment is equally limited, frequently preventing the repair or replacement of defective equipment whilst at sea. The boats are unable to accommodate even medium size grabs or over-the-side towed seismic transducers. So for these surveys it will usually be necessary to mobilise a larger, more effective survey boat which, ironically, could have completed the whole survey more efficiently and reliably.

Cramped working conditions, inability to move around, lack of accommodation or domestic facilities and an uncomfortable ride in a small boat operating the required 10- or 12-hours on repetitive survey days in all weathers, will not produce the best work. That which can be produced is likely to be achieved under unacceptable working conditions at the expense of efficiency, effort and cost, by uncomfortable and tired survey personnel and crews working what is effectively a shortened and inefficient working day.

For estuarial or sheltered water surveys, these small boats are just suitable. For short duration open sea surveys, say 2 or 3 short days in fine weather conditions, they may be suitable. However, for extensive open sea surveys, requiring operations in a fair range of wind and sea conditions, especially when sidescan or seismic work is necessary, they are never suitable.

 Dillingham & Associates’ 12.2m MCA Cat II inshore survey vessel ‘Algier Rose’

The successful inshore survey boat evolved as a result of requirements of cost, size, draught, stability and manoeuvrability and ability to work and collect reliable survey data over a 10- to 12-hour working day in a representative range of meteorological and sea conditions, with minimum downtime. The result was a stable 10-15m LOA displacement or semi-displacement, 1-1½m draught day boat with adequate space for survey operations, a deck and stowage of spares. That is a vessel able to support the required number of survey personnel and crew, all necessary survey equipment, including shallow penetration seismic and to handle over-the-side towed transducers, grabbing and oceanographic equipment. 

These larger boats have adequate heated working space and accommodation and all domestic facilities for a minimum of 5 persons comprising the surveyor, assistant surveyor, client’s representative, skipper and crew (MCA Workboat Regulations do not permit single manning) for the required working day. Additional personnel could include a sidescan sonar operator/engineer and geophysical staff. With regard to heating, it should be noted that electronic survey equipment and computers, in addition to their human operators, work better in warm, dry conditions.

Small boats currently used for open water inshore surveys evolved, at the expense of practical efficiency, from the need to submit low bids to clients who often know very little about survey operations and whose main interest is to award the survey to the lowest bidder.

 Operators of traditional displacement and appropriately sized inshore survey boats have contributed to formulation of the Maritime and Coastguard Agency Workboat Regulations. These regulations have helped raise the previous survey boat standard from the usual ‘boat of opportunity’ - invariably the cheapest, smallest, oldest fishing boat in the working harbour - to purpose-built work and survey boats. Many survey contractors, in short-sighted pursuit of cost-cutting measures to appease their clients, have employed undersized boats and failed to maintain professional standards, thus returning to a familiarly unsatisfactory situation.

There is nothing stalwart or adroit about trying to carry out survey work from undersized boats in uncomfortable conditions, particularly when this affects the data quality and work rate, when more comfortable and cost-effective options exist. Use of such vessels for surveys requiring more substantial craft is unprofessional and benefits no one. By using undersized boats, survey contractors do their clients, themselves and their staff a great disservice and compromise their survey work. It would be to their advantage to make a professional stand favouring the use of adequately sized and equipped survey vessels, capable of doing the job properly, thus benefiting both their clients and the survey industry alike.

David Dillingham

David Dillingham served four years as a deck officer in the merchant navy before qualifying as a commercial pilot. He then spent five years flying in private air charter. On leaving flying, David learned to dive and joined Smit Tak International Salvage where he gained experience in marine salvage and civil engineering works.

In 1970 he formed Dillingham & Associates which carries out independent marine and underwater works and inspections on marine engineering projects. In 1990 he built and fitted out the survey/diving vessel ‘Algier Rose’ which has been employed by most major UK survey contractors for a range of inshore hydrographic, geophysical and marine environmental surveys.

David’s particular interest is shipwreck survey and diving; he is currently compiling a 7, 000 title worldwide shipwreck bibliography.