Special Solutions

During consultancy and during project management problems will arise which have not been expected. Wether we are in charge with consultancy or project management or wether we are called in for the solution of such problems: we have takled most of the typical problems in either capacity.

One group of problems is centred around echosounders. Echosounders are for the last 30 years in a state of stormy evolution. Single beam echosounders are working perfectly at cm-accuracy in waterdepth from centimeters to 10.000 meters. NarroWing the beamwidth, using special techniques like pulsing and using special phenomena like the parametric effect, the penetration in the seafloor has increased to 100 m and more. Techniques like beamforming and phase interference have evolved during the development of multibeam-echosounders and made them a very powerful instrument for bathimetry. This evolution has been enabled and driven by the progress of electronic hardware and digital computing.

Periphial instruments like heave-, roll- and pitch-sensors and sound velocity sensors have reached a standard which fits the measurement accuracy.

This development has serious repercussions in shipbuilding. Large transducer trunks have to be installed at the bottom of the hull in places where the space is scarce. Their installation has to reach accuracies, which are unusual in shipbuilding. The hydrodynamics in the area of the transducers have to be taken into account from the beginning of creating the ship lines. However since even detailed model tank tests cannot model air-bubbles the finished ship will not seldomly suffer from this effect, which is of no importance in normal shipbuilding, but will render echosounders ineffecient to dead. To avoid this situation, we have in some cases developed retractables (picture),example 2(video).

The multi beam and parametic echosounders on METEOR did not show any signal, when first at sea. We analysed the situation with

  • an array of acoustic transducers at different depths and in different locations on the hull.
  • a piping array which took water samples from similar depth and positions leading them directly onboard for visual airbubble control.
  • underwater cameras (video) at different positions, some with pan-and-tilt-units.
  • we scattered confetti in the port/starboard bowwater while underway, to observe the flow underneath the hull

At the end the bulbous bow of the vessel had be cut away as a result of our findings.

We encountered similar problems, but with different causes on MUDJUG (picture) , example2 (video) and KAPITAN SOROKIN, on KOMET`S survey boats (video) (nearly unchanged from WEGA’S successfully performing boats), on CAPELLA and on MARIA S. MERIAN. We were able to propose methods, which solved the problems in all cases.

We own the instrumentation necessary for observations under the vessel at different speeds. Our continuous exposure to and reflection of the reasons of this phenomenon have enlarged our experience in analysis and remedies.

With echosounder problems air-bubbles is not all, interference of different echosounders in water and ship`s noise are the next two problem areas.

In particular the latter is of increasing importance, since the sensitivity of the echosounders is increasing and the existence of the ship becomes a nuisance.

Both problems are best tackled during planning and building, i. e. with creating functional models and accompanying calculations, even parallel measurements and - last not least - discussions with the manufacturers.

Navigation instrumentation and its integration is an area of frequent concern. Although the advent of GPS, ECDIS, RADAR and fiber optical ring-laser compasses in the wheelhouse of all modern ships has made seafaring to a large extent another computer-job research vessels add DGPS, dynamic positioning systems, doppler logs and a large array of scientific equipment either directly or via a data management system (PDF). Scientific equipment on top puts a high challenge on navigation accuracy in data and in practice.

Again we tend to address resulting problems during planning and building. A system-view has to be adopted, constantly changing with detailed in-depth-investigation. The systematic organisation of acceptances and seatrials is the end towards which these efforts should be directed.

The demand put on handling gear by the evolution of sampling and measuring equipment has increased. It has increased as well with the challenge of operation in ever worse weather conditions.

We have followed the progress of winches, looking at problems in spooling accuracy, slack wire, power-systems, digital control systems. These problems have become less if capable subcontracters are selected, however the problems arise anew with the increasing complexitiy of systems with a number of winches space restrictions and additional requests for exchange of wires and cables.

Liftinggear has to cope with increasing weight and size of equipment like submersibles, ROV`s, corers and drillers. Consequently problems at sea with instrument stuck at high water
depths, troubled data transmission in 8.000 m long cables, control problems with stern gallons etc. do arise.

Having developed core handling devices for SAGAR KANYA, METEOR, SAGARDHWANI and MARIA S. MERIAN we have a wealth of experience both in conceptual and trouble shooting areas.

The goal of handling large and heavy equipment at sea without development of a pendulum movement is always a challenge. Our last contributions to this area are the scissor-frame on the stern gantry and the antipendulum device on the sliding beam of MARIA S. MERIAN.

Heave compensation is a field, which is particularly problem-prone. For MARIA S. MERIAN we have found a solution, which takes into account the power needed (from calculations at various seastates) and the place needed for integration.

This short discription of special solutions would be incomplete without mention of ship laboratory design and laboratory containers and their systematic use on research vessels, which we have engaged in to a considerable extent.