RESEARCH NEWS 1 Vol

MARITIME RESEARCH NEWS 1 Vol. 17/ISSN 0784-6010 2003

Maritime Institute of Finland 1 List of Contents:

Editor’s corner...... 3 Jerzy Matusiak

Ice load monitoring system for ice going ships....4 Mikko Lensu

Viscous-flow computations at full-scale ship Reynolds numbers...... 5 Jerzy Matusiak Juha Schweighofer page 3 Morison’s equation in statistical fatigue Mikko Lensu analysis of floating offshore structure...... 6 page 4 Jani Leskinen Ultimate strength analysis for new passenger vessels concepts...... 7 Hendrik Naar

Local impact strength of all steel sandwich panels...... 8 Juha Kristjan Tabri Schweighofer page 5 The Nordic Boat Standard and the Blue Shield have made their job...... 10 Jani Leskinen Gunnar Holm page 6 New type of dynamometers for pod-propulsor model tests...... 11 Ilkka Saisto, Ahti Ajo

Recent Publications...... 12

Hendrik Naar Cover Photo: Samuli Hänninen page 7

MARITIME INSTITUTE OF FINLAND Kristjan Tabri page 8 VTT Industrial Systems P.O.Box 1705, FIN-02044VTT, Espoo, Finland Phone +358-4561 Telefax +358-9-455-0619

HUT Ship Laboratory Otakaari 4, FIN-02150, Espoo, Finland Phone +358-9-451-3501 Telefax +358-9-451-3419 Gunnar Holm page 10 Editors: Saara Hänninen & Pentti Tuononen, VTT Industrial Systems Ilkka Saisto Maritime news home page: page 11 http://www.vtt.fi/tuo/institute/

2 EDITOR’S CORNER COMPUTATION FLUID DYNAMICS (CFD) AND MODEL TESTING

Computational methods have already established a firm The development of Finflo-ship would not be possible position as a tool of a preliminary hydrodynamic hull without the experimental research in the field of ship design. In Finland the industry uses on a routine basis, hydrodynamics. Even with a CFD-tool being developed the potential flow models when ranking hull versions in to a certain level we need hydrodynamic model tests. respect to the wave-making. The problems with the Tests are necessary at present and will be needed in the inviscid models are that firstly they are unable to give future for the final evaluation of the power requirement ship resistance and secondly they do not yield enough of a design. Model tests are also required in the process detailed flow information (ship’s wake, separation etc.). of validating the computational methods. Development These limitations are absent when using the flow models of the numerical methods and broadening the scope of which incorporate both the wave-making and the vis- their application is impossible without a thorough vali- cous flow modelling. These are usually tailor-made com- dation. puter programs dedicated to the needs of ships’ hydrodynamic design. This kind of method, called Finflo-ship, Especially for a novel ship design power prediction has been developed at Otaniemi. This method is in a based solely on the model tests and on the experience- stage of becoming a commercial software to be used by gained extrapolation may yield erroneous results. A com- the industry. bination of CFD and model tests seems to be the most promising mean of making reliable power prediction of The experiences associated with the recent applications a ship. Although this new approach is in the early stage of Finflo-ship are very good. The method does not only of development, it is becoming a serious alternative to predict accurately the resistance of a ship model but also the traditional approach. it is capable to handle the full-scale ship flows. Recently held seminar on the ‘Uncertainties of ship hull resist- Prof. Jerzy Matusiak ance prediction’ (http://www.hut.fi/Yksikot/Laiva/ HUT Ship laboratory Tutkimus/Seminar2003/index.html) gives the detailed information on this topic. Also, the article of Mr. Juha Schweighofer in this issue of MRN elaborates on the same subject.

3 ICE-LOAD MONITORING SYSTEM FOR ICE-GOING SHIPS

Mikko Lensu HUT Ship Laboratory

The past ice season has been a good re- tures and the ship hull is also a statistical selected structural members are minder of the hazards of ice navigation. process. Only a part of the encountered instrumented for load measurements. The Tankers navigating without a proper ice thick ice features damage the ice navi- second component, monitoring software, class in the Gulf of Finland, which has gating ship. The damage probability de- analyses the measured data using statis- not had as difficult ice conditions in fif- pends also on the ship’s operation, espe- tical models. Finally, a user interface dis- teen years, have hit the headlines, and the cially its speed. plays the load level and other relevant ships’ progress has been followed by a information to the ship officers. The main concerned public. The need to reduce the With the help of statistical models for challenge is the monitoring software, es- risk of oil spills that may follow from se- ice thickness variation and the ice-hull pecially the prediction function. In a typi- rious ice damage has been generally rec- interaction process, it is in principle pos- cal situation of tactical ice navigation, the ognised. sible to calculate the probability with ship enters a more difficult ice type. In which hull damage is suffered when the order to forewarn the crew of the dam- However, penetration of the ship hull by ship navigates in a certain ice type at a age risk, the statistics of the loading proc- ice features and the resulting environmen- certain speed. The models have two ba- ess should be generated for the new ice tal or human catastrophe is an extreme sic applications. Long-term statistics can type within a short period of time during scenario. Less serious hull damage – de- be used to develop ice rules for ice navi- which the damage risk is small. flections of plating or local collapse of gating ships, while short-term statistics some structural member – can also occur can be used to assist navigation. This is The usual method – fitting a statistical in ships that navigate following the ice best realised in terms of a monitoring sys- distribution to a histogram – cannot be rules. This does not necessarily mean that tem that follows the ice load level. If the applied to short periods. A simple and the ship is not suited to the ice conditions. level is too high, speed may be reduced straightforward method is based on the The pack ice cover has a large variation or another route taken. magnitude of maximum load occurring and very thick ice features are encoun- during a period. As the period lengthens, tered also when the average ice thickness A short-term load monitoring system has the expected maximum load also in- appears to be well below the risk limit. been developed by the HUT Ship Labo- creases following a certain rule. In most Such features are encountered with a ratory in a project funded by TEKES and cases the rule is a simple power law that probability that depends on the ice type. by NEMARC, which is a shipping com- appears as a straight line in a logarithmic The ice type can be described by statisti- pany owned by Fortum and Kvaerner plot. The line has two parameters, level- cal properties related to thickness varia- Masa-Yards (Lensu 2002). Any such sys- ness and steepness, and these parameters tion. The interaction between the ice fea- tem has three main components. First, determine the statistics that are required for the risk estimation. The line can be generated during short periods and the prediction is done simply by extending the line to longer periods in the future.

This simple approach also provides a method for studying how the load level depends on ice conditions and speed to the load. The steepness of the line is typi- cal to the ice type, and the level of the line depends on ice thickness. The more variation in thickness, the steeper the line. Fig. 1 compares level and ridged ice, and it is seen that during longer periods larger loads occur in ridged ice even though it would be less thick. A decrease in speed then reduces the level of the line without changing the steepness.

REFERENCE: Lensu, M. 2002. Ice navigation assisted by short-term ice-load monitoring. Hel- sinki University of Technology, Ship Figure 1. The lines in the plot can be understood as ‘ice loading states’. It is seen Laboratory report M-275. that not only thickness but also thickness variation changes the loading state.

4 VISCOUS-FLOW COMPUTATIONS AT FULL-SCALE SHIP REYNOLDS NUMBERS

Juha Schweighofer HUT Ship Laboratory

Numerical investigations of turbulent bulent flows at full-scale ship Reynolds ues based on measurements and tradi- free-surface flows are usually carried out numbers using the RaNS solver, FINFLO, tional extrapolation methods are less than at the Reynolds number of a model-scale were started in 1996. In recent years, at five percent, and the free surface can be ship. The results obtained must be scaled the Ship Laboratory, these skills have evaluated qualitatively correctly. This to full scale, which might cause errors in been improved, allowing the evaluation work is being continued in the EU project the case of new vessel types where the of turbulent flows around ships, includ- EFFORT (European Full-Scale Flow Re- scaling mechanisms are not known. Com- ing the evaluation of the free surface at search and Technology), where additional putations of full-scale ships are attractive full-scale ship Reynolds numbers. The ships are being computed, and respective as no scaling is necessary, and the allow- boundary layer is entirely resolved, the measurements are being carried out at ances may be reduced. The shape of the RaNS equations are solved without the model- and full-scale ship Reynolds num- hull, and the propeller may be optimised application of wall functions, and the free bers, Verkuyl and Raven (2003). with respect to the proper flow around the surface is evaluated using the moving- ship. grid technique with regridding. The ap- REFERENCES plication of this method to full-scale com- Schweighofer, J. 1997. Evaluation of the Existing extrapolation techniques re- putations of ships is novel. Fully Turbulent Flow over a Flat Plate for garding the evaluation of the final power a Large Range of Reynolds Numbers, Re- of a ship, e.g., the ITTC-57 or the ITTC- The numerical simulations performed at port M-226, Ship Laboratory, Helsinki 78 extrapolation methods, and novel ones the Ship Laboratory at Reynolds numbers University of Technology. 9 may be investigated with respect to novel equal to about 10 are related to the evalu- Schweighofer, J. 2003. Investigation of ship types. The first computations of tur- ation of the turbulent flow over a flat Two-Dimensional Transom Waves Using bulent flows solving the RaNS equations plate, Schweighofer (1997), the investi- Inviscid and Viscous Free-Surface at full-scale ship Reynolds numbers were gation of different realisations of the free- Boundary Conditions at Model- and Full- carried out in the early 1990s. surface boundary conditions on two-di- Scale Ship Reynolds Numbers, mensional transom waves, Schweighofer Doctoral Thesis in evaluation, Ship RESEARCH AT THE SHIP (2003), and free surface computations of Laboratory, Helsinki University of Tech- LABORATORY the ship, Series 60. The results with re- nology. At the Ship Laboratory of Helsinki Uni- spect to the evaluation of the resistance Verkuyl, J.-B. and Raven, H.C. January versity of Technology (HUT), investiga- are encouraging, as the deviations of the 2003. Joint EFFORT for Validation of tions and numerical simulations of tur- computed values from the expected val- Full-Scale Viscous-Flow Predictions, The Naval Architect.

3 C CT x 10 ∆CT [%] as e

Flat plate, Cebeci-Smith 1.465 -2.3 Flat plate, Baldwin-Lomax 1.473 -1.8 Flat plate, k-w SST 1.479 -1.4 Flat plate, k-e Chien 1.606 7.1 Engineering Sciences Data (ESD) 1.500 2-D model, “Ile” 8.192 -1.5 ITTC-78 8.317 Series 60 3.463 3.9 Kim (1981), extr. ITTC-57 3.331

Table 1. Computed total resistance coefficients compared with experiment (ESD), extrapolation with ITTC-78 method, and extrapolation of measurement with ITTC-57 method (Kim, 1981) for full-scale ship Reynolds numbers.

5 MORISON’S EQUATION IN STATISTICAL FATIGUE ANALYSIS OF FLOATING OFFSHORE STRUCTURES

Jani Leskinen, Trainee Research Scientist VTT Industrial Systems

This article is an abstract of the Mas- were used to determine the response’s Rayleigh model. The reason for the over- ter’s Thesis that was carried out at the fatigue load for different sea state condi- estimation is that the bandwidth effects VTT Maritime and Mechanical Engineer- tions. A first-order Hermite model uses were disregarded. The second-order ing Group 2002–2003. The objective of only the fourth moment of response’s time Hermite model takes into account also the the thesis was to simulate non-linear time history to determine the deviation from bandwidth parameter and predicted quite domain responses of an offshore floating Gaussian distribution. The second-order well the nature of the fatigue load in dif- structure with Morison’s equation. In ad- Hermite model is based on the standard ferent sea states. The results of the sec- dition, the stability and convergence of deviation, third and fourth statistical mo- ond-order Hermite model not only fol- the statistical parameters and the ments and the process’s bandwidth pa- lowed the trend of the fatigue in different Rainflow counting procedure have been rameter to determine the response distri- sea states, but the values were also close investigated using different time steps and bution. In addition, fatigue loads were to the Rainflow results. simulation time. Statistical models to es- calculated using the Rayleigh model, timate fatigue from non-linear processes which takes into account only standard CONCLUSIONS deviation of the response. The fatigue have been presented. Morison’s equation overestimated the loads were calculated for the motions of high-frequency range responses and is the spar and the bending moment in the HYDRODYNAMIC therefore better suited to extreme re- topside connection. The results from dif- MODELLING sponse procedures. Rayleigh’s fatigue ferent models were compared to the fa- The linear airy wave theory was used to model, which takes into account only tigue results from the Rainflow cycle generate an irregular wave. Amplitudes standard deviation of the response, over- counting procedure. In Figure 1 are and frequencies of different sine wave estimated the fatigue damage in all sea shown the relative fatigue loads of the components were obtained from the states. The differences were greater when models in different sea state conditions Jonswap wave spectrum. The frequency the bandwidth of the response increased. caused by the surge motion. The Rayleigh range was divided into equally spaced The second-order Hermite model can be model gave a conservative fatigue load intervals from which the frequency of used for early-state fatigue-damage esti- estimation in every sea state. The overes- each wave component was randomly se- mation, for screening the most severe sea timation was higher in the sea state where lected. The velocities of wave particles state conditions and for determining the the wave steepness had the maximum were stretched to the instantaneous wave relative fatigue damages between differ- value. In this sea state the non-linearities surface. Hydrodynamic loads on the ent sea state conditions. were also significant and the bandwidth structure have been determined by the parameter had the highest value. If the non-linear Morison’s equation, which kurtosis of the process increases, the fa- REFERENCES takes into account only inertia and vis- tigue load tends to increase as well. The Leskinen, J. 2003. Kelluvan offshore- cous effects. first-order Hermite model predicted the rakenteen Morison-mallinnus ja sovellus increase of fatigue due to kurtosis, but this tilastollisiin väsymisanalyyseihin. Mas- STATISTICAL FATIGUE led to an even greater overestimation of ter’s Thesis, Helsinki University of Tech- ANALYSIS the fatigue load when compared to the nology, Ship Laboratory, Espoo 2003, 78 In this research two Hermite models pp. + App. 67 pp.

Figure 1 Fatigue loads caused by surge motion in different sea state conditions. Values are relative to the Rainflow fatigue loads per cycle.

6 ULTIMATE STRENGTH ANALYSIS FOR NEW PASSENGER VESSEL CONCEPTS

Hendrik Naar HUT, Ship Laboratory

The basic task of the EU-founded DISCO (Development of innovative concept where the side shells and deck RESULTS structural concepts for advanced passen- plating of the superstructure are ex- The results are obtained by FEM and a ger vessels) project is to create innova- tremely thin. The third concept, KMY-5, fast method for concept KMY-1. The big tive global structural solutions, which can is a tower-type superstructure concept. difference between the two methods can guarantee that European shipyards will be be explained with the rough mesh in leaders in the cruise ship market also in FAST METHOD FOR FEM. Therefore the new more locally refined model has to be generated for the the future. In the project, Helsinki Uni- ULTIMATE STRENGTH versity of Technology is involved in an 3D FE method. Also the fast method has ultimate strength subtask, and this paper ESTIMATION several disadvantages, but they do not presents a short overview of the work The fast ultimate strength method is de- have such a dramatic effect. Therefore, done by HUT. veloped for passenger vessel application. the final conclusions can be made after It is based on the idea that the internal the new numerical results by FEM are INTRODUCTION loads in a ship hull can be estimated with obtained. All three concepts are analysed the help of beam equations. For a better Since the time when the first big liners with a fast early design tool. Concept understanding, see Figure 1. were built, the basic concept of the pas- KMY-3 is not significantly weaker than senger vessel has changed. Nowadays concept KMY-1. The results obtained for they are mainly built for cruises. The ships FE ANALYSIS concept KMY-5 surprisingly show that have become larger, and the upper struc- The finite element method is one of the this concept offers more strength than tures are more open on the sides. Con- most powerful tools for structural analy- other concepts. However, the results must struction and design methods have im- sis. It enables an accurate analysis of large be verified. Much effort is still needed, proved, and more optimised structures and complex structures. In the present and therefore the last year of the project can be built. Therefore, it is quite clear work the explicit FE code DYNA3D is is basically reserved for FE modelling. that in new ship concepts ultimate used for ultimate strength analysis. In the strength might be one of the concerns of project work the FE tool has been used the future. In the present project the main in order to verify the local strength mem- REFERENCES bers and global ultimate strength of a ship. task is to perform the ultimate strength Bleich, H.H., Non-linear Distribution of Global 3D modelling is a large task. The analysis for the new concepts using the Bending Stresses Due to Distortion of the model shown in Figure 2 consists of more FE method and to develop a fast design Cross Section. ASME Applied Mechan- than 200,000 elements. tool for the same purpose. ics Division, 1952. Fransman, J., The Influence of Passen- PROBLEM DEFINITION ger Ship Superstructures on the Response Modern cruise vessels are complex of the Hull Girder. RINA,1988. structures. The superstructure with a thin longitudinal bulkhead and side plating and a large number of openings is nor- mally not fully effective. Due to large dis- tortions and sheer lag effect, the simple beam theory for stresses and displacements estimation cannot be used. Therefore, most of the simple incremen- tal ultimate strength methods are not directly applicable. Also, the FE analysis will be more complicated, as now the proper modelling requires a model for the entire ship.

NEW CONCEPTS There are three new structural concepts developed by Kvaerner Masa-Yards for which the ultimate strength has to be estimated. The first concept, KMY-1, is similar to the existing structures. Concept KMY-3 is an ultralight superstructure Figure 2. Fast method for ultimate strength estimation. 7 LOCAL IMPACT STRENGTH OF ALL STEEL SANDWICHPANELS

Kristjan Tabri ACCELERATION FORCE LABORATORY HUT Ship Laboratory SENSOR TRANSDUCER EXPERIMENTS Improved welding techniques, espe- The behaviour of I-core steel sandwich cially laser welding, have made it possi- panels is studied in a series of laboratory ble to connect very thin sheets to each tests, where sandwich panels with four other and so to manufacture sandwich different configurations are tested. Gen- panels where thin faceplates are welded eral structure of tested panels remains un- to steel core structure. Sandwich panels changed during the tests and the only are efficient in means of global response changing parameter is the thickness of the as panel’s sectional modulus is bigger faceplate, which is varying between 1 to compared to conventional stiffened plat- 3 mm. I-core stiffeners are made of 4 mm ing. high yield steel plates. Height of the panels is 40 mm. The effect of core material Figure 4. Impact head The purpose of the study is to under- is investigated by filling some of the pan- IMPACT stand the behaviour of I-core steel sand- els with urethane foam. Material proper- NOZZLE wich panel subjected to a lateral impact ties of the panels varied from mild steel load. Furthermore, the aim is to derive with yield stress 179 MPa to high tensile an analytical model describing panel’s be- steels with yield stress 430 MPa. Tested haviour and the consequences of impact. panel is shown in Figure 1. Figure 2. Impact head Due to the impact, faceplate of the panel is deformed in high velocity, which indi- In the laboratory tests, the panels are hit cates that dynamic behaviour of materi- by an impact head, which has some pre- The most important results of the labo- als should be considered. To verify the determined mass and velocity. Maximum ratory experiments are plastic energy ab- proposed analytical model, measured data energy that can be obtained for the im- sorption of the panel and the extent of is obtained by laboratory experiments and pact head is up to 450 J, which is approxi- deformation. Plastic deformation energy by finite element calculations. The study mately equal to 45 kg dropped from the is calculated by numerical integration is based on the research conducted on a height of 1 m. Impact head is depicted in over the force-displacement curve. To national research project “Pilotti” as part Figure 2. obtain the mentioned curve three sensors of Kenno-Light Structures technology are used to gather data from the impacts: program and on EU-SANDWICH force transducer, displacement and accel- project. eration sensors.

FINITE ELEMENT ANALYSIS Finite element (FE) simulations allow to follow the impact process and to obtain the information about the behaviour of the sandwich panel during the impact. Main purpose of the FE simulations is to verify the assumptions made in deriva- tion of the analytical formulations. Simulations are carried out by explicit FE program LS-Dyna950d. Steel plates of the sandwich pane are modelled by using two-dimensional four node shell elements with thickness- known as Belytschko-Tsay elements. Material model Piecewise Linear Isotropic Plas- ticity is used to describe material properties. Urethane foam filling is modelled by using 8-node hexahedron solid elements and material model Soil and Crushable Foam with Failure.

Figure 1. Tested panel.

8 Analysis showed that the velocity pro- file could be approximated by linear line without a significant decrease in precise- ness. Furthermore, the analysis reveals that at the beginning of the impact, node that first contacts with the striking object obtains the same velocity as the impact head. Velocity of that node starts to decrease but the decrease is not exactly linear and the average velocity of the faceplate is 1.5 times smaller compared to the initial velocity of the impact head. FE simulations showed that the shape of the deformation is circular as it was also observed in laboratory experiments, see Figure 3.

ANALYTICAL Figure 4. Shape of the deformation FORMULATIONS Aim of the analytical formulations is to provide a possibility to calculate defor- mations in the panel when the properties of the striking body are known. Extent of Deformation energy of the faceplate of Amount of elastic energy absorbed by the deformation can be evaluated by the panel is derived as a function of ma- bending is evaluated by using plate theory equalising the kinetic energy of the im- terial properties and deformation shape. (Ikonen, 1990). Plastic bending energy is pact body with the deformation energy Shape of the deformation is described by determined by using the concept of plas- of the panel. As it is easy to calculate the linear line and polynomial as shown in tic hinge and the energy is found by inte- kinetic energy of the striking body the Figure 4. Extent of the linear approxima- grating the product of plastic moment of main task is to describe the energy ab- tion is determined by two constants C1 the panel, hinge angle and length of the sorption of the sandwich panel. As a re- and C2. Those constants are determined plastic hinge over the whole deformed sult of the impact, faceplate of the sand- by minimising the deformation energy of area. Amount of the membrane energy is wich panel stretches in all possible in- the panel using constraints put on by the evaluated by determining the strain value plane directions to resist impact loads and geometry of the panel and by the shape in every point of the faceplate inside the can attain large permanent deflections. of the impact body. assumed deformable area. Elastic energy Furthermore, impact energy is absorbed is then found by using Hooke’s law while not only by the faceplate, but also by the plastic membrane energy is found by in- inner supports, lower plate and by the fill- tegrating the product of flow stress of the ing if there is any. material and plastic strain of the faceplate. Energy absorbed by the filling material is evaluated by using Winkler’s foundation theory. In case of membrane energy also effect of the strain rate is considered.

CONCLUSIONS Comparison with laboratory experiments and FE simulations support the analytical model as the scatter between the results obtained by different methods is small. In the case of the plastic deformation energy the scatter is at worst 10%. Scatter is slightly larger in the case of the total deformation energy, where analytical model overestimates the elastic deformation energy especially in case of low deformation values.

REFERENCES 1. Ikonen, K., Plate and Shell Theory, in Finnish, Otatieto Oy, 1990 2. Tabri, K. Local Impact Strength of Sandwich Panels, Master’s Thesis, Espoo, 2003 Figure 3. FE analysis. Deformation in the panel.

9 THE NORDIC BOAT STANDARD AND THE BLUE SHIELD HAVE MADE THEIR JOB

Gunnar Holm boats under 5.5 m in length. The idea be- mum level and the market clearly recog- VTT Industrial Systems hind the good flotation characteristics was nised this with higher second hand prices that the boat should float in the event of for type approved boats. Because the sys- Type approval of pleasure boats accord- swamping or flooding thus giving “life tem was based on the initiative of the ing to the Nordic Boat Standard was ter- raft” security. The operators of the boats boatyards it was marketed to the end us- minated by the end of 2002. The 30 years put themselves at high risk when using ers thus inducing market demand. This of activity within the Nordic countries the boats in overloaded conditions both was a highly successful principle and at meant increased boating safety for Nor- in respect of number of people on board least in Sweden it was hardly possible to dic citizens and a strong foundation for and in respect of drinking. This was es- sell a boat without the Blue Shield in the the Nordic Boat building industry when pecially true in connection with summer- 80-ies. meeting the requirements of the EU Rec- house living were clearly “nonboating” reational Craft Directive (RCD). people used the boats occasionally for VTT played an important role in the de- fishing and other activities not really car- velopment of the standard during the 80- The Nordic Boat Standard covered type ing for good seamanship behaviour. Sta- ies and offered inspection services since certification of pleasure boats under 15 tistics gathered 1986-1988 for all acci- 1982. VTT built an inspection system ac- m of length in all Nordic countries. Sev- dents with deadly outcome clearly cording top the NBS and developed rou- eral hundreds of thousands of individual showed that the type approved boats tines for efficient work. It included in- boats got the Blue Shield in the Nordic hardly ever was involved in these kinds spection of drawings, inspection of the countries and many lives were saved of accidents. boats on site, inspection of production fa- thanks to a good safety level. It is worth cilities and procedures and test run of the noting that the NBS rules for commer- Another major issue was the scantlings actual boat. These procedures was ad- cial craft are still in force and under revi- requirements and the inspection proce- justed to complexity of the boat and for sion. dures adopted for quality assurance of the the smallest rowboats the actual tests were production. The way to calculate the di- in focus while the checking of the docu- The Maritime Authorities developed the mensions for the strength members was mentation got more important for bigger rules as a joint effort in the Nordic coun- simplistic and straightforward but it gave boats. tries with DNV and VTT acting as certi- in most cases proper and correct strength fication and boat technology experts in level. Separate type approval of the raw Finally it must be recognised that the the group. In this safety related work it materials was very important during the initiative and support the Maritime Au- was early recognised that the small row- first years of fibre reinforced plastics thorities gave the system was really im- ing and open outboard powered boats so technology. In the beginning not all as- portant for the safety of the boating peo- widely in use in these countries, were the pects of the materials were recognised ple. It was far-sighted and meant also a most significant factor to account for in thus. This was the reason for some qual- lot for the credibility of the boatyards par- accident scenarios. Statistics showed ity problems when new materials were ticipating in the system. Also important clearly that most of the accidents with brought in. Also the ability to maintain a is that the adopted safety principles and deadly outcome happened with these good quality level for long production experienced gathered in the valuable in- boats. Therefor proper freeboard and in- series was not well developed in the inspection work has successfully been used tegral flotation devices were ruled for dustry initially. The NBS ensured a mini- in the development of the EU Recrea- tional Craft Directive.

Venetyyppi – Båttyp – Boat type

Valmistaja – Tillverkare – Manufacturer

Suunnittelukategoria Båtkonstruktionskategori Boat design category

kW + kg

on sertifioinut venetyypin tuotannon har certifierat båttypen produktionen has certified boat type production

Päijän 471 with the Blue Shield has during the years been produced in 30000 units .

10 NEW TYPE OF DYNAMOMETERS FOR POD- PROPULSOR MODEL TESTS

Ahti Ajo, Ilkka Saisto gle is always same as it is in full scale. THE TRIAL MODEL TESTS VTT Industrial Systems When the pod device is rotated the pro- In the first tests new dynamometers peller location is correct in all rudder an- were used in a part project of national VTT purchased special dynamometers gles. When the steering moment is meas- Seatech 2000+ research programme. In for azimuthing propulsion units in 1992. ured there is no supporting reactions the device tests the effect of the size of The first commercial application was caused by driving shaft. These mean more the motor housing for the efficiency was model tests of the multipurpose ice- reliable results. One of the bases in the studied. The propulsion tests were done breaker- supply ship msv Fennica for design was demand for easy installation. with a cruiser model. In the propulsion Finnyards Oy. Thereafter these ATAPOD has no vertical driving shaft. test the interaction between different pod dynamometer devices have been almost Only cables are needed between the size and the hull was studied. The pro- exclusively used with pod propulsion re- model and the pod, this gives us possi- pulsion tests were also conducted with lated research topics either in open water bility to measure also pod propulsion de- different sterns and trim wedges. The re- tests, for application of pod drive to vari- vices with thin or no vertical struts. One sults are possible to utilise in a concept ous types of ships or in captive model of the installation advantages is also that design phase. tests for manoeuvring studies. ATAPOD has simple, removable propeller shafts for different propellers. Because of customers’ needs, VTT has developed a new type of dynamometer, called ATAPOD, for model tests of pod- propulsion units. The dynamometer op- nmax 27 1/s erating principle is identical to real pod Qpmax 12 Nm propulsor. The dynamometer consists of Tpmax 300 N the motor part in the pod and upper part for measuring the total forces (figure 1). Ppmax 1.3 kW The dynamometer measures directly pro- Fxmax, Fymax 250 N peller thrust and torque from the reacting forces of the motor unit. The total thrust, Qstmax 11.6 Nm side force and steering moment of the unit Length of the unit 240-279 mm are measured from the upper end of the pivoted axle. The dynamometer has com- Diameter of the unit 88 mm pact design, small overall size and ad- equate measuring range (table 1). Table 1. Technical data of ATAPOD

THE ADVANTAGES OF ATAPOD What makes ATAPOD unique? As in a standard measuring system, in ATAPOD the thrust of the propulsor and propeller are measured separately and the torque of the propeller is measured directly without angle transmissions. But ATAPOD has also several other advantages. There is a free angle between propeller axis and turning axes. This means that the tilt an-

Figure 1. A sketch of the principles of the ATAPOD dynamometer. Figure 2. ATAPOD dynamometer without pod covers.

11 RECENT PUBLICATIONS

LABORATORY REPORTS Hänninen, Saara. Suomen ja Viron Rytkönen, Jorma. Merikuljetusten uudet tuulet meripelastusseurojen alushankintastrategia. “Etelä- Itäisellä Suomenlahdella - öljykuljetukset vahvassa Suomen rannikkoseudun Interreg IIIA -ohjelma ja nousussa. “Suomenlahden tulevaisuus” seminar. Häkkinen, Pentti. Laivan sähköverkko. Espoo: 2003. liikenne” seminar. Helsinki, April 2, 2003. Finnish Kotka February 20, 2003. Kotka, Kymenlaakso En- 96 p. (HUT Ship Laboratory M-279). Maritime Administration, 2003. 20 p. [slides] vironmental Protection District; Helsinki University adult educational centre, Kotka, 2003. 37 s. [slides] Hänninen, Samuli; Lensu, Mikko. Aspects of ice load Matusiak, Jerzy. Two-stage Approach to Determina- monitoring analysed using Arcdev ice load database. tion of Large Amplitude Motions of a Rigid Ship in Rytkönen, Jorma; Sassi, Jukka. Testing on-board bal- Espoo: 2002. 60+60 p. (HUT Ship Laboratory M- Waves. 15th Nordic Seminar on Computational Me- last water treatment facilities in the laboratory scale. 274). chanics, Aalborg, Denmark, 18-19 October, 2002. Marine Science and Technology for Environmental Aalborg, Denmark, 2002. Institute of Mechanical En- Sustainability. ENSUS 2002. Newcastle, GB,16 - 18 Kujala, Pentti; Mäesalu Meelis. Tietotekniikka gineering, Aalborg University, pp. 1-10. Electronical Dec. 2002. School of Marine Science and Technol- laivanrakennuksessa, työryhmän loppuraportti. publication: http://www.ime.auc.dk/nscm15. ogy of the University of Newcastle upon Tyne; EU Espoo: 2003. 30 p. (HUT Ship Laboratory M-276). Martob Project; EU Treship Thematic Network Peltoniemi, Hannu; Bengston, Aaron; Rytkönen, (2002) Lensu, Mikko. Ice navigation assisted by short term Jorma; Köuts, Tarmo. Measurements of fast ferry ice load monitoring. Espoo: 2002. 53 p. (HUT Ship waves in Helsinki-Tallinn run. The Changing State Sassi, Jukka; Rytkönen, Jorma. The development and Laboratory M-275). of the Gulf of Finland Ecosystem. Tallinn, 28 - 30 testing of ultrasonic and ozone devices for ballast wa- Oct. 2002. Marine Systems Institute at Tallinn Tech- ter treatment. Marine Science and Technology for En- Rytkönen, Jorma; Bengston, Aaron; Peltoniemi, nical University; Estonian Ministry of Environment vironmental Sustainability. ENSUS 2002. Newcas- Hannu. Measurements of fast ferry waves in Helsinki- (2002) tle, GB,16 - 18 Dec. 2002. School of Marine Science Tallinn run. Espoo, VTT Industrial Systems, 2003. and Technology of the University of Newcastle upon 39 p. Research Report No. BTU034-031143 Riska, Kaj. The environmental safety of tanker traf- Tyne; EU Martob Project; EU Treship Thematic Net- fic during winter in the Gulf of Finland. work (2002) Joint EU - Russia - Canada - US Workshop, Brus- sels, 25-27 October 2002. pp. 51-63. Sonninen, Sanna; Kunttu, Susanna; Hänninen, Saara; CONFERENCE PAPERS Maskuniitty, Matti; Tuominen, Risto. Elektroniikan Riska, Kaj. Facilities, research platforms and häiriöt ja niiden tuottamat vaaratilanteet. MET Laiva- expenditions for Arctic-related technological re- alan luentopäivät: Laivojen elektroniikka. March 27- Happonen, Kai; Rytkönen, Jorma. search: requirements for the future. Joint EU - Rus- 28, 2003, Dipoli, Espoo. Meriteollisuusyhdistys ry Simulaattoritutkimukset satamien tuulirajojen sia - Canada - US Workshop, Brussels, 25-27 Octo- (2003). määrittämiseksi. Väylät & Liikenne. Jyväskylä, 9. - ber 2002. pp. 621-633. 10 October 2002. Suomen tieyhdistys (2002), p. 204 Sonninen, Sanna; Hänninen, Saara; Tuominen, Risto. - 207. Rytkönen, Jorma. The increase of marine oil trans- Riskiarvioinnit väyläsuunnittelun työkaluna. Väylät portation in the Baltic - a developing environmental & Liikenne. Jyväskylä, 9 - 10 October 2002. Suomen Häkkinen, Pentti. Koneenhuoneen yleisjärjestys. risk Nya risker och ökade säkerhetskrav - ändrade tieyhdistys (2002), pp. 259 - 264. Uutta ajattelua laivan konehuoneen suunnitteluun, villkor för trafik och transporte. Stockholm, 12 Nov. Turku, 23.-24.10.2002. Meriteollisuusyhdistys ry, 2002. TFK, Transportforskningsinstitut i samarbete 2002. Paper M 23. mellan TTF (2002) Häkkinen, Pentti. Reliability of Machinery Plants and Damage Chains. World Maritime Technology Con- Rytkönen, Jorma. Methods to restrict the invasion of OTHER PUBLICATIONS ference San Francisco USA, October 17-20, 2003. alien species. Seminar on the Environmental Impacts Electronical publication (only CD ROM). of the Maritime Industry, MS Silja Symphony, March 11-13, 2003. St. Petersburg Business Contact Centre Rytkönen, Jorma. Merenkulkuturvaa tutkimuksella. Häkkinen, Pentti; Domingo, Jeronimo. Factors Af- Kymenlaakso Polytechnic Institute (2003) Helsingin Sanomat, Vieraskynä. December 21, 2002. fecting Soot Fouling, Cleaning and Soot Fires in Die- (2002), p. 3. sel Engine Exhaust Gas Boilers. ICMES 2003 9th International Conference on Marine Engineering Systems Otaniemi, May 19-21, 2003. ICMES 2003, Electronical publication (only CD ROM).

AB HELSINKI UNIVERSITY OF TECHNOLOGY Ship Laboratory

12 Maritime Institute of Finland