Analysis of condition and development of program Orca3D

Discussion in 'Stability' started by Rabah, May 27, 2015.

  1. Rabah
    Joined: Mar 2014
    Posts: 247
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    Location: Bulgaria

    Rabah Senior Member

    Analysis of condition and development of program Orca3D​

    I track the program Orca3D since the first day of its occurrence. Since then till today the program has marked obvious progress. But whether it will suffice that for the program searched in the European and Asian market?
    Have seen, that except for calculations of bending moments and shear forces, already there is a capability to receive as well calculations and cross curves diagram.
    But creators of the program definitely have problems at calculations of Intact stability of the vessels according to the International code of IMO. Except for that the volume of criteria Orca3D Sample Source in the metric system is inexact - no Weather criterion with roll back angle. There is only in foots.
    Let's we consider two important problems:
    A. First from them this is the definition of parameter roll back angle on IMO
    Let's we see what is written in ABS Rules for Conditions of classification - High-speed craft, 2014 as we shall consider a similar example.
    In Part 1, Chapter 1, section 5 Regulations there is a point 5. International Code of safety for High-speed craft, 2000.
    From the newest edition of the program Maxsurf Stability / former Hydromax / it is visible that in HSC Code 2000-MSC 97/73/-Annex 8 Monohull Intact there is the following criteria:
    1.1 Weather criterion from IMO A.749/18/
    1.2 Area 0 to 30 or GZmax
    1.3 Area 30 to 40
    1.4 Max GZ at 30 or greater
    1.5 Angle of maximum GZ
    1.6 Initial GMt
    The parameter „roll back angle from equilibrium /with steady heel arm/” is specified in 1.1.
    For it is recorded 25deg, but there is a capability to change.
    All already know that IMO A.749 has new edition: IMO Resolution MSC.267/85/ which has come into force from 01.07.2010. In it roll back angle is determined for each vessel and for each concrete event of a loads / that is with different VCG / separately. Values, different than 25deg will obviously be received.
    In program Maxsurf Stability and Delftship Professional this angle is calculated automatically.
    Let's see what the position of the program Orca3D is.
    Here roll back angle is fixed on a constant 25deg as it is made at calculation of Intact stability for vessels of US Navy.
    To be approximated to requests MSC.267/85/ I have used the value received by Maxsurf Stability for model which I publish here.
    With the received value 12,8deg I have tried to create criteria, similar created in Orca3D /see attached PDF file/. I consider only criteria which concern to all types of ships. Not consider about intact stability at circulation or simultaneous congestion of all passengers to one side /crowding/.
    But in Orca3D v.1.4 WIP there is no capability to make a new criteria just so as they are required on MSC.267/85/.
    You see, that in my version there is only one heeling moment from a static operation of the wind /steady equilibrium/. There is no second heeling moment from a dynamic operation of the wind /gust equilibrium/.
    Therefore when it is compared coefficients of weather criterion K=Area1/Area2> 1 under the three programs, we shall see that at Orca3D /see Fig 6 and PDF file/ K=7,538 at VCG=1,0m from BL /i.e. 1,705m from the lowest point of keel/, and at remaining two programs accordingly: K=5,217 with Maxsurf Stability /see Fig 7 and Fig 8/ and K=5,235 with Delftship Professional /see Fig 14/.
    Calculations carried out for the model specified further in "B".
    This variance is received owing to the fact that Area1 and Area2 are defined in Orca3D concerning horizontal line of Steady Heeling Arm, but according to rules of MSC.267/85/ it is necessary to define concerning horizontal line of Gust Heeling Arm.
    B. Now we shall consider second important problems - limitation of the maximum value of VCG
    When the Intact stability on Orca3D is calculated there is one more extremely unpleasant moment. But that it have understood, firstly it is necessary for you to meet with model. Published here model Pilot vessel L16,5m-mod is created by me under the drawing General arrangement /without Linesplan/, published in site Boat, as modification from prototype „Safehaven Marine” pilot vessel “Interceptor 55/16,5” for port Aden /see Fig 1 till 5/.
    This model has the following characteristics:
    Lightship 24t, Full Displacement 27t, material GRP
    L=16,5m; B=5m
    Maximum operational Speed 25-26kts
    Engines 2xVolvo D16, 650hp each
    CLASIFICATION of prototype “Interceptor 55/16,5” - Lloyds Register of Shipping (LRS) SSC Rules as applied to Pilot Vessels and United Kingdom MCA Category 2 offshore Pilot boat code /up to 60 miles from a safe haven/

    I have accepted BL apart 0,705m up from the lowest point of keel.
    If you want additional information about hydrostatics of this model and calculations on water drags and capacity /Planing analysis report/, see on site Boat <>
    As there is no information about CG of Full Displacement, I have tested on Delftship Pro how much there can be maximum value VCG that criteria of the International code about Intact stability IMO-MSC.267/85/ were executed. For calculation I put LCG=LCB=5,717m at D=27t /i.e. T=0,923m/.
    The maximum value was received VCGmax=1,75m /see Fig 13/.
    But each attempts to make calculations of Intact stability on Orca3D with VCG=1,4m or VCG=1,6m blocked the program, but at other two programs acceptable results were received:
    Shared data at Т=0,923m are:
    - Windage area Aw=39,3 m^2 /see Fig 4/;
    - Center of Windage area VCGw=2,412m from BL /see Fig 4/
    - Coordinates of Downflooding points /Ventilation Openings for hull/:
    X=2m; Y=±1,55m; Z=2,57m
    - Full Displacement D=27t
    - LCG=LCB=5,717m
    Comparative Table of results /see Fig 17/

    The logical question is follows:
    What for any outcomes from program Orca3D if to accept VCG>1m are fail?
    The answer is hidden in parameter “Initial Plane Height for Free Float Iteration”. I guess that he is entered that the designer could be guided about the maximum draft of model and providing of the minimum freeboard.
    But interesting in this event is that fact, that this parameter always coincides with VCGmax / that is with the maximum allowable value for VCG/.
    In comparison with the other two programs, this limitation obvious is the main obstacle to receive actual, practically possible values for the coefficient K.
    Practically it is very difficult to realize VCG=1m from BL, it is means the keel to fill with a dry ballast that has played the role ballast as for sailing yachts. But it is poorly probable. On mine genuine value of VCG is probably equal 1,5m -1,6m.

    Conclusions from the Analysis:​

    1. What is made Orca3D till now for Intact stability is absolutely not enough!
    2. A long time ago it was necessary Orca3D to cease to tread in one place, it is necessary to decide problems on Intact Stability and to be removed sharply forwards to following overall objective - Damage Stability and Unsinkability.
    3. Must to create a library for stability and unsinkability criteria, analogous contesting programs.
    Users of the program necessary to have a capability to use as criteria under national rules and norms US, as well on other Classification rules of Ships construction and under International rules IMO, ISO and SOLAS.
    Only thus to be increased interest and search of the program in Europe and all over world.
    4. To create a demo model /or models/ for illustration of usage of criteria. It at once to attract young students and just diplomaed engineers.
    5. It is necessary a possibility to make 3D models by importing 2D drawings and JPEG images /for example at scanning old Linesplan of existing ship from a paper/.
    6. It is necessary a persistent work for achievement levels of Maxsurf Stability from Bentley System, but I think that it is the conceivable purpose. As Maxsurf too has the lacks - for example cannot be imported IGES files of trimming surfaces in Maxsurf Modeler.

    On the first sight if the person is not go deep in sense of things then this Analysis is the terrible criticism of the program Orca3D will say. But I do not think at all so. I think that my criticism is creative! I believe that creators of the program will cope with provocation!
    Let's wish them a successes and good luck!
    NA Razmik Baharyan - Bulgaria, May 2015

    Attached Files:

  2. cristianon
    Joined: Aug 2015
    Posts: 20
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: indonesia

    cristianon Junior Member

    sir please, could you give me the linesplan and general arrangement in 2d or 3d design in cad file from your boat. cause i want to analysis it's seakeeping with modifying it's bow.
    thank you
  3. Rabah
    Joined: Mar 2014
    Posts: 247
    Likes: 7, Points: 18, Legacy Rep: 50
    Location: Bulgaria

    Rabah Senior Member

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