Creating a Maxsurf model from existing design

Discussion in 'Boat Design' started by alex_1, Feb 16, 2015.

  1. Rabah
    Joined: Mar 2014
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    Rabah Senior Member

    Hi Tansl,
    Let's see what is really made till now.
    You have tried to help Alex, but your experience was unsuccessful - your model on Maxsurf has no keel, deck and transom. Except for that he is looked very badly if to see at bilge spray wedges.
    As against you I have had time to make good model and Alex have already thanked to me with the letter.
    And now let we shall update your notes:
    1. My calculation really is only approximate because regardless of the fact that there are data of prototype “Interceptor 55” about volume of tanks of fuel and drinking water, Alex yet has not picked self-sustaining period for the his project, signifies still it will be not clear how much is the weight of fuel, drinking water and food reserves. That is mean deadweight capacity and its centroid is still unknown. We know just the ship light displacement 24t, full displacement 27 t, but yet we do not know any centroids.
    I wrote to him that all this should be determined with calculation, then to pick criteria about an intact and damage stability so that were fulfilled the requirements simultaneously on LR and ISO and to make calculation on Maxsurf Stability.
    2. Before the beginning of trip, in a port when the vessel has total displacement, from 100 % of store, fuel and people, always draft aft = draft fore /that is mean without a trim relatively BL, adopted at designing / .
    To assert opposite, it is very incompetent.
    Designers in extremely rare events receive initial /projected/ trim.
    It is not necessary to confuse an initial trim of a dead ship in the water to a running trim angle when the fore is lifted from for the elevating force on the bottom.
    3. The problem about VCG is very disputable.
    Citation from the executive specification:
    „ The Interceptor has a wide beam and full keel, this provides the necessary high levels of directional stability needed, to prevent any yaw and roll that can induce broaching, when surfing on the face of a big wave. This beam, coupled with a very low centre of gravity are the designs key factors in being able to run safely, in big quartering following seas.“
    From the citation it is visible that we have “full keel“. Probably that he plays the role of a ballast keel as for sailing yachts. That is mean the ballast in the keel sinks CG of the ship for deduction of a good intact stability at 5 metric waves. So that my assumption that VCG=1,4m from BL is quite reasonable. From the lower point of the keel this distance will be 2,105m as it is specified in Planing Analysis Report.
     
  2. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    Dear Rabah, I will not argue with you. Insist on every one of the things I've said in my previous post. I do not want to give you more publicity. You should reconsider some of your assumptions, imo. I wish you much success in your profession.
     
  3. Rabah
    Joined: Mar 2014
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    Rabah Senior Member

    Dear Tansl,
    Thanks for advisories and kind wishes, but I insist that you knew, that I was not worse than you or what - be other ship-building expert, writing in the forum, is familiar with the International code about an intact stability of vessels.
    But let we go on on your notes:
    4. Flooding points
    From just now published image it is visible, that the lower edge of ventilation cut-outs is almost on equal levels from the upper edge of the door-coaming for the superstructure. On my calculations it is on Z ≈ 2,6m from adopted by me BL which is on 0,705m from the lowermost point of keel.
    As the door is near to CL, follows that for the offset it is necessary to take more dangerous event at which water will penetrate in the hull, that is the most removed from CL point of the lower edge of air vent, Y = ± 1,55m.
    5. IMO Criteria
    From IMO A.749 /the new supplemented edition calls IMO Resolution MSC.267/85/ International Code on Intact Stability/, I have accepted “ Minimum design criteria applicable to all ships ”.
    What are they, it is visible from the enclosed calculations.
    For rough, approximate calculation of an intact stability for the most reference event of loads - Full Displacement, these criteria are quite sufficient.
    6. Wind force
    In program Delftship Pro as well in Maxsurf Stability, the wind pressure which has maximum value 504Pa for unlimited navigation area is accepted only.
    But if we want to make calculations of an intact stability on ISO 12217-1 or approximately at program Orca3D then it is necessary to use wind velocity Vw.
    In the IMO MSC.267/85/ there is no term “ Wind force ”, there is only “ Wind pressure ”.
    7. Angles of wind steady and gust equilibrium
    In calculations Delftship Pro it is received:
    Angle of steady of wind ϕ0 = 7,1 ⁰
    Wind gust equilibrium angle = 10,6 ⁰
    Area A = 3,718m.deg and Area B = 10,32m.deg
    Weather criterion K =10,32 / 3,718 = 2,77> 1
    Up to now program Delftship Pro has not given me any motive to doubt in its calculations.
    But it is possible to test easily all if to make analogous calculation on Maxsurf Stability /look at files in this publication / .
    It is visible that K = Area1/Area2 =276,36 % = 2,76> 1
    8. Angle "teta1" must be greater than 20 ⁰??
    From the published files, made with program Maxsurf Stability is visible that agrees IMO MSC.267/85/Ch2:
    IMO roll back angle ϕ1 = 14,8 ⁰
    In the Delftship Pro outcome is too most:
    | ϕ1 | = |7,1 ⁰| + |-7,6 ⁰| = 14,7 ⁰
    At last I too have advisory to you - only one:
    Dear Tansl, before could declare that what - be calculation is erratic, you should prove it with calculations!
    _____________________________________
    NA Razmik Baharyan
     
  4. TANSL
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    TANSL Senior Member

  5. Rabah
    Joined: Mar 2014
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    Rabah Senior Member

    Hi All,
    Obviously that Tansl any more have not remained other arguments, but he does not want to recognize that has written not quite considered text. It remains his problem.
    I have planned to help the young student and have made necessary. Further he decide as how to make. I wish him good luck in development of the degree project.
    Calculation on stability criteria on Maxsurf Stability it is possible to see in the added file.
    ________________________
    NA Razmik Baharyan
     

    Attached Files:

  6. Rabah
    Joined: Mar 2014
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    Location: Bulgaria

    Rabah Senior Member

    I have made one more check:
    I has tested at so chosen stability criteria how much can to be the maximum allowable value VCG for full displacement.
    It has appeared that at VCGmax=1,75m the ship will not meet the requirements any more criterion of weather.
    If instead of VCG=1,4m to accept VCG=1,6m <1,75m then K=1,73 > 1 by Maxsurf Stability at roll back angle 15,7deg and at GMt=1,058m. But GMt must be to correct for effect of free surfaces of a liquid load on an intact stability. Must do not forget it!
    _______________________________________
    NA Razmik Baharyan
     

    Attached Files:

  7. shekarina83
    Joined: Sep 2016
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    Location: Israel

    shekarina83 New Member

    Dear Mr. Razmik Baharyan,
    I want to ask you a few things regarding creating a hull for a fishing boat, I couldn't find your email on LinkedIn. How can I contact you?
    This is my email:
    Shekarina83@gmail.com
    Best regards,
    Karina
     

  8. Rabah
    Joined: Mar 2014
    Posts: 256
    Likes: 10, Points: 18, Legacy Rep: 50
    Location: Bulgaria

    Rabah Senior Member

    Hi Karina, see your email!
    NA Razmik Baharyan
     
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