Wild

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Viewing 15 posts - 1 through 15 (of 35 total)
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  • in reply to: Re: A mistake of delftship for yatch design #34843
    Wild
    Participant

    I’m not quite sure whay you would want the location of LCB to a moving reference point.
    Yes, LCB to the midship makes sense. But using a reference point of the WL of any draught (not DWL) makes no sense, since it provides no information at all.

    Even for yachts the midship location is a fixed location. The exact location can be different (point of largest beam on the DWL, or the position of the maximum cross section area for example) but it is a fixed location, not moving with an increasing draught.

    Can you perhaps quote exactly what your book is saying about this?

    I assume we are talking about LCB%% for a SAILBOAT?

    As Marven pointed out, LCB%% location might be different depending on a definition someone use. Exact LCB location will be FIXED point for a boat in equilibrium (and DS gives it in hydrostatics report). It would be nice to specify “midships” term for a sailboat FIRST (1/2 DWL, Largest beam on DWL, Max cross section).

    Depending on defined “midships” location, settings for correct calculation of LCB%% will be different.

    So, DS should calculate correct LCB%% depending on a reference point. Even if reference point moves during “shaping the hull” process.

    P.S. Metin_mehel, it is better to write only something IMPORTANT for a reader in capital letters.

    in reply to: Re: A mistake of delftship for yatch design #34834
    Wild
    Participant

    To be fair to both sides, I have to say that DS does not market itself as Sailboat design software. It market itself as a BOAT design program.

    DS GIVES “True” LCB position (X coordinate of LCB). In this thread was already given 2 ways how to calculate LCB%% for SAILBOAT correctly. It is just need to know this limitation of DS in this case.

    And yes, Hull transformation is a big help if used correctly.

    Every software has its limitations…

    in reply to: Re: A mistake of delftship for yatch design #34830
    Wild
    Participant

    Remember the LWL is theoretical, when you finish building your boat she may not float in the LWL that you calculated originally.

    That how you know you designed it WRONG 🙂

    Cruzmayora, we can talk about DS’s Cons&Pros all day long… At this point it is clear, that DS need some improvements when user can specify different hulls’ types and related calculations. Software suppose to make life of the user simpler, not to complicate it.

    P.S. Do not rely too much on hull transformation… It can ruin your design.

    in reply to: Re: A mistake of delftship for yatch design #34825
    Wild
    Participant

    :woohoo: :silly: :laugh:

    Cruzmayora,

    Finally you got Metin_mehel point!

    Now try to change underwater profile of the model in X direction on both sides (just grab some control points which will change X location of waterline and move it left and right by mouse). Do you need to do all your calculations again???

    If I need calculator to verify that DS calculates LCB%% correctly, it may be better to do it without DS at all. Just on my calculator 👿

    in reply to: Re: A mistake of delftship for yatch design #34816
    Wild
    Participant

    It would be nice if DS could do it automatically according user preferences (at this time DS does it differently, giving incorrect information). I really do not see a reason why DS cannot do it correctly. May be I am missing something?

    Agree. Changing hull form in longitudinal direction (or draft) require (at this time) constant adjustments of the the model (to move it to correct coordinates) if you want to get LCB%% right. Which is inconvenient. That was my test to “cruzmayora” about getting correct LCB%% for default “new” DS model.

    in reply to: Re: A mistake of delftship for yatch design #34812
    Wild
    Participant

    So location of the Midship section in the Half of LOA, and having the posibility to located in any place that the designer choose, as Delftship does, is in my opinion a very good and flexible feature.

    Easy test. Make new (default) model which DS generates. Now try to get LCB %% right 🙂

    DS “KNOWS” location of LCB for the model, just does not want to calculate LCB%% correctly.

    Tell us how YOU got the right calculation for LCB%% in DS (what steps) for default model….

    in reply to: Re: A mistake of delftship for yatch design #34808
    Wild
    Participant

    It’s easy to check with the following formula:

    LCB [%]=100 * (LCB [m]Midship location[m])/ LWL[m]

    I am getting the same result as in formula ONLY IF
    – “I move aft of waterline to X=0”,
    AND
    – “enter ‘Length on waterline’ as Length in project settings”
    AND
    – “check Default at 0.5L”

    In all other cases it gives different LCB%% results than formula you provided. Changing shape or draft of the model will require to move model and adjust project settings (length=LWL).

    in reply to: Re: A mistake of delftship for yatch design #34807
    Wild
    Participant

    They all are correct. LCB means Longitudinal Center of Buoyancy. This can be either an absolute value (in your case 5.796) or a relative value in percentages. In this case the location of the LCB relativly to the mid ship section is calculated as a percentage of the waterline length. It’s easy to check with the following formula:

    LCB [%]=100 * (LCB [m]Midship location[m])/ LWL[m]

    I suspect that “Midships location” is what confusing.

    Is it 0.5*LWL?
    Is it coordinate with largest (underwater) cross sectional area?
    Is it 0.5*LOA?
    Is its coordinate from X=0
    Is it from aft X coordinate of LWL?

    Example:

    Looking for LCB location in DS PRO (default model 12m, 3.7m, draft 0.5 m. After creating model, change draft to draft = 0.775m)

    Draft = 0.775m

    Coordinates from X=0

    Base model LOA = 12m
    1/2 LOA = 6m

    LWL = 11.21m
    1/2 LWL = 5.605m

    Max Cross sectional Area “X” coordinate ~ @ 5.7m

    WHICH ONE?

    Just curious… Why in hydrostatics report DSPro does not give coordinate for largest cross sectional area? It gives the value for larges area, but not its coordinate…

    in reply to: Re: A mistake of delftship for yatch design #34805
    Wild
    Participant

    I have similar question about LCB location in DS report.

    Let’s take model generated by DS 4.38.129

    Start New Model -> 6, 5, 12.000, 3.7, 0.500, Meters

    1. Project Setting -> Hydrostatics -> Coeff based on “Actual dimensions of submerged body”
    Midship default =0.5*L = 6m

    View -> Design Hydrostatics:
    Length on waterline = 9.605
    Beam on waterline = 2.942
    LCB = 5.796m = -2.127%

    2. Project Setting -> Hydrostatics -> Coeff based on “Actual dimensions of submerged body”
    Midship = 7.75m (position of largest cross area)

    View -> Design Hydrostatics:
    Length on waterline = 9.605
    Beam on waterline = 2.942
    LCB = 5.796m = -20.347%

    3. Project Setting -> Hydrostatics -> Coeff based on “Dimentions from project settings”
    Midship default =0.5*L = 6m

    View -> Design Hydrostatics:
    Length on waterline = 9.605
    Beam on waterline = 2.942
    LCB = 5.796m = -2.127%

    4. Project Setting -> Hydrostatics -> Coeff based on “Actual dimensions of submerged body”
    Midship = 7.75m

    View -> Design Hydrostatics:
    Length on waterline = 9.605
    Beam on waterline = 2.942
    LCB = 5.796m = -20.347%

    5. Change Project Setting -> Main dimentions to 9.605m, 2.942m

    Project Setting -> Hydrostatics -> Coeff based on “Actual dimensions of submerged body” OR “Dimentions from project settings”
    Midship = 7.75m

    View -> Design Hydrostatics:
    Length on waterline = 9.605
    Beam on waterline = 2.942
    LCB = 5.796m = -20.347%

    6. Change Project Setting -> Main dimentions to 9.605m, 2.942m

    Project Setting -> Hydrostatics -> Coeff based on “Actual dimensions of submerged body” OR “Dimentions from project settings”
    Midship = 5.25m

    View -> Design Hydrostatics:
    Length on waterline = 9.605
    Beam on waterline = 2.942
    LCB = 5.796m = -4.730%

    So-o-oooo… As you see location in meters for LCB is 5.796m (no matter what), but LCB %% is different. WHICH ONE IS CORRECT????

    in reply to: Fonts are incorrect #34794
    Wild
    Participant

    I made some minor corrections in translation and condensed column headers. But table looks ugly both in Russian and Englisch.

    Attached zipped russian.lng file and screenshot of table at ‘View – Hydrostatics…’ report.

    Maybe changing page’s orientation from Portrait to Landscape (in report generator) will fix this problem? Does DS use fixed font for reports?

    in reply to: Fonts are incorrect #34774
    Wild
    Participant

    If you are experienced user of Russian localization, you may help me to make correct interface translation — at first Pro (as it released already), and then it may be used for Free.

    Sorry, “Dislucky”, I rarely use DelftShip Free. I do not like new DS interface at all. I like how it looked in DS 3.20, but not a new one. I will stick with FREE!ship instead (it has everything I need for modeling and “old-good” interface I like).

    New Russian localization for DSFree 4.38.129 seems to work now. Sorry, I cannot give any comments on the correctness of interface translation.

    in reply to: Fonts are incorrect #34769
    Wild
    Participant

    DS Free 3.20 vs 4.38.129

    I was told that on DS Free 4.38.129 it does not looks like Russian. System: Win XP Eng with multi-language support

    Image attached… If it goes trough….

    Attachments:
    in reply to: Keel and rudder wizard – Strange Volume CoG #34760
    Wild
    Participant

    Volume does not match as well :huh:

    in reply to: Can’t get draft information in hydrostatics! #34655
    Wild
    Participant

    Check for leak-points in that area. FreeShip or DelftShip will stop calculating hydrostatics if find leak point below calculating waterline. Set small step for draft range.

    Or Try to change draft (small step at one time) in Project Settings and run hydrostatics report. See where it gives warning.

    Check all points on center-line. See if Y=0 there. If not, correct it.

    in reply to: Dimention’s grid does not start from zero anymore #34001
    Wild
    Participant

    DS v3.2

    1. Zero line in Z direction (baseline) stay 0 and only other lines are being recalculated if entire model moved in vertical direction.
    2. Zero X line (X-baseline) changes from 0 to an amount the model was moved in longitudinal direction.

    I was surprised, there is no way to correct intersections in “Intersection” window or delete only one intersection.

    Solution which works so far to bring X baseline to 0.

    – Select entire model (Select->Select All)
    – Move model that far-end point has X=-0.0001 (Transform->Move->Longitudinal axis->needed amount)

    At this point base X axis will start from negative point. Note: If only END point has X=0 you will not be able create X=0 intersection (need to have surface?)

    – View->Intersections->Stations->Delete All stations (trash can icon)
    – Add station (+1 icon), enter 0 in “New intersection” dialog, click green check mark. It will create 0 X-baseline.
    – Move model +0.0001 in X direction. Transform->Move->Longitudinal axis->0.0001

    Now model has 0 X-baseline and end point has X=0 coordinates.

    -Recreate as many stations as needed with needed distance between it.

    Kind of inconvenient, but works.

Viewing 15 posts - 1 through 15 (of 35 total)