Hull Offsets for SS United States

Discussion in 'Boat Design' started by johnhazel, Jul 9, 2014.

  1. johnhazel
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    johnhazel Senior Member

    Thankyou TANSL!

    The table of offsets for Michlet that I am looking for has 81 rows and 41 or 81 collumns. Each row represents a station along the hull starting with the foremost station. This foremost station is specified to be a row of zeros and represents the foremost point of the hull below the waterline. From there each next row represents a half frame at equal spacing along the hull till row 81.

    Each row starts at the maximun draft and is a list of 81 comma separated values representing the hull half width at equally spaced waterlines with the last value being the halfbeam at the water surface

    The file off1 is an example representing the hull shown in the michlet screengrab attached here.
     

    Attached Files:

  2. TANSL
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    TANSL Senior Member

    I think I've understood correctly. I'll get the 81 cross sections half width at 81 water lines.
     
  3. TANSL
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    TANSL Senior Member

    Johnhazel, here is the new table of offsets. I hope to be successful this time because the work is important. However, do not hesitate to ask for what you need.
    If there are any errors, I hope you can apologize.
    If I may comment (thank you), it is surprising that, in the twenty-first century is to give 6561 data to calculate anything and, what is more terrible still, you have to get them "manually".
     

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  4. johnhazel
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    johnhazel Senior Member

    That looks very good TANSL, very very good. The additional stations seem to have captured the bow bulb feature and therefore the wave drag calculations can be expected to represent this hull's behavior. So you have done the hard part. I will get output after getting back home. (It is 90 minutes before my 3.5 hour canoe race in Grayling Michigan right now)
     
  5. johnhazel
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    johnhazel Senior Member

    Here is the first try in calculating the bare hull drag of SS United States. Thanks to Leo Lazauskas for Michlet and TANSL for generation of a detailed table of offsets. This is just a first try please take a look and suggest improvements. Also find attached the Michlet 9.20 input file used for this calculation.

    The Blue Ribband record setting average speed was 34.5knots = 17.75m/s and that speed is just where the wave drag stats to climb.
     

    Attached Files:

    Last edited: Jul 21, 2014
  6. Leo Lazauskas
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    Leo Lazauskas Senior Member

    1. The offsets should be comma-separated in the table. I don't guarantee it
    will work as expected using tabs and/or spaces.

    2. Do you have another table with offsets above the static waterline?
     
  7. johnhazel
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    johnhazel Senior Member

    OK attached is in.mlt with comma separated offset table.

    TAMSL might be able to address #2. Considering a Flotilla run Leo?
     

    Attached Files:

  8. TANSL
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    TANSL Senior Member

    I have information to get what you want. However, I fear that changing the draft again I'll have to change the frame zero and therefore have to generate again the other frames.
    Not a dumb job and I've done it twice. If it is really necessary, I'll do it a third time, of course.
     
  9. Leo Lazauskas
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    Leo Lazauskas Senior Member

    Yes, I want to try out some new methods for squat and resistance which include better accounting for free-surface effects and viscous pressure resistance.
    And the lines TANSL generated look so smooth they are irresistable :)
    (Except a few jagged edges at the stern).
     
  10. TANSL
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    TANSL Senior Member

    Feet (lowest point) of the frames has been impossible to define them correctly. There was not enough information. But please Leo, what do you mean jagged edges?. I wish I could improve in the future.
    I'm sure a good Loftman, without being a naval architect, would find defects in the fairing. Even I see them but I think it is irrelevant for calculations that we are talking about.
    Thanks for praising my work.
     
  11. Leo Lazauskas
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    Leo Lazauskas Senior Member

    I was looking at the 1st image at the left of johnhazel's post #35
    Maybe I am seeing jagged edges when it is just the shaft housing at the stern.

    My pleasure.
     
  12. TANSL
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    TANSL Senior Member

    These lines, due to the flexibility of NURBS curves, have been drawn as curves while should be straight horizontal lines. Represent the stern profile which is as shown in the accompanying figure. The axes of the propellers are somewhat higher.
    More "worrying" is the definition of bulb (red ellipse).
    If it were the fairing for construction drawings undoubtedly would have to correct these errors.
     

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  13. johnhazel
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    johnhazel Senior Member

    TANSL, Leo can use the waterline and station spacing you already have. All he needs is to extend the number of waterlines so that the part of the hull above the water is included. My guess is if you use the 81 stations and 81 waterlines (9.5m draft) you already produced and just include another 40 waterlines with the same spacing making an 81 stations and 121 waterlines (14.25m draft), Leo with jump for joy and the results he produces, he being the author of Michlet and Flotilla, will be a widely studied result. TANSL you have done something significant here. Thankyou.
     
  14. TANSL
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    TANSL Senior Member

    I'll try to explain with a simple example. If I have calculated some frames as for Figure A, when the depth increases, as in Figure B, the frames needed for Michlet are not the same as for "A". In fact they all are different.
    I greatly appreciate your words. I know better than anyone the job rating and I am amazed at how much my hydrostatic model values ​​are close to the original (that is the true measure of the quality of work). So I feel uncomfortable talking about "jagged edges".
    Cheers
     

    Attached Files:


  15. johnhazel
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    johnhazel Senior Member

    Leo are you looking at the cutout in the skeg where the rudder balance (part of rudder ahead of piviot axis) goes?
     
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