Inclining Experiment....

Discussion in 'Stability' started by Sunny.K, Feb 8, 2009.

  1. Sunny.K
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    Sunny.K Sunny.K

    Can someone help me with this inclining Experiment??

    If I'm to conduct an incline experiment on a double hull boat of like 39meters and a displacement of like 445tonnes but there was new renovations to the boat.....

    I need to know where I could find informations on how to perform the experiment or someone can help me. I understand using pendulum and weights but how and where should I have to drop it from is what i need (whether bridge deck, main deck etc) and what actually should I do?? please if someone can help it would be much appreciated??

    Regards,
    Sunny
     
  2. Guillermo
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    Guillermo Ingeniero Naval

  3. Ad Hoc
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    Ad Hoc Naval Architect

    It worries me that if you are performing an inclining expt yet do not seem to know the basics. Are you a qualified naval architect?
     
  4. Sunny.K
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    Sunny.K Sunny.K

    This experiment is gonna be done by a Naval Architect...this is for my own learning purposes!! so when the experiment is done I would already have a clue....I wanna learn every operations that is happening in this shipping company in PNG....like I said before I am engineering graduate of other discipline but wants to shift into marine and naval so I could study it and continue on to uni with it........
     
  5. Ad Hoc
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    Ad Hoc Naval Architect

    If another Naval Architect is doing it and are you with him? why not ask the naval architect....this is the most obvious route!

    Not being picky here, but if you have "one to hand"...it is the most logical person to ask...and they can explain to you in real time not bitty by email
     
  6. Sunny.K
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    Sunny.K Sunny.K

    true...
     
  7. Sunny.K
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    Sunny.K Sunny.K

    but it is always good to have your own info and researches!!!
     
  8. Ad Hoc
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    Ad Hoc Naval Architect

    Guillermo gave you that already....
     
  9. Ike
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    Ike Senior Member

    if you simply google inclining experiment you will find lots of references
     
  10. Sunny.K
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    Sunny.K Sunny.K

    what if I can't be bother reading alot of ********...to get the right thing you need the place!!!:D:D
     
  11. Joakim
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    Joakim Senior Member

    How typical is it to use a digital inclinometer? What is the reason for not allowing it to be the only tool used? With current technology and some care a digital inclinometer can be at least as accurate as a pendulum and is not affected by wind and the skill of the person reading the pendulum.

    I have designed and made some digital inclinometers, which have an accuracy of 0.5% (of angle difference) +- 0.01 degrees and a resolution of 0.001 degrees.

    Joakim
     
  12. Guillermo
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    Guillermo Ingeniero Naval

    Digital clinometers are only good if the vessel doesn't roll at all when at the inclining experiment, unless they have means to promediate readings, as it is very difficult to do that by 'eye'.

    Most inclining experiments are performed in waters that are not perfectly flat (sea is not a pool) and so the vessels always move slightly, making the digital clinometer to show constantly varying measurements difficult to 'catch' if they are not provided with the adequate software. Those are easier to estimate when using pendulums, although some practice is required.

    I use one or two pendulums, depending on the length of the vessels, promediating 10 pairs of deviations for each weight movement. If conditions are good enough, I also use a digital clinometer only to cross-check results after we calculate the angles from the pendulums readings.

    Pendulums are great if conditions are not perfect (which happens most of the times). They are also cheap...:)

    Cheers.
     
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  13. Ad Hoc
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    Ad Hoc Naval Architect

    Using the digital inclinometer is also bit of an over kill. Considering everything else is "rough". For example, how accurately can you read the draught marks??..look at the systematic percentage errors of this whole procedure and you'll see the displacement can vary considerably.

    The more accurate you try, the less accurate the answer. A series of good rough estimates are far better than one single attempt at an accurate answer. I would never believe an answer of 0.001 degree too
     
  14. Guillermo
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    Guillermo Ingeniero Naval

    Totally agree.
    For very small commercial fishing boats, where it is imposssible to mount a pendulum, we use a simple air bubble clinometer, with precision of only 0.5 deg. That's enough precision when you're measuring 14ยบ tilts, as the 1964 spanish norm asks for (not to reach that angle, nor submerge the sheerline, using some heavy test weights).

    Cheers.
     

  15. Joakim
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    Joakim Senior Member

    Yes, of course an appropriate software is required. My inclinometer records the angle 10 times in a second for one minute (600 samples), draws a curve, calculates an average and error estimates for the average for each of the 9 measurements for the standard test.

    I actually think just the opposite. A digital inclinometer is better when the conditions are not perfect. I have done some comparisons of an experienced pendulum user vs. my inclinometer. In perfect conditions the results are just the same, but in rough ones a much better linearity was achieved with the inclinometer.

    Pendulums are cheap, but requires more space and work, especially when you are required to have several of them. Which digital inclinometer are you using? How much did it cost?

    Ad Hoc:

    As I said, the accuracy is not 0,001, which is the resolution. Thus you can distinguish an angle difference of a 0,001 (e.g. putting a single A4 sheet under one end of a 5 m bar), but neither of the angles are 0,001 accurate.

    For the actual on water measurement in good conditions you will get repeated measurements to +-0.01 degrees from each other. The conditions need to VERY bad in order not to achieve +-0,1 degrees. That would need rolling of several degrees and actually wind is much worse than waves, since wind can cause a shift in the average, especially for sailboats.

    Joakim
     
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