Appendages in resistance calcs

DELFTship forum Hull modeling Appendages in resistance calcs

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    • #34355
      John Owles

      Hello there,

      Under the Appendages tab of Resistance Calcs, the inputs are greyed out. Can anyone give me an indication of why and how to input rudder/propeller data?


    • #34423

      Hi Jayoh,

      I own a licensed copy of the Pro version, and even it it, there are a few things that are greyed out. I’m not sure what add-on modules in need to or want to purchase next to activate these features.

    • #34424
      John Owles

      Hello Otaku,

      I also have the licenced Pro version which, after the learning curve (still contuing), I am now getting on very well with. Even with the v4.27 though, I still do not know how to activate the greyed out bits.

      Judging by the response to my question it may be a mystery to go with the meaning of life, the universe and all that. Answer: 42?

      Seriously though, they look as though they could be useful and probably interesting. Have you got your head around the operation of waves that are now integrated into hydrostatics.

    • #34425
      John Owles

      Hey Mike,

      In your capacity of all knowing guru…

      Do you have any idea of what these greyed out parts in resistance calcs are about?

      eg. Transom data etc. in Hull data
      Rudder and propeller etc under the Appendages tab.

      Also how does the new waves in hydrostatics operate?

      Any ideas?

    • #34426

      If we’re lucky, we might see a patch that enables us to play with the feature as a demo or limited functionality feature to help refine hull shaping and fairing. If we are super lucky, it might be added to the Pro version, even if it is somewhere in between limited functionality and fully functional.

      You might want to open a sample file and explore the tanks features (a separate pro extension.) The file is. In c:program filesdelftshipsamplesdemo vessel tanks.

    • #34428

      Hi fellers,
      If you look in the manual 15.9 it gives you a general idea. Now Im quoting directly from the manual, there are 2 methods used to calculate resistance, One is the Delft Series which is for fin keeled yachts and the other is the Kaper method which is for canoes. The data is taken directly from your model so there is no need to fiddle with it, although there is a limited ability to manually input data of your own choice. If you want to test different hulls etc just compare the results in the graph.
      Marven also states……
      This resistance module has been completely rewritten in preparation of the addition of more resistance prediction algorithms that will be added with the next release.
      I dont know whats been added to the new version.


    • #34433

      Hi Mike,

      I reread the manual this past weekend and picked up on those items. I fiddled with the “Waves” properties sheet and entered some 9 meters high waves with 500 foot lengths (to be shorter than my model’s LPP. The resistance calcs didn’t seem to change. I wonder whether the waves functionality will visualize quartering and beam wave action. It would be FUN to set up some high sea states to check for wetness over the bow to determine whether i need a bullwark or a higher one, and whether green water will enter the hawsers, or how much my transom will see water shipping onto the flight deck.

      But, I MUST say i had FUN FUN FUN playing around.

    • #34434

      Hi otaku,
      I received this explaination from Marven regarding the new Wave Animation gif. So, I hope he won’t mind me sharing it with you and others.

      (Dynamic means that additional forces, like wave damping and accelerations are taken
      into account too. This is not the case, the animations are static because for each frame the position of the ship is calculated as if the
      wave is frozen in time. If an equilibrium is found then the wave moves a bit to the aftship and the process is repeated. It’s a very important
      difference. But although it’s a static process it provides some understanding and insight about how the ship behaves.)

      So its a visualisation tool to help you in the design process.

      To me its the start of the quest for the Holy Grail of marine software, a fully dynamic animated Test Tank on your desk top.


    • #34435

      otaku wrote:

      I fiddled with the “Waves” properties sheet and entered some 9 meters high waves with 500 foot lengths (to be shorter than my model’s LPP. The resistance calcs didn’t seem to change.

      That’s correct. The resistance calculations are based on statistical tank data with still water. The results from the resistance calculations obtained by using a wave in the hydrostatics would be completely out of the valid range of the test data and therefore unreal. Not to mention the fact that the Delft series and Kaper are not really suitable for 500ft ships B)

    • #34437

      Hi Marven.

      I guess I must’ve misunderstood “waves” vs. static/still water. So, is this more about plunging and emerging from flat water that doesn’t respond the the ship’s presence? I should have looked closer at the animation on the web page to note the absense of disturbed, choppy, seas-like water.

      As for frame-by-frame or non-dynamic presentation, i’m fine with that, as it seems to be less resources-intensive.

      As to DELFT series numbers not being suitable for vessels of 500 feet, how unsuitable? Marketly/drastically, or on the order of 10% mis-calculation/underestimation of resistance? Currently, i get ~7,100 KN resistance for my hull, and if i recall correctly, that isn’t too far off of from a student paper regarding a stretched 5415 hull model taking the DDG-51 out to some 540 feet LPP/LBP. If i private send you my model would you like to use it for internal comparisons? I haven’t auto-faired it because i want to retain certain curves, and it’s not fully-marinized because my skeg is not quited right, and my sonar dome is just a place holder since any given navy would shape it according to the chosen sonar suite.

      Roughly, my model is 177m LPP, 21m beam at waterline, cb ~.48 at 6m draft, and cb around ~.53 or so around 7.1.

      Marven/Martjin, I don’t know how to profusely thank you/your team for the features and pricing. Now that i’ve figured out that i can import IGES models of my engine and shaftlines i can vastly easier fine-tune my hull earlier in the fairing process. I failed to appreciate it when it was possible in Free 3.x to export/import IGES. I guess i can try to continue helping by way of constant use and periodic feedback.

      I hope I didn’t split the thread too many ways…

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