Area and volume

Discussion in 'Boat Design' started by Saqa, Jan 3, 2015.

  1. Saqa
    Joined: Oct 2013
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    Saqa Senior Member

    I want to find out how much a hull will weigh if built using different materials and whether empty space or foam filled so I can use material density numbers

    Would it be a quick cheat that would give useable area and volume data if I did the following?

    Its a sealed hull like a tri ama

    Add to displacement weight to completely immerse the hull in the software and look at wetted area and volume displaced numbers in the results
     
  2. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    That is an interesting approach. However, unless the sheer is absolutely flat there will have to be an added correction.
     
  3. rwatson
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    rwatson Senior Member

    I dont understand why.

    If the 'software' is good enough, the results should be spot on.

    eg Freeship or Rhino cope with any type odd shape
     
  4. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    Nope...not even close.

    You appear to be posting many new threads all with very simplistic Qs. They all suggest that what you are doing is way beyond your abilities, and you should be seeking proper professional advice, otherwise, ask your tutor!

    The Q above is a prime example. To find out how much a vessel will weigh using different materials, is easy. You design it to meet the same SOR then you'll know. If you're unable to perform this basic task...QED.
     
  5. Saqa
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    Saqa Senior Member

    Maybe I missed it but I couldn't see where to look up hull weight and total surface area or hull volume in freeship. The simple drawing program I am using is easy to draw developable surface shapes but doesn't allow any input of material density. The only option is to select a displacement figure

    I am at a loss to work out surface area of a drawn shape which limits my ability to do the maths with material density to find hull weight to which I can add crew and equipment and come up with a tentative displacement figure

    I am able to sink the hull in that program by adding an extra vertical surface at centre line with flat sheer. This might give a wetted surface area and volume in the results. I only asked if that cheat would give usuable data as there might be some factor that I might have missed

    Btw I have already requested Jacques at Bateu about a professionally designed boat the likes of which I am after and its awesome to see him and Richard Woods looking at the issue in some detail. I think it is ok for me to have some very rewarding time playing with drawings and building some experimental models and such in alternate materials and methods as well and learn something along the way. Didnt mean to offend anyones sensibilities with my over simplistic questions
     
  6. Petros
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    Petros Senior Member

    it is much more complicated than just surface area and material density. each material has different strength properties, one would have to completely design the hull around your materials (such as wood, fiberglass, alloy, steel, carbon graphite), optimizing for each of the material properties, and than determine the volume you need of each. to complicate this each of the properties of these materials are not related or even propotional to the same charateristics of the other. For example, each material has a bending strength, a shear strength, a tensile strength, and an elastic modulus (how much it deflects under load), if fiberglass say is twice as heavy as wood, but it's moduls, is only one fourth that of wood, and perhaps bending strenth is about 3 times that, but shear shrenth is only 1.5 times. Each element would have to be examined and size, thinkness and shape determined.

    This of course is way too much work, what most designers do is compare statical data on the size and type of boats made with different materials, and choose one that is similar as their hull weight. You will have to find these statical tables somewhere.

    what you will find however is that for most of the less costly materials (wood, fiberglass, steel or aluminum alloy), similar boats with optimized designs for each, will weigh similar amounts. the only exception is if you have a very unusual design or are using costly exotic composites (carbon, titanium, etc).

    Most people choose the material they build their own boat from based on personal preference, past experiance, and skills and tools they already have.

    good luck
     
  7. Saqa
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    Saqa Senior Member

    Thanks for the pointers Petros

    The Shape I am drawing is based around a choice of two materials, either of those two options can be built to the exact dimensions

    One is welded HDPE 6mm sheeting based, filled with 2lb PU foam
    The other is 'solid' 8lb PU foam core sheathed with glass/poxy

    So based on the responses to my query about the cheat I take it that the general consensus is that:

    the total wet area of the sealed sunken hull will not give me usable data about surface area that I can use together with material density to calculate shell weight

    the volume displaced by the sealed sunken hull will not give me usable data that I can use together with foam density to calculate core weight

    So can can anyone help me understand why not? What am I missing? This would have to be an over over simplified version of my original question :)
     
  8. Saqa
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    Saqa Senior Member

    Why not? Why will it not give total surface area? Total volume? Why not even close as you say?

    You have made that call, is there a reason other then the personal criticism about my use of what is a forum on boat building?

    What is your problem with the threads I have started. I am asking about some things that I dont understand and I thot a boat building forum would be a good place to ask for some pointers. If it was already within my abilities then I wouldn't have to ask people like you. If you do not like my questions then do not address them. Just one liners like "not even close" followed by personal criticism is in very poor form. If you feel so strongly that the handful of threads I have started are so out of order then I suggest you report them to a moderator and if my asking a few simple questions is so out of order then I suggest you run to the same moderator and ask for my site access to be restricted so to save your sensibilities from being offended any further. I have requested designs from Richard Woods and Jacques on Bateu forum and looks like there is interest in that type of craft and there is some design collaboration happening from the pair on there. That is the actual commercial craft that I will be building if they release plans. In the meantime I am very interested in playing boats and experimenting with all sorts of crap, materials that they do not work with. I would appreciate some help in a few little things that others with more education could possibly help with

    I am not designing a vessel yet. I have a hull size and type in mind that can be built with two different build materials to similar strengths. I just want a quick way to find if building in that material would make for too heavy a boat. Why do you have a problem with this?

    So you have the scenario, sink a hull and read the wet area results and volume displaced

    You say claim not even close to obtaining a useable figure for surface area or volume with that process. Why not?
     
  9. LP
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    LP Flying Boatman

    Saga, I quick response to your questions.

    Design your hull in FS, make sure it is fully enclosed(watertight), fully immerse it and read the volume from the hydrostatics page.

    Make separate layers for the hull and the deck, apply material properties in the layers page. The layers page will give you surface area per layer (i.e. hull and deck). If necessary calculate volumes of surface materials to subtract from total volume to find internal volume for foam calulation.

    This should give you the quantities to do the calculations you want. I believe they will be close enough for your needs. If I can help you with anything else, let me know.
     
  10. Saqa
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    Saqa Senior Member

    Thanks LP, will give that a go again. I tried it previously but freeship gave an error saying draft is too large. Will try again, maybe I made a mistake. Carlson Hulls allows it though
     
  11. LP
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    LP Flying Boatman

    You made me wonder since a hadn't actually tried fully submersing a hull so I just went and did it with a kayak model of mine. I was a ble to get full immersion and hydrostatic numbers.
     
  12. Saqa
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    Saqa Senior Member

    Thanks LP, I tried again and it worked I think. Previously I chose too much draft which freeship didnt accept. I tried again with a hull height and it worked

    [​IMG]Capture by jonny.toobad, on Flickr

    I also entered the densities in layers dialog but I cant find where to pull up shell weight results

    So is there any reason I cant use the high lighted bits to work out shell weight and volume? Ad Hoc said not even close
     
  13. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    I always use the wet area to calculate the weight of the hull. The best and most accurate method, imo.
     
  14. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    Because here is your starter for 10:


    Well, lets have a look:

    Here:
    http://www.boatdesign.net/forums/design-software/trim-52253.html

    Yet despite the replies you still follow up with this:

    All this suggest is that you:
    1) do not know how to manually calculate this (which is not an issue as many students ask such simple Qs)
    2) you do not have a stability program to calculate it for you but more importantly
    3) the Q you are asking is beyond you even if you had #2.

    Ordinarily this would not be a problem. Easy to answer. But as seen here:

    http://www.boatdesign.net/forums/boat-design/cat-draft-52170.html
    and here:
    http://www.boatdesign.net/forums/boat-design/cat-draft-2-a-52182.html
    and here:
    http://www.boatdesign.net/forums/boat-design/help-hull-weights-52092.html
    and here:
    http://www.boatdesign.net/forums/boat-design/sea-seesaw-52130.html

    and so on….all based around the same thing.

    You are trying to design a boat with zero knowledge in the technical aspects of design. Nothing wrong with that. But just as any student of naval architecture finds, the more you learn the more questions you have. Yet they have tutors and books to seek their answers and 3-4years to learn and process all the information, yet you appear to seek the assistance of the forum to answer every single minutiae piecemeal question for you. And appear unsatisfied when you don't get the replies/help you seek.

    You should either take up a correspondence course in basic naval architecture, or the forum will no longer be BoatDesign Forum, it will be Saga’s Learning to do basic naval architecture Forum. Since you are constantly asking such basic question in a step by step process to the point such simple requests by the OP lose their credibility.

    Answer 1 or 2 questions on such basics is fine. But to teach you step by step over a long sustained period of time how to design a boat, is not what this forum is about.

    Nothing at all.

    However, you have constantly and consistently failed to grasp the reality of these “simple” questions.

    Design and I mean real design not the pretty pictures that most do, require many different disciplines to be understood and mastered and then they are all brought together and compromises of each are required to satisfy the SOR.

    Thus as I noted from the outset, if you want to know how....DESIGN it. The design will give you the answer no one else on this forum can. You need an SOR and thus a design based upon your SOR. If you are unable to do this then any follow up question is way way beyond your current abilities. Thus you need to do a correspondence course in basic naval architecture….as all your thread to date scream this very loudly.
     

  15. Saqa
    Joined: Oct 2013
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    Saqa Senior Member

    Ad Hoc, thats just silly. When you went and made a career out of making a list of the threads I have posted, you the the one with the SOR. Try to do a better job next time

    As for posting and learning through the forum. I do not see any rules where I cant ask about what my current interest is. If you have a problem sharing information and some specific education, guess what, no one has a gun to your head! You dont have to share

    I dont see why I need to go through the process you have listed for some experimental fun and asking for help on a related forum when I get stuck on something I do not have previous knowledge of

    I have googled, I cant locate hints of a freeware that can display trim. According to your logic the software category on a boating forum is the wrong place to ask about it. I request again, if my posts offend your sensibilities so much, don't read!

    And your "not even close" is rubbish. The shell can be built to required strengths from my material options and it appears the cheat is a usuable data extraction. Doesnt make your professional response worth much
     
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