How to calculate outside hull dimensions

Discussion in 'Wooden Boat Building and Restoration' started by Insomniac, Jul 25, 2018.

  1. TANSL
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    TANSL Senior Member

    I guess it only works for Windows, I've never tried it in MAC. Maybe you can do a test to see what happens. (although I'm afraid that Windows executable files ".exe" will not work, I do not know)
     
  2. Insomniac
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    Insomniac Junior Member

    Regarding this link I posted, I am trying to go about inputting my offsets into the txt format suggested in the article (shown in pic below). I am stuck on this step and was hoping someone would be able to offer some guidance. If I have understood correctly, each station represents the vertical "sections" of my offsets drawing, in my case labeled from 0-24 representing 1 foot sections. It seems each station has 6 measurements (2 for each hull panel). Yet, as this is a flat surface I don't know what my Z plane points would be; Also, the ends of the hull panels get tricky because the top of the panel sticks past the bottom of the panel, and I don't know what coordinate I would input for the bottom at the ends. Anyone willing to offer some guidance on how I could go about this process?
     

    Attached Files:

  3. Insomniac
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    Insomniac Junior Member

    Thanks I will give it a try. I can let you know how it goes in case you are curious.
     
  4. TANSL
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    TANSL Senior Member

    Of course, I am. Thanks.
    Regarding the points whose coordinates you have, if you tell me what you have and what you want to achieve, maybe I can give you a more agile solution than the link in your post (which by the way, I thought was too long and I have been too lazy to study it. Sorry)
     
  5. Insomniac
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    Insomniac Junior Member

    I gave it a try but ARQN won't open on my mac. Too bad because I was hoping to give it a try.

    If you could offer me a better solution that would be much appreciated. I don't blame you for not reading that page, I only recently got myself to study it in detail. Unfortunately it isn't as explanatory as I think it should be.
    Anyway, here is what I want to do:
    I have offsets for hull panels of a scull boat. I have attached a pic of one of the hull panels so you get the idea of what I am working with. I want to use these offsets to create a 3D model in a cad program (I have been using prosurf but am open to trying other programs, I also have autocad but have heard that isn't ideal for boat design). I could then use this model to run calculations on the hull at specific areas. Thats it really. Hull doesn't necessarily have to be faired, just accurate enough to run calculations. Make sense?

    Screen Shot 2018-08-05 at 11.43.14 PM.png
     
  6. rwatson
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    rwatson Senior Member

    I must apoligise for being tardy. I am currently "camping" in a second house without my CAD machine, and will be for another few weeks.

    I did start the research, using a model that had no transom or stem section, and found that it made the process much harder to get started.

    When I get back to it, I am planning to use the triangulation technique on the bottom panel of the hard chine model, where we know the length of the keel line, and know that has to be a straight line between the bow and the stern.

    Essentially, if we "pin" the centre of the bottom panel to the "floor", and then use the dimensions of that panel to triangulate from there, it should create the 3d shape.

    In many stitch and glue kits, they provide one or more bulkhead shapes, which would make a great starting point. For this exercise though, I want to prove to myself that it can be done without any of those shortcuts.
     
  7. rwatson
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    rwatson Senior Member

    I just saw that panel illustration, and I will explain the logic I am going to try.

    If you lay that panel flat on the Y axis, and pin the centre (station 12) to the Y line, you will get the keel line wandering over the Y line on the X axis, towards the bow and stern.

    No, if you just consider the first few stations towards the bow, from the centre, and you incline the chine line of station 9.8.7.6 up the Z axis, until the keel line fits to the Y line plane, you start to get the 3d shape that the panel produces.
     
  8. TANSL
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    TANSL Senior Member

    Thank you for the answer @rwatson, as I was saying, your method has awakened my expectations and I am looking forward to knowing it, understanding it and, if possible and with your permission, programming it in my applications.
     
  9. TANSL
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    TANSL Senior Member

    @Insomniac, I can provide you with a program, developed in language lsp (language created to interact with AutoCAD), which allows AutoCAD to read a .txt file, with the coordinates of the points and draw them on the screen. With this you can draw the splines or polylines that pass through those points.
    If you send me the file with the coordinates of the points, I will see what can be done. I could also draw those points and send you the AutoCAD file.
     
  10. Insomniac
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    Insomniac Junior Member

    That would be excellent. Very kind of you to make this offer. I am interested both in trying that program for myself, as well as seeing what you come up with. I emailed you at the address I found on your website (seems there is no way to message you through this forum) subject line "Offsets from Insomniac." Let me know if you have further questions or need more details. I look forward to seeing that program, as well as your AutoCAD drawing, should you decide to go forward with that.
     
  11. Insomniac
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    Insomniac Junior Member

    Good to see you back on this thread. Very interesting. That is sort of what I was imagining for how it should work. The specifics of how this is done is beyond my current CAD skills, but I am very interested in figuring this process out and will look forward to any further details you may offer.
     
  12. TANSL
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    TANSL Senior Member

    Insomniac, I received your email with the information. That's not a table of offset or anything like it. There is no program in the world that allows something to be done, automatically or semi-automatically, with it. You just have to know how to draw and understand what the designer wanted to explain. To make matters worse the dimensions are in feet and inches, which is a great difficulty for me. I will study your drawing to see what I can do but it is clear that I have the same tools as you: AutoCAD and a drawing with very poor explanations (not to mention a letter so small that it is very difficult to read). In short, all are advantages.
     
  13. Insomniac
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    Insomniac Junior Member

    Huh
    Given this drawing was labeled "Hull Panel Offsets" I mistakenly assumed these were offsets. Now that I have googled offsets I see they are very different from what I have.
    Anyway, given I have full size drawing of the hull panels that can be printed at the full hull panel size for tracing purposes, I am thinking it must be possible to trace these in AutoCAD, which would give me my hull panels. Once they are in AutoCAD, perhaps I could create my own table of offsets from the drawing and then import those coordinates into another program that could stitch them together, or follow @rwatson 's method of putting them together if that gets explained in enough detail. Am I right in thinking once I have the panels in AutoCAD I could create my own table of offsets?
     
  14. rwatson
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    rwatson Senior Member

    The "offsets" you have there are just to enable you to create the flat panel.
    You certainly could create them in Autocad based on that drawing. That step would be needed to start to "develop"them, because you need the diagonal measurements to calculate the "points in space"

    The final offsets you want are the points in 3 dimensional space, to get "bulkhead" sizes.

    The are two different things.
     

  15. TANSL
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    TANSL Senior Member

    @Insomniac, with the data that you have provided us you can draw on a board the pieces of the hull, in its flat development. But, if we do not have a method like the one that Rwatson is studying, it's going to be very difficult to get anything else. You need to draw the cross sections to get the table of offsets. But, once the cross sections are obtained, you no longer need the table of offsets.
     
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