3D Cad (Lesson 101)

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by superjacent, Jun 19, 2009.

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  1. Jan 24, 2012 #141

    topspeed100

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    Isn't any computer program still just a substitute for a pencil ?

    400 lbs is a lot.
     
  2. Jan 24, 2012 #142

    Aircar

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    What is the source of the 400lbs overweight claim? (could be in the building --almost has to be if true -- or way too optimistic estimation --was the aircraft 400lbs heavier than other comparable aircraft or just the calculated expectaton ? ie "over" what, weight or best guess ?
     
  3. Jan 24, 2012 #143

    autoreply

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    Did they change anything major after the video? There (2:00) they mention 180-220 lbs extra.
     
  4. Jan 24, 2012 #144

    topspeed100

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  5. Jan 24, 2012 #145

    autoreply

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  6. Jan 25, 2012 #146

    Wagy59

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    Well, I couldn't stand it any longer after reading all the posts about cad and drafting and blah blah blah, so I downloaded Rhino and some other stuff, just to see what the fuss was all about. First thing I did was import the twin I'm working on in Autocad. After fooling with it for a few minutes, this is my opinion of this goofy Rhino program as opposed to autocad,
    Ahh like it...AH LIKE it A LOT!!!...Really...I'n not kiddin..I liked it as soon as I turned it on...Did i mention I like it?
    But I still think most people must be spaz's with autocad...And from one to spaz to another, I'm not a big fan of it either....I just ended up using it a lot and over time, taught my self to do some pretty advanced 3d work with it. Once autodesk included a lofting tool with the 2007 version it changed everything..Almost my entire drawing (the 3D part) of the twin was done with lofting
    But did I mention AH LIKE RHINO? Rhino is cool..I'm going to fool with it some more and see how much I can learn about using it and what I can do with it that I cant do with autocad, (or at least is difficult to do in autocad).
    Honestly, after reading all the posts on here about autocad I started realizing I apparently do far more with it than most folks..Guess I just didn't realize it was so painful & impossible:gig:
    I mostly agree with ya'll..autocad is somewhat of a piece of crap for 3d work but it's amazing what you can do with it if you work at it. Took me quite a long time to get to the point I'm at now with it, but I'm a bit stupid...er..I meant stubborn!...yeh..stubborn...thats it...;)
     
  7. Jan 25, 2012 #147

    Jay Kempf

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    Yup, Autodesks 3D kernel has always been a bit grumpy. And the methods of construction, well, um, less than straight forward. I don't use Rhino, but I did use AutoCAD a lot to the point where I started thinking like it. I am reformed now. Solidworks does really well, especially if you want to build something using machine shops and laser and punch houses. Rhino from what I can tell is the lofting tool of choice for those that are building sailboats and some less than production aviation houses. All the more modern systems work well. Quoting Joliet Jake... "I see the light!" :)
     
  8. Jan 25, 2012 #148

    topspeed100

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  9. Jan 27, 2012 #149

    Wagy59

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    I dunno...I like Rhino...I'm open to anything that can do "stuff"..But I've used Revit at work, both structural and architectural variants and yeh they are good at keeping track of materials and whatever but still pretty much suck as far as bugs and general pain in the rear to use and stay accurate...I still say everyone that thinks autocad is obsolete is just a big sissy..LOL..Sorry..couldnt help it..I think autocad is excellent despite it's short comings and price, but the I'm starting to realize I can do things with it most people don't do simply because they never got that far with it.
    49.jpg
     
  10. Jan 27, 2012 #150

    Wagy59

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    And the rendering is of a drawing that is extremely accurate and one that I can pull template and dimension off of quite easily..It's not just a pretty picture that is slopped together
     
  11. Jan 27, 2012 #151

    Inverted Vantage

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    Wagy59, that looks awesome. What software did you make that in?

    Would anyone be interested in CAD and 3d modeling lessons, by the way? The two are different but very related. :)
     
  12. Jan 27, 2012 #152

    Wagy59

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    And by the way, forgive me if I seem overconfident, because I'm not..I'm actually pretty humble, but this silly thing is going to happen and it will fly well. All ya have to do is look at it and if you know anything you have to conclude that yeh..thats an airplane ..Ok..I know its about details..like horizontal tail incidence relative to wing etc etc , on and on..I know all that crap...doesnt mean I wont listen to ya...All my life, I've always kept my mouth shut and listened...That be why I so **** smart!:gig:
    I dare you to tell me this wont fly well....
    50.jpg
    See?..It just looks "right"
     
  13. Jan 27, 2012 #153

    Inverted Vantage

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    Nice work on the canopy to tail transition, that always gives me trouble on my airplanes.

    You should at least do some basic analysis of it before you start building things; even just build some RC models to test out the looks and handling. But yea, what you're saying does have some basis in reality - there's at least one famous aircraft that was designed when it's chief engineer sat down (or sat someone down - the aircraft is either the Supermarine Spitfire, or it's raceplane predecessor) on the floor and the plane was drawn around them in chalk.
     
  14. Jan 27, 2012 #154

    Wagy59

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    I'll build a model and fly it..dont worry....i was building models of lifting bodies of all thing's in the the early 60's, along with the more normal models
     
  15. Jan 28, 2012 #155

    Matt G.

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    If that's the route you want to go, I'd recommend reading through this document: http://www.nasa.gov/pdf/483000main_ModelingFlight.pdf

    You'll need to be careful scaling it such that you get realistic results. As you'll discover when you read through it, geometry, mass, engine power, etc. all scale differently.

    Also, as not to put all of your eggs in one basket, so to speak, there are many, many good design books written that you can use to design and analyze the aircraft before you build it, and also compare to the model results.
     
  16. Jan 28, 2012 #156

    Wagy59

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    Also, It isn't like I just thought it up overnight . I 'm not going to argue with so called "know it alls" that like to tell you it cant be done because they just know better cuz they built somethin once or twice or done somethin one time or flew a kite over My. Everest once and **** it, it just wont work cuz they say so...Most humans are full of BS is the reality...gotta filter through it all and take whats real and legitimate ....the world is just literally overcrowded with people like that..Not to say everyone on here is that way....not at all..I am paying close attention to everything said on here...Some of these people like Orion and others have a wealth of information and experience..So i listen to em...They help me be less stupid like I naturally izzz....
     
  17. Jan 28, 2012 #157

    Woodenwings

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    OK....

    Lets talk about surfacing and mass properties again,
    Anyone lofting a prop?

    :lick:
     
  18. Jan 28, 2012 #158

    Woodenwings

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    What did you mean by the thing below exactly?
     
  19. Jan 28, 2012 #159

    Inverted Vantage

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    I generally use the term CAD as parametric model creation, which is what's done in SolidWorks and Inventor. Parametric modeling is history-based, which means you can dimension out a part with relations and operations, then go back and edit those and have the part update in the future. It's very powerful for designing things where dimensions are critical and subject to change. I think more generally CAD refers to designing something with the assistance of a computer; you don't need 3d modeling to do it.

    3D modeling is a more blanket term for digital 3d model creation. For instance, parametric solid modeling, polygonal modeling, subdivision modeling, and surface modeling, are all types of digital 3d models; the data is very similar and there are a few conversion utilities out there (the poly to surfaces/parametric solid is pretty new, I can't recall the name of it off the top of my head, but it's like $300 IIRC). There are techniques in CG model creation that make better models; it really is a craft just like making it with your hands. A great parametric model, for instance, will allow a lot of flexibility in the edits. A good polygonal mesh will flow well for animation or be very efficient in conveying the form. Depending on what you're modeling for, there are different types of mesh creation techniques and tools that can help you accomplish the task.

    I was also gauging interesting for maybe an online class or something, I don't know. Just throwing out a line to see if anyone wants to bite. :) It wouldn't be for awhile, probably not until summer at least. Why did you ask?

    Since this is a 3D CAD thread, this is an example of sub-division modeling that I've been working on for some time now for a client (since I haven't graduated uni for another 4 months, I'm doing it real cheap for him). He wants to turn it into a CNC cut mold for an R/C airplane. The modeling technique I've chosen is less dimensionally accurate than a parametric solid-based model; however, for many of the complex shapes and curvatures of the P-51, it is easier to create something that looks the same and is relatively close. If he also wanted to design internal structure, I would be hard-pressed to do it in this program, and I would probably do it in a NURBS surfacing program like Rhino, which is more flexible and easy to model than solids, but is more dimensionally accurate than a polygonal model (which can be made to be just as accurate, they just typically aren't, and it really depends on the program and the desired mesh).

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    This image is a wireframe, showing the construction. In polygonal modeling, data is inferred from connecting three vertices together to create a flat face. This is how real time 3d programs, like games, typically store and render 3D data. In a modeling program, like modo, the one I'm using, these are often made into "quads", which can be triangulated into the base two triangles. Quads allow faster manipulation of higher detail (more polygon) meshes quicker, but in rare instances can be less detailed, and require more attention to keep poly "flow". Proper flow allows you to select loops, which are connected lines of quads or their edges (edge loops). This allows for easier, smoother manipulation, and more reliable rendering. A n-gon, which is a polygon with n sides, will behave strangely when rendered, as the program tries to determine the best way to, at it's root, triangulate it.

    This is where we run into one of the major limits of computer modeling vs. doing it with a slide ruler (though in practice it never really affects anything); in the digital world, there is either 1 or 0, so when you take that super fine mathematical curved surface in NURBs and go to 3D print it, it gets broken into triangles to create flat surfaces. I think that's enough for now, I'm starting to go off onto a tangent, haha :)
     
    Last edited: Jan 28, 2012
    Chlomo and craig saxon like this.
  20. Jan 28, 2012 #160

    Jan Carlsson

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    I just made these two, That really is two slightly different prop, beside the obvius, left and right hand rotating, for the Bugatti 100P

    Bugatti - Crome.jpg
     

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