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Thread: Modeling Tubular Frame

  1. #21

    Join Date
    May 2015
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    I'm learning a lot more than I asked for in this thread and really pleased to read some techniques about tube bending! Back to my project for a moment... would you have a suggestion on how to orient the reference planes (datums) as I begin to build my model of the fuselage? Logically one plane will bisect the fuselage top to bottom, essentially the projection of the vertical centerline of the airframe. So considering the other two planes, maybe the other vertical plane should be establish by the mounting points of the engine mounts? What about the horizontal plane - this has me a bit stumped. Not sure what makes sense. Certainly others (probably you guys) have faced this same dilemma and hopefully have come up with a well thought out conclusion. My thanks again!!!

  2. #22

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    Dec 2016
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    Zionsville, Indiana
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    Think about how you are going to build your fuselage. You will want to transfer measurements from you drawing to you building fixture or table easily.

  3. #23

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    May 2015
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    lathropdad, your point is well-taken. Although I am not building a fuselage (I am reverse engineering a certificated aircraft) I can understand your point: think ahead to consider what the model will be used for. I have some thinking to do.

  4. #24
    cwilliamrose's Avatar
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    Nov 2013
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    In the case of my fuselage I also took measurements of the actual fuselage (as welded) and modeled that instead of what the drawing said it should be when I was building it. This airplane is derived from the S-1S so it is similar in many respects but not the same. I actually started out just modeling the tail section which I did to design leading edge struts and attach points for the horizontal stab. I later used that work as the basis for the full fuselage model. I mention this because I ended up doing things bass-ackwards instead of the way the S-1S drawings were done.

    So, what I did was start at the tail post and work forward instead of starting at the firewall working aft. I do have a firewall plane which gets used a lot since the front plane is back at the tailpost. Having it to do over I'd start at the firewall with the front plane. The top plane is the CL of the upper longeron tubes which are flat when viewed from the side. The right plane is on the fuselage CL as viewed from the top.

    Name:  Fuse Weldment Planes, Front View.jpg
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    Name:  Fuse Weldment Planes, Side View.JPG
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    In my case it was easier the put the top plane on the upper longeron CL instead of at the top of the longerons as the factory drawings were done. The factory doesn't have a good way to measure from the center of a tube so they use the outside instead. When you're modeling a weldment it's easier to put your upper longeron layout sketch on the top plane so that's what I did. I do have to remember this when I'm looking at the S-1S drawings for reference.

    I'm betting your fuselage isn't as simple as mine and there's no really obvious place to set the top plane. You may just have to pick something and live with it. You'll be making a lot of planes anyway so it's no big deal.
    Last edited by cwilliamrose; 06-29-2017 at 08:34 AM.

  5. #25

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    Dec 2016
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    Zionsville, Indiana
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    Here is another SW weldment drawing. I did this from the fuselage drawings.
    Attached Images Attached Images  

  6. #26

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    May 2015
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    That is very helpful, and actually makes good sense in my situation too. There is a tube which receives the horiz stabilizer spars that makes a perfectly logical reference feature through which the top plane of the model can pass. Thanks for the images - they help a lot.

  7. #27
    I'm trying to follow the guidelines in this thread but I don't understand exactly how Weldments works in Solidworks. The Insert/Weldments tab is grayed out and I can't see to figure out why. Also someone above posted the dimensional drawings from VR3, can someone explain how to get those into Solidworks?

  8. #28
    cwilliamrose's Avatar
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    The files you download from VR3 go into the SOLIDWORKS Corp\SOLIDWORKS\lang\english\weldment profiles folder. I put mine in a subfolder called 'Aircraft' so they were separate from the other non-aircraft shapes.

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