24 Replies Latest reply on Jul 31, 2014 3:10 PM by Rick McWilliams

    mirror composite curve

    perry leets

      is it possible to mirror a composite curve about a plane?

      I'm working on a helicopter fuselage, I have the loft profiles set up and some guide curves, but I was still not happy with the results.

      I created a compound curve along points where there are changes in tangencies and hope this will "smooth" things out. The curve though is on just one side of the fuselage though and I need it on both sides. I could create another curve like I did the first, but then there would be no guarantee that they are identical.

      any suggestions?

      thanks

        • Re: mirror composite curve
          Jerry Steiger

          Perry,

           

          A workaround is to build a surface off of the curve, then mirror the surface. Now Convert Entities on the appropriate edges of the mirrored surface. If you are really worried about the symmetry, you might actually go to the trouble of using Convert Entities on the appropriate edges of the original surface as well, rather than using the original Composite Curve. That way the two sides have gone through more similar processes.

           

          Jerry S.

            • Re: mirror composite curve
              perry leets

              I'm not sure I'm following you Jerry. The only tool I know that can create a surface from just a line or curve is the extrude surface tool.

              With a composite curve which is VERY non-planar that does not work. There are no surfaces, or edges, in the model yet, just loft profiles and guide curves. In the picture below I've hidden the other guide curves so that all that is visible are the loft profiles and the composite curve (blue) which I want to mirror to the opposite side.

               

              fuselage skin, Bell 206B.JPG

                • Re: mirror composite curve
                  Jamil Snead

                  It appears that you can't do a surface extrude from a composite curve, but you can do one from a 3D sketch even if it is non-planar. You just need to select a direction to extrude. So one option is instead of a composite curve just start a 3D sketch and convert each element of the curve. Then you could extrude that sketch and mirror the surface, then convert the edges of the surface and the mirror together.

                   

                  Another surface you can create is a sweep, and that will work with a composite curve as the path. You would just need to make a sketch with a short line segment or something that pierces the path on one end, then you can sweep it.

                  • Re: mirror composite curve
                    Jerry Steiger

                    Perry,

                     

                    In addition to Jamil's suggestions, I think you can use a Ruled Surface.

                     

                    I would be inclined to make just half of your surface and then mirror it, rather than trying to mirror the guide curves.

                     

                    Jerry S.

                • Re: mirror composite curve
                  Rick McWilliams

                  I get very beautiful aircraft fuselages using conic surfaces. These are super smooth and easy to define. All sections are conics and the tangency is for sure. An add in from cadcampomponents is required.

                   

                  M7 cockpit abstract.JPG

                  • Re: mirror composite curve
                    perry leets

                    Here's the part file if anyone wants to play with it and possibly offer suggestions.

                    I'm getting a bit frustrated with it. Depending on wether I implement it as a loft or boundary surface different things will fail.

                    When I do a loft, all the profiles will add just fine (from "FS61" to "tail fore") but it will not add all the guide curves. If I implement it as a boundary surface it will not add the last profile ("tail fore") but it may allow all the guide curves.

                    Also, no specific curve or profile consistently fails to add, it depends on the order I select them!

                    Plus, if the boundary surface fails for any reason it gives NO indication why. At least the loft will tell you if a guide curve does not pierce a profile or something!

                    I think SW could use a little beefing up here.

                    I was considering manually adding curves to the other side of the model since I cant mirror them, even if they are not perfectly symmetrical. Considering the problems I'm having with the curves though I may opt for just creating one side of the model and mirroring it.

                      • Re: mirror composite curve
                        perry leets

                        By the way, can two (or more) guide curves converge to a single point, or is that problematic?

                        • Re: mirror composite curve
                          Jamil Snead

                          I'm playing around with the part right now, but here are a couple general suggestions:

                           

                          1. I also think for simplicity's sake doing half first an then mirroring is a good idea.

                          2. It might help to make a sketch of the top and bottom profile converted from your "side" sketch, and use those as guide curves.

                          3. For lofts when it is in the preview stage before you check ok it usually shows 1 set of connectors (green). You can right click on one and select "show all connectors" and then it should show more connectors (cyan), and those are essentially guide curves. A lot of times when a loft fails it's because the connectors for one of the profiles are rotated funny, so you can go an manually reposition the connectors to get a smoother transition.

                          4. Sometimes lofts go funky when the different profiles are made of different types of entities (arcs, lines, splines), or if they have different numbers of entities chained together. Changing every sketch to a single spline with the Fit Spline tool can sometimes make lofts perform better.

                            • Re: mirror composite curve
                              Rick McWilliams

                              Watch out for tangent problems at the mirror plane. Solidworks boundary surfaces and lofts often generate hogbacks or butt cracks at the mirror plane. Adding a surface to force tangent may just round the problem. Conic surfaces are second order curves so that they cannot make an inflection in the middle of the curve. Most airplanes and helicopters use conic surfaces for the fuselage. The nose of a fuselage requires some care for the conic surface to close perfectly, the profile and plan guide curves must meet perpendicular to the spine. The nose is technically a singular point. GW3D add in from cadcamcomponnts.com does this beautifully.

                               

                              snap 80 pv3.JPG
                                • Re: mirror composite curve
                                  perry leets

                                  cadcamcomponnts.com doesnt give a lot of information on their webpage. no manual, no tutorial and no cost!

                                    • Re: mirror composite curve
                                      Rick McWilliams

                                      The cadcamcomponents.com website is a bit cryptic.  They sell through solidworks vars so the pricing is obscured just like Solidworks pricing. It is not hard to get a free 30 day demo. The price is about $1500. The features generated by this addin have all of the capabilities of native Solidworks features. A part with these features can be manipulated by a copy of Solidworks that does not have GW3D.

                                       

                                      GW3D has many useful functions that were strangely omitted from Solidworks. Among them is a mirror curve.

                                       

                                      The features tha I use the most are:

                                      Conic surface, tubular surface, map to plane, conic curve, offset curve, mirror curve, helix solid, freeform swept.

                                       

                                      Your helicopter shapes would be better using boundary surface with a longitudinal guide curve and less sections. If you need to arrange connectors you do not have true control of the geometry. In all cases look carefully for butt cracks and hogbacks.

                                  • Re: mirror composite curve
                                    perry leets

                                    I have been playing with a version of the model that is cut in halve longitudinally but that creates some if its own issues.

                                    The wide part of the fuselage is flat, top and bottom, but as it nears the tail becomes circular. So in the areas where it is getting circular I had to add horizontal lines to the endpoints where the circle was cut in half. "Overbuilding" the surface which I planed to trim, then mirror. Its still giving me some problems with the guide curves though, and makes editing the original loft profiles kinda messy.

                                    Yes, I do tweek the connectors to get them lined up more closely, but when showing all connectors it can get pretty ugly and when moving one of those it seems to create yet more connectos (which are not well aligned)!

                                    Finally, the loft profiles are made from different entities (arcs, lines and splines) so I can control radius's a little better. However I do a fit-spline on them once they are how I want them.

                                    I also just tried breaking the loft into a couple of features, rather than one big loft. That helps but I cant re-use the curve entities that were used in the first section (non-curve guides I can re-use just fine). Its getting pretty frustrating!!!

                                      • Re: mirror composite curve
                                        Jamil Snead

                                        I hear ya. I ran into the same issue of only being able to use a guide curve for a single loft. I guess you just have to make a bunch of duplicate sketches. Here's my best result:

                                         

                                        fuselage1.PNG

                                        fuselage3.PNG

                                         

                                        What I ended up doing was:

                                        -Trim each profile sketch to one half.

                                        -For each profile that wasn't a single spline do Fit Spline.

                                        -First do a loft of the rear portion. With single spline profiles I think it will only start with one set of connectors, but you can add more. So I manually added two connector sets as shown. I only used the bottom portion as a guide curve. For some reason when I added the top also it wouldn't show me the connectors.

                                         

                                        fuselage4.PNG

                                         

                                        -Tweak around with those connectors until the rear portion looks ok.

                                        -Do a loft of the front portion. For the profile connecting to the back use the edge of the previous surface rather than the sketch, and set the constraint to Tangency to Face. I added two sets of connectors again.

                                         

                                        fuselage5.PNG

                                         

                                        -Tweak those until the front looks right, then mirror and knit.

                                         

                                        I have SW2014 so you wouldn't be able to open my part file, but I've attached a parasolid in case you want a better look at what I came up with.

                                          • Re: mirror composite curve
                                            Jerry Steiger

                                            Jamil,

                                             

                                            Your pictures on this and some other threads seem to have disappeared. I suspect that you moved or deleted the images that are linked.

                                             

                                            Jerry S.

                                            • Re: mirror composite curve
                                              perry leets

                                              Thanks for all the effort in helping me with this!

                                              I ended up going with a part that contained complete lofting profiles (not ones cut in half). I ended up manually creating guide curves on the other side. They may not be perfectly symmetrical, but they are pretty darn close. Strangly, after adding these other curves the loft behaved better when I expected it to be more difficult!

                                              Oh, and yes, to answer my own question, you DO NOT want guide cuves to converge on a single point. It didn't effect the surface, and actually made a pretty nice surface. When I went to thicken the surface it was a problem. The thicken would bomb when it hit where the guide curves came together.

                                              I added a picture of the finished model (its still missing some items, engine cowlings skids, etc.) while its not perfect, its good enough for what I need it for and pretty close to the real McCoy.

                                              206b.jpg

                                            • Re: mirror composite curve
                                              Jerry Steiger

                                              Perry,

                                               

                                              Depending on your preferences, another option besides using Fit Splines is to make each of your profiles with the same number of segments, splitting elements on the profiles with the least number of segments. Careful placement of the splits will often mean that the default connectors work very well.

                                               

                                              Jerry S.