6 Replies Latest reply on Sep 13, 2014 7:50 PM by Joseph Pope

    Loft is not lining up points

    Joseph Pope

      Hello,

      I have created an airfoil from a 2d set of points and a 3d set of points and then lofted them to make the surface.  The problem is at the trailing edge of the airfoil the loft seems to have cris-crossed the final few points (second to last point on one side goes tot he last point on the other and vice versa).  Can anybody explain how i fix this.  I have included a zip with the files.

        • Re: Loft is not lining up points
          J. Mather

          Joseph Pope wrote:

           

          Hello,

          ... and a 3d set of points ....

          Aren't those points planar?  Why a 3D sketch?

           

          I recommend using a few points as possible and you might want to include some guide curves.

          • Re: Loft is not lining up points
            Kelvin Lamport

            The trick with lofts is to make sure that both sketches are selected by clicking near the same relative points. Doing so ensures those points are connected as the start of the loft.

            1 person found this helpful
              • Re: Loft is not lining up points
                Paul Cullen

                Kelvin is correct

                 

                You have 80 segments in each sketch. you have to make sure to select close to the same end of the corresponding sketch segment in each sketch

                 

                In the image below I have selected the right hand end of the line close to the sharp end of your sketch

                loft 1.JPG

                Below you will see that I have selected the right hand end of the corosponding line in the 3d sketch. You will also see that SW has placed a blue do on the right hand end of the line

                loft 2.JPG

                SW has also place a blue dot on the right hand end of the first line I created, If I had selected a different line or the left hand end of the line the blue dot will be closest to where I had selected and the loft would be twisted. You can drag the dot along the sketch if you did not select the correct place in the sketch and this will take the twist out of the loft

                loft 3.JPG

                 

                You now have a finished loft

                 

                loft 5.JPG

                 

                If you want to make a smoother loft. edit your sketches and using the fit spline command convert all the straight line segments into a spline and then do the loft to end up with this

                loft 4.JPG

                 

                Paul

                1 person found this helpful
              • Re: Loft is not lining up points
                Mark Biasotti

                Hi Joseph,

                 

                As Dr. Mather has suggested, most airfoils are created using a spline, not line segments. Is there are reason you are doing it this way? You can keep your line/points, but you might want to try to create new sketches and create a spline that mimics the shape of the airfoil cross section or use an equation curve.

                 

                See attached EDU version

                 

                There are lots of little things that you need to know about using splines but they are very appropriate (and indispensable)  for this type of application. 

                • I created a single spline using  7 points starting at the trailing edge but leaving the last point approx. to the first point (do not connect)
                • then I made the leading edge point tangency/magnitude handle at the leading edge vertical in  direction by clicking on the widget and then RMB and clicking on the vertical contraint in the minibar.
                • I then held down <ALT> key and dragged the end dot of the vertical widget to symmetrically adjust the magnitude at out.
                • I then split the leading edge at the interim spline point  (select spline and RMB>split entity)
                • then connected the points of the "two splines" at the trailing point back together
                • and then did some adjustment of the tangency vector and magnitude handles
                • and then used these instead of your sketches for your loft.

                 

                Mark

                • Re: Loft is not lining up points
                  Joseph Pope

                  Got it!  Thanks for all the help gents.