Reference Points and G3 continuity

[AJ_8664249]

Dear PTC-Community,

I am trying to use a curve for creating airfoils. My geometry requires a smooth curve. My control points have to refer to points, which I referenced by parameters. So, I want to change the spline geometry with points, which are referenced by parameters.

For a smooth curve, I try to use G3-curves. However, with using splines I get kinks in the curve since splines do not have the G3 continuity feature.

If I try the Style Tool, I can use ISDC degree 5 curves, but I cannot reference my points. Only the start and end point are snapped by holding the shift key, but not the other points in between them.

Is there a feature to model the spline as a G3-curves or to reference the control points of a style curve?

Greetings

[tbraxton]

Control points of splines and ISDX curves cannot be used as a reference for other features. You can define datum points for the spline/curve to pass through that can be controlled directly. Have you considered this approach?

You can also import an .ibl file and use this for a curve through points approach.

[kdirth]

Not quite sure how you are trying to reference the points.

If you are trying to go through the points with your curve, you can hold shift and select each point in order.  The ends can then be controlled using the tangent tab.  If you need to control the curve at each point you will need to make multiple curves from point to point.

[AJ_8664249]

Thank you for your answers. However, I think my approach is less promising. So I am looking for alternativ solutions.

Kind regards

[KenFarley]

In a previous life, I worked with airfoil shapes all the time, for turbine blades/stators. To represent the airfoil shape, a data file of points was used for each planar section of the foil. The critical thing about the files was the distribution of the points. The spacing of points was larger on the majority of the airfoil on the suction and pressure sides of the shape, and would get smaller as the points approached the leading or trailing edge of the shape. If I recall correctly, we used over 100 points each side (pressure/suction) of the airfoil.

Unfortunately, how those points were generated was very proprietary, and even if I had the mathematical techniques at hand to do so, I probably wouldn't be allowed to post them here. But, I'd imagine if you have a mathematical method of defining the points you are generating, you could perhaps generate points based on curvature at adjacent points? More points for more rapid change of curvature? I don't know. It's not an easy problem to solve, but there has to be some sort of "standardized" method used by people building windmills, yacht keels, etc.

I've had some complex curvature parts that I needed extendable surfaces for, and I have resorted to a .ibl file to get what I needed, but that was a lot of trial and error.

[AJ_8664249]

Thank you for your help. It seems that Creo does not has the feature, which I intend to use. Your solution probably work, but I take a different method and change my modelling process. 

Kind Regards,