How can I make a helix line up the side of a funnel?

Hello SketchUp forum!

Essentially I need to wrap a helix line up the side of this funnel, so I can use that contour to create a spiral staircase from the bottom to the top. I’m now at the point where I’m lost in the library of extensions I’ve installed trying to achieve this, and cant seem to figure it out from the youtube tutorials, so I’m reaching out to the community!

I would very much appreciate if anyone could help me out with this. Also Very open to any tips on the right extensions. The shape of the stairs will have to change as they go up as the overhang becomes more flat on the top of the funnel.

thank you !


I used Spirix to generate a helical set of triangles and then intersected them with a shape similar to yours … the result was not quite what I was expecting, but maybe it will work for you.

funnel.skp (482.2 KB)

Don’t know Spirix, but looked at its web page. It may be more complex to set up than you need - there are certainly options I don’t understand on reading about them. It seems to have been written for SU v8, but may well work in later versions, but I saw no indication that it has been updated for later SU versions.

If you want to try something that might be simpler, you could try the SU Parametric 3D Shapes plugin from
and use a Helical Ramp to intersect the funnel. You may have to View Hidden Geometry, and/or unsmooth or unhide the edges for the intersection to work (not at computer so can’t try it now).

Or possibly modify the code in that plugin for drawing a Helix, if you want to match the funnel curve more closely and have the formula for the curve cross-section.

If you import the attached model, you can scale the helix to fit your geometry and then create a helical line on the funnel by intersecting the shapes:

helix.skp (280.1 KB)

Did you check this site?

Didn’t see that one - but I’m glad to see it has been. Thanks very much for the update.

You asked the same thing at Sketchucation and not only has it been answered as Mitch made a plugin for that. I thought it should be shared here too:

Hey, John, thanks a lot for your suggestions. I dont know if I’m at the place where I can modify code- maybe i can convince my programer friends to help. :slight_smile:

Ill definitely try the plugin you named. much appreciated.


Hey Jim, thanks for this, I’m slow getting to it, but when I figure it out ill post the solution.

Hi @grevoir,

You haven’t related the premise of the design
It’s difficult to understand the necessity of modeling a three-dimensional helix when one might develop the curve in 2D, arrange the treads accordingly and then move them vertically.
Not nit picking … just being curious George :monkey:

Hey George, sure here goes. I am modeling a a funnel to be 3-d printed, and I would like to create a spiral staircase that wraps up the side of the funnel like a reverse tower of babel. I’m not sure if this will be the final design for my print, I’m just also trying to push my self education of Sketchup. You know how ideas work - you have them, and you get excited about them, and even thought they seem easy, they present problems. How would you suggest to achieve this by modeling the helix in 2d? I’ve been toying with different funnel shapes, and I would like to find the easiest way to draw the helix against the curve of the funnel so it fits it perfectly- then after that use a component stringer to multiply the stair up that line, but as the stairs reach the mouth of the funnel they will each individually have to be extended to reach past the overhang of the funnel. Any suggestions you would have would be greatly appreciated, thanks for the comment. :slight_smile: