Modeling an undefined curved shape around a cylinder


I am trying to model kind of undefined curved shape around a simple cylinder in order to 3D print it.
On the image below you will see what I am trying to achieve. The shape on top of the elements (these two lines forming a canal is an element that I do not need. All I want to do is draw the left (and the mirrored right side) on the shape that’s next to the cylinder. I am pretty good with basic SketchUp stuff but this left me clueless how to proceed.

Any thoughts or directions?

Thanks in advance!

I’m not sure I understand your question, as I don’t see a cylinder in your image (unless perhaps the near part doesn’t really taper, but looks that way due to perspective) and I don’t know what “next to the cylinder means”. But here’s a guess:

Draw a half cross section of the shape and then use follow me to “lathe” it around a circle.

I’m sorry for the bad explanation. Indeed it is not really clear what I call a cylinder. Here you can see what I mean. The blue is the cylinder and I need to make a model of the yellow parts.

The perspective really skews the dimensional perception of the object. The best would be to lay it flat on the floor and provide some pictures from above, left, right and some other angles. This shouldn’t be that hard to model with some dimensions and good photos.

Maybe you could create a shape like this and intersect it?



Unfortunately I do not have the physical model with me but I have the dimensions of the cylinder and I am trying to model something close to the real object. It doesn’t have to be 100% same as the dimensions of this curved shape is going to be hard to get anyways.

The rough shape should be something like this.

I think this is going to be hard to get aligned with the cylinder as the cylinder has specific dimensions and the top/bottom edges of this unknown shape must match exactly with the cylinder. Please check my last reply. I provide a profile of the shape.

add the skp file…

it looks relatively easy to do, but harder to explain…


Here is where I am currently. shape.skp (209.0 KB)

Oh this is a smart idea. I will have to do a lot of intersections and I will need to keep the cylinder as I will have to delete it at the end and keep only the “wings” to be 3D printed, but you gave me a really good starting point. Thanks.

I’ll appreciate other solutions too!

similar but different approach…

scale up by 100 first to make life easier for SU…


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Another really smart idea! Thank you that!

Unfortunately I was hoping for some trick that will skip the manual work and can produce much more dense and correct geometry which will be better for the 3D printer.

Regarding the scale - I am using real dimensions for the cylinder to the millimetre. Do you suggest to scale it anyways?

based on your cylinder:



model in meters and export as millimetres…

no real need for scalling when using metric…

i.e. in a ‘meters’ template, type 1.125, if you want 1.125 mm


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WOW this is amazing. Exactly what I tried to accomplish! Can you please tell me the names of these plugins that you use as some windows are too short and the names are not visible? Thanks!

I edited my previous post and add the list of plugins I used.

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as an aside:
it’s always best to use multiples of 12 for circles and arcs or curves, as they are divisible by the 4 which allows ‘magic’ inferencing of cardinal points…

I also think it best to know the basic tools before jumping into extension…



No doubt the basic tools must be mastered first and I did try to do it with basic tools but the solution that mihai.s provided is just awesome and will fit perfectly in my case.
I appreciate all answers. You are all awesome!