Trying to create a 3D Trapezoid with a Curve

Hi. I’m new to SketchUp Make and struggling to model a woodworking part that starts flat, then one end gets steam bent 90 degrees. The part starts out looks looking like this:

Length: 12.5"
Width: 1.75" on one end; 0.5" on the other (equal angles on both sides)
Thickness: 0.375"

The narrow end gets bent to 90 degrees with a 6" outside diameter (3" radius).

I’m only interested in modeling the finished part, but can’t figure out how to do it. Any help/guidance would be appreciated.

Or something like this, to many possibilities to guess.


Hi Kevin,

You could model the bent shape without the taper.
Then, use two temporary faces as cutting planes to create the taper.

See this model for ideas…
Tapered Radius.skp (110.7 KB)

Box, you’ve accurately captured the concept of what I’m trying to accomplish and your tutorial makes it look so simple. I’m obviously missing something because when I use the rotate tool the whole group rotates. I must be misunderstanding your comments.

Yes the rendering of the bent part looks like what I’m trying to achieve. I’m a SketchUp newbee and really struggling with this one. Thanks.

He’s using an extension, not the Rotate Tool! I think it is Fredo6’s FredoScale-Radial Bending.


Thanks for the tip. I haven’t used any Extensions yet, didn’t even know what thy were. Like I said, I’m new here.

So the next question is, when I try to download an Extension I receive the message, “One moment please…” The window then goes grey and freezes indefinitely. Why?

You can do it without an extension. I can describe the method, with pictures, but not an animation like Box.

Start by drawing a cross section. Use the rectangle tool and the Arc tools to get this, after deleting the extra cross lines at the ends of the arcs:

Push pull it to HALF the maximum width (7/8").

Make it a component, and open it for editing in Xray view (View/Face Style/X-ray)
Make rectangles across the cross section at the ends of the arcs

Draw the taper, so you know how wide the bent piece will be at each junction.

Now use the scale tool in turn on the top face, the bottom of the arc, and top of the arc.
Select the top face, and Scale the width of the top to 1/4".

Window select the rectangle at the bottom of the arc, and Scale the width to match the taper you’ve drawn below it (draw a line across at the join, to get an endpoint .

Then scale the top of the arc using the eyeball, or calculate what the width ought to be round the curve.

Clean up by hiding the rectangles.

Mirror the half you have made - either use the TIG Mirror plugin, or Move/Copy then Scale -1, and move the two halves together.

(Green scale -1)

Delete the faces where the two halves meet, while they are still apart.

Move the copy to join the original.

Delete the straight lines where the halves join, and hide the arcs.

Have just realised you could do it on a full rather than a half section, using the Scale about centre option instead of Scale about opposite point. Would make a slightly cleaner component in fewer steps.

Anyway, here’s the model resulting from the above steps, saved back to v2014 so you can open it in v2015:

Steam bent taper.skp (31.6 KB)

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Thanks John. The steps you laid out make sense and helps explain the underlying geometry.

In the mean time DaveR setup an offline GoToMeeting and introduced me in detail to ShapeBenger and to the many tools available to SketchUp users.

I really appreciate the helpful guidance from the members of this community.

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