"Extrude Srf Tapered" incorrect

Why can not I play a tapered extrusion (15 degrees) of this surface? the result is a solid which tends to a point, then incorrect.
(I could use the gumball to do this, but I would like to know why with the command “Extrude tapered” does not work?)

Thank you.

Extrude srf tapered incorrect.3dm(273.1 KB)

Please, try it to extrude this surface using the command “extrude tapered” (but without using the deformations of gumball).

Why can not I make this tapered extrusion? I’m wrong?

How thick of an extrusion are you aiming for here with a 15 degree draft? I find it works well at a 1 or -1 unit distance when using ExtrudeSrfTapered. At greater distance values the trimming step seems to fail with this trim border. I’m not sure if it’s a limitation of the command or a bug so I’ll file it regardless for development.

Thanks for the sample file!

Rhino is not smart enough to figure out what to do with that.

It is pretty simple to just extrude taper one of the objects and then
use polar array to finish it up.

TaperedExtrude.3dm(341.3 KB)