A way to make a solid version a 'Trumpet'.
The method is based on Max's marvellous _FXGraph3D and uses parametric equations from the equally marvellous MathMod.
Copy (Ctr-c) the following and then within Moi hit Tab and paste (Ctr-v)
_FxGraph3D cos(u)*sin(v); sin(u)*sin(v); cos(v)+log(tan(1/2*v));0;6.283;0.03;1.5;50;50;1;1;1;UV

Note. If you have done what I apparently have foolishly done and omitted the leading underscore of _FxGraph3D in your set up then you will need to omit it from the preceding line.

In (bottom right of) the _FxGraph3D dialog change Mode from UV to U then click on done.
Now select all the curves and execute Construct/Loft using Loft Style: Normal and Profiles: Auto
Delete (or hide) the curves. This should give you 'Trumpet' shaped surface with a slice out of it.
Select the surface and execute Construct/Offset/Shell using Thickness: 0.02mm and Direction: Centerline.
This should result in a solid.
Select the 8 edges that form the gap in the Trumpet, then copy (Ctrl-c) and paste (Ctrl-v) them and execute Edit/Join.
Then execute Construct/Loft using Loft Style: Normal and Profiles: Auto.
This should result in a solid filling the gap.
Select both solids and Boolean Union them together.
Here's the result: