More Boolean Confuson

I am having yet another issue trying to do a boolean function. Using the boolean split also fails. I think I may know why this is happening, but I don’t know how to fix it. I successfully booleaned one section on the same surface using the exact same method. One works and one fails. The only thing I see that doesn’t look right is the direction of normals on one of the faces. If you run the direction command you will see that one area appears to be going in opposite directions at the same time. I don’t know how this happened and I have rebuilt these surfaces using 2 rail sweep and blend but still get this strange outcome. I made a close up snapshot of the area facing opposite directions and included the work file I’m using as well. I created the pipe that I am trying to boolean by using the circle around curve, then the 1 rail sweep. Any ideas on whats going on here?
Thanks again for all of your expert help!

MC_Muffler -detail.3dm (439.4 KB)

Hi Jeremy,

If you zoom in closely at that spot, you’ll see that one of the surfaces doubles back on itself. It may be easier to see in wireframe.

Thanks Chuck, I see what your talking about. I will see what I can do to fix it. If you have any suggestions I’m all ears.
Thanks again!

This looks rather messy. Is there a particular reason why the side surface isn’t just a simple planar surface all the way from the one end to the other? It seems like this can be modeled with just a few simple shapes like so:

MC_Muffler -detail 001.3dm (144.9 KB)
I don’t know about any external constraints and interfaces of course…

I modeled it using 1 arc ( copied and rotated for the top curve) and 2 curves. Once I have the top and bottom pieces I tried using planar surface and it failed. I tried to keep it as simple as possible, but had to use other commands to create the sides. Now when I explode it planar surface works, but doesn’t solve the problem of the failing boolean.
I was able to get rid of the curve folding in on itself and recreated the sides with planar surfaces, but boolean still fails. The only other thing I can think of is creating this by deforming cylinders.

That is really not a good idea.
Just use correct arcs and straight lines.