Why is my loft puckering on top?

I’m trying to project the taper of a guitar neck so I can create profiles for a jig. The loft is perfect, and when I extrude through my secondary plane on the larger end it works beautifully, but on the smaller end it deforms and creates a dimple along the top.

Back up 1 step before the loft and show us the sketches you used please.

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Just a couple of half circles more or less.

What if you connect the topmost points of the two arcs with a line and use that line as a guide for the Loft? It may not show much difference on the lofted body but will help to create a more controlled body and the extruded body may not be deformed.

Anyway, when you select a face, the Offset Face tool is the default selection. Was this model the result of the Offset Face, or did you intentionally select the Extrude tool?

I see the 2 drawing A & B, How did you get to C? The problem occurs between B & C?

Maybe try removing the center line in the sketches, and then lofting, and offsetting.
I’m assuming currently you are doing two lofts, one for each half of the neck profile, then offsetting the face of each lifted body and getting this shape.

Are the curved radii in the sketches for the neck profile constrained/tangent to the box they’re drawn in? Maybe also remove/trim the rectangle guide as well.

Weird coincidence is I was drawing a guitar neck and jig last week for a tool my father wants to make.

Agreed, and also any extraneous lines as well.

So create a new Sketch plane that follows the taper of the neck and then draw a line on it connecting those two points?

Yes I used the offset face tool, not the extrude tool.

Yes the problem is between B and C. I used the offset face tool.

It does the same thing as a single loft without the center line. I added the center line to see if that would fix it. I removed all the extra lines and it does the same thing.

I’ve played with this a bit. Tried every suggestion here. I tried redrawing the shape as a single spline, both Control and Fit splines. It seems that an offset face of a lofted object created by a spline will begin to deform at some point. I’ve found a workaround for my purposes for the time being, but I would love to be able to use this method at some point.

Hi @Trey,
I checked this model a bit and I think offsetting the face will not lead to the expected result. The problem is that the whole cross-section is guided by the two parallel edges on the sides and the top of the curved face which is declining. When offsetting the face, the edges parallel to that face will be extended during the offset, which makes the declining edge extend below the horizontal ones on the side.
Is there a reason why lofting accurately sketched cross-sections on planes A and C was not a solution for you?

Thanks for looking. The point of the model was to generate accurate cross section sketches on planes A and C. I have measurements and profiles for the neck at the first and twelfth fret. I’m trying to generate accurate projections of them out past where the guitar neck would actually exist to create guide templates for a neck shaping jig. It’s weird to describe, but the pictures on this page from the plans I’m using should explain it better. If you have any suggestions for alternate ways to create what I need I would love it. I’m really a novice at this so it would not surprise me if I’m not going about it the best way.