Neck/body carve on neckthroughs - concave or convex?

The first thing I do is draw a parabolic type line from the bass to the treble side of the neck. I carve out below it until it feels right. Usually it feels right, I let it sit overnight, decide that I didn't take enough off and take more off (repeat 2 or 3 times). I want comfortable access to the 24th fret all across the fingerboard. That doesn't necessarily mean it has to be scooped to the 24th, it just means it has to be comfortable. I hadn't really thought of this before but perhaps someone with shorter fingers than mine would want it more scooped out than I leave it. Also I want the neck to get thicker before the end of the truss rod, which is usually around the 18th fret.

Incidentally on the actual carving, it's a lot of material to remove, I've tried a lot of different tools. My go-to now is an angle grinder. I draw the contour on each side of the neck and watch carefully to make sure I'm not going too deep. It's also important to watch the outside edge of the wheel, I have inadvertently hit the horn because I was so focused on the heel. It can make a mess in a hurry. The angle grinder leaves a pretty rough surface, I use a gouge and scrapers to clean it up.

One other problem area for me is always getting the transition to the flat part of the neck right. It's impossible to get that transition smooth unless you take a little off the back of the neck on the flat part. I have necks where I have cut them to the absolute minimum thickness prior to carving - that's a bad idea because you can't make that transition smooth.

I have a Carvin/Kiesel through neck here and I often use it as a reference when I'm starting to carve a neck heel. The carve on the back is more extreme than anything I do, I guess they trust their neck wood more than I do, or use longer truss rods. I know they embed carbon rods, so maybe they go further down the neck.

 

i like what jackson does:


unless you have a cnc mill at the ready and can just surface it with a ballnose tool, it's fairly easy to do with a dragon rasp and either shaped sanding widgets or scrapers to dial it in.

 

Here's the back of my four string fretless neck through built 32 years ago. Still stable and straight. Carve away!

 

I used to carve neckthrough heel like this...
(But only because Alembic does)

But now I do something that feels way better, full access to the 24th...
Same basic horn configuration, but the lines are better now as well ... I feel.

A "stiff" neckthrough needs no "heel" per se....
One concern is the last few inches of the neck, outside the influence of the truss rod.
If you're neck material is fairly flexible... you might need more support at the heel area.
But, all my necks are 5 to 9 pc. laminated,
...so I don't worry about it.

 

Then again.... it depends on the situation (IMO).
On this one, I couldn't bring myself to carve it out any more...
Party because of aesthetic rationale.
And partly because this bass will be subjected to "alternate" tunings AND overseas travel...
So I wanted it to be as stable as possible.
...although my paranoia is probably unfounded.
It really didn't matter here anyway, because the lower cut was super deep.