Interesting neck joint.

[Smallchewbacca]

I saw this in a recent post by Ko’olau on Instagram. It’s clearly a bolt-on joint, also indicated by the bodies that were also shown in the video. I’ve never seen this where the heel is hollowed out where it joins the body though. Can anyone shed some light on this approach?

 

[RickOlson]

Beau Hannam has a YouTube video where he walks through the process of fitting a bolt-on neck. Since a bold is doing most of the work you don't need the surfaces to contact to form a strong glue bond. Beau said that he makes the face that mates with the body slightly convex to make it easier to get a tight fit around the edge. This looks like a that idea applied more formally.

 

[Smallchewbacca]

that’s what I was thinking. If you need to do some slight sanding to perfect the fit, there is a lot less material to remove.

 

[Timbuck]

Some builders do it on dovetail joints ...by gouging out the relief (inner material) with a Dremel.

 

[mikeyb2]

As I understand it, this is quite common practice to achieve fine tuning of the joint by flossing the joint with sandpaper. This makes the area to be sanded smaller and narrower, and thus much easier. I do similar on guitars and have also used a radiused heel to achieve the same. I seem to remember Paul at Wildcat Ukuleles (member here) , also does this by routing the relief on the heel, whereas I normally use a chisel.
I must add that on the guitars there will be a tenon on the heel, that's mainly why I use a chisel.