I had this made by banjo luthier Zach Hoyt. It has a 12” diameter rather than the 11” that most banjos have. It also has something called an internal resonator. These are mostly used by makers of openback 5-string banjos meant for “Old Time” clawhammer playing. The rim is maple, and the resonator is walnut.
A good friend of mine that’s a luthier (mostly guitars and ukuleles) is going to build the neck. I’d have had him make the rim but he doesn’t have a lathe.
The neck itself will have 5 strings, and will basically be a cross between a tenor banjo and a cello banjo, the tuning being CDGAE. It’ll implement a multi-scale / fanned fret design, with the high E being 22.5” (same as a 19 fret tenor) and the low C being 24.5” (same as Gold Tone’s cello banjo).
Once I got it in I went ahead and installed all the hardware to make sure it all would fit correctly. I went with raw brass on the hardware, and even got a cool armrest made of walnut.
Here’s a collage I made of three pictures:

https://imgur.com/gallery/Q089GWG

If people are interested I’ll update with more photos once the neck is made, maybe even make a video.

Haven't seen that before. Am I right in guessing that the resonator is built kind of like a toroid-type ring mold?

_________________
"Time is the wisest counselor of all." - Pericles

"I remain not entirely convinced of it." - Nano

I’d never heard of that, but after a little reading it does sound like a similar process. As for how it applies to a banjo, it’s meant to boost volume and sustain. But with this comes a slightly increased risk of creating “muddiness” by reducing note separation.

This is what I was referring to, in case there's been any confusion:




I take it, then, that this slightly increased risk is less of an issue in clawhammer playing.

_________________
"Time is the wisest counselor of all." - Pericles

"I remain not entirely convinced of it." - Nano

Clawhammerists often seek a “plunky” tone rather than a bright one, so I guess that reduction in note separation could contribute to that.
As a side note, Old Time clawhammer banjo was actually my gateway to ITM, and when I bought my tenor banjo I decided to implement a plunkier sound rather than go for the more popular sound than can sound like an automatic rifle to my ears. So I opted for an openback rather than a resonator, and put a goatskin head on in instead of mylar. It’s undoubtedly not everyone's cup of tea, but it suits my ears better than what I often hear from other players.
But with this new Frankenbanjo I plan to edge closer to the brighter side of the spectrum and not go as plunky. I’ll undoubtedly tinker with it some, though, and figure out what sound I want to try to dial into. I even plan to do a comparison of metal of nylgut strings on it, and possibly even a mixture. This banjo verges on unknown territory so experimentation could lead to valuable info if the idea is intriguing enough for other builders to give it a shot. And I don’t see why it wouldn’t have potential to be popular; bouzouki luthiers have been implementing the same concept for years now with 10-stringed long scales (DGDAD, CGDAD, CGDAE, etc) and short scales (GDAEB, GDADA, etc).