MIMF

Today I am leaning towards some sort of very tight "basket-weave" to create back and sides. With some glued in linen linings, perhaps.

Anybody here been doing that sort of thing?

Still undecided! But I got my rough-cut cello neck in the mail today...
Will dowel those peg-holes, and do some sort of veneer over top!
It's really dry maple, and has a lovely ringy-pingy tap tone.

Now I've had a chance to take some measurements, been back to work on the blueprint ( leaning towards single-cutaway now)
Definitely fixed on the 19 inch scale length... and after much consideration, decided (at least provisionally) to skinny down the body thickness.
Looking at 3.4 inches now, including the (flat) top.

Was hoping I could get some advice on how to best make a super-big edge radius on the top . I'd like to have it extremely rounded, shooting for one inch eadius!

Have a couple of ideas: First would just to use a one-inch-thick spruce top, and cut away most of it on the inside.

Another idea would be to make a one-inch-thick "rim" around the whole top edge of the "sides", and then set a thin spruce top flush into that
( it would have bracing, etc underneath...)

IMO, the easiest way would be to put a 1" thick rim and glue the soundboard on top of that then rout your round over instead of trying to inlay the top into a recess. You might want to consider releiving some of the mass of that rim on the inside before you put the top on.

Yes, you are right, that would be a lot easier...

But any way I choose to do a "rim" - it's still going to have the obvious visible "banding". So I'll have to mock that up and see if I like it.

Today I was thinking that instead of a one-wood "rim", I could build up a rim out of dozens ( hundreds??) of little "blocks" - and create a sort of gigantic checkerboard binding visual effect, to use that rim to visual advantage - something like a modern-day Baja quinto or Baja Sexto often has...

Wow, I was passing through a nearby city today and stopped in at a music store with a very well equipped acoustic room.

Played a bunch of guitars, mandolas, banjos, banjolins. ukes, resonators, ect.

Surprisingly, the loudest and richest instrument in the whole room was an open-backed five string banjo with a metal rim.
The exact same open-back model with a wood rim was a bit softer. Various full bodied banjos ( some very expensive!) were much quieter - and some weighed a TON.
Most of the resonator guitars they had were fairly ordinary - sounded much like a normal acoustic.

I'm pondering, what's need for a back at all? That open back banjo sounded THREE TIMES AS LOUD as the $1000 mandola hanging next to it.

Now pondering if my Mandocello needs to morph into a banjo-cello!!!??! Or maybe an open backed resonator mandocello?

Incidentally, I've never touched a banjo in my life before, but found I could navigate around on them quite easily ( they seem to have some sort of open tuning)
Pondering if I should go back on Monday and grab that banjo....

The reason banjos are loud is because they have a super light weight skin head and a bridge that transfers the string energy quickly into it. Loud and quick attack and short sustain.

So, what do we need for 'loud' with long sustain???

Michael James wrote:So, what do we need for 'loud' with long sustain???

Build a piano

Seriously though, if you add "sweet tone" to loud and long sustain you have exactly what all luthiers are trying to figure out. Mostly everything is a trade off. Want it loud? Sounds harsh and banjo like. Want it rich and tuneful? What happened to the volume. Want both? Build it light and big and watch it collapse after a few years/months/days. Add to that most people a trained to hear a '60's Martin as "guitar sounding". Build it too differently and many people won't like it.

People have been working pretty hard on this guitar thing for several generations and haven't come up with many major breakthroughs for a reason. That having been said, I encourage you to build what speaks to you and never stop experimenting. An opened back banjo/guitar may just be the instrument you have been looking for!

So, what do we need for 'loud' with long sustain??

A solid body and electricity....

Well, perhaps we can look at the opposite side of the equation. What is it about a banjo that actually REDUCES the sustain of the string?

I think that pesky 'conservation of energy' law rules out the string vibration (once set in motion by a pluck of finger or plectrum) ever INCREASING.
So it's not that a piano, or sturdily-built guitar is actually 'making' the string vibrate louder, longer - rather it's just allowing it to continue vibrating at fairly high amplitude for as long as the initial impulse was able to swing it.


So, what is it about the banjo soundboard that makes our plucked string lose its energy (amplitude of vibration) so quickly??
After the initial attack, is the 'springy' banjo head actually ABSORBING the vibration of the string?

OK... a bit of research has cleared that up.... I see it's a trade-off between the string energy being dissipated all at first attack... or sustaining longer, albeit softer. Higher impedance soundboard keeps the energy in the string longer, etc. Complicated stuff!

Looks like this is fast morphing into a resonator mandocello. One with a removable back (attached via some tiny neodymium magnets).

And I have an idea for some kind of "nice" removable body now... with some sort of "i-beam" that stretches out from the neck to the tailpiece - and the soundboard / body assembly suspended in between.... I'm thinking of something along the lines of those "RiverSong" guitars from Kamloops ( I visited their factory last year...)

Sketch is REAL FUZZY... must ponder!!!

now with a seven-inch resonator cone... side views still very much work-in-progress

Well... laziness ("the mother of invention") got the best of me, so I decided to give this project the "clamshell" configuration, two thick slabs of Western Red Cedar sandwiched together and extensively hollowed out inside. (before joining!)

Probably with carved out "integral" bracing here and there. And possibly some carbon fiber stringers directly connecting the neck block to the tailpiece.
(Tailpiece design still very much undecided!)

That orange blob is some extra maple I will have to add to the neck heel, in order to support the last six or eight frets worth of fretboard...

Wow, two and a half years have passed and I still haven't cleared the bench for this! I guess the woods are getting more and more seasoned!
Have ALL the hardware ready, and neck and fretboard and body woods, AND also have an MDF routing template of the body outline (cut for me by a CNC company in NY).
Maybe this will be the year I finally start to make some sawdust!

I've just read this post - sounds very interesting - please make shavings and finish it! I'm very interested to see, and hopefully hear, how your various ideas turn out.

Cheerio,

Carl

OK, it wasn't 2018, nor 2019... but I'm PRETTY SURE its going to get done this autumn

(sigh) I was wrong... shooting for Autumn 2021 now (moving across the country this spring)