BODYBUILDING with Lazy radicals...

[Michael James]

Hi All!

I have decided it would be nice to build a sort of Mandocello-ish instrument.
8-strings, 4 courses, 19 or 20 inch scale length.
Maybe flat-top, maybe carved - depends on what turns up in the way of available ( aka Cheap but nice!! ) top wood.

But here's the rub... I don't want to bend sides!
Thinking of the "dugout canoe" body construction, (maybe built up out of multiple flat layers, so there's not so much routing) - or Venetian BowlBack "ribs" typa-thing.

Or better yet, something "ALTERNATIVE"!!!

So, I was wondering if anyone had any bright ideas...
Perhaps some sort of lattice arrangement - maybe a buckyball-based-lifeform?
(Flattened geodesic dome?)
I'm thinking of what might be EASY to glue up out of regular pieces, but strong and light and resonant too.
If in the end it had a sort of baroque appearance, so much the better...


One other thing, I want to build in a nice smooth edge around the top... nothing bugs me more than a hard edge digging in to my strumming forearm

[Bryan Bear]

Others will soon be by with suggestions for alternatives to bent sides. There is nothing wrong with wanting to do that but I wanted to weigh in encouraging you to try bending sides. This though scared me (and many others I'm sure) when I started out. I worked around having to learn to bend for a couple instruments but eventually I bit the bullet and learned how.

No matter what direction you go with this instrument, you will end up wanting to make more. That is just the way it is; you are signing up for a new addiction so you might as well embrace it now. It won't be long before you want to bend sides. Don't let it intimidate you. A pipe bender can be made with little investment and using it is not nearly as hard as it seems before you try. Learn to consistently thickness wood (through whatever means you wish) and know that you can go thinner than you think. Proceed with this instrument, but start practicing bending even if just with the scraps you generate from this project.

[Dan Smith]

My Uncle's buddy made this with match sticks, so there you go.

[Michael James]

Well, wonderful as traditional bending is, I really want to find a different way for this project.
I will be very, very limited for shop space (and equipment!)

It's going to be a fairly petite-ish thing, but I plan to make it very DEEP - maybe five or six inches, perhaps reminiscent of a guitarrón mexicano.

I haven't quite decided on the sound holes yet, but I'm pretty sure its going to have this sort of outline:

rough sketch version 7

rough sketch version 6

But still very much waffling on the double cutaway vs. the single cutaway... That single cutaway is still vexing me with its ever-so-slightly ugly upper bout!

The board there is for the top billet size ( before bookmatching )

[Michael Lewis]

For a mandocello ish instrument you need to consider the scale length and the strings you are going to use. START THERE. They tune from low strings to high C,G, D, A.

You might consider converting an existing instrument to meet your needs, as several guitars have been converted to such purpose.

[Michael James]

That's good advice, and I actually have been looking around for body donors... [CUE: theme from Frankenstein...]
But so far the only thing that looks appealing is one of those Washburn travel guitars, and I don't think I could bring myself to butcher a serviceable one (haven't found a wreck yet!)

Anyway, certainly more fun building something 'new' from scratch, especially if I can stumble onto something 'progressive'.
I'm mostly leaning towards a 19 inch scale, as I have a nice baritone uke that size, and it fits my fingers nicely.
Could go as long as 22, I suppose... but smaller means more top wood choices are likely to come my way.

rough sketch, 19 inch scale

This is the double-cut with a 19 inch scale (earlier drawing was 22.2, as it happens)
Those are Gotoh Planetary banjo machine heads, incidentally.
They just fit in my facsimile standard cello headstock template

A few years back I had a cheap little mandola or mandocello for a couple of days ( it was 19 inch scale, I am pretty sure - so halfway between mandola and mandocello proper, I think!)... and I enjoyed fooling with immensely.

If I can make one that sounds something like that one did, I'll be pleased.

[Jason Rodgers]

For the size of instrument, with ribs that deep, any sort of solid sides would make it oddly heavy. Everything in your design could be bent easily, or even laminated, except for those horns. If you're worried about the horn points, you could either redesign it to have pointed horns, which would require a miter at the tip, or the horn ends could be blocks that the sides are let into: ie, corner blocks that are exposed, maybe with a contrasting wood that matches the neck or butt graft or some other trim wood.

[Dan Smith]

Why so deep?

[Michael James]

Why so deep? Good question! It's only my intuitive response... I don't have any scientific basis.
But in my mind's eye I am visualizing a deeper body, sort of proportional to a bowlback mando.

As for any practical reason, I might be tempted to hypothesize that a more substantial "hefty" body could help to balance the large tilt-back of the cello headstock.

I'm conceiving this instrument to be the offspring of a viola da gamba...

viola da gamba side view

and a bowlback mandolin...

mandolin side view

Still pondering!! It will be some time before I firm up a 'side view" of my blueprint... still hoping for some novel construction technique to surface.

Incidentally, why couldn't a carefully constructed "solid" shell be just as thin and light as a bent-wood shell?
Or would that be just wildly impractical to construct?

[Michael Lewis]

3D printing?

I suggest you consult a string gauge calculator to determine the gauges of strings you will use before cutting any wood.

[Michael James]

3D printing is an awesome idea, and I do have Solidworks at the office, so could generate the file without too much difficulty. HOWEVER, it might be too expensive, since I do not own or have access to a 3D printer, and I'd have to farm it out to some 3D printing service. But hey, plastic worked for Maccaferri, it might work for me.

I tried the MPUSTC string calculator, and it postulates 77 KG of total string tension for an 8-string Mandola.

that strikes me as rather enormous, have to double check that elsewhere... Mind you, that was with all doubled strings and I want to do octave strings for the bottom two courses.

Actually, what am I saying - that's silly of me... I would never play in standard mando tuning anyway, I'll likely just tune it as if it were the top 4 strings of a 12-string guitar, capo'ed at the 5th fret to be GBEA. Possibly tuned all 4ths, but probably the same basic 'extra-light' tension. I tune my ukes down quite a bit, as I don't like them all "Plinky" - much better to my ears sounding like a classical guitar, and easier for string bending too

[Dan Smith]

I think if a solid shell was used, the end grain area would be very weak.
Although, the top and back may be enough to stiffen it.
Not sure, just a guess.
I wonder if laminating veneer over a mold could work?

[Clay Schaeffer]

You might be able to make a shallow staved back without investing in bending irons or heat blankets. A heat gun might be all you would need.
For the scale length you are proposing octave mandolin tuning might work better.

[Michael James]

That's an interesting idea - I could borrow a heat gun from my office... But it still begs the question of "how to make the sides"?
I still feel that there must be some really clever 'mathematical arrangement of interlocked pieces' Solution waiting to reveal itself.

The suggestion of "laminates over a form" holds some appeal... I had considered just doing a fiberglass or carbon layup ( a la Ovation or Rainsong ), but like the 3D printing idea, that firmly steers the piece into the realm of plastics. I'd really like to make something out of 'mostly wood', if I can just find a very elegant way that is appealing to my basic laziness!

[Mark Swanson]

You are making this much harder than it needs to be. Bending is the easiest and fastest and most durable of all the alternatives you have mentioned. The very early instruments have bent sides, because they learned it was the easiest way. Many times new builders are shy of side bending and want to re-invent the wheel, but I suggest trying it with some scrap wood and that might change your outlook.

[Bryan Bear]

Early on, when I was still trying to steer around bending, I used a heat gun to bend. It worked. But only just. . . I wet the wood and bent over a form while heating the wood with the gun. I got some separation (probably from using too much water) and it went really slow but it got there. I burned my hands quite a few times so be careful. IIRC, I clamped the side to the form as I went and then heated the whole thing once it was bent to get it nice and dry. I made a hot pipe before the next one and never looked back. I have seen some hot pipes that used heat guns as the source. That would probably be a better rout.

[Rodger Knox]

Using an old clothes iron as the heat source will reduce the burning of the hands.
Bending onto a form this way is actually very easy, as long as the side isn't too thick (less than 0.08"), and it's not a species that resists bending.

[Bryan Bear]

Rodger, I guess you do a separate for for the inside bends? I could see bending the waist on a form with an iron then flipping in onto an inside form, clamping the waist and finishing up. That sounds much better than the heat gun. I suppose if you are doing an oily wood, you should not use your regular clothes iron, or is that not really an issue?

[Rodger Knox]

Bryan, that's pretty close. On difficult woods, I'll get the waist bend close on the pipe, then clamp it on the form.
On easy wood, I'll just heat the waist area until it will conform to the form. And you do not want to use the iron for anything else after bending wood with it.
My wife goes through them pretty quickly, I've got two or three that she thought she threw away.

[Dan Smith]

Bryan, that's pretty close. On difficult woods, I'll get the waist bend close on the pipe, then clamp it on the form.
On easy wood, I'll just heat the waist area until it will conform to the form. And you do not want to use the iron for anything else after bending wood with it.
My wife goes through them pretty quickly, I've got two or three that she thought she threw away.

Thanks for the laugh, Rodger!
Ha ha