Mandocello build thread

[sunburst]

After shaping the neck shaft I went back to the transition areas and refined them some. I'll work on them more later, but this is enough for now and I'll proceed to setting the neck in the body.

[Timbofood]

Thank you so much John for sharing the whole project, it has been real entertainment, I don't build but, I'm certainly learning more than enough to know it's not a project I have any desire to attempt! Very very interesting!

[sunburst]

When setting a neck we must control "roll, pitch and yaw" throughout the process. to control roll, top and back center lines must remain aligned with the neck center line. For pitch, a simple gauge to measure projected height above the top, and for yaw, alignment of neck center line with the body center line.
Here's how I maintain center for the whole length of the instrument (yaw).
I prominently marked the center line on the end of the body, squaring it with the edge of the rim.

Since the neck angle doesn't allow for simply laying a straight edge along the neck and body, I securely taped this straight edge exactly on the center line.

I checked a reject mandolin rib piece against my table saw fence, and planed it straight. I used it as a straight edge to align with the neck center line using the taped straight edge to determine alignment.

[sunburst]

With those precautions in mind (roll, pitch and yaw), using chisel, incannel gouge, knife, files, chalk, and some sandpaper, I gradually went from this...

...to this.

As you can see, I managed to keep my center lines pretty well aligned.

[sunburst]

At this point, I laid the back in place on the rim, shaped the heel button on the back plate to a proportional size and shape that is aesthetically pleasing IMO. I removed some material from the neck heel in accordance with that.
This picture was taken before the one in the post above which shows the heel with the excess material removed.
To me, a graceful, aesthetically shaped neck heel is very important to the look of an instrument. Getting the right proportion, not too big, not too small, establishing good lines and curves in this area go a long way toward making an attractive instrument. I once saw a very old Martin guitar with a very nice slim, graceful neck heel and it made an impression on me. I've striven for similar results ever since. That neck heel was obviously hand shaped by someone who took great pride in his/her work, who wasn't rushed, who was not worried about being laid off or loosing his/her job to a robot or CNC... guess I was born too late...

[sunburst]

When we are sanding a mandolin for finish, there is a strong temptation to sand cross-grain in the corner where the neck heel meets the rim. If you look closely at most old Gibsons, including Loars, as well as other manufactured mandolins (and some hand built ones too) you can see the evidence of this temptation in the sanding scratches going across the grain, following the direction of the corner. To help me avoid that, I finish sand the neck heel and the body in the area of the neck joint before gluing the dovetail. Not only does that help keep me from sanding cross grain, it allows me to more easily sand the scroll next to the neck and the neck next to the scroll.

[sunburst]

With the dovetail joint fit and the neck heel and rim finish sanded, I glued the neck joint and let the glue cure. Here's the back surface and the top surface with the riser block milled down to the neck surface.

[tree]

2 things:

1) The curved shoulders of the dovetail seem like an impossible challenge to me. They're end grain, and it appears they're curved in 2 planes. Is the vertical curve in the edge of the shoulder a result of the taper around the curved rim? How much time did that take to fit, once you established your centerline target?

2) I had forgotten how big a beast this thing is until that full photo with your hand and straightedge in post 303 . . .

[sunburst]

The curve only appears to me in two planes. The taper of the neck heel is a curve, and where that curve intersects the curve that fits against the rim, another curve appears to be present. I think it's kind of cool how that happens.
How long did it take me to fit the dovetail? Too long. Fitting dovetails and bending sides are two of the jobs that I just can't seem to do quickly. With each bit of wood removed, the effect on all three, roll pitch and yaw, must be considered. That slows the whole process down for me. Guitar neck sets, with their almost flat rim surface, go much faster.

[David Houchens]

With each bit of wood removed, the effect on all three, roll pitch and yaw, must be considered. That slows the whole process down for me. Guitar neck sets, with their almost flat rim surface, go much faster.

Glad it's not just me.

[tree]

The taper of the neck heel is a curve, and where that curve intersects the curve that fits against the rim, another curve appears to be present. I think it's kind of cool how that happens.

Kind of cool indeed . . . and beautiful, as it happens.

It would be nice if there were some sort of jig that could help those of us with less experience or skill to sort it out . . . James Condino has a dandy sanding jig for a non-tapered dovetail, but I can't wrap my brain around how a tapered one could possibly work. For some problems, I guess the old solutions (trial and refitting with chalk) are still the best.

[sunburst]

Here are two strips of paulownia that will become the back linings.

I bent them over the hot pipe (that I use to bend sides)...

...then glued them into the rim, after first freshening the inside of the rim with a little sanding.

[sunburst]

After the glue cured I removed the cloths pin clamps. The profile of the lining is still rectangular.

I first shaped the ends of the bindings where they meet the blocks and where I don't have room to use a finger plane, using one of my favorite pocket knives.

The rest of the shaping was done with a small convex sole finger plane, leaving the linings with a fillet profile.

[Clinton Johnson]

Cool I really like that solid lining verses kerfed

[sunburst]

Here is a big, round piece of sandpaper that is meant to fit into my radius hollow forms for building guitars. It was sticky-backed when it was new, but it's been stuck to things and peeled loose from them so many times that it is no longer sticky-backed. Anyway, the most convenient reasonably flat surface in the shop is the table saw, so I clamped the sandpaper disc to the table saw to level the back of the rim along with the new linings.

The idea is to be able to sand the back of the rim perfectly flat by rubbing it on the sandpaper on the flat surface.

It hardly ever really works, though. The neck heel and scroll area usually needs special attention to get the edges done. With mandolins, I can usually manipulate things until I'm satisfied with the flatness of the rim checking with a straight edge. I couldn't do that with this bigger instrument, I guess because of the size, so I made a quick "sanding paddle" that doesn't really look like a paddle. It looks more like a wood scrap with a piece of sandpaper double-stick taped to one end... and in fact, that's what it is; a wood scrap with a piece of sandpaper double-stick taped to one end.

Despite the makeshift nature of the tool, I was able to get the back of the rim plenty flat for gluing the back.

[sunburst]

With the back of the rim sanded flat, I located the back on the rim and drilled holes for tooth pick dowels to locate the back for gluing.

The idea is to align the center lines of the back and rim and establish the exact position of the back on the rim for further work. Things like marking for trimming the back to size...

...and marking for hollowing out the inside of the scroll.

[sunburst]

Hollowing out the inside of the scroll is not something that directly affects the sound, but it saves a few grams of weight, and the accumulation of small weight savings can add up to a lighter instrument, so with planes, gouges and scrapers, I made it look like this.

[sunburst]

I carved away some of the head block for weight saving also. The block is paulownia, so it is very light anyway and the wood carved away doesn't make much difference in the instrument's weight, but it allows me to thin the back plate more in the head block area, and since the back plate is hard maple, there is more weight saving. Another small weight saving to accumulate toward a lighter instrument.
First a couple of incannel gouges, then the sanding drum in the flex shaft.

[sunburst]

With the back located with dowels, the inside of the scroll and the head block trimmed of excess material and the edge of the back plate trimmed to near the binding stage, I finally glued the back to the rim using a menagerie of assorted clamps and cauls.

With the box closed I'm done with lutherie for a while and I'll have to work on cosmetics and ornamentation until later when it's time for fret work and set up.

[sunburst]

I've tried various ways of cutting binding slots in mandolins over the years, starting with the Siminoff tool on a Dremel; the tool later sold by Stewmac. I tried laminate trimmer jigs...
Whatever I used, I always had to clean up the channel by hand to get it ready for bindings, even when the power tool worked pretty well and I didn't have to repair tear-out or other damage. Eventually I figured; if I'm going to have to do so much hand work to the channel anyway, I'll do the whole thing by hand, and I started to cut the top and back plate smaller than the rim outline by a little less than the thickness of the binding so that the ledge is mostly already there when I glue the plates to the rim. To finish the job of cutting for bindings I use a violin purfling cutter with the blade re-ground.

This blade shape not only makes the cutting edge much more durable than the rather fragile point that the tool comes with, but it also centers the cut on the guide post of the tool better so that I am able to follow the edge and get a more predictable cut. I've basically converted the tool into a small gramil.

[sunburst]

Of course, this tool nor any other tool, other than perhaps CNC, can do the tight areas of the scroll, so no matter what, the scroll binding slots are the most time consuming.
After using my modified purfling cutter, chisels, gouges, knives, files, sanding drums, emery boards, scrapers, and whatever else did the job, my binding slots were ready to install the bindings and looked like this.

As you can see, I've only rough carved the scroll so far. I cut the binding slots to delineate the shape of the scroll as well as the spiral up to the central circle of the scroll, and once the bindings are installed and cured I'll complete the carving of the scrolls with the bindings as guide lines.

[sunburst]

I installed the ivoroid bindings using Duco cement mixed with acetone and taped them in place using Stewmac's rather expensive binding tape. I don't really like spending that much for tape, but I haven't found any other tape that has the combination of toughness and "stretchyness", yet it peels loose from spruce with so little danger of pulling up splinters, so it is the best tape I've found for bindings.
Here is the instrument with the bindings glued and the tape removed. It wasn't bound a minute too soon! I thought I was going to beat it to pieces against lamps, tools, benches and other shop items. This thing is huge! Turning it and spinning it around to work on various parts of it takes up an enormous amount of space, and items in that space don't usually move out of the way when they see the mandocello coming.
I'll let the bindings cure and shrink for a while before doing more work, other than installing the point protectors when I get the material for them.

[tree]

Tool geek observation: what is it about brass and dark wood in a hand tool that makes it such eye candy?

I dig the purfling cutter - looks almost like a mini marking knife with a guide. But I don't envy you cutting the ledge (and everything else you have to do) around the scroll . . .

[Bernie Daniel]

.....This thing is huge! Turning it and spinning it around to work on various parts of it takes up an enormous amount of space, and items in that space don't usually move out of the way when they see the mandocello coming...

Hilarious There is never enough bench space even for little things -- looking awesome! Takes you back to when giant mandolins wandered the earth...

[BradKlein]

...I've basically converted the tool into a small gramil.

Extra point for using the word, 'gramil' which I'd never seen or heard, although I've used what I called a marking gauge for many years!