Mandocello build thread

[Tyler K]

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

That's what Mike Marshall always says right? It's a good one..

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I have some 2 inch square pieces of 1/4" thick ivoroid that I have been using for point protectors on mandolins for several years. Obviously, I can't cut the needed 2 1/2"+ point protectors I need for this mandocello from a 2" square, so I had to get this rather expensive piece of plastic.

It is a 2" by 4" piece of ivoroid (I started to cut it before thinking to snap a pic), so I was able to get the two pieces for the point protectors.


I used bone for point protectors for years, but I concluded that ivoroid is better because of several reasons. Finish chips off of bone pretty easily, and the points do take some lumps. The bone piece itself can be knocked off of the mandolin fairly easily because the material doesn't "give" like plastic. Dyes soak deeply into bone so it is difficult to keep clean while staining the mandoln. Ivoroid can be solvent welded to the bindings and the joints can be seamless. The color of ivoroid matches the bindings exactly, and so forth.

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To install the point protectors the first step is to cut away the wood of the corners between the bindings... at least, remove what's left of the wood after banging the points against things in the shop.
I squared the corners to the rim and filed/sanded the sharp edges to a more comfortable edge, then marked for the cut using a compass.

I like for the protectors to both be the same width and for that width to be about the same as the width of the binding.

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I simply cut away the wood of the corners with a pocket knife. As you can see, I left little tabs of wood to protect the binding from the knife blade. I removed that wood last.

I used a chisel to cut the binding for the dovetail shape of the point. I thought I had a picture of that but I can't find it. It will show up later.

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Using a chisel and a file, I fit the ivoroid protectors into the dovetailed bindings.

I did some preliminary shaping of the pieces before installing them to save some time and work later, but still left plenty of material so that the position of the point when the dovetail tightened was not critical.

I glued then in place with ivoroid mud (ivoroid dissolved in acetone) and a dab of Duco cement just to help keep things from drying too fast as I was pressing the points in place.

I taped the points in place to let them cure.

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While I was doing that, I was also working on the extender piece that goes under the part of the fingerboard that extends over the body of the instrument. I grabbed a piece of spruce scrap and roughed it to this shape.

I began the process of fitting it to the instrument by chalk fitting the glue surface. It is glued directly over the head block and the contact area is about an inch wide.

The extender will be separated from the riser black by .060" binding. I thinned these binding scraps to about .055" and used them to position the extender for fitting. This helps assure a tight fit later when the ivoroid is installed and the extender glued.

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After getting a good fit I was able to thin the extender to near it's final size and lay the fingerboard over it... but first I had to be able to securely place the fingerboard on the neck in it's exact position. I lined up my center lines and clamped the 'board in position...

...so that I could drill these little holes...

...for these little brass pins.

The pins serve to positively locate the 'board, and they will also align it later when I glue the 'board. (There are two pins in two different fret slots, I just took a picture of one.)

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With the board pinned in place, I could draw the shape of the extender...

...then cut it out using the bandsaw.

I use spruce for the extender because of the high stiffness to weight ratio and because it has the same wood movement characteristics as the top to which it is glued. I get a slight weight saving compared to the traditional hardwoods like maple, rosewood, or ebony, and I get a glue joint with less movement and stress when humidity changes cause wood movement. The extender to top glue joint is important structurally because of the constant pressure on the joint from string tension, so I want a strong, stable joint.

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After further shaping of the extender I made a tapered clamping caul to install it. I have one of these for mandolins, but it just seemed too small for this, so I made another. I clamped the extender to the tapered caul and drilled two holes through the extender and into the caul.

I then put the extender in place and drilled through those two holes into the surface of the top.

The holes are for toothpick dowels to positively locate the extender for gluing. I also use toothpick dowels to keep the caul in position during gluing and clamping. Now I can pin the extender in place and reduce the thickness to near final thickness, so that the fingerboard surface is straight from the neck onto the extender.

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Meanwhile, I still have this bit on binding to deal with at each side. I cut the binding with a razor saw and a slim file until a piece of .060" binding will just press into position.

I have a couple of strips of 1/2" wide ivoroid. I scored and broke off a couple of small sections to fit between the riser and the extender.

1/2" is not wide enough to do the job here without a little creativity, so I shaped the pieces and put them in like this.

I believe some guides call for a continuous piece of plastic here, but there are reasons that I don't do that. On reason is, it is not easy to get the edge of the riser and the end of the extender both perfectly straight every time, and with the gap in the center of the plastic piece perfect straightness is not important for a tight fit at each side. The main reason, however, is shrinkage. Plastics tend to shrink differently from wood, and a continuous piece can later pull in or bulge out after finishing resulting from shrinkage. That is much less likely to happen with two pieces.

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I heated up my hide glue and glued the extender in place. As you can see, the tapered caul makes it so that the clamps are aligned for good pressure. The contour of the back would cause problems with a non-tapered caul. The taper also helps the clamps direct a little of their pressure toward the riser block to tighten the pieces on the binding material.

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After the glue dried I removed the clamps and flooded the binding pieces with acetone to "weld" then in place.
Attachment 159633
As I wait for corners and these binding pieces to cure, it looks like this.
Attachment 159634

[sunburst]

I realized I forgot to show you what the extender looks like.
I've never liked the look of an extender that hides back up under the end of the fingerboard, especially when it is obvious that no effort was made to make the thing presentable, as if it can't bee seen at all. I prefer an extender that sort of looks like an extension of the neck. One that extends all the way to the edges and the end of the fingerboard, and is finished to match the instrument.
Attachment 159635

[Timbofood]

I know I've said this before but, thanks John, this has been so much fun for even a non builder to watch progress! All the little things that go into making these fascinating instruments explained and illustrated so nicely! Thanks again.

[sunburst]

With the extender glued in place I milled (sanded) the whole top surface of the neck/extender straight and flat, then sanded a little bit of drop-off from the 12th 13th fret area to the end of the extender to get the surface ready for gluing the fingerboard. That flattened the bits of binding that protruded.

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I also flattened and refreshed the glue surface of the underside of the fingerboard.
I've found that hot hide glue can draw color from the dark wood of a fingerboard and glue squeeze-out along the bottom of the fingerboard binding can leave a dark line, so I started sizing the underside of fingerboards with a wash of dilute hide glue.

The glue wash dries pretty fast, and when it's dry it only takes a few strokes with a scraper to remove any lumps or uneven areas so that the glue surface is flat and smooth.

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The drop-off that I mentioned is the reason for using two clamping cauls to install the fingerboard. One has holes to accommodate the brass pins that position the 'board. As you can see, I've used this caul before and that is why it has several holes in different positions. Both cauls are slightly over-radiused so that they apply pressure mostly along the edges of the 'board.

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After a dry run or two, I warmed the neck and the fingerboard for a little extra working time, applied hide glue and quickly clamped the fingerboard in place.

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Here's the glue squeeze-out after drying and removing the clamps and cauls.

This shows that I left the neck just a little wide. That allows me to adjust the board to the center line if needed without running into trouble on one side or the other, and it allows me to shape the sides of the neck to blend the bindings into the neck shape.

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After filing/scraping/sanding the edges of the neck down to the bindings I was able to see what my glue line looks like. It came out nice and clean looking.

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A little work with an incannel gouge...

...followed by some work with a half round file, and the riser and extender are ready for sanding.

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With the last two frets installed into the slots where the brass pins were...

...I'll wait a little longer for the corner protectors to cure and shrink before starting to scrape and file the bindings and begin sanding the instrument to prepare for finish.

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Bindings have cured for a while and I've carved the edge of the top and back of the scroll to the chosen binding width. I'll continue carving the scroll. I've left it very rough-carved until now. The bindings now determine the outline of the scroll curve, and the rise of the edge of the scroll from the rim to the scroll button. That rise determines the ramp of the crest of the scroll from the top and back to the scroll button.
It is difficult to see, and even more difficult to photograph what I'm looking for here. A want the ramp of the crest to follow the upward sweep of the binding, but not exactly. It's just an eyeball thing. I tried to standardize it early on but found that that didn't work for me, so I have to judge it by eye each time I carve a scroll.
The line I'm looking at is the line you can sort of see in the top and back against my improvised black background. Not only do I want that ramp to be aesthetically pleasing but I want a reasonably close symmetry between the top and back.

I got that line by carving, turning, looking until the line looked good from all directions.
Now that I have said "good enough" on that, I have established the scroll ramp and I can put the curve of the crest anywhere I want to as long as it lies within the flat produced by the establishment of the ramp.
I like for the scroll to display a constant convergence from the outline of the body all the way to the scroll button. That includes the outline of the scroll itself, the space between the scroll and the button, area between the crest and the outer binding as well as the area between the crest and the inner binding. It would seem that that would dictate exactly where the crest would be located, but it actually allows quite a bit of leeway, so I generally have to draw, erase, re-draw and fine tune the line for the crest of the scroll until I finally declare it "good enough". This one turned out like this.

I drew the line on one side then transferred it to the other in order to maintain symmetry, even though we can't see both sides at the same time. I guess it's the same reason we don't put two different kinds of hub caps on each side of the car...

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The parameters of the scroll are now outlined and all I have to do it connect the dots, so to speak.
I used gouges, knives, chisels, planes, scrapers, and any tool that did the job to carve between the bindings and the crest.
Attachment 159776Attachment 159777
I can still massage the crest from side to side a little as I continue to carve, so if the line doesn't look quite right to me I still have the chance to improve it.

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I planed the bindings down in width. I used 1/4" bindings rather than the 3/16" i usually use on mandolins, but I didn't want them to be fully 1/4" wide, just potentially a little wider than 3/16" because of the size of the instrument.

A curved scraper reestablished the re-curve into the binding and started to blend the scroll carving into the plates.