Building a 13 Course Lute, Start to Finish, 13: Gluing in the Belly (After a Dozen Little Jobs get Done)

Hello friends, and welcome back.

In today's post I have a number of small and relatively unspectacular jobs to describe, all leading up to one big and quite spectacular job--gluing in the belly of this 13 course lute.

In our last episode, I glued and shaped the sitka spruce fingerboard spacer, and then made final action adjustments by slightly lowering the edge rib. Along the way, I checked the action by stretching out lengths of nylon fishing line from the bridge to the nut, using graduated wooden spacer blocks to measure string heights. Everything looked in good shape for gluing in the belly.

As I finished up the last post, I said I would have about a dozen little jobs to do before I could tackle the big one. That was just an estimate, not a precise count. So here's what I did--let's see how many there actually are.

1. Make a belly drawing.

This is a full-scale drawing of the belly done on a sheet of drafting paper. It's not a theoretical document, but a practical record of the belly as I've made it before gluing into the body. I first trace around the belly, and project the locations of the bars using a straightedge. Then I measure and record belly thicknesses and bar dimensions. I also include information such as the amount of curvature I have put into certain bars during gluing, the weight of the belly, and so on. On the right hand side, I've left space to write comments on the various thicknesses and characteristics of the materials I've used on the whole lute, such as the material and thickness of the ribs, the materials used for the bridge (and the weight of the bridge), and impressions of the soundboard gained through tapping and flexing throughout the joining and thicknessing processes. I also write down specific musical tones and overtones that I hear when tapping both the barred belly and the body, and any impressions I have about (as the case may be) the freedom, restriction, richness, complexity, loudness, balance, etc., of the sound of the belly as I tap it in various places, both on and off the bridge. This drawing is for my files, and I have one of every lute I've made.

Projecting the location of the bars.

Measuring and recording belly thicknesses.

2. Make and glue a label.

I have three lutes on the go, so I will need three labels. I use some medium-thickness watercolour paper, and a jar of black ink into which I dip a calligraphy pen, and just sit down and write labels for about 5 or 10 minutes. I am by no means a skilled calligrapher, so I just make a bunch and choose the ones that look best, that are clear and have a nice balance and energy. Nobody's going to spend too much time looking at my label, but I want it at least to be legible through the screen of the rose.

I make sure to stick it down at exactly the position of the rose.

3. Chamfer the front edge of the top block/fingerboard spacer.

This is a standard procedure I do for all lutes, and it is meant to assist a future repair person who might, at some point (far off in the lute's future, I hope) want to remove the belly. The chamfer allows a palette knife to slip more easily between the belly and the block/ spacer.

 Note that I don't extend the chamfer all the way over to the edge rib, but instead finish it a few millimetres away in a 'lark's tongue.'

4. Drill a pilot hole for a strap button.

I do this after the final action adjustment (i.e., after trimming the edge rib) so I can be sure to locate it a specific distance from the edge of the bowl. I make the hole big enough that I can fit a small reamer into it. (I'll fit the strap button after varnishing.)

5. Glue a paper patch over the top block/fingerboard spacer.

This is a piece of handmade paper that covers the top block/fingerboard spacer and extends a little way up the neck. The 'tongue' of the belly will eventually be glued down over it. During the life of the lute the belly will be securely glued, but should a repairer eventually need to remove the belly entirely, the layer of paper will make removal in this area much easier. I have had occasion to remove a belly that was not glued with this paper layer--that is, glued wood-to-wood--and it took a long time, was destructive to both the belly and the top block, and necessitated some careful rebuilding of the belly before re-gluing. It's much better to think ahead, and be kind to a future generation. (A good motto in all we do, in my opinion!)

I saturate the paper with glue and rub it into place--much like I did when I glued down the rose pattern, in in episode 6.

When the glue's dry, I feather out the edges of the paper with files and a small sanding block.

6. Make a caul to fit the top block/belly tongue.

With the paper layer in place and the edges feathered, the top block area is in its final shape. Now I can create a caul that will fit that area perfectly, and hold down the belly tongue securely when I glue it.

This is my top-block gluing rig, in two pieces. The top-block caul itself is on the right. It's a piece of jelutong that I've cut out to fit the area exactly, then carved to fit the countour of the fingerboard spacer/top block. I've covered it with a layer of cork, then added a strip of masking tape along the edges to make sure that it will press down the edges of the belly when I glue it in.

Here's what it looks like in a dry run: two wooden cam clamps supply ample pressure.

And a side view. 

I mentioned in the last episode that one of the things I needed to watch out for when shaping the top block and fingerboard spacer was whether the belly, with its arched upper braces, would fit closely, especially at the outer edges. Now I have my answer: the belly fits well.

Okay, I think I'm just about ready to go with gluing in the belly. Just a few more things to do before I start--less jobs to do than just a checklist of things that need to be in order.

7. Dehumidify the workshop.

This is part of my routine in the workshop everyday. Weather conditions are such that I need only keep my small space heater running on low to maintain a humidity in the low-40% range. Today it is at exactly 42%, which is perfect for the job I'm about to do.

8. Prepare the glue.

The night before gluing the belly, I soaked two normal batches of hide glue. They will both be ready for heating and use in the morning.

9. Give the bowl and belly a final brushing-out.

Just to ensure that no little bits of dust or wood shavings will be rattling around once the belly's glued in.

10. Tape the belly in place with masking tape, spaced approximately 2" apart.

The belly should fit exactly. I take one last look all the way around to make sure that the belly will fit down tight onto the edge rib. I also make sure (one last time) that the outline looks good, and that no ill-fitted bar ends are going to elbow out and make a bump in my beautiful shape.

11. Assemble all tools and materials on the work bench.

I will need: a soft pad (a folded camp blanket covered by a sheet of soft cloth) along the edge of the bench; the top block gluing caul assembly, including two wooden cam clamps; 1" masking tape dispenser, clamped to the bench edge; an electric iron, on a medium-high setting, along with a cotton cloth folded in four; hide glue warming in my glue pot; my glue brush and palette knife. I think I'm just about ready.

My glue, glue brush and palette knife. Note that I've cut off most of the knife handle, so that it's easier to use (and less likely to tip over my glue jar.) The glue, by the way, is very dilute: I've probably added twice as much water to it as I would for a normal batch of hide glue.  

And there is one more job to do before I can glue, bringing the number to a magic dozen:

12. Chose music to listen to.

This operation will take about a half an hour, so I need to choose the right tunes. Here's what seemed right today.

And so we begin. Most of the photos you will see below are from a staged series of dry-runs. Once I get started, it's nearly impossible for me to stop work to organize a timer shot, so these photos are the next-best thing.

Here's the view as I begin. I hold the lute in my lap, against the padded bench edge. The glue is close by, and just beside it, my tape dispenser is clamped.

Starting on the bass side, I locate the first bar above the rose, and from that point down toward the bottom of the belly, I lift the tapes. 

With my left thumb I lift the edge of the belly slightly, then dip the palette knife in the glue pot and get some glue into the seam. I work in about 4-to 6-inch segments; I don't want to slop a lot of glue in, only make sure that there is some on both sides of the joint, the belly and the rib edge. 

Here's another view of my dry-run demonstration. Once I have sufficient glue in the seam, I will pull down the tapes and reattach them, then add more pieces from the dispenser. 

As I work my way around the belly, I turn the lute in my lap, and hold it securely against the bench.

Here's a shot from the actual gluing process. I secure the glued area with a complete coverage of masking tape, but I leave the leading edge of the glued joint untaped so I can work a little glue back into it before moving forward.

Eventually I get all the way around the belly to the treble side, to the first bar above the rose (where I started gluing on the bass side.) Now I can lift up the belly tongue, and use the palette knife to spread glue under it and down each side to the point where I've already glued.

With the whole perimeter securely taped, I can now get my top-block caul in place and tighten up the clamps. I check for good fit and squeeze out around the top block area.

Finally, I run over the whole perimeter with the medium-hot iron on a folded cotton cloth. I don't want to press down with any force; I only want to apply a little extra heat to the glued joint.

And that's about it. It's pretty simple once all the prep work is done, and you get down to doing it. The belly is taped in place before the gluing begins, and you only work in small segments at a time, so there is no question of misalignment or movement.

Although it's a simple and secure process, there's a certain finality that I feel at this stage. It feels a bit like a capsule has been sealed, with all one's experience, knowledge and hopes for the future inside. So much preparation has been built-in to this point; all the work I will do from now on will be to bring it to fruition.

I'll see you again soon!