Building a 13 Course Lute, Start to Finish, 9: Fine-fitting the belly, Locating the Bridge

Hi there, friends. This time out, as the sign says, I'm going to talk about fine-fitting the belly into the waiting body of this 13 course lute, and then locating the bridge. I've already done a 'rough' fit of the belly, by doing a preliminary trimming of the bar ends; now I'm going to get down to the business of giving this lute a sweet shape that corresponds to the outline that I drew on the belly a couple of episodes back, before I glued on the braces.

Just before I do, could I ask a small favour? I get a few comments and questions regarding these blog posts. Some--though very few--appear in the actual comments section of the blog; most have come to me either through social media, personal messaging, or email. The favour is this: if you have a question or comment, would you mind leaving it on the blog, in the comments section below? I'm happy to answer, but I would prefer to do it here, so that those questions and answers become part of the post, to clarify, correct, or otherwise comment on it--for the benefit of all readers.

(There's no reason to be embarrassed to ask a question, but if you'd rather not use your real name, please feel free to use a pirate name or your luchador alias. Your secret's safe with Google.)

On with the show.

As you might recall, when I initially cut off the bar ends I left them a bit long, on purpose. It's difficult to saw the bar off at exactly the right spot on the first go, so that the length of the bar and the angle of the cutoff are both correct. I leave them a bit long, so that I may trim them more carefully, using a small chisel rather than a saw.

To figure out exactly how much to trim them, I need to fit the body down over those bar ends. So, the first thing I need to do is remove the false belly, which I do simply by slipping a palette knife around the false belly edge, separating it from the rib where I originally spot-glued it with weak size.

I then set the edge rib carefully down against the ends of the bars. The photo below shows how I hold and view the work, though I haven't quite got the edge rib all the way down yet (that's one of the problems with using a camera with tripod and 8-second timer--I don't always get the event staged exactly as I want to.)

Imagine about one second into the future: the edge of the rib will be down against the belly, and the ends of the bars will be resting against the inside surface of the edge rib. I can then take a sharp, soft pencil, and make a mark on the belly, right against the rib, opposite each of the bar ends.

Please keep in mind that during this process, I'm not attempting to press the entire outline of the lute down over the bar ends (since the all the bars are over-long, it won't actually fit.) Instead, I do it in three sections. In the photo above, I'm working with the bass side. When I've made marks for all of the bar ends there, I'll turn everything around and mark the treble side. Finally, I'll work with the bottom of the body, and mark out the bar and tab ends there.

Here's a well-focussed photograph of my knee. Actually, what I meant to show here is how I hold the edge rib against one of the tabs on the bottom of the belly while I make my mark.

Here's what I get when I lift the body away--a pencil mark outside the drawn body outline that shows me exactly how much I need to trim this tab. 

And so I trim it, using a small chisel (1/4", with the handle cut off--perfect for small operations like this.) On the upper left corner of the photo, sitting on the edge of the bench you see a little jar of water and a brush: if I dab the end of the bar with a bit of water, the chisel cuts through the end-grain a lot more cleanly and easily.

When I get close to the outline, I start fitting the body down all around and looking carefully at the way the edge ribs curve. I want a smooth outline, so if I see a bar end that needs a little trimming, I'll take the time to do it. (Even a small adjustment can make a big difference to a graceful shape.) I also carefully flex the edge rib against each bar end, to feel whether the angle of the bar-end cutoff matches the true angle of the rib.

When the bar ends are trimmed and the outline looks good, I tape the belly securely into the body with masking tape. I make sure at this point that I've really located the belly carefully, by matching body and belly centrelines at the bottom, and neck edges (marked on the belly) at the top.

Now I'll move onto the next step in the process: locating the position of the bridge on the belly. I want to do this very accurately, because I'm finding and marking the exact spot where I want to glue the bridge.

Most of the time during the working process, I protect the sharp veneered edges of the neck by covering them with masking tape. However, right now I want to see the edge of the neck clearly, because that's one of the crucial references I use to locate the bridge. I've rolled back the masking tape, and there it is.

When I originally lay out the shape of the lute on my working drawing, I have a very clear idea how far I want the first string to lie from the edge of the neck (which, essentially, is also the edge of the fingerboard.) This distance is very important for the playability of the instrument--and anyone who has ever tried to play a lute with a first string that's too close to the edge of the fingerboard will know what I mean. The distance can vary a little bit, according to a few factors--the length of the neck, for instance, or the preferences of a client who's a very experienced player--but whatever those factors are, I want to have them worked out completely before I start building the lute.

So, I have the edge of the neck, and I have the position of the chanterelle in relation to it. This means I should be able to run a straightedge down that line, and somewhere along it will be the location of the first course on the bridge. But where? And what will be the angle of the bridge in relation to the first course?

The clearest and most foolproof way for me to find this out is just to set my layout drawing down on top of the lute, and see how things match up.

The drawing is done with 4H pencil on drafting mylar, and shows the positions of the neck edges, the first course, the bridge, the rose, and the body outline.

If I've done my work carefully so far, things should line up pretty well. The neck angle is good, the location of the rose is very close, the belly outline is fine... I should be able to just go ahead and mark. (If on the other hand some crucial piece of alignment is off--for instance, the neck angle's not quite where I want it to be--then I need to move the drawing around a bit, to compensate, making sure that the crucial relations of the neck edge and chanterelle are maintained.)

The rose centre and the bottom of the belly are two reference points I use to locate the layout drawing.

Using the working drawing to mark the position of the bridge allows me to get the correct angle of the bridge, which is tilted slightly upward on the bass side. 

Here's how I mark: a pin prick right through the mylar, at exactly the point where the chanterelle meets the glued front edge of the bridge.

I make another careful pin mark on the bass side of the 13th course, at the bridge's glued front edge.

I tattoo the pin pricks lightly, with a sharp, soft pencil.

And there it is--one of my two bridge location marks.

Now all I need is a bridge to glue there--and making that will be the subject of my next post.