Archive for November, 2018

Two Bass Bars

Please share with your friends!

Two Bass Bars

How I install bass bars:

The bass bar in a violin-family instrument serves to support the bass-foot of the bridge, and the bass-side of the front plate (also called the “table” or, the “soundboard.”) Without adequate support in the proper place anong that side, the bass tones will sound quite flabby and unconvincing. The following is only a description of how install the bass-bar, not telling anyone else how it ought to be done.

We always make the bass bar of European spruce, with the grain vertical to the plate; thus, flat-sawn to the bass-bar, itself. I begin by laying out two locations, one seventh of the distance from the center seam to the widest part of the bass-side edge at both upper and lower bout. That usually translates into about 15 mm off the center, at the widest point of the lower bout and 12 mm off center for the same place in the upper bout. I strike a line through those points , checking to see if it is far enough away from the inner eye of the bass-side f-hole to actually accommodate the completed bass-bar If it is not, then I move the line over a couple of millimeters, as needed, to gain clearance at the f-hole. Then I measure 40 mm inboard along the line from the upper and lower edges of the plate, to designate the end locations for the bass bar.

I cut the bass-bar blank to length, and plane it to the appropriate thickness, then hold it on the lines I have laid out, essentially perpendicular to what will be the plane of the ribs. I use a compass, set to the maximum gap at the bottom center of the bassbar, to scribe the contour of the plate onto each side of the bass bar. (Notice that, due to the compound curves of the violin plate, the two marks will not be the same. This is important.) Once I have both sides traced in accurately, I carve away the excess wood outside the line, to follow the line as closely as I can manage. I try to achieve a straight line between the two, regardless of where the two lines go, because that will follow the complex curves of the plate.

I double-check the bass-bar against the plate, and usually it is surprisingly close to fitting, at this point. So I use a strip of the paper-gauze tape available in pharmacies, about an inch wide, to cover the layout lines I had scribed into the plate, and then proceed to chalk-fit the bass-bar on top of that tape. The tape is very thin, so that I can see the lines through it (although I do trace them again onto the tape, to make them even easier to see.) But the tape is also so thin that, if I can get a perfect fit on the tape, when I remove the tape, I will have a perfect fit on the plate, as well, and no chalk residue to remove.

The hardest thing for me to learn in chalk-fitting, was to only remove the transferred chalk and the wood immediately under it, not the whole area. Frequently the culprit in an imperfect fit is actually quite a small area, so it is counter-productive to remove too much wood.

I chalk the tape, along the layout lines, and then press the bar into place, sliding it lengthwise a few milimeters back and forth to pick up some chalk;. I plane or scrape off the high spots where the chalk transferred, then try again. When I get a more or less full transfer of chalk from tape to bass-bar, I know the fit is acceptable. Then I carefully remove the tape, and (finally) glue and clamp the bar into place. Usually, I trim the bar a little, first, so it is nearly the correct shape on the top surface, so the clamps will fit more easily.

One bass bar is complete: the other has only been trimmed to make it easier to clamp.

One bass bar is complete: the other has only been trimmed to make it easier to clamp.

 

After the glue has dried and the bar is rigidly secured, I use finger-planes to trim the bar to the size and shape I want.

Beginning with a medium-sized finger-plane.

Beginning with a medium-sized finger-plane.

 

Finishing with a small finger-plane.

Finishing with a small finger-plane.

 

Final touch-up with small plane and scrapers.

Final touch-up with small plane and scrapers. The camera angle is what is making the two bars look so different.

 

Installing the top plates

So, the next task is to complete the inner edgework, and then install the top plates on the rib garlands. I plane a tiny bevel around the edge of the plate that will face the ribs; then file it to a curve, nearly quarter-round, flush with the outer rim of the plates. Then I position the plate on the garland as precisely as possible (sometimes things seem to have moved a bit, so I have to compromise a little.) Finally, I loosen a few of the spool clamps at a time and slip hot hide glue into the joint, using a thin palette knife. I clean up all around, so as to not leave glue on the outside of the violin.

Spool-clamps.

Spool clamps can look like these, or even more simple: sections of closet rod with all-thread bolts. There are a lot of possible options.

 

Finally, the plate is fully glued and clamped, and I wait for it to dry.

Guarneri copy top plate installed with hot hide glue and spool clamps.

Guarneri copy top plate installed with hot hide glue and spool clamps.

After the top plates are installed, I trace the European Maple back plates and cut them out. Here are the two garlands with the top plates installed and the back plates cut out:

Completed Garlands with plates.

Completed Garlands with plates.

 

Next stop will be arching the back plates.

 

Thanks for looking.

 

If you found this post helpful, please share with your friends!

F-Holes and Graduations

Please share with your friends!

F-Holes and Graduations

F-hole Incision and Final Arching

In my last post, I told you I would “talk about F-holes, next time”…and we are doing so. But final arching, as well as graduation have to be completed before we actually cut out the f-holes, so, first things first:

I lay out and incise the f-holes after the arching is (mostly) completed, but before beginning any graduations. (I had a few mishaps years ago, when I graduated first, and subsequently discovered that my plates were actually too thin where the f-holes were to be laid out. I learned from the error, and I check the thicknesses around my already-in-place f-hole incisions, before beginning graduation, now.)

I laid out the distance from the upper edge of each plate to where the bridge would go. That is where the inner “nicks” of the f-holes will go. I measured back from there to find where the inner edges of the upper eyes of the f-holes would go, and laid out not only that longitudinal position, but the lateral distance off center, to the inner edge of each eye. Then I repeated that process for the inner edges of the lower f-hole eyes, and I was ready to use a template to scribe in the actual perimeters of the f-holes. I simply aligned the clear plastic template (traced off the full-size photos of the original instruments) so that the inner nicks were on the bridge line, and the inner sides of both upper and lower eyes were at their correct locations. I pressed the template firmly, so that it followed the curvature of the plate, and traced with a very sharp pencil.

I try to bear in mind that the pencil line will actually be “inside” the actual footprint of the f-hole, and I will remember to adjust it later. For now, however, I incise the perimeter of both f-holes fairly deeply, so that the marks will not disappear as I complete the final arching. (In the photo below, I had also traced around the incision with a very sharp pencil, to highlight the cut, so I could see it from any angle. Otherwise it can be hard to see.)

F-hole layout and incision

F-holes laid-out and incised.

 

Final Arching

I have learned that arching is one of the most important factors in violin sound. I use two “markers” for determining the final arching.

The first: I can see that, when viewed from the side of the instrument (at least, the ones I am concerned with), the f-holes on the old master instruments appear to have the main stem nearly parallel with the plane of the ribs. I have no idea whether that is truly important as far as aesthetics, but, I have also observed that, when left to my own instinct (or lack thereof) as to proper arching, my f-holes invariably end up resembling an “S” laid on its side. So, it is a “marker” that tells me my arching is a bit “off”, if nothing else. That is why I incise the f-hole perimeters deeply enough so that I can adjust the arching to get the stems of the f-holes parallel to the rib-plane, and be fairly sure that, at least that part is better than it was before.

The second “marker” is even more mundane: I made “arching templates,” traced from the posters, so that I can actually check and see that my arching closely follows that of the old masters. It is fascinating to me, to see them drop into place, one by one, as I carefully plane and scrape away the last few “humps”. I know that many makers are convinced they do not need such a “crutch”, but I see it as only a tool. I would never claim to be able to draw a perfectly straight line by eye and hand alone, and I shamelessly use a straight-edge for such a task. Arching templates are the same thing, in my estimation. Whenever I use them, even on a plate that I thought to be very close to correct, I invariably discover that it was not as good as I thought it was.

Using arching templates and scrapers to perfect the arching contours

Using arching templates and scrapers to perfect the arching contours

 

The truly-completed arching is not terribly different than the rough-arching I had completed before incising the f-holes, but that sort of difference can make the difference between “acceptable” and “extraordinary” sound. When I first began using such templates, I immediately got a different response from players. They said, “This one is different! Whatever you did on this one, do it again!” (Okay…will do!) So…now I do it on every single instrument, and try to make each one better than the one before.

 

Graduation

What we call “graduation” is simply the process (and results) of carefully carving the inside arch to match the outside arch, leaving a specified thickness between, which could all be the same, or they could vary according to some sort of deliberate scheme designed to project well, or to give superior sound in some other way. Or it could be following a “general plan,” but, beyond that, be fairly random. There are all sorts of patterns and plans.

In this case I attempted (at least in a general way) to mimic the graduations of the original old master instruments whose pattern I was attempting to follow. (In case you have not read the previous installments, these two are to be modeled after the 1715 “Titian” Stradivari instrument and the 1735 “Plowden” Guarneri del Gesu instrument, respectively.) Their graduations are pretty thin, so this is a little scary, to me. I hope it works well.

I use a gouge to rapidly carve out the rough wood, until I am approaching the proper thicknesses, but then I switch to a toothed finger-plane for rapid, but controlled, wood removal. When I am getting close enough that I am fearful of going too far, I switch to a non-toothed curved-sole finger plane and carefully bring the thicknesses down to my target measurements.

Carving rough graduations

Carving rough graduations

 

Planing rough graduations, using toothed finger-plane

Planing rough graduations, using toothed finger-plane

 

Checking graduation using shadow-lines.

Checking graduation using shadow-lines.

 

Final check of graduations.

Final check of graduations.

 

Two plates with graduation completes.

Two plates with graduation completed.

 

 

 

F-Holes

The F-holes are pretty much “locked-in,” now; the only thing remaining is to actually remove the wood inside the f-hole lines. The first order of business is to remove the circular portions at the upper and lower eyes of each f-hole. For this, I use a tool called an “f-hole drill”, which my grown children purchased for me a few years ago. It  makes perfectly round holes, ranging in size from 5.5 mm up tp 10 mm in diameter, in 1/2 mm increments. I center a 3/32″ diameter hole in the center of the round portion of each eye, and then, using the correct bit, I insert the guide pin into that hole and gently rotate the tool to incise the hole, forst from the outside, and then from the inside, to prevent splintering, but completing the cut from the outside, so that in case any splintering does occur, it will be on the inside.

F-hole drill with cut-out plug from lower f-hole eye

F-hole drill with cut-out plug from lower f-hole eye.

 

All f-hole eyes cut: ready to remove remaining wood.

All f-hole eyes cut: ready to remove remaining wood.

 

Then I use a very thin, sharp knife to complete the incisions around the perimeter until the wood pops out cleanly.

Final f-hole wood removal.

Final f-hole wood removal.

 

Completed f-holes, ready for cleanup and final shaping.

Completed f-holes, ready for cleanup and final shaping.

 

I will continue to fine-tune the shape of the f-holes up until I begin varnishing, but, for now, they are complete.

The next thing will be the bass-bar in each top plate. The bass-bar supports the bass-side foot of the bridge, and the bass side of the plate. It is necessary in order to achieve the rich deep tones on the bass side of the violin range. So…next time: bass-bars!

 

Thanks for looking.

If you found this post helpful, please share with your friends!