Archive for October, 2015

Building a Double Bass

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Beginning with the Design of a Double Bass

Baby Steps: Learning to Walk

I knew a few things from having built a previous bass, but I still lacked confidence. So when the International Society of Bassists had their recent convention/competition in Fort Collins, I attended and took a few photos, and tried to observe as much as I could, so as to absorb information I badly needed.

Matthew Tucker was there, which was another reason I wanted to attend. He and I built our first basses simultaneously, but he went on to excel at making basses, while I reverted to smaller instruments for the next ten years. I  kept telling myself I wanted to build another bass, and even bought wood and patterns, etc. but it is such a huge, daunting project that I never got started.

My first bass was a “gamba-cornered” bass, modeled after an instrument by William Tarr. Ironically, when I went to Ft. Collins, that particular bass was there!  Mine was only loosely modeled after that instrument, not a true copy, but I had worked from a book by Peter Chandler, and there were photos in the book of that bass, and, sure enough, it was at that show. I didn’t particularly care for flatback basses (still don’t), so I had modified the plans and made my “Tarr” model a carved-back bass, otherwise very much like his great bass. It was only my sixth instrument, and there were lots of things I wished I had done differently, but it played very well, and was moved to Illinois with the family for whom it was made, so I never saw it again.

Tarr-model bass

That first bass. Notice I didn’t even know what the little white felt things were for… 🙂

That first bass was a nice start, but I was pretty much “flying by the seat of my pants”: I did what the book said, and called the author a few times, to get more specific instructions, but when it was done I was amazed that it actually worked well…there was virtually no planning; just muddling along and plugging away until it was done. It had an “E-flat” neck, but I didn’t even know what that meant, much less how to achieve a “D” neck, which evidently is more popular. But the youngster for whom it was built was thrilled with it, and I am told that he is still playing it today.

Choosing a Design

I had bought several plans for famous basses, and may still eventually copy one of them, but Matthew Tucker filled me in on how to design a neck to be a “D” neck, and the ten years of building smaller instruments (2 cellos, five 5-string fiddles and a host of violas and violins) gave me some practical insight as to proportion, aesthetics, and varnish. So, after seeing all the makers there at the ISB convention, and seeing the prize-winners, I decided to actually give it a go, and design my own bass, aiming for a soloist bass, as opposed to an orchestral bass.

The orchestral basses tend to be big all over, and harder to access for repertoire work, though they sound great. The one I am designing will be smaller in the upper bouts, to make it easier to play, but still pretty full in the lower bouts, and deep in the ribs, for big sound.  I wanted a more graceful scroll than the one on my first instrument, so I designed that as well, and followed Matthew’s instructions to get a “D” neck.

I spent many hours sketching, erasing, and sketching again, using 1/4″ graph paper, so that when I finally came up with something I liked, I could more easily transfer it to “engineers grid paper.” It took two 24″ x 36″ pages taped together to get one sheet big enough to work with. I transferred all my sketches to the big sheet, then used a small, needle-point awl to punch through the paper into the door-skin (1/8″ plywood) of which I would make the actual templates. Then I cut out the templates, filed and sanded them to the exact smooth shape I wanted, and coated the edges with wood-glue to add some stability. (The thin plywood is pretty fragile, but inexpensive, so I tend to use it.)

I made the F-holes a good deal larger than some instruments have, hoping for better mobility of the bridge area, as well as easy flow for air.  The f-hole template was cut from thin clear plastic, flexible so that it can be formed around the front plate to transfer the shape.  Also, this will be a “violin-cornered” bass, as opposed to “gamba-cornered”. It is more difficult to build, but I like the looks better. 🙂

I already have the maple for back, neck and sides, and I ordered European spruce for the belly and bass-bar. All I really accomplished today was the completion of the mold template, the neck and scroll template and the f-hole template:

New Templates with sketches

New Templates with sketches and tools

But– the game has begun! Now I can use the mold template as I build the actual mold, get blocks in the mold, and shape the blocks to receive the ribs. One step at a time! I will keep you posted.

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5-String Commission Delivered

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Five String Fiddle Went Home

We (my wife and I) went to the home of the customers who had commissioned the Koa Five-string Fiddle. They received us graciously, and were thrilled with the new instrument.  We spent an hour or so visiting, playing the instrument, etc. and finally left to go back home.

The new owners graciously volunteered to lend me the 5-string Koa fiddle in April to show at the Marylhurst University Musical Instrument show. So, if you come to the show you can play the curly Koa Five-string fiddle.

Here are pictures my son took the night before we made delivery:

Front view

Front view

 

Bass side

Bass side

 

Treble side

Treble side

 

Back view

Back view

 

Bass side scroll

Bass side scroll

 

Treble side scroll

Treble side scroll

 

Back side scroll

Back side scroll

 

Front side scroll

Front side scroll

 

Bass side f-hole detail

Bass side f-hole detail

 

These photos were a lot better than the ones I took, so I thought some people might like to see them. If you want to see the fiddle in person, please come to the show. I hope to have a double bass done by that time, too, but we will see what I actually accomplish.

I will try to post progress reports on the bass project, too.

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5 String Progress Report #17: Finally done!

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Five String Progress Report #17: Finally finished, Set-up and Playing!

Fair Warning:

I got cranking on the task again, and did not take photos until the job was done.

The photos are at the bottom of the post, so if you want to skip all the narrative, you can scroll to the bottom, and just look at the fiddle.

What I accomplished was to:

  • Dress and polish the fingerboard
  • Install, file to final shape (including string grooves) and polish the nut
  • Install the sound-post
  • Drill and finish the string-holes in the pegs
  • Fair in the ends of the nut with the sides of the upper end of the fingerboard
  • Polish the saddle and endpin
  • Polish the “handle” portion of the neck one last time, and
  • Touch up the varnish around the saddle and other “dings”
  • Rub about 2-3 drops of shellac into the neck: just enough to seal and polish it
  • Fit the bridge
  • Fit the tailpiece
  • Install the strings and chinrest
  • Play that thing!

Dressing the Fingerboard

When we last looked at the fiddle, the fingerboard had been permanently glued in place, but it had not been planed to the proper curvature, either logitudinally, or tranversely. I want the completed fingerboard to have just enough “scoop” longitudinally, that there is nearly a string’s width of clearance under the center of the largest string. This seems to help prevent buzzes, among other things, and helps with intonation, I think. The transverse curve is set at a 42 mm radius. I have a steel template I made of scraper stock that is flat on one side, and has the 42 mm curve on the other. I primarily use it to check the curve, but I can also use it to scrape, and sometimes I do so. All the board-dressing has to be done with the nut removed, obviously. It is smart to mask off the scroll with something, too– tape rags over it, maybe, to prevent hitting it with the plane.

I began with the small “hammer-handle” curved-sole plane, reducing the surface in the center of the board; then a very small, cheap stanley plane, razor-sharp and adjusted for a fine cut. I checked every few minutes to see how the curve was developing. When it began to look reasonable, I switched to a scraper, working diagonally across the board, to get rid of the plane marks. Then I switched to a coarse Swiss file, held flat on the board, and working up and down the board until all the “dull-spots” had begun to be shiny. I check the curve again when it is all smooth, then switch to abrasives, using a hard plastic block that looks like teflon, but is some sort of high-density plastic they use at work sometimes. This was a scrap, and it works well for a sanding block, though a hard wooden block would be fine. It is about 3″ long, 1-1/2″ wide, and 1″ thick.

I started with about 100 grit, then almost immediately switched to 400 grit, then to 600 and finally 1500 grit. With each change, I worked up and down the board until all the board had the same look. After the 1500-grit work the board was very shiny, and exactly the right curvature in both directions.

Installing the Nut

The nut ultimately has to support the upper ends of the strings, just a scootch above the surface of the fingerboard: about the thickness of a good business card is ideal. bear in mind that every “non-open” note is actually touching the fingerboard, so the closer you can get to the board without touching it, the better. This does require that the fingerboard be perfectly dressed, without even the slightest humps or hollows, otherwise it will buzz.

I had already shaped the nut so that it was about a millimeter taller than the end of the fingerboard, exactly the width between the end of the fingerboard and the beginning of the pegbox cavity, and curved to perfectly match the top of the fingerboard. Also, the top of the nut has to “roll off” into the pegbox smoothly, so that there is no sharp break in the curve as the strings go over the nut toward the pegs. We are trying to avoid any unnecessary stress risers in the strings.

I glued the nut in place using the amount of hot hide glue that covered the end of a toothpick. It doesn’t take much at all. Some people only glue the nut to the fingerboard end, not the neck. In some ways that makes sense to me, but I am still in the habit of gluing to both surfaces. Probably I ought to change that: just think about it–the pressure of the strings is holding the nut immovably in place– the only reason you need the glue at all is so that you don’t lose the nut when you are changing the  strings. (Ah, well…next time, maybe.)

Soundpost

While the glue on the nut was drying, I fit the soundpost. I want the completed soundpost to start out about one post width behind the treble foot on the bridge, and pretty much centered on that foot, laterally. In addition, I want it vertical: parallel with the vertical edges of the end and corner blocks. so I remove the end-pin, shove my bi-focals as close to the hole as possible, and, using a bright light source, I maneuver the soundpost into the position I want it. Too tight is better than too loose, as I can keep trimming until the fit is perfect. I can’t put wood back, though, so if I make it too short, the game is over and I have to begin again. (I have done that many times. This takes practice, believe it or not.) A perfectly fitted soundpost is airtight on both ends, just tight enough that it will not fall over when you change the strings, and in exactly the right spot. I will share how I adjust it, though there are undoubtedly as many opinions about that as there are luthiers, so I expect many will disagree. The adjustment has to come after the strings are tuned.

String-holes in the Pegs

By this time, the nut was dry enough I could handle it without fear of knocking it loose, so I could drill the string-holes in the tuning pegs. I used a 1/16″ bit, in an “egg-beater” style hand-cranked drill, to pierce the pegs.

Knowing that the pegs will work their way deeper, over time, as they are used, I have deliberately cut the pegs just a tad short, so that as they work deeper, they will not stick out the other side of the pegbox too far. With that in mind, I also place my string-holes slightly toward the fat end of the peg, inside the box, so that it will not eventually disappear into the other cheek of the pegbox.

I mark the locations with the tip of my small knife, and drill them out, avoiding going through into the pegbox back. What I did this time was to drill part way, and then remove the peg, and complete the hole with the peg held freehand. A lot of luthiers make a drilling jig, that emulates the pegbox, and holds the pegs firmly, and is much more accessible while offering no danger to the fiddle. (I keep telling myself I need to make one of those…one of these days I will get around to it.) After drilling the holes, I dress the ends of the holes with a round file, so they offer less stress to the strings where they pass through the holes.

String-grooves in the Nut

At this point I felt confident that the glue had set on the nut, so I carefully measured and scribed the string grooves in the nut. Then I filed each groove, using an appropriately sized file. As I said before, I use the little tip-cleaning files available in welding shops. You have to make sure you are actually getting the file-type cleaners…the new ones are just twisted wire.

I cut each groove down until it seems the right height above the surface of the board, but I know it will require some fine-tuning once the strings are actually installed. I extend each groove over the curve, and aiming the direction I want the strings to go. I slope the outside two strings inward a little to keep the strings from rubbing on the inside of the pegbox cheek.

Final Polishing

I also file and scrape both ends of the nut, to fair them into the sides of the upper end of the fingerboard, then polish the sides until the joint is very smooth. I polished the saddle and the end-pin, until the ebony glowed like jewelry. I realize it will get dull later, but for now it looks great.

I went ahead and polished the “handle” portion of the neck one last time, using 600-grit and then 1500-grit. Finally, I used a tiny artist’s paint brush to touch-up the varnish any where it had been scratched or in any way damaged during installation of the fitting, and, applying a dime-sized dot of shellac to a rag (about 2-3 drops), I rubbed it vigorously into the handle portion of the neck to seal it against sweaty hands and to polish it so it glows. (Nice-looking fiddle!)

Fitting the Bridge

I no longer use sandpaper in cutting a bridge. I have finally gotten good enough at spotting what needs to be trimmed that I can achieve full fit without resorting to abrasives or even chalk-fitting. This is a job for a sharp knife, and a “calibrated eyeball”.

I begin by setting the bridge blank (I used a Milo Stamm bridge blank this time) on the belly of the violin, centered between the inner nicks of the f-holes. I position the bridge with the branded side toward the tailpiece (away from the fingerboard).

I tip the bridge toward the tail-block just enough to make the “south side” of the bridge perpendicular to the belly (at that point). Then I usually slide  a sharp pencil along the base of the feet on the south side, to establish the curvature of the belly on the feet, so I know where to begin.  When I am done, I want the back side (tail-piece side–south side) of the bridge to be perpendicular to the belly, and the feet to have achieved an “air-tight” fit in their respective spots. When I have managed that starting point, I can begin carving away all “excess wood” on the upper part of the bridge.

I carve using a very sharp, fairly large knife, to get the feet fitted to the top. To complete the fit, I sometimes switch to a very sharp, slightly curved scraper. Once the feet fit perfectly, I hold the bridge firmly in place, with one hand, and slide a pencil along on the fingerboard with the other hand, with the pencil projecting out far enough to scribe the curve onto the bridge. That line will not be correct, but it gives me a place to start. I usually raise up the center of the curve about 3 mm; the bass side about 2.5 mm; and the treble side 1 mm. I fair in the curve across the top, so that it is similar to the fingerboard but more sharply curved.

I trim the top down to that new line, or just above it a millimeter or so, and establish the string positions, making small notches for each string, in exactly the right location, but knowing that the height will be wrong. I then set the height using the strings. I install the tailpiece and all the strings, spacing them out across the bridge, in their respective slots, and measure the height of each string. I want about 5 to 5.5 mm on the C string, about 5.5 to perhaps 6 at most, on the G string, the same on the D, , a litle lower on the A, and about 3 to 3.5 mm on the E string. I check, calculate about how much to take off on each string, if any, then usee a string jack to raise the strings so I can remove the bridge. The string jack will also maintain tension while I work on the bridge, so I can just slip it back in and check the height as I work.

When the string heights are right, I complete the trimming of the bridge, removing all excess wood. I open the “kidneys” and “heart” somewhat, lower the knees, thin the bridge from front to back, so that the upper edge is about 1 mm to 1.5 mm thick. I thin the feet so they are about 1 mm thick at the toes, and thin the ankles appropriately, as well. I don’t like the look of a fresh-cut bridge, so I rub that fresh-white bridge on the back of my head, where there is enough oily scalp under the hair, to take off the white, and leave a thin oily film that looks a little more subdued.

At that point I tune the violin, and check the height of the strings at the nut. I loosen one string at a time, and file the grooves until the strings come very close to the fingerboard, then re-tune.

Adjusting the Tailpiece

This time I got lucky, and arrived at the correct adjustment on the first attempt, but usually I have to take the strings back off, and adjust the tailpiece. What I am after is to get the ratio of the vibrating string length to the “afterlength” between the bridge and the tailpiece to exactly a 6:1 ratio. In this case, the vibrating string length was exactly 330 mm, and the afterlength (measured from the contact point the bridge to the contact point on the tailpiece) was exactly 55 mm. Couldn’t be better!

Installing the Chinrest

There are many types of chinrests, made of many different substances. I have made them from scratch, and have bought ebony, boxwood, Rosewood, and bakelite chinrests. People have different tastes and needs (Allergies are a problem for some people, using some substances…Cocobolo is a bad one for some people; Rosewood for others.) I used bakelite, this time, on the theory that it is light, and will not dampen the vibration of the instrument very much. Besides, I have never heard of anyone having an allergic reaction to bakelite. But fittings are pretty easy to make, and if someone wanted a curly maple chinrest, or whatever, I would certainly make it for them.

Play-in, and Soundpost adjustment

I can’t prove that “play-in” really happens. Most players feel that something changes in the instrument over the first month or so of playing…and that it happens faster if one plays aggressively, loudly, and frequently. So, initially, I play a lot of double-stops, re-tune frequently, and play a lot of scales and songs that are simple enough I can manage them. (I only play by ear, and nothing fancy; Hymns, waltzes, etc., and a few celtic pieces thrown in…)

I adjust the soundpost to try to get the best balance from string to string, and the best quality of sound I can coax out of the violin. I begin by tuning very carefully, then I play the G note on the C string, for instance, and alternate between the open G and the G note on the C-string, listening to the quality of sound, and the relative volume, brightness, etc.  If one is significantly weaker (say, the C-string is weaker  than the G), then I fudge the soundpost very slightly toward the weak-sounding string. Usually just a tiny move is sufficient. once I have adjusted so that the balance is fair across all five strings, if I want it brighter as a whole, I can move the soundpost slightly north, etc. I still want it close to vertical, and still have to have that “air-tight fit”.

Over the next week, I will play it a lot, and keep checking the sound, the balance, etc.

Results?

This seems to have about the strongest C-string of all the five-string fiddles I have made. I don’t know if it is due to the Koa wood, or the special arching I experimented with this time. I really hope it is the arching, as I probably can repeat that, but may never get to work with Koa again. The only way to find out is to make another fiddle of some other wood, and duplicate the arching.

The balance is good across all five strings,and quite strong…definitely on the bright side. I expect that the hard heavy Koa wood, in thin graduations, affected that aspect of the sound. The sound is clear, even in higher positions on the bass strings. My anticipation is that, as it plays-in, the sound will open up a good deal more, and mellow somewhat.

Gotta do another one….

Here are the photos:

Finished Front

Finished Front

 

Finished bass side

Finished bass side

 

Finished Treble side

Finished Treble side

 

Finished Back

Finished Back

 

Bass side scroll

Bass side scroll

 

Treble side scroll

Treble side scroll

 

Back of Scroll

Back of Scroll

 

Front of Scroll

Front of Scroll

 

Lower

Lower “fleur-de-lis”

 

Upper

Upper “Fleur-de-lis”

 

 

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5 String Report #16: Adding the Fittings

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Five String Report: Adding Fittings

End pin

I failed to take any photos of this, but– it is pretty simple: I centered a hole on the center joint between the lower ribs, and centered between the plates. I drilled it first to 1/8″, then to 7/32″, and finally reamed it with a 1:30 tapered reamer… the same one I use for tuning pegs. I shaved the endpin blank to the correct size and taper using my peg-shaper, while gripping the endpin with a special homemade gripper. I shaved the endpin until it would just barely fit into the hole, leaving a little clearance between the collar and the rib surface. (There is a photo of it later on…)

 

Fingerboard:

In the photo below you can see some of the tools I used to fit the ebony fittings to the violin. Looking at the fingerboard, you can see the three “dots” of glue that secured it to the neck while I was shaping both the neck and the fingerboard. When I re-install the fingerboard, there will be glue on the whole faying surface. The carved out portion will help to lighten the fingerboard, and apparently helps tone.

Fittings waiting to be shaped and installed

Fittings waiting to be shaped and installed.

The black mechanism is the peg shaver I use. The block next to it is the gripper I use for end-pins. The endpin blank is right next to the shaper. The small ebony block between the shaper and fingerboard is the nut blank. The larger ebony block midway along the fingerboard is the saddle blank. The fingerboard has the shape laid out that I intend to carve away, and the gouges and scrapers on the right are the tools with which I did it.

So, one of the first things I did was to make sure my tools were sharp, then I went all around the edges of that trough shape, carving away small chips of ebony to produce a shallow trench all around the edge. Then I carved as best I could with the gouges, until I decided it was time to get the planes into the fight. The little Ibex plane worked well, but the little wooden homemade plane actually worked better, because it has a deeper curve in the sole. It was made of a small section of a broken hammer handle, a piece of scraper blade, and a threaded steel plate to adjust tension and hold the blade in place.

Fingerboard ready for installation.

Fingerboard ready for installation. This part took me about an hour. Ebony is hard stuff.

 

Saddle

Next I worked on the saddle: I cut my saddles with radiused front edges, so as to avoid saddle cracks, which are extrmely common in violin-family instruments…partly, I am convinced, because virtually everyone makes them with square corners, which adds a huge stress-riser to that location in the spruce. To me, that is asking for a crack. I try to avoid suich things.

Saddle footprint with curved front corners.

Saddle footprint with curved front corners.

Some luthiers try to avoid cracks by leaving a small gap on the ends…that makes good sense, too, but why not eliminate the “notch” altogether? Just my opinion…. Either way, you have to remove the wood of the violin front plate to receive the ebony saddle. I use a thin knife to slice through the spruce, and then a flat chisel to loosen the piece being removed. I set aside the piece in case it turns out I made an error of some kind, and need to put some back. It is a whole lot easier to match grain from the piece you just removed, rather than from some random piece of spruce.

Once the saddle fits the mortise perfectly, leaving a small gap on each end (about the thickness of a business card), I glue the saddle in place, and forget about it. Here is a photo of the finished saddle. I didn’t take photos while I was carving. I get pretty wrapped up in what I am doing and forget to take pictures.

Saddle and endpin

Saddle and endpin

 

saddle and endpin

Another view of the saddle and endpin. (Pretty ribs, huh?) Varnish touch-up still has to happen.

 

Pegs

The next issue was the pegs. I wanted them done before I installed the fingerboard, simply because I wanted to be able to set the instrument aside so that the glue under the fingerboard could dry, and not feel that I was being prevented from working.

I had earlier drilled pilot holes in the pegbox, so that I would have guides to help keep the holes perpendicular to the centerline. So I reamed out those holes, all to approximately the same size, using the same reamer (1:30 taper) as I used for the endpin.

Then I sliced a shallow groove next to the collar, on each peg, all the way around, using a very fine razor-saw, to avoid breaking off the collar. (Doesn’t always work, but it seems to help.) I shaved the pegs until they fit the holes, at nearly the right depth, then “greased ’em up” with peg dope, and worked them in, so that the holes and pegs fit perfectly. Later I trimmed off the excess length of each peg on the far side of the pegbox, domed and polished the cut ends, so they would look nice, and put the pegs back in place.

Saddle and pegs installed.

Saddle and pegs installed.

 

Fingerboard Installation

Last, I installed the fingerboard…I had marked ahead of time the exact location where the nut and fingerboard were to meet; so now, all I have to do is put the fingerboard exactly where it was before (against that line) and glue it in place. I positioned it using a single spring clamp and aligned the upper end as closely as I could, then aligned the lower end as well, and added a large spring clamp in that location. Finally, I re-adjusted the upper and lower clamps until both ends were perfect.

Then I removed the lower clamp, and, using a thin palette knife, I ladled hot hide glue into the space between the neck and fingerboard, sliding the blade up the neck as far as it would comfortably go, and replaced that clamp so that it squeezed out hot hide glue all around. I cleaned up the excess quickly, and double checked to make sure that the position was again perfect.

Then I removed the upper clamp, and repeated the gluing routine, but this time, as I cleaned up, I kept adding more clamps, removing a previous one, and wiping carefully, until I had four clamps in place and no glue drops where they did not belong.

Fingerboard installed with hot hide glue and spring clamps.

Fingerboard installed with hot hide glue and spring clamps.

That was pretty much the end of the day. My hands were tired and hurting, and I had other things that needed to be done. Much later, I got back and removed the clamps:

Side view with fittings.

Side view with fittings.

 

Back view with fittings.

Back view with fittings.

The nut will have to wait until the fingerboard has been planed and scraped to exactly the right curvature, and polished smooth. We call that “dressing” the fingerboard.

After that it will be “set-up” time.

My next post will show the finished fiddle, strings and all.

Thanks for looking.

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