Wet down the wood,to raise the grain and accentuate “problem” areas
I wetted the whole bass down with coffee, mainly to raise the grain a bit, but partly to add a little color to the white wood of the Sitka spruce belly. The Oregon Big Leaf Maple is already pretty colorful.
Back plate, wetted with coffee.
Then I turned the lights off in the workshop and went over the whole bass, inch by inch, with a small flashlight, held at a low angle, to make shadows wherever there was a discontinuity in the surface. As I located them, I scraped or sanded away the problems, before moving on. It took quite a while, but I was pretty happy with the outcome.
Mineral Ground
The next step is to coat the wood with a mineral ground: a suspension of extremely fine particles of gypsum in water is what I use. I brush it on, one section at a time, rub it in vigorously, to get the tiny particles into the pores of the wood; then rub off any excess, with a rag. It always looks as though I took all of it back off, until it dries.
Mineral ground in progress; sides nearly dry; back only begun.
Mineral ground continuing: Back is 2/3 complete, and beginning to dry.,
Mineral ground complete on back and sides of bass. Drying rapidly.
After the ground is fully dry, I sand all over with fine abrasive, to remove any dry patches of excess mineral. There will be very small discontinuities that have been filled by the mineral ground: this is desirable, and I am not trying to remove those places.
When the ground dries, the bass will be stark white, but when I apply the sealer, to lock the mineral particles in place, the mineral ground becomes completely transparent, permanently. It will never be visible again.
So, here is the bass, with the gypsum fully dry, mounted in my varnishing fixture, and ready for the sealer:
Ready for sealer.
Sealer
I am currently using rosin dissolved in turpentine and alcohol as a sealer. The liquid (alcohol first, then turpentine) evaporates, leaving the rosin in the pores of the wood. When dry, this helps prevent the varnish from soaking into the wood, so as to minimize the sound-dampening effect of excessive varnish penetration.
This is the part of finishing I like best: it seems almost magical to see the stark white of the mineral ground disappear instantly and permanently as the sealer permeates the gypsum and renders it transparent, so that the beauty of the wood is revealed.
I begin by sealing the front plate.
Then I rotate the bass in the fixture and seal the ribs.
Then I work on the back plate, and continue…
Until the whole thing is done! Here is the front view.
And here is the back!
After the sealer is dry, or just before it is completely dry, I rub down the surface of the wood with alcohol, to pick up any rosin that may have remained on the surface. When the sealer is fully dry, I go over the whole surface, lightly, with fine sandpaper, to pick off any bits of wood fiber that may have raised during the ground and sealer process.
Varnish plan
I always begin with a yellow varnish: I like the way it shines through the darker pigmented varnish when all the finishing is complete. In this particular case the maple was dark enough that even the yellow varnish will end up looking pretty dark. So, though I will still begin with the yellow, I will have to add a good deal of darker varnish on the front, to balance the color with that of the back. This is just a type of “Judgment call” that the maker must always consider when finishing an instrument. As I add coats of varnish, I will pay attention to which areas need darker varnish, and which could use yellow or clear varnish.
The last time I posted, I had temporarily installed the neck, and (I thought) I had glued the neck heel root in place, as it was to be a permanent part of the corpus, glued to both the neck mortise and the back button.
So the bass looked like this:
Bass with temporary neck set.
Side view, showing neck heel break-away joint.
The heel root looked like this:
Heel root positioned and glued to mortise, using hide glue, with paper break-away joint.
I was so confident that everything was right, that I even sawed off the excess heel root, visible in the above photo, and planed it flush with the back of the neck block, in preparation for installing the back plate. But! When I broke the paper “break-away joint” (see the above photo) the heel root gently let go of the mortise and was completely loose. (Rats!)
It turns out that hide glue doesn’t stick to carbon fiber plate! Ok… so I had to start over, and this time glue it home with epoxy. I put a plastic bag around the neck heel to protect it, coated the heel root with epoxy on the bottom and two sides, and slid it all back into place, this time bolting the neck in solidly, and clamping the heel root tightly against it. It all worked this time.
Beginning the purfling of the back plate
While the epoxy was curing, I decided it would be a good idea to at least install the “purfling weave” portion of the back plate purfling, before installing the plate. I figured it would be easier while the plate was still loose. The reason I wait until the back plate is installed to do the rest of the purfling, is that the corpus often changes shape a little when the mold is removed, so I can’t guarantee that the overhang will still be the same. If I have already installed the purfling, then I am stuck: but if I have not, then I can maneuver the overhang to being as close as possible to what I wanted, and install the plate, then plane away excess all around until the overhang looks right again, and finally put in the purfling so that it looks as though everything just worked out right, to begin with.
Cutting the slots for the lower purfling weave on the back plate.
This is a weave that I came up with for my very first five-string fiddle and which I have tried to incorporate on all my subsequent five-string instruments. It is just a modified “fleur-de-lis”…nothing really special, but I like it. I use the same design, upside down, in the upper end.
Picking the waste wood from the upper purfling weave.
Upper weave slot nearly complete.
After cleaning the slots out, I used heat and water to bend the purfling strips to fit the curves of the weaves, and glued them in using hot hide glue.
Both purfling weaves completed on the Oregon Big Leaf Maple back plate.
I planed the weaves flush with the plate after they were dry, using a gouge, a small finger-plane, and a scraper. You can see the beginning of the rest of the purfling slots, how they will connect to the weaves.
Purfling weave planed flush.
Closing the corpus
I finished scraping the interior and then laid the corpus onto the back plate, positioning it carefully, adding spool clamps, and constantly checking the overhang all the way around. When everything was as close as I could get it, I removed a few clamps at the bottom block, used a thin palette knife to ladle in the hot hide-glue, and replaced the clamps, tightening them securely. I added more clamps over the glued area, then repeated the process for the next section on either side of the bottom block, and worked up around the sides that way: removing clamps, inserting glue, replacing the clamps and adding more…until it looked like this:
Closed Corpus.
I still had not put the magnets into the cover plate, because, when I added the reinforcements to the cover plate, it changed the curvature, and it no longer fits cleanly into the access port flange. (Rats, again!) So I kept wetting and clamping the cover plate in different configurations until I got it to a close fit, then I added the magnets.
Here are the magnets in the cover plate.
Annnd… it turns out they are too weak. (Sigh…) I will have to order some bigger magnets after all.
At any rate, I was now ready to correct the overhang all around, and begin the final purfling.
Overhang corrected, beginning final purfling.
Tracing in the slots for the final purfling.
The bottom end of the back plate has the same design.
Carving the Channel
After the purfling was completed, I still needed to trim back the purfling and carve the plate channel. This involved marking the edge crest all the way around, about 2 millimeters inside the outer perimeter, and carving the channel to barely touch that line. I used a sharp gouge, in the manner of a drawknife, to carve the channel, then used a riffler file to smooth the outer curve, where it meets the crest line.
Using a gouge as a drawknife, to carve the channel.
(I actually made a very short video of how this works, but I was unable to successfully link it to this post. Sorry.)
After the channel was complete, it was time to begin final edgework:
Beginning final edgework on back plate.
And the same for the front plate.
The goal is to make sure that the edge contour is correct all the way around, and that the plate channel fairs smoothly into the surface of the plate, without ridges or lumps. Getting the light at a low angle across the plate makes shadows which will show me where the lumps and ridges are so I can scrape them away.
Using shadows to complete edgework.
It suddenly occurred to me that my bass-varnishing fixture requires that the end-pin hole be drilled, so I drilled the endpin hole but did not ream it to the taper it will eventually have. On smaller instruments I usually varnish before drilling the endpin hole, so that there is no likelihood of causing sags or runs where the varnish brush touches the hole. But on the bass, I have to have that hole as a place to attach the support for varnishing. (I can’t hold the bass in one hand, and the brush in the other, as I can with a violin!)
End pin hole drilled.
And, that is pretty much where it sits, for the moment! The bass is ready for final varnish-prep, which will involve wetting down the whole surface to raise the grain, so I can sand it smooth again, then repeating until the grain no longer responds to moisture. Then I will rub in a compound to add color to the wood itself (not a stain, which might “reverse” the grain colors) and a mineral ground to close the pores in the wood. Finally a sealer locks in the mineral ground, and I will be ready for varnish.
So there is the bass corpus, ready for final varnish prep!
Five string double bass corpus ready for varnish prep.
One of the problems with creating a double bass whose neck is removable for traveling is that there has to be a way to connect and disconnect the neck. Thus you have a choice– will the fasteners be visible from the outside, or hidden inside?
I have seen several examples of both, and I really prefer the hidden fasteners approach. BUT! That also mandates that there be a way to access the interior to tighten or loosen the fasteners. I have chosen a 3/8″ diameter bolt (tensile strength exceeding 5,000 pounds) and a large flat washer embedded in Epoxy on the inside of the neck block. The bolt extends through the washer and the neck-block and engages the threaded insert in the maple wood of the neck heel (see below.) So…the next step is to consider a side-access port through one of the C-bout ribs,
Threaded Insert in the heel of the removable neck.
Access port
I chose to make the access port through the bass-side c-bout rib: the player will reach up through the port with his or her right arm to access the single bolt in the neck-block. As an added bonus, the soundpost is also easily accessible, as it will surely need to be re-positioned after having the bass apart for travel. (In fact, it is so nearly guaranteed to be loose, that I intend to provide a pocket in the instrument case for the soundpost, as well as the bridge, the tailpiece, and the neck assembly, etc. That way there is no question: as you reassemble the neck, you will also re-set the soundpost, after the strings are on, but before it is up to tension.) Finally, as another luthier pointed out, if there is ever repair-work to be carried out inside the bass, this access port makes it a much simpler task, thus saving money and time.
So: how to carry out the access port plan? I positioned the proposed hole on the bass-side c-bout rib, roughly centered, and laid out a 5-3/4″ circle. I cut out the circle using an X-acto knife, then smoothed the cut edges with a file and sandpaper. I wanted to use that piece for the closure, as well, so I couldn’t afford any damage to either the rib or the cover plate.
Side access hole laid out.
Initially, I had thought I would employ a drawer-pull-type handle as a means to open and close the access port, but I didn’t care for the looks, so, after further reflection, I chose to make a simple “finger-hole,” instead. I reinforced the single-thickness of rib-stock with two more, especially near the center, so that the rib would be stronger, and so that the edge of the rib where the finger contacts it will be 6mm thick instead of 2 mm, thus much more comfortable.
Proposed access cover plate with pull-knob.
Side-access cover plate with finger hole.
I reinforced the actual c-bout rib by adding a second thickness of ribstock to the entireinside of the existing rib, and I cut a slightly smaller hole in it so that the closure plate had a shelf to rest against. Also, this is the surface into which the neodymium magnets will be inset, to hold the closure plate in place.
Side access hole with reinforcement plate inside and neodymium magnets.
(I realize that the above photo looks a little as if there were a plexiglass cover on the hole, but those are not reflections: you are looking through the hole at some pads behind the bass body. I was using the pads to protect the front plate, earlier.)
I added the reinforcement to the cover plate and sanded the interior of the finger-hole to be very smooth.
Reinforced cover for side access port, with holes for neodymium magnets.
Cleaning up the interior
While the glue was drying on all the above assemblies, I took the time to complete the shaping of the blocks and linings, so as to be ready to close the corpus, once all the interior work is done.
Planing the ribs to shape.
I used a knife a gouge and a small plane to shape the linings and blocks. Then I used a scraper to ensure that it all was acceptably smooth.
Shaping the blocks.
Neck Set
I had checked and re-checked the fit of the neck-heel into the mortise in the neck-block, until all the measurements were correct, and then I had drilled a pilot hole through the neck-block into the neck heel. That established the position and range of both holes, so that when I drill for the insert and r-drill for the bolt, the holes will still be in line with one another. I bedded the large plate washer in epoxy on the inside of the Sitka spruce neck-block, so that the bolt would not be able to gradually wear a hole deeper into the soft spruce.
With the neck temporarily in place, I could check to see how much of the excess neck-heel “root” would have to be sawn off and planed flat. You can see, also, that I had glued the heel-block “root” onto the neck-heel proper, using a sheet of paper between them as a “breakaway” layer, so that when everything was correct, I could easily pop the neck free from the root.
Temporary neck-set.Close-up photo of the paper breakaway joint.
As it turned out, hot hide glue does not bond well to carbon-fiber plate. So, after I discovered that the neck-root was actually not glued home, I was forced to choose epoxy as a final bond for the portion of the neck that is intended to remain permanently in the neck mortise. I don’t like doing this, as epoxy is not reversible, but there was no viable option. After making that choice, though, I took a sharpie pen, and wrote, inside the mortise, a notice to any later repairers, that those three joints (bottom and both sides) at the neck root are epoxy. (Sorry)
But I can put the neck on and take it off and put it on again, and it fits correctly, and all the measurements have remained correct.
And it is looking pretty good:
Neck set complete.
Next time we will talk about the final work before closing.
There are five measurements to consider in setting a neck on any violin-family instrument:
Obviously, the distance between the nut and the upper edge of the front plate is a critical measurement. One has to know what is required for the instrument in question and make a mark on each side of the neck heel, as to how deeply it is to be inserted into the neck block.
The height of the overstand (distance between the top edge of the front plate and the joint between the fingerboard and the neck.) This measurement is taken from the front of the upper edge of the front plate, right beside the neck, vertically, to the top edge of the neck, proper (joint with the fingerboard.)
The last three are all angles: The plane of the “floor of the neck mortise” must be perpendicular to the centerline of the instrument, and the plane of the bottom end of the neck, proper, must be perpendicular to the centerline of the neck, laterally. If these are both correct, then the fingerboard should project directly along the centerline of the front plate. Any lateral variance from centered is not good.
The centerline of the neck mortise, from front to back, must be perpendicular to the plane of the plates, laterally, so that it literally “connects” the centerline of the back plate to the centerline of the front plate. Simultaneously, the “footprint” of the neck heel should be bilaterally symmetrical about the centerline of the neck heel. The result should be that the plane of the neck face (when viewed from the scroll) should be parallel with the plane of the plates. (No “twist,” or “roll” in either direction.)
Finally, the “Projection angle” should be such that the height of the “projected fingerboard angle” should be at the appropriate height for the instrument in question at the bridge line. (This can either be literally measured as a projection height at the bridge line, or, if you know how high the end of the fingerboard will be if all other factors are correct, you can simply measure it there. The danger in this is that if the other measurements are not quite right, and you simply measure the height of the end of the fingerboard, then the projection angle will be wrong, and you will not discover it until it is too late to correct it. (Ask me how I know!)
Planning the Neck-Set
In the case of a bass, with a removable neck, as well as all the other enormities of a double bass (as opposed to the smaller instruments) I had to not only consider the five measurements listed above, but consider how to achieve those angles reliably when removing and reinstalling the neck repeatedly. It all has to come together correctly without the customer having to “measure” anything, except to correctly carry out the assembly and minimal set-up.
Cutting the Neck-mortise
I had already cut the “footprint” of the neck-heel, so I took measurements and laid out the proper shape on the end of the neck-block, where the mortise was to be cut. I worked from the centerline of the neck block, so there was less chance of ending up with a skewed neck.
Neck-Mortise laid out.
Then I turned the corpus over and began sawing the sides of the mortise, using a thin-bladed Japanese pull-saw:
Sawing the neck-mortise.
Once I had the two sides sawed out, I sawed across the line between the two sides and separated the rectangle of the front plate wood from the neck block, to expose the neck block, allowing me to use chisels for most of the remaining removal of wood from the neck-mortise.
Ready to chisel out the neck-mortise.
Chiseling out the neck-mortise.
Neck-mortise complete, with homemade projection gauge.
I checked the fit continually until all five measurements were correct, then removed the neck from the mortise, and began fabricating the “removable neck” apparatus that will enable the player to pack up his or her bass and transport it safely.
One of the things that concerned me was the possibility of wood changing shape through wear or stress. And, since the neck is to be secured by a bolt, how can I be sure that the bolt will not gradually wear into the wood, causing a loose fit?
After fitting the neck to the corpus, as outlined above, I inlaid 1/16″ Carbon Fiber plate on both sides of the neck heel, to provide smooth, stable fit every time and simultaneously guard against a heel crack, as the CF plate is not only inlaid into the sides of the neck, but it is bedded in epoxy, so it is a permanent part of the neck heel, providing support as well as a smooth surface to the sides.
I used screws and epoxy to mount bars of CF across the ends of the “joint” between the neck heel and the portion of the neck heel that will be permanently mounted to the corpus (and secured to the block and button,) so that a bar of CF on the neck heel slides under a similar bar in the mortise, thus providing an anchor of sorts.
Carbon fiber reinforcements and locking joint.
Locking mechanism for five-string double bass removable neck.
Locking anchor-bars for removable neck.
Then I re-attached the two portions of the neck heel using a piece of paper glued between them, so that I could check the neck-set one last time, before gluing the root end in place and drilling the removable portion to receive the bolt. The paper provides a “breakaway joint” that will be relatively easy to separate after the heel root is glued home. it is only glued with a few “stripes of glue on each face, so the paper will tear apart and allow me to extract the removable portion the neck and finally complete the drilling, installation of a threaded insert, etc., and thus complete the neck set.
When I last posted, the back plate was in progress, but even the arching was not completed, let alone the interior carving. Now it is all complete, the front plate has been installed, and the fingerboard, the neck and the tailpiece are underway! Things are moving along!
I did make a set of arching templates before moving on with the arching:
Set of cross-arching templates for the five-string double bass.
Those templates helped me to see the shape more clearly, and to know what changes to make, to improve.
So, here is the completed back arching, after scraping, so that you can see the flame in the Oregon Big Leaf Maple back:
Arching complete on back plate. Pretty wood, isn’t it?
Inside Carving
Carving the interior is always a daunting task…that is a lot of wood to move! But, one scoop at a time, it does get done!
Beginning the inside carving of the back plate.
Once I had the whole plate beginning to take shape, I carved “dots” all over the plate, checking thickness as I carved, until I had a pattern of correctly graduated “dots all over the plate. Each dot had a measurement written in the center, matching the graduation “map” I had chosen to emulate.
Then it was time to “connect the dots.”
Graduation “dots” for back plate.
Connecting the dots.
Graduation of the back plate is nearly complete.
It is always amazing to me how light the plates become after all that waste wood is removed. In this picture, you can see how thin the plate is, with the graduation complete.
Graduation of the back plate is complete.
I took the plate inside, and stacked all the parts together so that I could see the progress:
All the main parts complete, and stacked on the garland.
What is next?
I needed to complete the neck, which means I needed to design, cut out, and shape the fingerboard and glue it to the neck block so that I could finish shaping them as a unit. Meanwhile, I could install the front plate, and get ready for the neck-set, once the neck was ready.
Front Plate installation
I completed a preliminary shaping of the blocks and shaped the linings, front and back. Then I carefully positioned the garland on the front plate, and temporarily clamped them together, using several spool clamps.
Garland and Front plate assembled and clamped.
Then I removed the clamps from one area at a time, used a thin palette knife to slip hot hide glue into the joint, and re-clamped immediately, adding more clamps as needed. Then I moved to the next area and repeated that pattern. Soon I had the entire front plate glued, and secured to the garland with clamps.
Front plate and garland assembled, glued and clamped.
And, when I removed the clamps in the morning, the project was beginning to look like a bass!
Front plate and garland, with the clamps off.
I liked the looks so much, I stacked the parts together again, to see how it would look, all together. The back plate is just sitting there, again, not bent to fit the garland or anything. I will add purfling after installing the plate, I think, so I can be sure the overhang is correct, and that the purfling follows the finished edge.
Back plate sitting on garland assembly with front plate, and neck assembly.
There is still a long way to go, but I will put more in the next post.
When I last posted, I had flattened the back plate, using a plane, but the shape was still oversized.
Flattened back plate for 5-string double bass.
So I traced out the plate shape using a small section of plastic pipe as a guide, and a ball-point pen inside the pipe to make the mark. Then I cut out the plate using my very old Craftsman “Auto-Scroller” saber saw.
My beloved wife, Ann, bought me this saw when we had been married for less than two years, and it has served me well for the last 38 years, but this may be the final plate it will cut out. It overheated rather badly during the cut. 🙁
Back Plate traced and cut to shape.
Once the plate was cut out, I used my curved-sole scrub-plane to remove waste wood, and rapidly bring the plate to near the proper thickness around the edge. As the thickness gets close to the target dimension, I switch over to the Ibex Finger-plane with the toothed blade and the wooden handle, to complete the thicknessing of the plate edge. The Oregon Big Leaf Maple is much more difficult to carve than the Spruce was, both because it is harder, and because the grain is highly flamed, meaning that it changes directions every centimeter or so, resisting all efforts to smoothly plane off the wood. The toothed plane helps, but when I start getting close to the right thickness, I will have to switch over to a scraper before the tear-outs from planing are too deep to be removed.
Arching of the back plate is underway.
You can see the longitudinal arching template in the above photo: it is just a thin piece of plywood with an 11′-3″ radius circle section cut out of it so as to leave the correct arching height in the center. I used that to help me establish the longitudinal arching. The Ibex plane is on the plate, and the scrub-plane is almost out of sight behind a small block-plane in the background. The small block-plane is helpful for smoothing the ridges left by the scrub-plane.
I am working to the rough sketch I made before beginning, with the plan for the back arching: (I did change the plan a little. I realized that I could extend the arching a little further “north,” as I have tapered the entire garland a little, so that the bend in the upper bouts will not be so severe, and the arching may be able to follow it a little way before flattening out to avoid the compound curve. It’s worth a try, anyway, and will not hurt anything.)
Rough sketch of arching-plan for the back plate.
Arching of the back-plate still in progress. Scrub-plane is more visible in this picture.
My hands and shoulders were getting too tired, so I went inside and used small finger-planes, files, and scrapers to refine the scroll. I am waiting on an order of carbon-fiber reinforcement materials to complete the neck, but other than that, I am pleased with how it is turning out.
Scroll is nearing completion.
I also completed the scraping of the Sitka Spruce belly, and it is pretty much ready to be glued to the garland.
Front plate and Garland, ready to be joined.
I pretty much wore myself out on this stretch: I’m looking like a tired old man, here. And I thought I was smiling…
The luthier with five-string double bass in progress.
As I said in the post regarding tools, I built the little curved-sole scrub-plane with the specific intent of using it to carve out the inside of the Sitka Spruce front plate for this Five-string Double Bass.
Rough-carving the interior, using the scrub plane.
Carving Dots
As the depth approached the correct value, I began switching over to the palm plane, there in the foreground. But as it turned out, I actually had a long way to go before I was anywhere near too thin.
I used the bass caliper to register thicknesses all over the plate, and then began carving “dots” at each location, to the desired thickness.
Carving “dots” of correct thicknesses all over the plate.
As I found (or created) spots that were at the correct thickness, I wrote in the thickness, and highlighted them in yellow, to warn myself against going any deeper. Eventually, I had mapped out the entire plate at least approximately according to this diagram from Peter Chandler’s book “So you want to build a Double Bass”:
Graduation map from Peter Chandler.
He had derived these measurements from a fine old master bass by Domenico Busan, which conveniently happened to be disassembled for repairs and restoration. He said that he had subsequently used these values on all his basses, and it always worked well. (Sounds good to me!)
I kept carving until I had “dots” all over the plate.
Thicknessing Dots completed.
Connecting the Dots
Then I began “Connecting the Dots”:
Connecting the dots.
As I planed away the excess wood, the “dots” got smaller and smaller, and, in some areas disappeared. By that point I had switched over to the palm plane which is less aggressive and makes a smoother surface.
Planing with the Palm Plane.
But eventually, it was pretty much all done, and time to cut out the f-holes. However, I decided to install the purfling first, and then cut out the f-holes.
Purfling installed:
I did not take pictures while this step was in progress: I just got going and pressed on until the job was finished, then took a few pictures. Sorry. I don’t always think about pictures.
I used this old purfling marker to trace my lines, then a thin-bladed knife to slice along the lines to make a slot…then picked out the waste wood and inlaid the purfling.
Old purfling tool: missing part replaced with maple.
Upper bouts with purfling installed.
Bass F-hole incised and center-bout with purfling.
Cutting the F-holes
I used a coping saw to cut out the f-holes. It was slow and laborious but it worked, and there was little chance of any catastrophic errors. The result was two f-holes cut within a millimeter of the line and no errors. It is starting to look like a double bass!
F-holes cut out.
Rough-cut f-hole ready for refinement.
Using a knife to refine the f-holes. ( I will finish them with a file.)
Bass-bar fitting
Fitting fixtures for fitting the Sitka Spruce bass-bar.
I use a very thin paper gauze tape for chalk-fitting bass-bars.
This is the tape I use, along with sidewalk chalk.
Paper tape with chalk applied.
The trick is to press the bar into the chalked tape, and “wiggle it” slightly, to pick up chalk on the high spots. then plane off just the chalked places and do it again, until all of the bass-bar comes up with chalk on it. That achieves a perfect fit. When the tape is finally removed, it takes all the chalk with it.
Then I warm the wood using a heat gun, apply a liberal coating of hot hide glue to both surfaces and clamp the bar in place. I leave it overnight to dry, just to make certain it will not pop back off (I have had it happen.)
Bass bar fitted, glued and clamped.
Installed bass-bar, ready to carve to shape.
The properly-installed bass-bar still has to be carved to the appropriate shape. I use planes to accomplish the carving.
Beginning to carve the bass-bar.
Bass bar nearly complete.
Bass bar complete
Interior of completed Front plate sitting on the garland.
Completed front plate resting on the garland. (Starting to look like a double bass!)
Back Plate Vision
There is still a good deal to be done, before I can install the Front plate, so I am stopping there for the time being.
But I really wanted to get a foretaste of what the Big Leaf maple of the back is going to look like; so I planed the inside and outside of the back plate flat, just to have a look at it:
Back plate inside surface.
Back plate outside surface.
It is pretty stuff! I am really looking forward to seeing it completed.
An elderly couple of friends gave me a large pile of highly flamed “fiddleback” maple, hoping I could build fiddles of the wood. This was Big Leaf Maple wood that the woman’s father had salvaged specifically because of the beautiful grain, perhaps fifty years ago, while making wood to heat his home.
Unfortunately, the wood turned out to be riddled with worm damage so that most of it is unusable. I felt bad about it, because she had hoped, all through the years, to have a box or something made of the wood, and now it seemed to be lost.
I had just repaired my bandsaw, though, while in the process of building the five-string double bass, and was busy cutting up billets of violin-wood to see what I really had that would be useable. I salvaged a few pieces of their maple wood that (maybe) could make a violin, and enough thin slices that I thought I would try a box for her.
When most people think of a box, they are thinking of a rectangular enclosure of some sort: but, I’m a violin maker! So…I bent the wood into an oval, and went from there:
There was not enough solid wood to do very much, so the heavier sections are from a different tree; one cut from the yard of my wife’s family home.
Gift box showing bent body, inlaid top, solid base and lid.
I inlaid the fiddleback maple section about 3 mm thick, into the lid which was also flamed maple, but not as spectacular. I trimmed it with purfling left over from the building of the five-string double bass.
The sides were only a little over a millimeter thick and bent around a hot iron made for that purpose. But they would be too fragile, if that was all that was there, and there would also be no secure way to fasten them to the base. So there is a 4 mm raised section glued to the base and the sides wrap around that “plug.” I added a 5 mm thick ring around the top, the same size as the bottom plug, in order to reinforce the upper edge.
Then I inlaid a 7 mm wide by 2 mm thick band of bent willow wood into the lid, positioned so that it fits cleanly inside the upper ring. As it happens, the lid fits perfectly in one direction, but if you turn it 180 degrees, it is very loose. So I stamped my name in the base and the lid: when you open the lid, if both are readable or if both are upside down, then the lid will fit.
Interior of bentwood box.
I varnished the bentwood box pretty much the same as I do my violins, and delivered it the following Saturday.
Both the husband and wife seemed quite pleased, so I am happy too.
So, when I saw that there were two sections of “scrap” left over, near where the neck end of the five-string double bass back was cut out, I realized that a 5-string fiddle back could fit into each of those two pieces.
So, I salvaged the wood, and not only got two backs, but also the neck blanks for two 5-string fiddles.
Five-string fiddle back cut from the scrap left from a 5-string double bass back.
Arching the Plate
Five string fiddle begun, with back and neck from scrap from a 5-string double bass back.
I really like the look of the Oregon Big Leaf Maple back wood. I enjoyed arching the plate.
Five-string fiddle back arching nearly complete. It is sitting on the five-string double bass garland whose back provided the scrap for the fiddle-back.
Purfling the Plate
On all my five-string instruments I usually include a purfling weave. It is a modified fleur-de-lis I designed for my first five-string fiddle and have continued to use on subsequent work.
Five-string fiddle back with purfling slots incised and ready to complete.
In this photo, the slots for the purfling have been incised, but not cut deeply, so the next step is to slice deeply enough that the waste wood can be removed from between the cuts, and the purfling strips inlaid in the resulting slot.
I will include the purfling process in subsequent posts.
When I last posted, I had the garland pretty much complete, and the materials were prepared for the neck and the front and back plates. I had cut the back plate roughly to shape, in order to use as much of the “fall-off” material from the back plates, as possible, from which to make the neck.
I went ahead with the neck and scroll, just because I find it encouraging to have some of the “pretty” work done, as it makes me feel that I am making progress. You can see the neck progress, here.
But at some point, one has to go ahead with the task of bookmatching the plates and getting them ready to carve.
Sitka Spruce front plate halves for the five-string double bass.Rough shape of the five-string double bass back plate, with the template for the neck. The neck was cut out of the scrap from the back.
So, for the front and back plates, the next thing on the agenda was to plane the center-joints absolutely flat and straight and then glue them together. It took two tries on each of them, as it turned out that while they were technically “straight”, and if I put a try-square at any given point, they seemed to be square…in reality, there was a longitudinal twist to the surface I had planed, and the fit was not acceptable. (sigh…) No big deal… I just had to saw the joint back apart, and try again.
Finally, I got everything lined up correctly; then I glued and clamped the plate halves together, and produced the plate banks, ready to trace the actual shapes.
Sitka spruce front plate for five-string double bass, bookmatched, and ready to glue.
Front and back plates, bookmatched, and ready to trace shapes.
Tracing the plates
Sitka spruce front plate, ready to trace the shape.
Ready to trace the shape of the garland onto the front plate.
Using a pipe spacer to trace the shape of the garland onto the Front plate.
Tracing the plate out with a pipe spacer like that enables me to establish a very even overhang of about 4.5 mm. The problem is, it also makes round corners, which I did not want. So I had to correct, the corners, using a long straightedge to “point” the corners toward the center of the plate at the far end, and then use circle templates to extend the curvature of the plate edge above and below the corner to meet the straight lines. (Incidentally, the reason I have stopped using a washer for a spacer, is that any washer small enough to have the right distance from outside to inside also is so thin that if there is the smallest change in the fit between the plate and the garland, the washer will slide under the garland, changing the overhang distance to zero. The thin slice of PVC pipe never does that.)
Cutting out the Front Plate
I used an old Craftsman “Auto-scroller” saber-saw (Hand-held jigsaw) to cut out the perimeter of the front plate. Ann, my beloved wife, bought me that saw 36 years ago, when we had been married for only about three years. That little saw has a lot of miles on it!
Cutting out the completed shape of the front plate. I am not attempting to cut exactly to the lines. I will correct to the lines, after the arching has been completed.
Inside view: the cutting is complete: the front plate is ready for arching.
Outside view of the front plate.
Arching is Next:
Before I could begin arching, I needed to mark the intended plate thickness: I used a marking tool to scribe a line all the way around the plate at 6 mm. Before the plate is done, this will be reduced to 5 mm in most areas. I used a ballpoint pen to highlight the groove so that I could more easily see it when I am working, and not accidentally go past it.
Edge-thickness scribed into front plate.
Then I secured the plate in a cradle especially made to fit this design, and secured it in place by affixing small squares of 1/4″ plywood around the perimeter so that the plate will not shift laterally, while I am working on it. The reason the little stop-blocks are so thin is that I do not want them to be in the way when I am planing the edges.
Front plate secured in a work cradle.
Tools for arching: cradle, gouges and planes.
Sculpting the front plate arch.
Front plate arching in progress!
Planing the arching surface smooth.
Some of the planes used to shape the bass.
Shadow line defining the longitudinal arching shape.
Transverse arching shape.
Arching nearing completion.
Arching and outline completed.
Time to lay out the F-holes!
F-holes laid out, incised, and inked.
When I build the smaller instruments, I inside the f-hole perimeters quite deeply, knowing that, without exception, I end up needing to correct the arching, using the f-hole side-profile as a guide. I want the “stem” portion of the f-holes to be essentially parallel to the plane of the garland-plate joint when viewed from the side. On the violins and violas I have built, I have universally found that, in spite of my best intentions, I have left too much “puffiness” in the area of the lower wings of the f-holes and I need to plane away more wood. If I have incised them deeply enough, I don’t lose the marks when I remove the wood.
I was quite pleased to find that, on this instrument, the side profile was exactly what I had hoped for, as soon as I laid it out. So I incised them, but not very deeply, and then inked them with a ball-point pen, so that I could easily see them while perfecting the arching later, using a scraper.
So– the next step will be to complete the “graduation” of the plate– carving away the majority of the wood thickness from the inside of the plate, so that the plate is the correct thickness all over…ranging from 9mm at the center, all the way down to 5mm in the flanks.
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