Posts Tagged ‘mold’

The Garland

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The Garland

Shaping blocks and Bending ribs:

Inner curves of corner-blocks, and both end-blocks, first

I learned to shape only the inner curves of the corner blocks, initially, as well as the outer curves of the end blocks, because if I shape both curves on each corner block, then there exists the possibility that, when I clamp the center-bout ribs in place for gluing, the tips of the blocks may deflect outward, instead of holding their respective shapes.

Also, after the c-bout ribs are glued in place, when I shape the outer curves, in preparation for receiving the upper and lower ribs, I shape the ends of the c-bout ribs at the same time, so that they simply continue the curvature of the blocks, to a feather-thin end condition, before gluing the upper and lower ribs in place. Then, when I trim the upper and lower ribs, it is easy to make the glue-lines between the c-bout ribs and the upper and lower ribs completely invisible, matching the corner of the trimmed ribs at the corners of the instrument garland.

So, here is the mold with the blocks shaped as described above:

Blocks shaped in preparation to installing certer-bout ribs.

Blocks shaped in preparation to installing certer-bout ribs.

 

Ribs are Next

When using figured wood, I have to make a determination as to which angle the figuring will follow on the instrument. I thought I could just copy whatever the Old Master (Guarneri del Gesu) had done, but, as it turns out, he used highly figured wood for the ribs, all right, but the flame (curl) in the maple went directly across the rib at nearly exactly 90 degrees, whereas mine is quite slanted. So, I have to make a decision: Will I have the curl slant “up” (north) from the back side to the front, or the other way– from front to back?

Really, I simply have to make it consistent, on both the treble and bass sides. Some makers have the slant in the C-bouts going the opposite direction from that of the upper and lower bouts. Some, also, have used a single rib across the two lower bouts, and thus had the flame slanting one way on the bass side and the other way on the treble, and then matched the center and upper bout rib curl to the lower bout rib, so that the grain was consistent all the way around, instead of being mirrored between the two sides.

That sounds good: but, in the first place, I haven’t enough rib wood to pull it off correctly; and, in the second place, it can potentially cause problems later on, if the plates shrink (they are made of wood, remember!) and the ribs have to be shortened a little, to match. If there is already a joint at the center, it is relatively easy to simply shorten each side by a millimeter or so, as needed, and re-shape the end-pin hole. But if the bottom wood is all one piece, the repairer will have to cut through that bottom rib, and establish a new center joint; so the two halves will no longer match perfectly, though it will be pretty close.

Anyway: I usually would first thin the ribs to a consistent one millimeter thickness, and then cut them to length, carefully laying them out as to location and orientation, before bending. This time, I consulted with one of my teachers, who assured me that Guarneri ribs were a little thicker. So, since the ribs came to me at 1.3 mm, I will consider that to be the ideal thickness for this particular instrument.

Ribs

Ribs for new violin (one is already on the mold.)

 

Then I can bend all the ribs, individually, and set them aside ready to be used. In the case of the C-bout ribs, I clamp them into the mold, where they will cool, and stabilize, in exactly the correct shape. Afterward, I used a small brush to slip glue into the joints, and secure the C-bout ribs permanently to the corner blocks.

First (Treble side) C-bout rib installed.

First (Bass side) C-bout rib installed.

 

Second (Bass side) C-bout rib installed.

Second (Treble side) C-bout rib installed.

 

When the glue holding the C-bout ribs had dried sufficiently, I shaped the outer curves of the corner blocks appropriately: You can see, in the  photograph, below, that the center rib-ends have been shaped along with the outer curves of the corner blocks, so that they will cleanly fair into the curves of the upper and lower ribs.

Final shape of corner blocks.

Final shape of corner blocks. C-bout ribs are shaped along with the corner blocks.

 

I then immediately installed the upper and lower ribs in their respective places. In this particular case, I chose to install the lower ribs first. After the glue dried for a few hours, I installed the upper ribs.

Lower bout ribs installed.

 

All ribs installed.

All ribs installed.

 

When the glue holding the upper and lower ribs had dried sufficiently, I trimmed the ends to the correct length, and filed them smooth. The only “end-grain” showing will be the ends of the upper and lower ribs at each of the corners. I try to make them square with the centerlines of the corner blocks, so that it gives the inpression of a “mitered”corner, but with no apparent glue-joint: the joint is exactly along the corner of the squared-off rib end. The first priority is to have the rib end at the right angle, so it will appear to be perpendicular to the plane of the garland. The next is to file them to look “square” with the corner, as I explained above. Finally, some creative scraping of the C-bout rib-ends will usually move the glue joint to be exactly on the corner of the upper or lower rib, and make it essentially invisible. This one is close:

Corner, nearly complete

Corner, nearly complete: a little more scraping will make that joint invisible.

 

Linings

The only thing left to complete the garland is to install linings on both the front and back sides. The way I have chosen to use my mold (“French” method…ribs flush to one side of the mold) precludes my adding the back linings until after I remove the mold. That is fine: I also intend to leave the mold in place until after I have set the neck, so I have quite a way to go on that step.

Not everyone installs the neck while the corpus is on the mold. I began doing it when building my first cello, and it helped so much with neck-setting that I have continued it ever since. I deliberately allow the heel to “run wild”, in terms of length (or height, depending on how you are looking at it), so that it protrudes past the back of the neck block a little bit. When all my other items (angles, measurements, etc.) are exactly correct, I glue the neck in place, and before installing the back plate, I simply trim the back of the neck-heel flush with the back of the corpus. Then the back plate fits perfectly, and I am not struggling to get that joint tight. But… I am getting ahead of myself…. 🙂

I cut strips of willow to the appropriate dimensions for linings and then plane them smooth; then bend them to fit the curves of the violin, and finally, cut them to the appropriate lengths, and install them. Willow responds very well to both bending and carving, which is why I prefer it for lining material. I can bend all the linings in just a few minutes, and they will all hold their shape until I am ready to use them.

Bent linings, ready to be cut to length and installed.

Bent linings, ready to be cut to length and installed. Willow is easy to bend: These linings all started out like the straight one in the photo.

After the corners are all dry and secure, and trimmed, I cut two small mortises in each block, to receive the linings; then cut the linings to exactly the right lengths for a tight fit. The linings serve two purposes: they strengthen the edge of the ribs, which would otherwise be quite fragile; and they triple the gluing surface area bewteen the rib garland and the plates.

When I have all the linings fitted correctly, I remove them one at a time, apply hot hide glue, re-insert the linings, and clamp them in place, using tiny spring clamps. Sometimes one or more areas are more stubborn, and require a heavier clamp. Then I use something with more authority.

Linings fitted, glued and clamped.

Linings fitted, glued and clamped.

 

So: there is the garland (rib-structure), essentially ready to use! Next time we will level the garland, and use it to trace the shape of the front plate. At some point before attaching the front plate, I will also trim the linings to a triangular cross-section, so that the inner edges taper to a thin transition, and do not add a stress-riser to the ribs. I’m not certain whether it would affect sound, but the Old Masters did it that way, so I will follow their example. The corner blocks also will be trimmed back to be fairly minimal. I will carve away the end-blocks to each be the shape of half an ellipse, but I will leave them fairly robust, for strength.

Mold with blocks, ribs and linings.

Mold with blocks, ribs and linings.

You can still see traces of ink and glue on the blocks, looking like gaps…that will all go away when I level the garland.

 

Thanks for looking.

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New Project!

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New Project!

“Pellegrina-esque?” Violoncello da spalla?

I had been pondering (glumly) what to build for the next show at Marylhurst University, and had nearly decided upon one of two “niche-market” items…either a very large “violoncello da spalla”, or an emulation of David Rivinus’s “Pellegrina.” I had spoken to Mr. Rivinus a couple of years ago, and he told me that, for years, he had encouraged other luthiers to use his design, as a partial solution for some of the “work-related injuries” associated with playing large violas…but no one took him up on it, so he just produced them himself for the rest of his lutherie career, ultimately making 100, or so, of the odd-looking instruments. They were all sold, ultimately, and he has stopped taking orders, so I considered “taking up the mantle”, so to speak, and producing instruments modelled after his work. But, as I said, that really is rather a “niche-market” viola.

The violoncello da spalla is possibly even more specialized, as, though it is strung very much like a regular violoncello (cello), it has a fifth string (E), above the standard C-G-D-A of the cello, is only 19-20″ long on the body, and is generally played off the right shoulder, so that the lower bass-side bout is under the chin, and the bowing arm comes up from underneath, so that the player is nearly as comfortable as when playing a small viola, but the sound is that of a cello or extremely large viola–take your pick. Very little classical music has been written for these instruments, so I doubt there would ever be a lot of market for them, though I would love to build them.

But! in the midst of these ponderings, I had sent one of my teachers a couple of sets of photos of two of my recent violins, and, while he was quite encouraging and positive, he took the time to give me a carefully-considered, and quite detailed critique (what a treasure!) of both instruments, telling me what changes he would want to see, when comparing my work to one of the Old Masters (Guarneri del Gesu, in particular.) So! I changed course, and figured that I have just enough time to attempt another copy of the 1735 “Plowden” Guarneri del Gesu violin, of which I already have the “The Strad” poster, with actual CT-scans of the original instrument, and exquisite photos of the outside, along with technical drawings and tables of measurements.  Game on! New Project!

Guarneri del Gesu

(Bartolomeo Giuseppe Guarneri 1698 – 1744) was a violin maker  living and working in Cremona, Italy. He was one of the sons of Giuseppe Giovanni, and, though he was not very successful in his lifetime as a luthier (having to supplement his income by other means) compared to the more famous Antonio Stradivari, some of his later instruments are highly prized today, and sell for more than perhaps the very best Stradivari violins. Currently the very highest price (undisclosed, but reportedly in excess of $15M) was paid for the 1741 “Vieuxtemps” Guarneri del Gesu, on lifetime loan to Anne Akiko Meyers. I have never attempted an instrument modelled after the “Vieuxtemps”, but I have made two or three modelled after the 1735 “Plowden.” So that is the chosen model, again.

Starting from Scratch, Again

Checking the Mold Template against the Poster CT-Scan.

Checking the Mold Template against the Poster CT-Scan…I thought it had been exact, but there were some tiny discrepancies.

 

corrections

The black-marked edges are the places I corrected next. (Not much, really, but striving for perfection, here.)

 

Strad Poster of the Plowden

These are the photos on the poster front. The poster does not want to lie flat– I store it in a mailing tube, to keep it undamaged.

 

Checking the mold.

Checking the mold against the corrected mold-template: as it turns out, the corrections were all within the areas of the blocks– the mold is fine.

 

Blocks cut and fitted

Blocks cut and fitted…notice the differing heights, marked on the ends.

 

Blocks glued in place.

Blocks glued in place. I use Titebond for this task, but nearly nothing else.

 

Block shapes, as traced from the mold template.

Block shapes, as traced from the mold template.

 

The Wood for the New Violin

This will be a one-piece back of European Maple, neck and ribs matching the back, and a two-piece front plate of European Spruce. All were obtained from International Violin Co., of Baltimore, MD.

One-piece back, neck and ribs of European Maple, front of European Spruce.

One-piece back, neck and ribs of European Maple, front of European Spruce.

That trace on the back plate was put there by the wood-source people…it does not reflect the shape of this violin at all.

So! That is the Beginning!

I will carve the inner curves of the center-bout blocks next, so that I can bend and fit the center ribs to match those curves. Afterward, I will carve the outer curves of those same blocks as well as the tail and neck blocks, before bending and fitting the upper and lower ribs.

As a precaution against accidentally gluing the ribs to the mold, I already rubbed a paraffin candle all over the edges of the mold, where the ribs will touch, so that if an accidental drop of hide-glue ends up there, it will not stick. (Been there…broke the rib, before I figured out what was amiss.)

This is as far as I am going today…I am still recovering from hernia surgery last week, and I find I still tire easily. But I’m on my way, and will try to keep you posted, with progress reports, here

Thanks for looking.

Chet Bishop

 

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Building a Double Bass: Shaping the Blocks

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Shaping the Double Bass Blocks

Lots of Wood to Move!

As you may recall from the previous post, the blocks on this upright bass were pretty huge, compared to what they needed to be, so there was really a lot of wood to remove.

Mold with blocks and ribs

Mold with blocks and ribs. Blocks are still way oversized, and the ribs are still straight. Gotta change all that.

 

“Kutzall” Tool

So! A drastic need makes for drastic measures. Ordinarily, on a smaller instrument, I would use the bandsaw and oscillating spindle sander to shape the blocks, but this  mold is reeaaalllly heavy (over-built, I think…oh, well, it will be removed and the bass will be normal), even though it is a soloist bass, so I can’t see trying to manhandle it around on my big bandsaw. The saw could handle it, but the table for the saw is not big enough to hold the mold steady, and I am not strong enough to just hold it up there by sheer strength…. So… what to do?

This tool (carbide abrasive disc) is something my wife bought for me a year ago (Christmas), but I had never used it much. It is called a “Kutzall”, and it tears away wood incredibly rapidly, without loading up, and without burning the wood. So I used it to remove the large rough sections, then used the plane to remove the torn surface, and finally, to shape the blocks:

Kutzall disc, with 5

Kutzall disc, with 5″ DeWalt angle grinder: Not for the faint of heart! Absolutely wickedly effective, but not as dangerous as the Lancelot tool.

 

Stanley #100-1/2 Squirrel-tail Plane

It was about 37 degrees, F, outside, but the sun was bright, so I worked outside.

Smoothing and shaping the corner block

Smoothing and shaping the corner blocks, using a Stanley “Squirrel-tail” #100-1/2 hand-plane.

 

The little plane is somewhat hard to control, because the curvature of the sole is so extreme, but, if it is sharp and if the blade is set for a very shallow cut, it works well.

sharp plane

It does have to be sharp! (Time to sharpen….)

 

Stanley # 100-1/2 curved-sole plane

Stanley # 100-1/2 curved-sole plane…for those of you who are unfamiliar with it.

 

stanley plane

I was able to shape the blocks pretty close to finished shape with the little plane, but there are some irregularities. I have another tool for that problem.

 

The bottom block was planed entirely with a low-angle plane (also Stanley– can’t recall what number.) but it worked very well, and the bottom block was easy…I didn’t use the grinder at all on this one. So here are all the blocks, pretty close to finished:

Bottom block planed with a small, flat-sole, low-angle plane.

Bottom block planed with a small, flat-sole, low-angle plane.

 

And, here you can see the finished blocks, ready for sanding:

All the blocks, ready for coarse-sanding.

All the blocks, ready for coarse-sanding. The small plane leaves ripples. The sanding tool should remove them all.

 

Homemade PVC Sanding Tool

As I mentioned earlier, the oscillating spindle sander I have would not be tall enough for these blocks even if I could manhandle the mold up onto the machine. So, I made this little sanding tool out of re-claimed PVC fittings from the “Habitat for Humanity Re-Store”, and spent more on the little can of PVC cement from the hardware store than I did on all the other materials…about $2.50 at the Habitat store. I used PVC cement to affix the abrasive cloth to the pipe, too, and bound it up with strips of plastic bag until the solvent outgassed and the cement was set.

PVC sanding block

Sanding block fabricated from four PVC fittings and a 2″ section of 2″ PVC pipe, with a little piece of wood for the handle grip. Comfortable, efficient, and cheap.

 

The homemade sanding tool worked extremely well for the small corner blocks, and did very smooth work. On the neck block I used it cross-grain, holding the tool parallel to the “trough” of the curvature, and sliding it up and down the curve. It worked well, there, too, just not as perfectly as on the corner blocks. All in all, it is a very satisfying tool.

Sanding corner blocks.

Sanding the corner blocks.

 

Sanding the neck block,

Sanding the neck block, I kept the block parallel to the “trough” of the curve, and pushed it up and down, across the grain to get a smooth surface.

 

Change of Plans

You may have noticed that, though I had planned to use Willow for blocks and linings, those blocks are not willow: the corner blocks and end block are all Douglas Fir, and the neck block is laid up of three layers of clear, vertical grain Sitka Spruce. It was a matter of availability. I do have willow for the linings, and, as that in my preferred wood when I have a choice, that is what I will use. It cuts easily, bends easily, and is very pleasant to work with for both linings and blocks.

I have really felt that I was “spinning my wheels” on this project. It is large enough that I feel the necessity to work outdoors whenever possible, but the weather has not cooperated very well…it rained nearly every day for the last month. In addition, I have been struggling with a cold or some such virus. Today I was cold in the house when the thermometer read 75 degrees, so that is not normal. I finally felt a little better, this evening, and went outside for the few minutes it took me to sand the blocks, but it has been cold out, so I didn’t stay long.

Ah, well, that’s life. I’m grateful to be back on the project again.

Thanks for looking.

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Building a Double Bass: the Mold

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Building the Double Bass Mold

Planning the Mold

I designed this upright bass mold to be collapsible and to allow me to affix the blocks to the mold with screws, so that there is no glue to have to separate later.  I also wanted the mold to be slender enough from front to back that I could install the front and back linings without running into the mold, so I gave myself a 1″ clearance between the front and back faces of the mold and the front and back edges of the ribs. Since the back will taper in the upper ribs, losing two inches of depth between the middle of the upper bout rib and the top rear edge of the neck heel block, I had to accommodate that taper as well: I simply made a 2″ “step” in the mold to allow the taper to occur.

Finally, I wanted the mold to be stout enough to allow me to handle it without fear of damage. So, the construction is of 3/4″ plywood, spaced by blocks of 2 x 6 and (in the upper half of the upper bout) blocks of 2 x 4. The corner block mounts are of 1 x 6, so I do not have to use large screws to affix the corner blocks. The neck and tail block mounts are of heavier stock; 2 x 4, and removeable, to allow the mold to collapse laterally, and clear the ribs for removal.

Using the Mold  Template

In the last post, I had completed the mold template, and had commented that I would use it to make the mold, and then, later, to establish the shape of the blocks. So this is how that works:

I bought two quarter-sheets of 3/4″ plywood from Home Depot. That is a pretty expensive way to buy plywood, but it solved two problems:

  1. I really don’t need a whole sheet of plywood, and
  2. Even the quarter sheets were difficult to get into my car…but not impossible.

I took the quarter-sheets home, and positioned the mold-template flush with one end of one of those sheets, and offset by two inches. I am building a collapsible mold, and I want 4″ clearance between the mold halves. I don’t need that much for mold removal, but I do need enough for my hands and forearms to reach up inside the mold and remove the screws holding the molds to the blocks. So a 2″ offset on the template will result in a 4″ gap down the center of the mold.

I traced the mold template onto the quarter-sheet, and it looked like this:

design traced onto mold plywood

Template design traced onto mold plywood.

You can see that I also laid out the location and outline of the instrument blocks, the block mounts and all the spacer blocks that would become part of the mold. This took less than half of one of the quarter-sheets of plywood, so I sawed the sheets into strips, 11″ wide , and about 39″ long, and stacked them into a “sandwich” of four pieces, held together with two screws, countersunk flush with the surface. Then I sawed the whole sandwich out on the bandsaw, and smoothed the edges with the oscillating spindle-sander.

I cut all the needed blocks to complete the mold, and I was nearly ready to begin assembly.

All the mold parts

All the mold parts–the four mold quarters are still screwed together in one piece.

It was tempting to take the mold quarters back apart at this point, but, fortunately, it occurred to me that I could do all my drilling at once, so things would line up, and so that I only had to drill each hole once. So I made a drill bit out of a welding rod and drilled every screw location through all four plywood quarters. (Welding rods are way too soft for most uses; they use extremely low-carbon steel for the core wire of welding rods, but it was OK for this soft plywood.)

long drill-bit

All the holes in one step.

Finally I separated the quarters, and countersunk all the screw-holes.

Separated mold-quarters

Separated mold-quarters.

Assembling the Mold

I laid the mated pairs side by side, and lined up perfectly, then transferred the block locations and lines to each panel so that I could see where the blocks were to fit, on all four pieces.

Transferring lines

Transferring the lines– it looks kind of funny, because the center 4″ is missing.

Then I assembled my spacer blocks and installed them:

spacer bocks installed

Front and back with spacers.

Once the spacers were attached with screws, the front and back were pretty stable and I could begin assembly. The back plate still needed to be cut off at the beginning of the rib taper, so it could accommodate the taper, but I began by assembling (as many as possible of) the internal members to the front plate of the mold. It turned out to be pretty easy.

Beginning Mold assembly process.

Beginning mold assembly process.

Then I positioned the back plate pieces on the internal blocks and screwed it down tightly. I have used no glue in the mold, so, if I need to make modifications it will be easy to do.

Front of mold

Front plate of the (nearly) completed mold.

 

Back and side of bass mold

Bass mold showing back plate “step”, and corner block mounts.

 

Bass mold with neck template.

Bass mold with neck template for size comparison. Upper and lower block mounts are not yet installed.

The way by which I had intended to attach the upper and lower block mounts does not appear to be workable, so I will have to re-think that part. I had planned to install them on hinges, and to be able to screw down a steel bracket on one end to secure them, but it turns out that it will be too difficult to access the screws, so I will have to give it some thought and re-design that aspect of the mold.

At any rate; that is where the project stands for now.

I called the wood supplier, and they assured me that my European Spruce should show up today or tomorrow. No problem, really, but I want to get those plates joined soon. (I already have the local Big Leaf Maple in my shed, waiting to be used.) By this weekend, I hope to have the blocks installed and shaped, the front and back plates joined and the ribs cut. We’ll see how it works out.

Thanks for looking.

(P.S. : The wood showed up this evening… Good looking stuff!)

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Progress Notes on Another 5-string (post #1)

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Five String Fiddle Progress

A fellow approached me a few months back, asking whether I could build a five-string fiddle of some exotic wood which he had bought almost 33 years ago, and which he had hung onto all this time. Of course I am delighted to make an instrument that is special to a client, so I said “Sure!”

Wood

Here is the wood (Nice stuff! I can see why he hung onto it!):

The wood from which this fiddle will be built.

The wood from which this fiddle will be built.

 

The neck, back and ribs will all be cut from this block. Actually there will be a fair amount left over, so I will try to use it in an efficient manner so that he can use the scraps for something nice, too. The front plate will be spruce. The blocks and linings are willow…not sure which specific variety.

Templates–Patterns

Here is how the pattern will fit–with lots of room left over:

Wood with patterns

Plenty of extra from which to cut rib-stock.

The section from which the back plate will be cut will be sawn into two pieces, each half the thickness of the original block. The two pieces will be glued edge to edge, so that they are “bookmatched”: that is to say that the straight edge of the mold template will become the centerline of the back plate. (I will show photos of how it is done when I get to that part.) The same thing will happen with the spruce for the front plate.

Progress and Plans

The five string fiddle will be built to my usual “Oliver 5-string” Pattern. So, the first thing I needed to do was to cut the ribstock using a band-saw. (I sliced them off at 2mm thick, later to be thinned to 1mm thick before bending to shape.) I also cut willow blocks for the four corners and the two ends.

Ribs and blocks with wood and patterns

Ribs and blocks with wood and patterns

Then I needed to glue the blocks into the mold, and mark them for their outer shape. This shape will be the inside shape of the ribs, and the blocks will become a permanent portion of the finished instrument. The mold will be removed as soon as the rib structure is safely glued to the front plate (not pictured here.) Once the glue was dry, I laid the mold-template on the centerline of the blocks, and scribed around it with a pencil.

Blocks glued into the mold, and marked for shaping.

Blocks glued into the mold, and marked for shaping.

After the blocks were marked, I was ready to begin shaping them. I really only want the center curves shaped to their final profile: the rest of the corner blocks need to stay a little thick, so as to guarantee they will not deform when I am gluing and clamping the center ribs in place. I went ahead and shaped the end blocks as well, as that does not hurt anything.

C-bouts and end blocks shaped to receive ribs.

C-bouts and end blocks shaped to receive ribs.

Here’s a side view of the same thing:

Blocks and Mold, side view.

Blocks and Mold, side view.

Once the center ribs are bent to the correct shape, I will glue them to the center bout surfaces of the corner blocks, and after the glue is dry, I will shape the outer surfaces to receive the upper and lower ribs. From that point forward, it will begin to look more and more like a violin.

I will keep you posted.

Thanks for reading.

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