Posts Tagged ‘How to build a cello’

Channel cut and final arching begun

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Purfling channel and recurve begun, with final arching on the way.

Mark the crest, first

There are several ways to do this, but I used a compass, with the pencil withdrawn a few millimeters. I wanted to establish the crest of the edge about 40% of the way in from the outer edge of the plate to the edge of the purfling. In this particular case, the purfling is 5mm from the outer edge, so I set the compass for 2mm, and carefully traced all the way around the plate, so that I had a visible guide to follow with the gouge as I carved out the channel.

What gouge?

I used three different gouges: two have a curvature about like the ball of my thumb…no idea what specific sweep…one with a long handle, the other quite short. The third is a much smaller gouge I used specifically in the corners. Every few minutes I stopped and honed the gouges, or at least stropped them. You have to work very carefully to avoid tear-out in carving the channel on very curly maple. I used a rotating motion with the gouges, so that the wood and purfling was being sliced away, and was less likely to split.

What plane?

Once I had the channel cut all the way around, I switched to Ibex planes and began fairing the curve from the bottom of the channel up onto the highest areas of the plate. Occasionally I switched to a tiny flat Stanley plane to smooth out the ridges left by the curved sole Ibex planes.

It is still pretty bulgy, but looking better. All still quite rough…at this point I am more anxious to move a lot of wood than to move it smoothly. As I get closer to the final shape, I will take pains to make sure everything is smooth.

Here are a couple of pictures…not terribly clear, but I think you can see the progress.

channel and recurve cut...final arching begun

Still too high all over, but the channel is cut, and the final arching is begun.

Cello corner with channel cut and final arching begun

Same corner as before, with channel cut and final arching begun

I was getting pretty tired, so I am going to call it a night. I hope to get more done tomorrow night.

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Rough arching completed on back plate

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One-piece back, rough-arched, ready for purfling.

Final arching is yet to come

This is all I got done tonight. The edges are all at about 6mm, now, and the rough contours of the arching are complete. Tomorrow, I hope, I will finalize the edge footprint, so that it is exactly the shape I want the cello to be. (I waited until the edges were thinned, because it is much easier to make small adjustments to a plate when it is 6mm thick than to do so when it is 35mm thick, as it was two days ago.)

Flattening and thinning the rough plate

Two days ago, I worked the thick plate from 35mm down to 29mm, and decided to start from there on the rough arching. I may bring it a little lower yet…I haven’t decided yet just how high I want the back arching on this cello. I am thinking a little higher than the last one. The original Davidov is pretty flat…I may still emulate that curve.

Rough Arching

Tonight I simply worked a flat area all the way around the plate, at about 6mm (which I had marked ahead of time with a marking gauge), and then used a variety of tools to bring the shape of the plate to a “cello-shape”, though still a little plump.

Cello edge-thickness marked with marking gauge

Edge-thickness marked with marking gauge.

This (above) is actually a photo from the previous cello…I forgot to take a photo of the edge mark on this current cello before I began carving. Once I have the edge shape exactly the way I want it, I will probably take it down to 5.5 or even 5mm. The 6mm mark was just a good starting point for rough work. I ran a ball-point pen around the groove, too,  after scribing it with the marker, so I could see it more easily, as it was sort of dark out in the shop. So, this is how it looks now.

Rough arching on one-piece back-plate for cello.

Rough-arching completed–almost ready for purfling.

Purfling is next

Once the edge is exactly the shape and thickness I want, I will mark the purfling groove location, and begin cutting the groove for the purfling. Once the purfling is completed, I can finalize the outside arching before beginning the inside carving. When this is completed, it will be a maximum of 8.5mm-9mm in the center area, fading out to 4mm or so around the flanks, and back up to 5mm at the edge itself. I have a long way to go. It is certainly pretty wood, though. That is always encouraging.

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Cello garland lined, and Back plate cut out

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Cello linings completed; One-piece cello back plate traced and cut out…ready for arching

Back linings completed first

This morning I got up early and installed the back linings on the cello. While the hot hide glue dried, I set up a violin for a friend, whose grandfather had left it to him.

Tracing the plate

Once the glue was dry, I removed all the clamps, planed the ribs to be fairly level, and traced the outline of the back plate, using a very short section of aluminum tubing (5mm long, 25mm diameter, 3.5mm wall thickness) and a ball-point pen, to trace around the ribs and mark the maple slab from which the back was to be cut. The tubing is tall enough (5mm) to never slide under the edge of the ribs, even if there is an irregularity on either the ribs or the plate, and the 25mm diameter rolls along steadily and easily along the side of the garland itself, making it a fast, pleasant task.

Cutting out the plate and refining the edges

I cut the plate out on a bandsaw, only using a scroll saw for areas too difficult to access on the bandsaw. Then I smoothed all the edges on an oscillating spindle sander. I do not use many power tools, but the saw and the sander are two that I consider indispensable at my age. They save me a lot of wear and tear on my joints. I have built instruments using all hand tools…no power tools at all…but I do not consider it a virtue, and probably will never do it again, if I can help it. I still have the bow-saw I built for that fiddle project, and all the files, planes and scrapers. The only one I no longer use at all is the bow-saw. It hangs on the wall reminding me of that early violin.

So…now the cello garland (still on the collapsible cello mold) and the back plate look like this:

One-piece cello back plate with garland on mold

Cello garland on mold, with one-piece maple back plate

Arching is next…but I am pretty tired, so I don’t think I will start today.

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Cello linings installed (front)

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Willow cello linings installed, glued and clamped.

Purpose of the collapsible cello mold:

My cello mold is built with a front and back “spacer”, each of which is removable to allow installation of linings. Each is held in place by a few drywall screws. I got tired of the repetitive motion of turning the screws by hand, and bought a very cheap  electric screwdriver, barely sufficient for the task. I will later make a special attachment for it so that it can turn the tuning machines on double basses…that’s another task that wears out my wrists. Anyway– in less than two minutes I removed the front spacer, and the cello looked like this:

Cello mold with ribs installed, linings ready to install--front spacer removed.

Cello mold with front spacer removed and linings ready to install.

Dry-fitting the linings:

Then I cut the mortises into the blocks, fitted the linings (that I had bent earlier) into their respective places, and prepared for gluing. So, with the linings dry-fitted and ready for gluing, it looked like this (notice that only the center linings have clamps at this point; that is because they want to relax away from the rib, while the upper and lower linings straighten and tighten against the rib):

Willow cello linings dry-fitted, ready for gluing.

Cello linings (willow) installed dry, ready for gluing.

You can see the importance of the linings, by comparing the two photos above: without the linings, the ribs are only about 1.5mm thick…not very strong, nor is there sufficient gluing surface on that thin edge. So, with the linings in place the edge is about 5.5mm thick, which significantly strengthens the edge, and more than triples the gluing surface.

Hot Hide Glue and lots of clamps!

Once all the linings fit correctly, I heated up my glue, prepared a container of hot water, and my various brushes and palette knife, and, one by one, I brushed on the hot hide glue and clamped each lining in place. Those little spring clamps work pretty well. I got them from Home Depot, and they have served this purpose to my satisfaction. Occasionally there is a reluctant joint that needs more pressure, in which case I use a larger clamp, or one of those little f-clamps. (You can never have too many clamps!) After gluing and clamping, the cello looks like this:

Cello linings glued and clamped in place.

Cello linings glued and clamped.

Once these linings dry, I will remove the clamps and repeat the process on the back side. the back has a slight taper, from tail to neck. At the bottom block, the ribs are about 113mm tall. At the neck they are about 108mm tall. So I will want to plane the ribs to those approximate dimensions before I install the linings. One thing you can’t see in the photos is the fact that I fit the linings just a little high…slightly “proud” above the rib edge. I want to make sure that whatever planing needs to be done is primarily removing willow, not curly maple. I will accomplish final leveling with a sanding board, however, just before tracing the shape of the plates, from the shape of the completed rib garland.

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Bent Willow Cello Linings

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Cello Linings, Willow, bent and ready to install

The linings I sawed up yesterday are now bent and ready to install.

While the bending iron was warming up (which takes about 20-30 minutes, especially in cold weather), I used a very small hand plane to smooth the edges of the linings, since some were still a little rough, especially if they had been the outside edge of the strips I cut from that beat-up 4 x 4 I brought home.

Once the iron was hot enough to make water droplets dance on its surface, I dampened each lining strip one at a time, and used a metal bending strap to force the wood against the hot surface of the (aluminum) “bending iron”. These linings are about 4mm thick, so I gave each segment a full 15 seconds to heat up, or 20 in the case of the c-bout linings which were to endure a tighter bend. As I heated one section, forced against the flattest curve of the iron, I counted seconds, then shifted the wood sideways to heat the next section, still maintaining the curve of the first, and so on, until the entire lining strip had the curve I wanted it to have. You can see that I deliberately over-bent them: I do so because it is pretty easy to straighten them out a little, to adjust them to fit tightly against the ribs.

Here is what they look like now:

Bent willow cello linings ready to install.

Bent willow linings, ready to install with hot hide glue.

Tomorrow evening, depending on how tired I am when I get home, (or probably Friday, since I have to go to bed very early Thursday in order to get up at 2:30 AM and go teach a code clinic class before my regular work begins on Friday morning) I will remove the front section of the mold (notice the screws holding it), which will allow room for the linings to be installed. I will cut the little mortises in each side of each block, to receive the ends of the linings, then brush hot hide glue onto each rib and lining, one set at a time, and clamp them in place with little spring clamps. After the front linings are dry, I will repeat the process with the back linings.

Starting to look more encouraging, now.

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Cello Linings for Free!

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Free Willow Sources

I like to use Willow for cello linings and cello blocks, but willow is not a common timber to be able to just go and buy. Last year I got a small log of it, from a limb that blew off someone’s tree, but I have not yet cut it up, so, in spite of the fact that I “have” it, it is not particularly accessible right now.

Bruce Harvey, of Orcas Island Tonewoods,  once suggested that I learn what willow grain looks like and start watching the pallets and dunnage at work. (Apparently, though it is not popular for much else, it works for pallets and the like.) It took me a while to really learn what the grain looked like, but eventually I learned to spot it, and sure enough, a week or so ago, I spotted a likely candidate in a stack of dunnage (the timbers used to separate parts of a load of steel, for shipping purposes). I grabbed it (a 4 x 4, a little over 3′ long, dirty and battered) and checked it by whittling one corner. Bingo! Pay-off!

Tonight I needed a pile of linings for the new cello I am building, so, though I got home late after teaching a class, I walked out to the bandsaw, and, in five minutes (literally) I had a stack of linings big enough for two or three cellos…and lots more left over. (Thanks, Bruce!)

Tomorrow night I will get home a little earlier and expect that I will bend them all and install all the front linings. The following evening (or maybe Friday), I can install all the back linings. Then, Saturday, I can trace the back plate, I hope. (I haven’t even joined the front plate yet, so it will have to wait. Maybe I can get that done this weekend, too. 🙂

I’ll post pictures in another day or so. A pile of linings isn’t very exciting, unless you are building a cello. 🙂

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Cello progress

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Cello ribs installed in the mold, glued and clamped to the blocks.

Yes, you have to keep the wood warm!

The weather outside persisted in temperatures hovering just above freezing, so I brought the project indoors, heated the joints with a heat-gun, brushed hot water, slathered hot glue and clamped ’em home. Good glue squeeze-out all around; should be very good joints.

All ribs installed–glued to the blocks in the mold. Next step is linings.

Next Step: Linings

Actually, the very next step is to trim the excess rib length off the corners, and smooth them so that they are square-ended and straight along the edges…and parallel to one another. But that is a small enough task that I will combine it with installing the linings. The linings are a pretty easy, pleasant step in cello building…they are easy to make, easy to install, and the work goes quickly. That is what is next, and I should have it done pretty soon. Nice weather or no. 🙂

Thanks for looking.

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Small progress report on the cello–upper ribs installed

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Upper Ribs installed–Pegbox carved deeper

Tonight I shaped the upper sides of the upper corner blocks and the lower sides of the lower corner blocks to receive the upper and lower ribs.

Shaping the Blocks

I did some of the shaping on my oscillating spindle-sander–a very handy tool which has paid for itself many times over–and some with an incannel gouge (Curved, but beveled on the inside face, rather than the outer face), finally smoothing with a half-round rasp.

More work for the Bending Iron

I noticed that during the time the bent ribs have been languishing in the unheated shop, they had straightened a little, so I turned on both the bending iron and the glue-pot, and while I waited for them to get hot, I carved some more on the pegbox of the scroll. It is nearing completion, in terms of depth and inside dimensions, but there is a whole lot left to go before it is anywhere near final completion. It takes about 20-30 minutes for the bending iron to get really hot, and that is about right for the gluepot as well.

Installation procedure

I dry-fitted the ribs first, to make sure that once they were glued in place, both ends would fit correctly and the length of the ribs would lie flat along the curve of the mold. Then I loosened the lower end and slathered the hot hide glue on, and clamped the rib into the curve with a clamping caul (a elongated wooden block shaped to force the rib tightly into the curve of the corner block.) Once the corner block end was in place, I glued the upper end to the neck block.

Note to self: warm the wood before gluing!

The shop was awfully cold, and the glue was gelling very rapidly. I hope I achieved a good joint– if not I can correct it tomorrow. I should have heated the joints with my heat gun, before applying the glue, but I wasn’t sure where it was, and didn’t feel like stopping everything to go look for it…so I just worked very quickly. 🙂 We’ll see how it turns out.

My other work: barge-building

Tomorrow, Ann and I will attend a barge launch at Gunderson, LLC, in Portland, where I work. We build large ocean-going barges, and rail freight-cars, there. Here’s a video of an earlier launch, if you have never seen one: http://www.gbrx.com/Videos.php?expandable=2

(I would rather build cellos…) 🙂 When I get home I will try to get the lower ribs installed, and the pegbox completed.

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Beginning a New Cello

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Starting a new “Davidov” Cello

I decided a new cello was in order, and I hope to have it completed in time for the Marylhurst Musical Instrument Makers Show, the last weekend of April.

This will be another “Davidov” 1712 Stradivarius model, similar to the one on my Chronology page (instrument #16), but with a one-piece back. I like one-piece backs, but they are not very common on a cello. This wood (back, sides and neck) is from the same maple log as that from which instrument #19 (five-string fiddle #2) is made. The belly will be Sitka spruce. I plan to make the whole instrument darker than the last one was. Here is a photo of the slab from which the back will be made:

This is a slab of old-growth Big-leaf Maple heartwood. Not everyone will use heartwood, but I like it. I planed some of the rough surface off so that you can see the flame in the wood.

I will try to post photographs of the progress, as the cello emerges.

 

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