Posts Tagged ‘arching’

5-String Progress #9: Back Plate

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Five String Fiddle Progress: Back Plate

Flattening the back of the garland

After the glue was completely dry, I removed all the clamps from the linings and cleaned up the interior: that is to say, I tapered the back linings, so that they faired smoothly into the ribs, and I shaved and scraped the blocks to their final shape.

Then I rubbed the back surface of the garland (rib and block structure) on a “sanding-board” to level the back of the garland, and to ensure that the back of the neck heel was completely level with the back of the garland. That way, I can fit the back plate absolutely flat against the garland, and trace the shape.

I didn’t take a picture of this procedure, this time. Here are some taken when I was building a cello:

Sanding board with cello garland

Sanding board with cello garland

 

Flattening a cello garland on a sanding board.

Flattening a cello garland on a sanding board.

I make pencil-marks on the edges of the linings, ribs and blocks, all around, and scrub until the marks disappear. When all the marks are gone, the garland is flat. It gets pretty vigorous and physical, but it is quite effective.

Here is the flattened garland, ready to trace the back plate:

Flattened garland.

Flattened garland. Notice that the neck heel is dead-flat level with the back of the garland.

As you can see, the blocks are quite smooth, now, and the linings taper gently into the ribs. After this point, there will be no more changes to the interior of the corpus, except as it directly affects the back plate.

Tracing the plate

I clamped the plate to the corpus, carefully centering the glue-seam of the back plate on the centerline of the neck and the end block.

Garland centered on plate

Garland centered on the back plate

 

 

Garland clamped to the plate.

Garland clamped to the plate.

Then I traced around the garland using a ball-point pen and a flat washer whose flange is exactly 2.5 mm wide, so that my line will be 3 mm from the ribs, all around. I watch carefully to make sure the washer stays flat on the plate…they have a tendency to flip up and follow the pen. I work along the perimeter, giving several strokes to every part, so that the line will be visible against the dark wood. Notice that this procedure makes “round” corners. I will modify them before cutting them out, so that they are the correct shape.

Tracing the shape of the plate.

Tracing the shape of the plate, using a washer and a pen. (Yep, that is a Gunderson pen!)

 

And, there is the plate, almost ready to be cut out:

Traced plate, ready for cutting out.

Traced plate, almost ready for cutting out.

One thing I do, that I forgot to photograph, is that I re-shape the corners. I use a straight-edge to connect a line from the end of the rounded corner where the pen circumscribed the corner of the rib to the center glue line at the location where the purfling will cross the far end of the plate. (Or, you can just use a 30/60/90 triangle to lay out a 30-degree angle off the center glue line on the end of each corner. But I do it with the straight-edge.) Then I continue the curves of the inner bouts to connect with the straight lines I just scribed in, and the corners are complete. I use a sharp scraper to remove any ink lines that are not part of the perimeter outline, and then I really am ready to cut out the plate.

Cutting out the plate

I use a band-saw to cut within a millimeter of the line, and then use an oscillating spindle sander to perfect the edge, right up to the lines. These and my drill press are pretty much the only power tools I use, though I have occasionally used an angle-grinder with a coarse sanding disc to remove rough excess wood, on larger instruments.

I run my fingers around the edges looking for lumps, and work those out as well, using a file as needed. Here is the completed plate blank:

Plate cut out and ready for arching.

Plate cut out and ready for arching.

At this point I also sketch in the interior graduation plan–just the outline of the inside boundaries of the plate, so that I know where I am going to carve. There is no reason it has to be done at this point, but it helps me remember which side was outside and which inside…and that really does matter, as the plates are vitually never exactly bilaterally symmetrical. If I forgot and arched the wrong side, the completed plate would never fit the garland (ask me how I know…).

Interior Graduation boundaries sketched on correct side.

Interior Graduation boundaries sketched on correct side.

You can see that there are numerous bark inclusions in the wood, which I will fill with matching wood…but I will wait until the arching is complete before I attempt to fill the holes, so that I do not plane away my plugs. It is unsusual to use wood with holes in it like this, but it is also unusual to use anything other than maple for a violin back. Five-string bluegrass fiddles are not burdened by the same 300+ years of tradition as violins, though, so exotic woods can be used. This wood has amazing flame and figure in it, and the plugged holes will not detract from the beauty of the wood.

Before I begin arching, I establish the edge-thickness all the way around, using a “wheel-style marking gauge“, set to 4 mm. It has a tiny sharp wheel that does the marking, and it makes very cleanly scribed lines.

Edge thickness marked

Edge thickness marked on correct edge. (Notice the bark inclusion on the other edge)

Beginning arching

I used a Japanese-style pull-saw to cut the approximate height of the plate thickness on each of the corners, so as to avoid unnecessary stress on the corners while carving the arching. It looks a little odd until the arching is complete, but it avoids the possibility of breaking off a corner. I use a large, sharp gouge to reduce the edges and begin the arching; then a toothed finger plane to continue the curves until I am very close to the desired shape. at that point I will switch to a smooth, curved-sole plane and bring the arching to nearly exactly the desired shape. From that point on, a variety of scrapers will be my only shaping tools, for fear of tearing out wood along the figuring .

Here are some photos of the progress. This is very hard, difficult wood to carve, and my hands are giving out, so this is about as far as I am going tonight:

Beginning arching 1

Beginning arching: notice the saw-cut corners, and how the one has been carved almost to a normal curve.

 

Arching back plate in cradle

Different viewing angle: The cradle is thick pine, with a plywood door-skin, to secure the plate. Inside, it is cut away, so that the plate can fit arched-side down. The plywood is right at 4mm thick, same as the finished plate.

 

Continuing arching back plate

Continuing arching. Still quite a way to go, but I am getting tired.

So…that is it for today. Pretty fancy wood, isn’t it? The customer bought it in Hawaii 33 years ago, or so, and has dragged it around all these years, until he decided that he wanted a five-string fiddle.  Probably the only opportunity I will ever have to make a fiddle out of curly Koa,  but it is really going to be a beautiful instrument.

My hands are getting too tired to work effectively. I will try to get more done later this week.

Thanks for looking.

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Five-String Fiddle Progress Report #4: Graduation

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5-String Progress Report #4

Graduation

Graduation begins with measuring in the spots where it already feels a little thin, so as not to make a fatal mistake and carve right through the plate. (It happens!)

Once I know where I am free to carve, and where I need to take it easy, I begin by carving cross-grain with a medium-large gouge. I check periodically with a caliper. When it begins looking closer to the right shape inside, I measure again, and double check those special spots.

carving inside violin front plate

Beginning graduation, using a gouge.

Then I go after it with a toothed finger-plane. This is really just an Ibex 18 mm finger-plane with a toothed blade, and a wooden handle added to save my fingers. I originally added that handle to keep from blistering my forefinger and thumb, as I had done so on every single instrument up to that point. (That was my #16 instrument– a cello.) I was surprised to discover that it also gave me much more power and control so that I was able to set the blade deeper and carve much more aggressively, taking off much thicker shavings.

Toothed plane use

Using a Toothed Finger Plane to further the Graduation process.

Once it is smooth inside, and within a millimeter or so of completion, I switch to a smaller finger plane and cut more gingerly, until it is all within a few tenths of a millimeter of the goal thicknesses, and then I finish with scrapers. Here is how the plate looks at that point:

graduation...inner arching.

Graduation nearly completed– the skewers are only there to create shadows so that the contiour will show in the photograph.

inner arching.

Another view, at a lower angle. There are still a few lumps to smooth out, but the graduation is essentially complete.

Usually, by that point, I am beginning to see the interior of the f-holes, too, because, as you may recall, I had incised them pretty deeply. Once the inside is complete, I finish cutting the f-holes. Many people use a jeweler’s saw, a fretsaw, or a coping saw to cut out the f-holes. I generally just use the knife, except that I do have a special tool for cutting the round upper and lower eyes.

And that is what I will show in the next post…which, hopefully will be sooner this time.

Thanks for looking,

Chet

 

 

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Five-String Fiddle Progress post #3

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5-string progress #3

Arching and F-holes

Last time, I had traced and cut out the top plate, and actually, I began the work on it, thinning the plate to the desired arching height– but that is when I discovererd that there was a bark inclusion that extended right through the upper bouts. So, for those “sharp-eyed” among you, who notice that the grain has changed; Yep. It surely has! Too bad…I liked the grain of the spruce in the plate I first chose, but it turns out it was just a little too interesting.

So, on this plate, all I have done is the outer arching and the layout and incision of the f-holes. After completing the arching, but before final scraping, I laid out the distance from the upper edge of the plate to the “stop” line (where the bridge will stand) at 195 mm, then laid out the distance between the upper eyes at 42 mm. I used a plastic template that I made years ago (cut out of an old flexible face-shield– the kind welders use when they are grinding steel) to lay out the shape of the holes, then incised them deeply with a thin knife. They would have been virtually invisible in the photos, so I traced them again with a sharp pencil after incising them, so that you could see them in these photos.

Arching and f-holes

Arching complete, f-holes laid out and incised.

Arching: Final Check

Next I checked the arching by sighting edge-ways at the plate, to see whether the main stem of each f-hole is fairly parallel to the rib-plane. Usually I find that I have left the arching a little too “puffy” around the lower stem and lower eye area of the f-holes and need to plane away a few more strokes to get the stems lined up. I don’t think the looks of the f-holes are the main issue, here– the shape of the arching is fairly critical to the sound, as best I can understand, and this is just a “marker” for me to check.

Side view of f-holes.

Checking to see that f-holes are aligned with rib-plane.

Obviously, this alignment is something I have to do before I try to complete the inside carving, or there might not be sufficient thickness left to do the final adjustment. I try to estimate and get this area as close to correct as possible before laying out the f-holes, but I have had to adjust them at least a little, every time, so far.

After I am satisfied with the overall shape of the arching, I use scrapers to reduce all the lines and ridges left by the finger planes into a smooth continuum.

Graduation: Beginning the Interior

Once I have the outside arching the way I want it, I can start on the inside, and the final graduation of the plate. I hold a pencil in my fingers so that about 9 mm protrudes onto the plate, and then run my fingers around the edges…nothing precise about it: it is just a guideline for carving. I want to leave this area untouched until the last bit when I am scraping the inside, before installing the bassbar. I use the same template that I use for the final shape of the end blocks to scribe the shape of the area to be glued to the blocks. I scribe in the corner blocks  with a curved scraper that just happens to fit the shape I want. All this outer perimeter area will be left flat until the last step before installing the bassbar, and/or installing the plate on the ribs. I want just the gluing surface flat when I am ready to install the plate.

Inside front plate, before carving

Inside carving plan.

Preparing for Graduation: Measure First!

It pays to use a caliper and check the thickness all over before beginning to carve. I do have a mental image of the desired shape of the interior, but I do not have a mental map of the thickness of the plate, so I measure at least the areas that already feel pretty thin to my fingers, and decide how much should come off in each area. As it turns out, this time, no areas are really borderline, but some are within 1.5 mm or so, so I will be careful around those places. I am aiming for about 3.5 mm down the middle, fairing down to 2.5 in the upper and lower flanks. and a few places 2 mm, very likely. I will try to leave some areas a little thick, where there is a likelihood of cracking, but in general, I expect this will be a pretty thin plate…the spruce is a little dense (which I have had good results with in the past), so it can stand to be a little thinner than usual.

After the inside is carved and scraped to my satisfaction, I will complete the cutting out and shaping of the f-holes, then chalk-fit and install the bassbar. I will post photos of all that.

Thanks for looking.

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Building a Cello–Step #9

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Step #9–Arching the Plates

Arching the Plates

If one looks at a violin-family instrument from the side, to see the front and back longitudinal arches simultaneously, it is easy to observe that the front and back are not arched the same. Some may argue that they began identical, but that since the stresses on front and back are not the same, the wood has crept, and the Old Master instruments are no longer the same shape they were when they were new. OK…I wasn’t there 300 years ago, so I don’t know…and if I had been, I’ll bet I wouldn’t remember. But we can see that, however they were back then, they are not the same now, and the best instruments have certain things in common: The back is essentially a circular curve; perhaps more accurately a curtate cycloid curve, or, possibly a catenary curve. The Curtate Cycloid seems to fit the best…it is sometimes called a hypocycloid, too. But the front is different– there is an area in the high middle that is nearly flat, by comparison with the back. The area between the f-holes and between the bouts flattens out considerably, compared to the back. This is an important difference, and is critical to the sound. Go online and look at a bunch of side-view photos of fine old violins. Once you see it, it is unmistakable.

Until a maker masters this aspect, it is really wise to make a set of longitudinal and cross-arching templates, and use them religiously until you can see the arching and tell whether it is right or wrong by personal experience. The archings will keep you out of trouble, just as using a map keeps a person from getting lost.

Make the templates and Use them!

I used the drawings on the back of the Davidov poster to trace and cut out a set of arching templates. I have enough experience to start out without the templates, but not enough that I trust my eye to just cut the arches by instinct, or something of that sort. Here is the rough arching before I used the templates…you can sort of see the “table” area in the middle, where the shavings are sitting.

Rough Front arching, showing the Semi-flat area in the center.

Rough Front arching, showing the Semi-flat area in the center of the Sitka Spruce Cello Top.

I rough out the front and back, using gouges and planes, and get the area around the edges pretty close to exactly the thickness I will want the finished edge. Then I intall purfling (which we talk about in the next topic), and use templates to finalize the arching. I have made a few instruments, so I have the confidence to get pretty far along in my arching before using a template. There is nothing wrong with using them from the first attack.

Here is the back, ready for purfling, but before using the templates. Still too “puffy” in places, but looking like a cello back.

Rough Back arching cello

Rough back arching, showing the curvature of the Oregon Big-leaf Maple cello back

 

Here are the templates in use (notice the purfling is in place).

Front arching Template in use

Front arching Template in use

Back arching template in use

Back arching template in use

Here are the transverse arching templates: they are used in the same manner.

Transverse arching templates

Transverse arching templates

When the arching matches the templates as closely as I can manage, I begin using scrapers to smooth and give final shape to the plates. Then it is time for inside arching. But first, we need to talk about purfling, since that was done in the middle of this article.

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Five String Fiddle (slowly) Handmade in Oregon

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Five String Fiddle Progress

Life is what happens while you are making other plans, they tell me. This season has been loaded with distractions. I worked a lot of late hours at Gunderson, Inc. where I was teaching classes on Welding Supervision.

Two young fellows were coming to the house a couple of times per week to work on instruments they were building. One was working from a kit, but had zero experience with tools, so it required a great deal of personal attention; the other built from scratch, and is nearly finished with a very nice 15-5/8″ viola, a fairly faithful copy of the 1580 Gasparo da Salo viola. (Funny, when those young fellows are here, I don’t get a thing done on my own work.) I did begin three 5-string fiddles, months ago, but have only made measurable progress on one; the Spalted Maple 5 string fiddle.

I took two weeks vacation between Christmas and New Years, but ended up being sick nearly the whole time. Besides, my daughter was home from school for that two weeks, so I had reason to be distracted. 🙂 I did get a couple of work days in, but it has been a struggle.

Finally, I have several repair jobs going, each of which really needs to be done, so, to make a long story slightly shorter, things haven’t turned out as planned.

Double Purfling Complete, Including Purfling Weave on Back

The maple for the one-piece back is some Oregon Big Leaf Maple that was given to me by a local landowner and forester a few years ago. This is the third instrument I have made from that tree. It is a relatively soft maple, and has had a very nice tone, so far, in my experience. I have made one five string fiddle from it, so far, and one cello.

The Spruce is Sitka– a one-piece sitka front plate–  only the second time I have ever seen one, and it is some of the toughest spruce I have ever worked with, which I think will make a good, thin, top plate for the instrument, as I have made one instrument before with very similar spruce, and it turned out a winner, as a bluegrass, celtic and country fiddle. But it was not fun cutting the double purfling by hand, as every “winter grain” was so hard it would catch the knife blade and try to turn it.   However, here is the progress so far:

Progress on 5 String Fiddle

Progress on Five String Fiddle

Today I will make the final corrections on the front and back arching and cut in the f-holes (I hope), then begin graduating the front plate. Hopefully, by next week, I can have the corpus nearly completed. Maybe somewhere in there, I can get a good run at the other two fiddles, as well. I really need all three completed by the time of the show in April. There will be about 500 people per day, coming through that show, and some of them will be fiddlers. 🙂

We will see; I am feeling somewhat less than optimistic, however, after the experiences of the last three months.

Thanks for looking.

Chet

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Front and back plates fully arched, f-holes incised

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Final arching is complete

Low-angle light and Scrapers

Today I used low-angle light to reveal all the humps and hollows, and used scrapers to bring all of them to a smooth continuum of curving wood.

“Flat F-holes”

Once I had the front plate fairly smooth, I laid out the f-holes, and incised them deeply. My reason for doing this is that every single instrument I have made, the arching proved to need correction, as revealed when I laid out the f-holes. Invariably the arching was too “puffy” around the lower ends of the f-holes, so I had to re-carve that area. Finally it occurred to me that if I cut the lines in, they would remain visible as I carved, and I would not have to lay them out over again. That turned out to work pretty well, so now I routinely assume I will have to correct the arching, and I incise the f-holes, then view the plate from the side: what I am aiming for is that the general shape of the f-hole will seem to lie in a plane parallel to that of the ribs when the instrument is assembled, rather than describing a lazy “S” from the side.

Here is an example from an unfinished viola, from several years ago:

Flat F-hole

Flat f-hole

It is not something “exact”, but more of a general impression. One way or another, it allows me to see when my arching is not right, and correct it.

So, here is the top plate with the f-holes incised. I will finish cutting them out after the inside carving (graduation) is nearly complete.

Cello Front Plate with f-holes incised

Cello Front plate with f-holes incised

Here’s an end-view…doesn’t show much:

End View of Cello Front Plate

End view of Cello Front Plate

And a sort-of  “3/4” side-view…trying to show the curves:

3/4 view of cello front plate

3/4 view of Cello Front plate

Here’s a close-up of the c-bout with the f-hole incision (I used a special f-hole cutting tool to incise the circular parts):

Cello C-bout with incised f-hole

C-bout with incised f-hole

Annnd the back plate: (still may be a bit puffy in spots…I will work on it more later. Right now my hands are hurting from all the scraping) That’s all for today! I’m worn out.

Side view one-piece Cello back plate

Side view one-piece Cello Back plate

End-view of one-piece cello back-plate

End view of one-piece cello back plate

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Front cello purfling channel cut

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Front Purfling Channel Cut: Final Arching Begun

First mark the Crest of the channel, then cut the channel!

When I first began making fiddles, it had never occurred to me that there was a specific distance from the edge that I should aim for– I just started cutting, and eyeballed the whole edge. As a result I had some very rough-looking fiddles. Now I mark about 40% (2mm, in this case) in from the outer edge, and cut my channel so that the edge of the channel hits that mark, while the top of the purfling gets trimmed back so that it is clean and smooth.

I used two gouges to cut the channel–a small one to carefully trim back the narrow lip of wood between the purfling groove and the marked crest, and a larger one to cut the rest of the channel.

Then Begin The Final Arching

Once the channel was relatively close all the way around, I began cutting the longitudinal arching down to the final level. I will not complete it tonight…I had two phone calls and a customer (future) show up, so that took up a bunch of time, and now it is getting late. Here’s what it looks like for now:

Cello Front Purfling Channel Cut

Cello Front Purfling Channel Cut

Cello Front Lower Bass Corner

Front Lower Bass Corner

Anyway…that’s it for tonight! The Spruce cuts very easily with a small, sharp plane. I hope to complete the arching tomorrow evening.

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Cello top purfled– ready for final arching

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Cello Top Purfled and ready for Final Arching

Fresh Purfling

Here is the cello top, freshly purfled, hot hide-glue still wet. Tomorrow night I will try to complete the final arching and lay out the f-hole perimeters.

I had some distractions tonight, but that is life. Life is what happens while you are trying to complete your projects and plans. Embrace it or fight it, that is simply how it is.

This spruce has very pronounced winter grains, which were hard to cut smoothly for the purfling slot, but the plate rings like a big bell if you tap on it. I think it will probably be a very good cello.

Freshly Purfled Cello Top

Freshly Purfled Top

Anyway, tomorrow evening when the glue is dry, I will cut the channel and begin finalizing the arching. If I get it close, I will try to get the f-holes laid out and outlined. After that it will be time for graduation of the plate (carving the inside arching).

Press on!

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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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