Day 178: Throwing Money Down a Soundhole

I've spent a pretty good chunk of change building out the shop, acquiring (the right) tools, and learning lessons far and wide. One of the best purchases I've made is the Shapeoko 3 XXL CNC machine. While it's largely a hobbyist's model, I love the darned thing. It fits perfectly in the shop and doesn't care which software I use to generate gcode to make it run. I use Autodesk Fusion 360 (for CAD/CAM) and two packages that came with the machine, Carbide Create and Carbide Motion, to also make designs and run the machine.

The worst thing about having a tool like a CNC machine is that it's a lot like a hammer - once you have a good one, everything starts looking like a nail. Fortunately, a CNC is not a one-stop answer for everything. In fact, it's quite limited in what it can for for me as I complete the instrument. Of course, as I learn more, that will change, but, for now, it helps me muddle through tasks that would otherwise be quite difficult to accomplish. Case in point: Cutting the rose hole into the soundboard.

I considered several ways to accomplish this. I thought about a hole saw, but had visions of the soundboard ripping to shreads under its marginally sharp teeth. Then, I thought I'd use the CNC and tried cutting the hole with an upcut router bit. A bit is defined partially by which way its spirals wrap around the bit when you hold it up by the end that is inserted into the router. If the spirals wrap to the right, it's an upcut bit; if they wrap to the left, it's a downcut bit. Some bits even have a combination of both.

An upcut bit drives the shavings and cut, as you would think, up toward the top of the cut. This is best when you want the bottom edge of the cut to be clean because this will leave a fuzzy top cut. When I tested an upcut bit, it left a fuzzy edge around the top circumference of the test material that was simply not acceptable. So, I headed to Lowe's and could only find a Dremel downcut bit, which didn't work too very well at all - it left steps in the cut, which is never a good thing. Eventually, I ordered a 1/4" downcut bit off of eBay and sat back to await its arrival.

In the meantime, Owen Daly recommended I visit him to observe how he cuts his soundholes using a circle cutter that fits into the drill press. I then remembered I had purchased one years ago and dug it out only to discover it was from that Harbor place and, basically, was a piece of junk. The test cut photos below attest to this.

The second one actually burned the wood. While I enjoy the scent of mahogany smoke as much as the next guy, it was not that pleasant this time around. I did a little research and realized I needed a better cutter, but, as with nearly every step of this project, life intruded and I was pulled away on other matters.

Until the downcut bit I ordered arrived. Then, the fun began.

The first thing I did was to run several test cuts on some cherry. Because the soundboard is roughly 3mm thick (less in some places), I set the cut pass depth at .5mm (which would require 6 passes based on the 3mm thickness of the soundboard) and let her rip.

I was quite pleased with the quality of the cut - no fuzz whatsoever - so I set the soundboard up on the CNC, held my breath, and went for it.

The result was a perfectly cut hole with a diameter of 69mm.

I shared a photo of the cut with a friend who owns a large CNC and he said, "That's one expensive circle." My reply: "Yeah, I just threw $1500 down a soundhole." Rest assured, I'll keep at it so I can amortize the cost of the machine into other cuts. Besides, it's really kinda fun.

Until next time...

Day 177: Deja Vu All Over Again

After the sizing episode, it was time to start gluing stuff to the soundboard. I started by lining out where the bridges and four foot end pins would go using a marking tool and punch.

Then, I threw some glue on the eight foot bridge and proceeded to get it down. I cut the heads off a few nails and used them as guides inserted into the existing holes. Once the go bars were in place, I removed the nails.

A word about go bars: This is an ancient method of clamping (or cramping for my friends in the United Kingdom) that probably goes back to the Egyptians, if not earlier. It simply uses the tensile strength of thin pieces of hardwood to bind whatever you're gluing to whatever is receiving it. In this case, it's all about pushing the bridges into the soundboard.

After 24 hours, I removed the go bars for inspection and all was well.

I then proceeded with the four footer, only there was a small hiccup - the damned thing snapped while I was bending it into position on the plan that was laid over the soundboard. Rather than become upset, I simply cut, bent, spokeshaved, and glued up a new one. All steps were completed within 48 hours. Easy peasy. So easy, in fact, I'm thinking about changing the company name to Tortuga Early Instruments Harpsichord Bridge Company.

Now that the bridges are in place, I need to cut out the sound hole (especially before I start gluing things to the back of the soundboard). I'm not going to disclose how I'm cutting it at this time, though I'll throw you a hint: Clean No Cars.

On a couple of tangentially related notes, I acquired a nice holly log from a woodworking friend. Thanks, Kate!

Like the PEEK from Robert Webster, I now have enough holly to make jack tongues for the rest of my days on the planet.

Another generous friend, Geir Bremnes, sent me drawings he has made of an I. Ruckers 1640 single manual that resides at the Rijksmuseum in Amsterdam. He's one of the kindest people I know and has asked me to pay it forward as a way to repay him for his generosity.

I'll be posting more about this instrument in the days ahead. Thanks again, Geir!

Until next time...

Day 176: Curling for Fun and Profit

Once I settled on the locations of the bridges on the soundboard, I could go ahead and make some more drastic measures to get things into place. For instance, the best way to position the bridges into the soundboard is to drill holes into them and nail them to, say, a piece of plywood under the soundboard.

As you may recall from my last post, I positioned the bridges according to their original locations on the R.K. Lee drawing of the 1640 as it currently sits in the Yale Collection of Musical Instruments. It was fairly nerve-wracking driving nails into my beautiful, pristine soundboard, but it was required, so there you go. And I did likewise with the 4' hitchpin rail, which will be mounted on the reverse.

More than anything, these become positional guides during glue-up, which will happen this weekend.

Another interesting aspect of soundboard preparation is the application of "sizing". Size is simply diluted glue. In this case, it's diluted glue made from animal protein in an 11:1 water to glue ratio. Sizing is typically used for later gluing because it will soak up and guide full-strength glue during a gluing session. In this case, it's intended to tighten up the soundboard, enhancing it's tonal qualities.

Now, the really interesting aspect of this exercise is the curling it produces on the incredibly thin (2-3mm) jointed piece. The top did not produce much curling (this is probably a photo from after it had settled down a bit).

The back was another matter entirely.

As I like to say, "Oh, boy." As nerve-wracking as driving nails into the precious thing was, watching it curl like this put my teeth on edge, so I stepped out of the shop for a couple of hours. When I returned, this is what I saw:

Whew. The little fella had settled down considerably and I could breath much, much easier. Of course, this is what Owen Daly said would happen. I trust him completely, but it was still interesting to observe.

Another aspect of the sounboard is the apparent discoloration. The photo of the top was taken while it was still pretty wet with the size. When it's dry, it maintains a consistent cream color. This was intentional. When I purchased the wood, it was in a stack of "piano wood" that had been sitting in a retail space for the better part of 15 years. This resulted in the outside of the wood darkening a bit. I purposely put the darker sides on the reverse. Once the soundboard receives the bridges and a little paint, all will be well.

Until next time...

Day 175: In the Green

After input from master builder, Owen Daly, and much research and deliberation, I believe I've come up with the proper placement trajectory for the bridges. This all began when Owen noticed something might be a little off with the placement of the bridges that would affect the ultimate tone of the instrument. In the absence of having specs on the original instrument this copy represents (the A. Ruckers 1640 single at the Yale Museum), I found string speaking lengths in "the O'Brien book" for an A. Ruckers 1637 single and recorded them (see table below).

Now, the instrument in Ernie's eBook Most Excellent represents a ravalement (later alteration) of the instrument, making it wider, which I believe would affect the placement of the bridges. Yet, I had a nagging suspicion I would want to stick with the original placements. This presented a secondary problem: I didn't have a drawing or any detailed information on the original instrument.

This is when Owen came to the rescue by loaning me his copy of the drawing done by R.K. Lee in 1971 of the original instrument at Yale.

This was a revelation. Based on the drawing, I created a spreadsheet comparing the 8' and 4' string speaking lengths (typically done for all Cs and Fs as a quick gauge) using all the data I had at that time. All measurements are in millimeters.

8’ Miller 1640 Yale 1637 AR* 4’ Miller 1640 Yale 1637 AR* c''' 171.5 169.5 171 c''' 89 80 83 f'' 257.5 259.5 258 f'' 132.5 126 129 c'' 331.3 345 348 c'' 174.5 169.5 173 f'  485.5 512 531 f'  253.5 245 258 c' 623.5 677 698 c' 332 324 338 f 884.5 927 963 f 450.5 450 474 c 1073 1111.5 1165 c 544 545 580 F 1320          1368 1351 F 695 697 717 C  1393.5          1409 1366 C 800.5 787.5 736 *Germanisches Nationalmuseum, Nuremberg, No. MIR 1073

As you can see, the figures in the tenor and at the hook vary a bit, yet all of the Yale 1640 figures are either very close or nearly the mean between Miller's copy and the 1637, especially with regard to the 8' numbers.

At this point, I marked out the 1637 and 1640 pins on the Miller plan. The orange marks represent the 1637 and the green represent the Yale 1640.

I now must make a decision: Do I follow the Yale green points or Mr. Miller's CAD drawing? Interestingly, when I laid the bridges onto the R.K. Lee drawing, they were a nearly perfect fit to the Yale 1640 marks with little final bending during glue-up required.

My inclination is to follow the green marks wherever they may lead. Regardless of my decision, the bridges will be glued down this week. Finally.

Until next time...

Day 174: Making Room and Holding Space

As I mentioned in previous posts, I recently acquired a CNC (Computer Numerical Control) cutter/router. It's an amazing tool that I've already used to great effect. I made space for it when I knew it was coming to Tortuga Early Instruments Worldwide Headquarters, but I failed to completely understand just how big the thing would be. It's big. Like 48" x 48" big. I had it sitting on the assembly table for the better part of two months and, when it came time to get back to working on the instrument soundboard, found myself in this predicament:

You can see my dilemma. Now, my good friend and building mentor, Owen Daly, was about ready to break a foot off in my ass because he had asked for string speaking lengths for all Cs and Fs between the eight foot nut and bridge and it appeared I was making excuses for not sending him the data. I had not sent it because I was fed up with the lack of space. The shop is already small enough, you know? So, I did what I always do - I engaged Cheapest Guy Alive Mode and jumped onto Craigslist.

Within minutes, I found what I was seeking: large pallets I could take apart and use to build a stand for the CNC. And they were right up the street. And they were yuuge, like three feet by six feet with 2 x 8s running their lengths. This was a major score and I was able to fit them all into my beloved KIA Soul with the help of my lovely wife. After nearly an entire day of cutting, cutting, cutting, fitting, and screwing, I managed to create this:

It's a little tight between the new stand and the end of the Roubo, but you make do with what you've got, right? Besides, I can just swivel the seat around and use the drill press table to my left as a computer stand when running the machine. So, mission accomplished. And I reclaimed my entire assembly table.

I feel like I'm working on a football field and I like it. Now, back to the soundboard.

The first thing I did with the soundboard was to fit the plan to it using the parameters supplied by Mr. Miller in his eBook Most Excellent. Once that was completed, I spoke with both Mr. Miller and Owen about fitting the bridges. I'm going to end up drilling holes near the Cs and Fs between strings and use these as alignment points with small nails. Yep - I'm drilling through the bridges into the sounboard and nailing them all to the assembly table.

I'm currently taking my time getting things lined up properly because, honestly, the thought of doing this makes my poor, old stomach hurt. But it must be done. I'm hoping to have everything solid within a couple of days.

As I thought about gluing the bridges to the soundboard, I realized I would need cauls for the glue-up procedure. A caul is simply a fitted piece of wood that sits between the subject of the glue-up and whatever you're using for clamping (in my case, it will be go bars) and spreads the clamping pressure across more of the subject piece. So, I started to make cauls in two pieces given the fact that one side would need to be cut at a 30-degree angle to fit on the bridges properly.

I'll have enough to clamp and glue both the eight and four foot bridges.

On a couple of tangentially-related notes, I was able to attend the Western Early Keyboard Association (WEKA) Spring Soiree this past weekend. Several performers, including Owen Daly, entertained us on instruments made by Owen and Paul Irvin, both master builders. It was a wonderful time with like-minded people and I look forward to the next gathering.

Owen is playing his Vaudry copy while Paul looks on

And, finally, I must give honorable mention to another shop improvement: Roubo bench tenon plugs. I know what you're thinking: "Whada?" Well, when I cut the mortises for the bench, I did a pretty horrible job until I discovered a way to cut them that resulted in minimal tearout, which happens a lot with a laminated spruce beam. Naturally, I discovered this on the last mortise, so the other three were pretty rough.

One day not long ago, my friend, John Finn, said, "Hey, why don't we just plug those tenons?" The voice of experience always rules the day at Tortuga Early Instruments, so I took him up on the offer to help. A couple of days ago, he showed up with a template, a plunge router, and clamps - I made and served breakfast. A couple of hours later, all four tenons looked like this:

An amazing transformation. Two or three coats of Watco Clear Danish Oil and all will be well. Did I really need to do this? Heck no. But, sometimes, the better part of valor is attending to appearances. Thank you, John. I couldn't have done it without your help and guidance.

Until next time...

Day 173: Pulling Out the Big Gun

I've gotten quite a lot accomplished since my last post; unfortunately, most of it has been related to climbing the learning curve on some CAD/CAM design software I'll be presenting in the next few weeks. In the meantime, I ended up finishing the eight foot bridge. I did not use a band saw, which I know would have been quicker, but I really did enjoy the process I chose: Drawknife and spokeshave work. Initially, I started with the spokeshave.

I quickly realized I would need to take off more meat with every stroke, so I pulled out the Big Gun.

With a little support from Mssr. Roubo.

Things went swimmingly until...

I was done.

Just look at that hook.

While I found cherry much harder to work with than beech, I can see how it might help produce a more pleasant, ringing tone. The physics behind tonewoods and how they can amplify (or dampen!) the acoustical output of an instrument are well know, so I won't belabor them here. Suffice it to say, a wood that's more "plastic" without some brittleness (for lack of a better term) might not be the best choice for a soundboard. In this case, cherry is the better choice for the bridges.

While working on the eight-footer, I managed to also mostly complete the four foot hitchpin rail, just need to finish sanding the sides to even things up a bit.

This piece will be glued to the reverse as opposed to the obverse, which will get the bridges, of the soundboard, as will the cutoff bar and ribs. I'm preparing the blanks for those in the photos below and will continue to work on them throughout the week.

Until next time...

Day 172: Getting the Eight-Footer Locked Down

The four foot bridge has been steamed, bent, spokeshaved, and otherwise prepared for installation (still need to cut to length, but I'm not a detail guy). The eight foot is another matter entirely. When comparing it against the plan, the angle was not as acute as it needed to be. As I was testing it against the form, I heard a loud CRACK and you'll never guess what happened. Yep, this:

Just a scratch, right? So, it was back to the drawing, or steaming, board as it were. One thing I should call out is how to read wood. In this case, I had bent the thing with the flat sawn part of the piece on top. This created an akward bend that resulted in the break. Granted, I probably could have made it work, but I paid closer attention on the second bend and faced the quarter sawn side face up. Though I did this, I still didn't achieve the angle required by the plan, so it was back into the steamer and form. Again.

Only this time, I used the four foot part of the bending form because it would allow me to overbend the stick to account for springback, something that's pretty common when bending wood, especially material that's been kiln dried; it just wants to go back to its original shape when removed from the form.

As you can see, the bend is sharper. A little TOO sharp, perhaps?

Nope, it fit the plan spectacularly well. Time for a celebratory adult beverage. Oh, wait, what's that? Why, it's a pitch pocket in the worst possible location.

Given the fact this side will get a small bevel, I knew I would be spokeshaving most, if not all, of the pocket away, but decided to check with master builder Owen Daly just to be sure. Fortunately, Owen said it's not a show-stopper and that there are a couple of ways to handle it if and when necessary. Based on this information, two things then occurred: 1) Happy dance and 2) Preparation for tacking on the bass hook I had cut a little earlier.

I taped the pieces together, drew a slanted line, and cut them on the band saw. When I checked the joint, it was good enough for government work, so I glued it up.

And now we wait until tomorrow to trim things down. In the meantime, I turn my attention to the four foot hitchpin rail that will be mounted to the underside of the soundboard. This one is made from poplar and will be cut to size - no bending involved (thank the Good Lord Above).

Until next time...