First Cello Build

Tom Griffin
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Re: First Cello Build

Post by Tom Griffin »

Looks like I'm not allowed to edit my own post, so I'm reposting it to correct some errors with the pics. I'm also adding a pic of the bass bar installation.

I reached a milestone in the project and got the body closed up. It was a shame to cover up the work that went on inside, but it's good to see the hard part done. The thing emits a nice clear tone when tapped on the back, so it seems to be working as it should. I also got started on the neck by sawing out the rough outline. Now it's time to get to work and start carving the scroll. I think I can see light at then end of the tunnel.

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Barry Daniels
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Re: First Cello Build

Post by Barry Daniels »

Tom, you can edit your post by clicking on the pencil icon at the top.
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Tom Griffin
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Re: First Cello Build

Post by Tom Griffin »

Barry Daniels wrote:
Mon May 11, 2020 4:04 pm
Tom, you can edit your post by clicking on the pencil icon at the top.
The edit function is apparently short lived, because the pencil icon no longer appears. It's even gone on the post I created today.

Tom
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Barry Daniels
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Re: First Cello Build

Post by Barry Daniels »

Yep, you are right. I think you have 30 minutes to edit a post, then the concrete sets up.
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Tom Griffin
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Re: First Cello Build

Post by Tom Griffin »

The mortise is cut to attach the neck, but I decided to wait until all the carving was finished. I've seen it done both ways, but it seems like it would be a lot easier to do with the neck unattached. Most of the carved features are at least roughed in, but I still need to carve the backside of the volute. I've definitely learned to respect wood carvers, because this stuff takes forever. I plan on taking extra time to make everything as smooth as possible in hopes of saving a lot of scraping time later on, but not sure my gouging skills are up to the task. At least the final scraping can be done with the neck attached. Once that happens, all I have to do is fit the tuning pegs and fashion a rough nut, and the thing can be strung.

Tom


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I cheated and hogged some of the peg box out on the mill to save the time and aggravation of doing it all with chisels.

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Generating the flat surfaces on the inside was much more difficult than the curvy stuff.

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The mortise was fitting using chalk to spot the high areas and then chiseled and scraped to size. About a 1mm gap was left at the bottom so the neck could be wedged in when glued.

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The saddle, or lower nut, to mount the tailpiece that the strings attach to.

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The projected height of the fingerboard at the bridge is critical and I ran a bit short of material on the heel dialing it all in. Turns out there is an error in the plans that I missed that contributed to it. No biggie though, it just means the button that the heel butts up to will be slightly smaller than it should be.

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The fingerboard is temporarily mounted for fitting. The part that extends past the neck will need to be thinned out after the top surface is shaped.

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The bridges come very thick and rough and require extensive fitting. Not really looking forward to that, but it will be one of the last tasks before varnish.

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The neck has been very roughly shaped with rasps. I still haven't broken out the templates for the final shape. Just going by eye for the moment.

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Tom Griffin
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Re: First Cello Build

Post by Tom Griffin »

I've been delinquent in keeping up with my progress, so it's catch up time.

The carving on the scroll is complete and it just needs to be finish scraped. The entire instrument will require that, so when all of the construction is done, I'll scrape everything just before varnish to keep it clean.

The dyes arrived for the varnish, so it's about time to cook. I plan on using the recipe provided by David Ireland on YouTube to make it. I want a deep burgundy color, so the plan is to stain it all light brown after the sealing (ground) is applied, to make it all an even color, and then put a coat of red and a coat of blue varnish over it. Since the layers are transparent, the brown should show through the red and blue layers, resulting in a burgundy color. Or I may just use one coat of purple varnish to keep the thickness to a minimum. Of course it will all be proven on scrap before anything touched the cello. I also plan on blackening all of the chamfers, and the inside edges of the sound holes and that will go on under the final layer of clear.

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The backside of the volute was a challenge because the carving covered a large area and it was difficult to keep it all the same depth. The trick was to make multiple small passes and then clean out the remaining wood that was left.

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I made a tradition pencil sharpener type peg shaver, but couldn't get the thing to cut cleanly. Having never seen one up close, I was likely missing a key design feature. After beating on it for way to long, I eventually tossed it in the trash can and made a fixture to hold the pegs in the lathe and used the taper attachment to turn the tapered section to size. I was able to match the taper reamer pretty darned close and it made for a nice tight fit.

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There is a lot of conflicting information out there on the shape of the fingerboard, so I just gave it my best shot. After stringing the cello and setting the string heights, it looks like I got close, but may want to pick up another fingerboard and try it again. They were so cheap, I knew I should have bought a couple.

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The nut was well oversize and required final shaping after being mounted. The string height at this end is about 1/3 the diameter of the strings. There are small grooves in it to guide the strings toward the appropriate tuning peg.

I strung the cello up tonight for the first time and it was rewarding to hear it make sound. It's been about 48 years since I last played one, so it wasn't great sound, but hopefully that will improve. :D

Tom

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Charlie Schultz
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Re: First Cello Build

Post by Charlie Schultz »

Fabulous!

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Bob Gramann
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Re: First Cello Build

Post by Bob Gramann »

Wow!

Tom Griffin
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Re: First Cello Build

Post by Tom Griffin »

Thanks guys, it's been a fun project.

I learned a lot of new skills from it and have a new pile a wood for an acoustic guitar that I'm ready to apply them to.

Tom
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Steve Sawyer
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Re: First Cello Build

Post by Steve Sawyer »

Tom - this has been fascinating. Looking forward to the finishing.

W/regard to the carving, my current build (an electric bass) has a hand-carved fillet around the edge of the body (the width of the fillet varies, so no way to machine it short of a CNC router.)

While it is, as you say, a slow and painstaking process, I really enjoyed it! I’m thinking now of how to incorporate carving into the next build too!
==Steve==

Tom Griffin
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Re: First Cello Build

Post by Tom Griffin »

Thanks Steve,

I'm North for a couple weeks, so the cello is on hold, but I did find time to cook the varnish before I left. It turned out well, but was a pretty scary process working with melted pitch and 600° oil.

Do you have pics of your bass project? I've seen some pretty impressive relief carvings in solid bodies before, so that may be something to consider. The head might also be a good place to apply some carving.

Tom
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Steve Sawyer
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Re: First Cello Build

Post by Steve Sawyer »

Sure - it isn’t particularly sophisticated carving, but achieved what I was shooting for design-wise. And yes, I have a “guitar gallery” folder in which I’ve saved a couple of really spectacular carved bodies - way beyond what I think I’d ever be capable of, but definitely good grist for the idea mill (like one that has a Ridley Scott Alien carving!!)

I’ll send you a pic via PM as I don’t want to drift this great build thread! Assuming I really have figured out this finishing schedule, I’ll be posting pics and the techniques I used in the finishing section.
==Steve==

Tom Griffin
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Re: First Cello Build

Post by Tom Griffin »

I've been spending a lot of time North lately, but I did find time to cook the varnish. The object of varnishing a cello or any similar stringed instrument, is to seal the wood so the finish doesn't soak in, stain it to get a consistent color and apply multiple very thin coats of colored and clear varnish. The end goal is to create a protective and aesthetic coating on the surface of the wood, but not alter the acoustics of it.

The varnish is made from a linseed (flax seed) oil base, rosins, lime/ash water to clarify it and turpentine. I blindly and faithfully followed the directions on a YouTube video by a violin maker who seems to know his stuff. The procedure was to heat the flax oil to 600ºF and hold it there for about 90 minutes to thicken it. That was a bit tense because the auto ignition point of flax oil is 650ºF. The whole process was carried out in the middle of my driveway just in case. There is another YT video that shows a guy adding the turpentine to the oil before it had time to adequately cool and the result was spectacular! The rosin is then melted and added to the oil, the temperature raised again to cross link the molecules of the mixture, which enables it to cure. The lye solution (water filtered through ashes) and lime is also added and the result thinned with turpentine to the desired consistency, about that of 90 weight gear oil. The finished varnish does not readily cure on its own, but requires a UV light source to help it along. Sunlight was the traditional source of UV, but I opted for a couple of UVC bulbs in an enclosure to do the job.

The next task will be to experiment with the sealer (ground), which is a water and glycerine mixture, and dyed varnish on scrap wood to get the desired effect. My goal is a very deep burgundy color so I plan to stain (dye) the wood a light brown, and apply layers of red and blue varnish to get the burgundy color. The colors are aniline dyes, so the finish will be transparent and allow the wood to show through. I'm sure it will be an adventure.

Tom

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