New Koa and Spruce

Construction and repair of Classical Guitar and related instruments
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Peter Oberg
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New Koa and Spruce

Post by Peter Oberg » Fri Jul 11, 2014 9:55 pm

Every few years I like to build something I want to make. I have had this set of koa since the 1998 GAL convention, the only one I've been to, where I remember Eugene Clark giving a talk on French Polishing and how he likes to scratch up the surface across the grain before starting to polish, but that's an aside.

I thought I would share with the forum some of my process. Nothing proprietary here, just straightforward intuitive/anecdotal guitar making. I'll update the thread with new photos when time allows.


The koa has some nice, deep curl and a set of sides off the same board. The spruce is bear claw Englemann I bought from Larry Stamm.
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Here are the back and sides with some alcohol to show the color. I love koa-it's kind of open pored but bends really easily and scrapes to a beautiful sheen.
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The top is loaded with bearclaw and was not easy to plane. Each claw is like end grain so a bit steeper angle on the plane and a skew cut is definitely required.
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One side bent and in the mold, and the other wet and ready to bend.
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I decided to laminate the sides, and left both the koa and the cypress pretty much full thickness, so the sides are about 4.5mm thick.
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This is my setup for gluing the blocks. The neck block has a few coats of shellac on it, and is cedro. The tail block is Port Orford cedar.
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The rim with blocks ready for linings. At this point the edge of the sides has been profiled to receive the back, and the foot has been rough shaped.
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Back linings being glued. I use poplar these days-inexpensive, available, bends easily. I use solid linings for both back and top.
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The body with linings. Next thing is to plane the linings to the contour of the edges and refine the edge that receives the back.
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This shot shows the neck block with its pad that increases the support under the fingerboard. You can also see how wide the combination of double sides and linings ended up.
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petermc61
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Re: New Koa and Spruce

Post by petermc61 » Fri Jul 11, 2014 10:06 pm

Thanks Peter, great post. They are the thickest sides I have ever seen or, I think, heard of. Are they the thickest you have ever made? Any other luthier ever made thicker?

Regards
Peter

mmapag
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Re: New Koa and Spruce

Post by mmapag » Fri Jul 11, 2014 10:18 pm

Lovely Koa! Together with the bearclaw in the top, it should be visually stunning. Some of the nicest I've ever seen. I also wonder about your thoughts on the thickness of sides.
'13 Esteve 7 SM
'75 Takamine 132 S
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jaujau
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Re: New Koa and Spruce

Post by jaujau » Sat Jul 12, 2014 6:32 am

looking very good so far!

I'm wondering how does the front neck block gets attached to the side frame? it looks like the endgrain of the block is glued to the sides.
do you use epoxy for that application?
Marinovski Vyacheslav

iim7V7IM7
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Re: New Koa and Spruce

Post by iim7V7IM7 » Sat Jul 12, 2014 11:17 am

Peter,

Thanks for sharing your build with the forum.

As a guitarist, I always enjoy build threads as a small window into the craft of luthiery. It is always a treat!

I am more of a jazz guitarist than a classical player, but I can imagine that most classical clients want hazelficte-free tops and Brazilian Rosewood back/sides (just a guess). I assume that you are making this guitar for sale or for you personal use?

I happen to like the look of bearclawing, but I am not a traditionalist when it comes to guitars. I am sure that domestic woods like Osage Orange or African woods like Wenge might make fine classical guitars. Even in the steel stringed world, traditions tend to dominate client wood choices.

I actually have a carved back guitar (D. Stevensonii) currently under commission that will be made from bearclawed Carpathian Spruce.

Thanks Again
2015 - John Buscarino, 650 mm, Carpathian Spruce/Honduran Rosewood
2014 - Peter Oberg, 640 mm, Western Red Cedar/Black Cherry

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Steve Ganz
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Re: New Koa and Spruce

Post by Steve Ganz » Sat Jul 12, 2014 7:28 pm

Thick sides... Have you done that before?
Steve

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Peter Oberg
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Re: New Koa and Spruce

Post by Peter Oberg » Sat Jul 12, 2014 8:54 pm

Peter, mmagap, and Steve-

Regarding the sides, I have laminated by reducing the thickness of each set to finish at around 2.6 or 2.7 mm, and I have done like I did here before as well, using full thickness sides on each half. I had it in my mind when I started the instrument that I was going to use double linings on the top-I'm using a 645 mm scale on the larger of the two body sizes I generally build with, so I wanted to reduce the vibrating area in the lower bout by doing this. I was also thinking about laminating the koa with yellow cedar to soften the sound a bit and stiffen the sides. This way I didn't need to use the second set of linings, and the cedar is so light the extra weight is not appreciable. I'm sure the body HZ will shift a little but I'm never measured it. And the bending and laminating goes more smoothly with thicker sides, at least for me.

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Peter Oberg
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Re: New Koa and Spruce

Post by Peter Oberg » Sat Jul 12, 2014 8:57 pm

jaujau wrote:looking very good so far!

I'm wondering how does the front neck block gets attached to the side frame? it looks like the endgrain of the block is glued to the sides.
do you use epoxy for that application?
Yes it's end grain. I size it with glue, and then wet it out again and clamp. The fit conforms so well that even though it's end grain I think of it as a solid joint. Additionally the neck and body are going to be joined with a loose tenon so the rim assembly will be pinched between. I use titebond.

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Peter Oberg
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Re: New Koa and Spruce

Post by Peter Oberg » Sat Jul 12, 2014 9:01 pm

iim7V7IM7 wrote:Peter,

Thanks for sharing your build with the forum.

As a guitarist, I always enjoy build threads as a small window into the craft of luthiery. It is always a treat!

I am more of a jazz guitarist than a classical player, but I can imagine that most classical clients want hazelficte-free tops and Brazilian Rosewood back/sides (just a guess). I assume that you are making this guitar for sale or for you personal use?

I happen to like the look of bearclawing, but I am not a traditionalist when it comes to guitars. I am sure that domestic woods like Osage Orange or African woods like Wenge might make fine classical guitars. Even in the steel stringed world, traditions tend to dominate client wood choices.

I actually have a carved back guitar (D. Stevensonii) currently under commission that will be made from bearclawed Carpathian Spruce.

Thanks Again
You're welcome! Another wonderful domestic wood is cherry. I would build all day long with cherry and Port Orford cedar if I could, for back and sides.
This guitar will be for sale, probably end of August. Good luck with your new instrument!

iim7V7IM7
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Re: New Koa and Spruce

Post by iim7V7IM7 » Sat Jul 12, 2014 9:08 pm

I have never seen a Cherry guitar. It has a similar density and hardness to mahogany. Is it high or low damping? How would you characterize its euphonic coloration compared to better understood tropical woods as a reference?

Thanks Peter for the well wishes. I won't receive until next spring.
Peter Oberg wrote:
iim7V7IM7 wrote:Peter,

Thanks for sharing your build with the forum.

As a guitarist, I always enjoy build threads as a small window into the craft of luthiery. It is always a treat!

I am more of a jazz guitarist than a classical player, but I can imagine that most classical clients want hazelficte-free tops and Brazilian Rosewood back/sides (just a guess). I assume that you are making this guitar for sale or for you personal use?

I happen to like the look of bearclawing, but I am not a traditionalist when it comes to guitars. I am sure that domestic woods like Osage Orange or African woods like Wenge might make fine classical guitars. Even in the steel stringed world, traditions tend to dominate client wood choices.

I actually have a carved back guitar (D. Stevensonii) currently under commission that will be made from bearclawed Carpathian Spruce.

Thanks Again
You're welcome! Another wonderful domestic wood is cherry. I would build all day long with cherry and Port Orford cedar if I could, for back and sides.
This guitar will be for sale, probably end of August. Good luck with your new instrument!
2015 - John Buscarino, 650 mm, Carpathian Spruce/Honduran Rosewood
2014 - Peter Oberg, 640 mm, Western Red Cedar/Black Cherry

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Peter Oberg
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Re: New Koa and Spruce

Post by Peter Oberg » Sat Jul 12, 2014 9:28 pm

More...

Chiseling out for back braces. Does anyone do this differently? I have seen pieces set between the braces, which makes sense if you don't have long enough cross grain pieces. Many years ago I found some Honduras boards that were 20" wide and 6' long, enough for ten lifetimes worth of reinforcing strips!
Image

Back braces being glued in the mini go-deck, which stores under one of my benches and works with the ceiling to prop go bars. Braces are already profiled, and the two lower bout ones are taller than
the two in the upper bout. Also POC.
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Cutting the brace ends back to fit into the mortices in the linings.
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The clamping setup for gluing the back on. The body is in the mold and setting on a 'lifter', which is 3/4" Baltic birch that the mold slips onto, and 'lifts' the body above it giving access to the edge of the sides and holding the body firmly. Spring clamps are made from dryer hose clamps that were cut. The wooden screw is putting light pressure in the foot area.
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Interior shot while being glued. This method allows for complete cleanup of squeeze out, and adjusting the fit of the slightly angled sides and the brace mortices.
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The body ready for the shaping of the edge to receive the top.
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Another view of the koa. You can see the small rabbet around the edge of the back. I'll do this after gluing the top also-that way the plates are out of the way when I go to scrape the sides
prior to routing for bindings and purflings. The rosette blank is on the bench in the background.
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This is the rosette blank with the gold-ish pearl inlaid. I'm getting ready to screw it down and using a circle cutter, cut the ID out to within a few thousandths of the OD of the concentric lines ring that
goes on the inside. Then I'll true the OD edge up and laminate the lines on the outside, then reduce it's thickness and inlay it.
Image

iim7V7IM7
Posts: 147
Joined: Fri Jun 13, 2014 10:41 pm

Re: New Koa and Spruce

Post by iim7V7IM7 » Sat Jul 12, 2014 9:44 pm

Chiseling out for back braces. Does anyone do this differently? I have seen pieces set between the braces, which makes sense if you don't have long enough cross grain pieces. Many years ago I found some Honduras boards that were 20" wide and 6' long, enough for ten lifetimes worth of reinforcing strips!

Actually, Petaluma, CA luthier Bruce Sexauer does it the opposite way...:-)

Check out post #207 on this forum thread:
http://www.acousticguitarforum.com/foru ... 92&page=14
2015 - John Buscarino, 650 mm, Carpathian Spruce/Honduran Rosewood
2014 - Peter Oberg, 640 mm, Western Red Cedar/Black Cherry

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Peter Oberg
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Re: New Koa and Spruce

Post by Peter Oberg » Sun Jul 13, 2014 6:29 pm

The fixture for rosette building. The little arms hold the inside and outside elements while gluing.
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Rosette is in.
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The low cross braces go on first.
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Fans are notched to go over the cross braces.
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Bracing lowered and profiled, then ends tapered.
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The completed top.
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Squaring string slots on back of head.
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Cutting the ramps.
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Completed ramps.
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Laying out the relief area.
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Completed head.
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Figured maple bindings.
Image

iim7V7IM7
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Re: New Koa and Spruce

Post by iim7V7IM7 » Sun Jul 13, 2014 6:51 pm

Beautiful work Peter. Thanks for sharing....
2015 - John Buscarino, 650 mm, Carpathian Spruce/Honduran Rosewood
2014 - Peter Oberg, 640 mm, Western Red Cedar/Black Cherry

Paul Micheletti
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Location: San Diego, CA

Re: New Koa and Spruce

Post by Paul Micheletti » Mon Jul 14, 2014 11:56 pm

Sweet. Keep the updates coming! The stippled headstock relief area looks great.

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