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3 Piece Back Question
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10101&t=17756		 Page 1 of 2
Author:  JJ Donohue [ Thu Jun 26, 2008 12:40 pm ]
Post subject:  3 Piece Back Question
I recently acquired a few cherry billets that are a bit narrow to allow 2 pieces to construct backs on all but parlor-type bodies. Nonetheless, I am thinking about making 3 piece backs using Cherry or other species as the center panel.

My question relates to what other species would be compatible with cherry as far as normal expansion is concerned. I would imagine that if one species expands at a different rate than the cherry that cracks would likely appear.

Has anyone had experience along the lines and what woods should I be considering?

TIA
Author:  Hesh [ Thu Jun 26, 2008 12:52 pm ]
Post subject:  Re: 3 Piece Back Question
JJ bro I have never liked the look of a three piece back especially when a different wood is used for the middle panel. No offense intended to anyone who has done this.

If it were me and I had the cherry that you have access to and was concerned about differing rates of expansion I would do this: Make the center panel out of a book-matched, angle cut like a herringbone butt wedge, two panel cherry section and then frame it with the two out side panels being cherry also. In reality this is a 4 piece back - all cherry and the two out side panels would have a thin, no wider then 1/8" dark strip defining the joint.
Author:  JJ Donohue [ Thu Jun 26, 2008 12:57 pm ]
Post subject:  Re: 3 Piece Back Question
Hesh wrote:
JJ bro I have never liked the look of a three piece back especially when a different wood is used for the middle panel. No offense intended to anyone who has done this.

If it were me and I had the cherry that you have access to and was concerned about differing rates of expansion I would do this: Make the center panel out of a book-matched, angle cut like a herringbone butt wedge, two panel cherry section and then frame it with the two out side panels being cherry also. In reality this is a 4 piece back - all cherry and the two out side panels would have a thin, no wider then 1/8" dark strip defining the joint.


Thanks...Opinion duly noted.

Can anyone answer the original question regarding differing expansion rates?
Author:  Barry Daniels [ Thu Jun 26, 2008 1:20 pm ]
Post subject:  Re: 3 Piece Back Question
The largest amount of expansion is from side to side, so it would not affect a 3-piece back configuration. Also, most any wood you choose will expand to some degree along with the cherry, so I really don't think you are going to have any problem in this regard.

I like 3-piece backs. A piece of curly maple between the cherry halves would look great. Also, curly walnut would look nice.
Author:  JJ Donohue [ Thu Jun 26, 2008 1:37 pm ]
Post subject:  Re: 3 Piece Back Question
Thanks Barry. That's exactly the kind of info I'm seeking. Looks like I may have more combos available to me than first thought.

I'm sure Howard took this into consideration when he did "Dovetail Madness".

Does anyone have any pics of such backs?
Author:  RaymundH [ Thu Jun 26, 2008 1:48 pm ]
Post subject:  Re: 3 Piece Back Question
JJ - I bought some small sets of light mahogany from Darren Hippner and a couple of East Indian wedges from the Martin store on North St. for the sole reason of making a Shawn Colvin "style" instrument. The material was dirt cheap and I just love the look of the guitar (personal opinion) Martin uses two decorative strips between the two species which may act as "expansion joints?"

You can see it here:

http://www.usd.edu/smm/PluckedStrings/G ... uitar.html

Also, I think one of Kevin Gallagher's students just did a snazzy looking 2 species 3pc back as well. He showed some pictures here on the forum a little while ago.

Ray
Author:  JJ Donohue [ Thu Jun 26, 2008 1:58 pm ]
Post subject:  Re: 3 Piece Back Question
Thanks, Ray. Nice...I like the headstock treatment as well.
Author:  Dennis Leahy [ Thu Jun 26, 2008 2:28 pm ]
Post subject:  Re: 3 Piece Back Question
Hi JJ,

In terms of the back surviving, I think you can use any species of wood that would have been acceptable in a 2-piece back. The overall, cumulative expansion and contraction is all you need to be concerned with. As an example of why I'm 99.999% sure of it, think of a back made of _____________________ (fill-in the species) where the board was well-quartersawn along one edge of the board, and gradually falls off to rift and then finally flatsawn at the other edge of the board. (This is actually pretty common.) The board is resawn, and the quartered edge becomes the seam. Now try to look up in a wood shrinkage table what the expected rate of shrinkage will be for the back... It isn't all quartersawn (radial, on the chart), and it isn't all flatsawn (tangential, on the chart.) There will theoretically be more movement in the flatsawn portion of the back, but the overall back will experience the cumulative effect of all the wood across the back.

Having gone through a phase of furniture making where everything I built for myself had stark contrast, such as using Walnut and Maple together (I'm sitting at a desk of curly Maple trimmed in Walnut as I write this - sheesh), I have become weary of stark contrasts. I wonder if that is what Hesh is reacting to as well. Many 3-piece backs feature a stark contrast for the wedge. Also, I am a symmetry nut, and I sometimes see the wedge of a 3-piece back with grain or swirls or colors that are off to one side, and that can get my knickers in a knot. (Not really, I just don't like it as much as a symmetric back.)

One wood combination that I know works very well (to my eye) with Cherry is Walnut, especially after the Cherry has altered (UV and oxidation) to its darker shade.

I agree with Hesh on creating a 4-piece back that is a faux 3-piece back, by making the wedge itself a bookmatch:
Image

Dennis
Author:  gozierdt [ Thu Jun 26, 2008 2:31 pm ]
Post subject:  Re: 3 Piece Back Question
I don't have an answer right off the bat, but here are two references every luthier should
keep in his Bookmarks:

USDA Wood Handbook:
http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr113/fplgtr113.pdf

Forest Service Center for Wood Anatomy Research
http://www2.fpl.fs.fed.us/

You should be able to answer your question in one of these.
Author:  RaymundH [ Thu Jun 26, 2008 2:38 pm ]
Post subject:  Re: 3 Piece Back Question
I almost forgot the Martin DM3MD Dave Matthews signature guitar is also a two species 3 pc back (and headplate)...EIR and Padauk.

There's one in the Martin museum....Very cool place!
Author:  kburner1 [ Thu Jun 26, 2008 2:47 pm ]
Post subject:  Re: 3 Piece Back Question
My father and I completed a week long class with Kevin Gallagher in May. It was an amazing week of learning and building, here are a couple pictures after spraying the box.

Image

Image
Author:  Rvsgtr [ Thu Jun 26, 2008 4:02 pm ]
Post subject:  Re: 3 Piece Back Question
Here's a curly walnut dread I finished in January with curly maple wedge in back. No problems with expansion/contraction, etc. and I love the look and the playability. It gets a lot of nice comments. I agree with some of the others, maple or walnut would be a nice contrasting wood to use for the wedge.

Best of luck.
Author:  Colin S [ Thu Jun 26, 2008 4:31 pm ]
Post subject:  Re: 3 Piece Back Question
I personally love three piece backs, I was talking to Steve Kinnaird about this recently after his posting of his three piece back SJ, and how the three piece back took the 'fat backside' look away that the SJ and cousins usually have. Some of the best guitars in the world are made with three piece backs, my own Kevin Aram (a $10k guitar) has a three piece BRW back. Of the 88 Torres guitars recorded in Romanillos, only 30 have two piece backs while 37 have three piece backs and 21 multiple pieces. In my lutes I have used up to 21 piece backs and often in alternating woods, recently rosewood and London plane. There is a very long tradition of using more than two pieces for the back. JJ you have no need to worry about expansion differentials just use what you want.

Colin
Author:  Bob Long [ Thu Jun 26, 2008 5:26 pm ]
Post subject:  Re: 3 Piece Back Question
This one is Walnut from 2 different trees.
long
Attachment:
fullbackvanderwallnut.jpg
Author:  JJ Donohue [ Thu Jun 26, 2008 6:24 pm ]
Post subject:  Re: 3 Piece Back Question
Dudes...I'm really diggin' this post now! I hadn't realized that we'd get to see so many fine examples of 3-backs! Thanks to all for posting and thanks for the info on compatibility. BTW, I can never drool over too many examples, so keep em' coming.

I'm really looking forward to my first trials!
Author:  Burton LeGeyt [ Thu Jun 26, 2008 6:43 pm ]
Post subject:  Re: 3 Piece Back Question
Hey JJ! This is a 4 piece type 3 piecer, the center wedge is bookmatched. No problems.

Attachment:
11-16 back.JPG


This one had the sapele just a bit too thin for a small size guitar so I used a wider than normal backstrip, which made it look a little like a 3 piece.

Attachment:
guitar 5.JPG


Let's see your Cherry.
Author:  JJ Donohue [ Thu Jun 26, 2008 7:13 pm ]
Post subject:  Re: 3 Piece Back Question
blegeyt wrote:

Let's see your Cherry.


Nice, Burton...I especially like the spalted back strip.

As far as my cherry...I have 2 billets that were just recently cut... they are currently drying in my attic. I'm going to let them dry for the rest of the summer and then start slicing some of it up so it can dry faster.

I expect to be scoring some Walnut as soon as my brother in PA gets some of his logs processed.
Author:  Dennis Leahy [ Thu Jun 26, 2008 7:30 pm ]
Post subject:  Re: 3 Piece Back Question
JJ Donohue wrote:
...I have 2 billets that were just recently cut... they are currently drying in my attic. I'm going to let them dry for the rest of the summer and then start slicing some of it up so it can dry faster.

Hi JJ,

Have you checked with any sawyers that have experience with green wood destined for lutherie? Ken Hodges and Grant Goltz would be good resources. You may not want to dry the billets before you resaw the wood - at least in some species. Just a thought.

Dennis
Author:  JJ Donohue [ Thu Jun 26, 2008 8:43 pm ]
Post subject:  Re: 3 Piece Back Question
I checked with the Zootman and Mario on this. They recommended what I'm planning to do, at least with the Cherry. More patience on my part would probably be better but I agreed to a compromise.
Author:  Steve Kinnaird [ Thu Jun 26, 2008 9:32 pm ]
Post subject:  Re: 3 Piece Back Question
Here ya go, JJ.
My most recent 3-piece back, and thanks tio Colin for the kind remarks.

Your 3=piece will have no more trouble than a two-piece as far as expansion problems go. In fact, it might be a wee bit in the other direction!

Attachment:
IMG_6745_WEB.jpg


Steve
Author:  JJ Donohue [ Thu Jun 26, 2008 10:20 pm ]
Post subject:  Re: 3 Piece Back Question
That's a stunner, Steve! Thanks for the inspiration...again!
Author:  Sam Price [ Fri Jun 27, 2008 1:27 am ]
Post subject:  Re: 3 Piece Back Question
Of course there is the option of making a 3-piece back look seamless, if the grain is matched well. This would largely depend on the wood you have available.

I must admit, I really like the look of the center pieces on the examples above. I have a good bandsaw that will only resaw up to 6"; with billets, a multi piece back is the only option I have.
Author:  JJ Donohue [ Fri Jun 27, 2008 1:48 am ]
Post subject:  Re: 3 Piece Back Question
Sam...the options are really endless. The examples shown so far testify to that. Once I get the cherry sliced, I'll be laying out some possibilities. I really like the creative possibilities this represents as well as an opportunity to use some woods that might otherwise not have been possible.

As far as seamless approaches, my personal bias is to separate woods with purflings but I may in fact try your suggestion should the right pieces come together.

My only commercially produced acoustic guitar is a Martin 3-piece D-35 Dred which I just love...and someday I'm going to make a 12 string in exactly the same style. I've been looking at that 3 piece back for decades now and will finally be able to realize some repressed dreams of my own creations.
Author:  Howard Klepper [ Sat Jun 28, 2008 5:29 pm ]
Post subject:  Re: 3 Piece Back Question
I do make an effort to use woods with similar radial shrinkage percentages (if they are quatersawn, only the radial will matter), but it doesn't seem to be critical. For one, any back will shrink in low humidity, and if the joint is backed up with a cross grain strip the failure line will not be on the joint (it's likely to be alongside the reinforcing strip). Three piece backs are not really any worse off here than two piece: dry them enough, and they will crack somewhere. For another, once woods have dried, they don't take up as much moisture for a given humidity as they had at that humidity when first drying, so the real picture for shrinkage and expansion of cured wood is less than the shrinkage tables (which are from green to fully dry, usually kin dry) would indicate.

About the only risk I see if the woods had very different shrinkage percentages would be rippling or cupping, etc. And one just doesn't see much of that if dry, seasoned woods are used--even with rosewood/maple combinations.

I agree that it will often look better if the center is a bookmatch, so that the back is actually four piece. Depends on what you have to work with. Here's one now in progress with a one-piece center. Bookmatching the center wasn't an option; I made the center from an orphaned board. African blackwood and cocobolo, about ready for sanding.

Image
Author:  Steve Kinnaird [ Sat Jun 28, 2008 5:34 pm ]
Post subject:  Re: 3 Piece Back Question
Ooooh, that's ^ going to look pretty under finish!
Howard is that a commission or a spec?

Steve
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