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I have a really nice piece of Macassar Ebony that I have decided to build a guitar for myself with. The only problem is, it is a small piece of wood, only big enough for a 3 piece back, and it is flat sawn. I have some quarter sawn macassar that I cut up for the sides. It should work fine.
Now the problem. Once the back wood was resaw it became unstable. Even after trying heat and then months of pressing it with weight, it still wants to look like a potato chip. I am afraid to use it as is, but it is to nice looking to pass on.

So, I was thinking if I laminate some stable, quarter sawn Indian rosewood to the macassar it should be much better.

My questions are:

What thicknesses of the laminates would you use? I typically shoot for a finished back thickness of .12" to .13" Sound about right for a laminated live back guitar? Maybe .05" for the macassar and .07" for the indian rosewood?

What glue/procedure is best to laminate with? (I don't have a vacuum press)

Would there be any advantage in using a layer of nomex in the laminate and doing it with epoxy as if it were a double top?

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Joe Beaver
Maker of Sawdust

Not to rain on the parade, but if you have a piece of unstable wood ... laminating it and trying to tame it into a guitar sounds like something that will not go well. Maybe an obvious question but why not get a buildable piece of Macassar for your back set? Starting with good materials will serve you well.

Andy

I've not laminated a back but I recently started laminating sides and I'm very happy with the results. Most recently I've started using 2 slats of .050" sides and carbon fiber in the middle with West Systems epoxy. This results in very stiff sides. I've never used nomex so I can't speak to that. I would say that I'd use epoxy in your case though after testing coco/mahogany laminations with Titebond vs coco mahogany laminations with West Systems. The cutoffs with Titebond potato chipped and the cutoffs with epoxy were straight as an arrow. The titebond coco was also more well quartered than the West Systems coco.

I've never laminated backs but I can imagine that it's pretty similar to laminating sides for the most part. Just get even pressure. I'd probably use Mike Greenfield's method for clamping top/back to the sides as a basis for the design as it's pretty simple and cheap to accomplish. Essentially it's just MDF with plastic tubing screwed to it. For rims it's just a single sheet of MDF. For a back I'd probably double it up to ensure rigidity. The nice thing about the tubing is that it doesn't have to be perfect but will still apply even pressure because it's flexible. just leave adequate space between the tubing for space to expand during compression with clamps.

Make a sandwich:
2 pieces of MDF glued together and sealed to prevent warping
evenly spaced plastic tubing screwed into MDF
wax paper
lam#1
epoxy
Carbon Fiber
epoxy
lam#2
wax paper
evenly spaced plastic tubing screwed into MDF
2 pieces of MDF glued together and sealed to prevent warping

Clamp it with 8-10 (probably overkill) Bessy or similar clamps and if anything it might be too stiff to brace. I don't feel like editing the previous suggestions but having thought out loud you might consider doing all that but then instead of using a bottom piece of MDF just cover a radius dish (reinforced if it isn't already) with wax paper and clamp it the same way to that instead, then the radius is already set into the back and even less likely to potato chip especially after bracing.

Whatever you do be sure to share with the rest of us. I know I have a particular set of coco that has potato chipped up on me as well that might just be my avatar pic. This is how I'm planning to approach addressing that set if I can't get it straightened out in the next year or two. For now it's at the bottom of a stickered pile of zoot and prayers. In terms of thickness I'd probably lean a little thinner than 0.12", more like .050" for each piece if not less because the epoxy is going to stiffen the dickens out of the backs and you won't want them too tight to tune. I do prefer solid woods but if it's that tempting you'll have to post a pic to show us why! Good luck with whatever you decide.

I guess it depends what type of back you're going for. I've use macassar and Malaysian Blackwood (which seems about the same density) three times on om size. They all ended up around 70 to 75 thou. I guess you could just glue them up and thickness them to taste later, but it seems safer to do it beforehand.

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Pat

Andy,
You are right but.... I would not think of using it for a comissioned guitar or even a gift, but for me? Why not? Most of my concern centers around how will it sound. I worry about how to keep the back active. I wonder what would happen if I used nomex in the laminate? My hope is it will be a good looking guitar and a learning experience rolled into one build.

Joey,
Thanks for the info. After reading your post I will go with epoxy. The procedure for the side lamination is a good one, but what is the plastic tubing used for?

Pat,
After final sanding my backs end up around .10 - .12", and are ladder braced. I don't have the equipment to do sonic testing on them. I only do tap tones before assembly. I suspect I may not be getting the most useful information. Maybe you can talk about your thoughts/procedure that leads you to such thin backs? Bracing? I appreciate your feedback.

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Joe Beaver
Maker of Sawdust

I have not purposely tried to make an active back, but they have just come out that thin because it feels right to me weight and stiffness wise. I used typical ladder bracing on the backs and they are fairly stiff. I had about the same numbers with a very dense Rosewood. I have not tried irw. I have used maple, walnut and mahogany and they we're all thicker, just over .1.

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Pat

Very interesting Pat. Thank you

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Joe Beaver
Maker of Sawdust

I see. As a personal experiment, that makes sense. I would not be looking at laminates to make the back active. You might actually think about going the other direction. There are two schools of thought on guitars, and active and reflecting backs have both made excellent guitars.

Andy

I suspect you are right that a laminated back may not make the best active back. Maybe I should read up on non-active backs and how to couple them with the top. Thanks again for your thoughts.

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Joe Beaver
Maker of Sawdust

I've laminated many backs. These days, I do for all my more expensive work, I use solid for my cheaper guitars! The bottom line is - if you want to do this more than once, get a cheap vacuum bag set up. Once you do, it becomes very simple.



For core materials, you can use whatever you like. Nomex will make a lot more work and may even make a inferior back. A few Classical makers have done this, and most have abandoned this approach. My first few laminated backs, I used reject soundboards as the interior core. The main thing is, if you are concerned about stability of your outer material, you do need to make this "posh ply" to some degree. You can cross grain with cheap mahogany veneer, or with a material like silk or I've even used shoji paper.

If you really want to make a lot of work for yourself, you can laminate an arched back!



The process is something I may well make a video about someday, but that back is a laminate of spruce, maple and bubinga veneers. Looks nice though...

Glues - use whatever you like. Some like epoxy, some unibond, some PU, some titebond. They all work, they all have pros and cons.

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nigel

http://www.theluthierblog.com

Beautiful work Nigel. I've been thinking about doing the radius bindings. Any pointers on that?

When I see all the flat sawn 'Highly figured wood' (stump wood, crouch wood, etc.) used these days I am always surprised that more people don't laminate. How thick do your backs typically end up when all is said and done?

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Joe Beaver
Maker of Sawdust

One reason you can laminate - two - side pieces together is because the curve of the sides restrains the pieces from moving. With flat panels a "balance veneer" on the inside is generally suggested to stabilize the panel. ?It is possible that the back braces may perform this function???
If I were to laminate two different species I would make the "core" layer much thicker than the outer veneer, or try to select woods that had similar coefficients of expansion.
I veneer backs all the time, but the layers are matching veneers oriented in the same fashion they came off the log. I dry the veneer and laminate it with epoxy, so it is not the usual way it is done. My backs are .075 to .110 inch thick.

Binding - double up. Simple as that. Two layers of whatever you are using. Avoid maple for obvious reasons. Then go around with a radius bit in your binding jig. Much quicker to level these sorts of bindings.

Yep, using stump wood is pretty much asking for trouble, but that doesn't seem to stop folk.

Back thickness is down to you. Mine vary according to what I'm using. Often around 4-6mm. With a heavy radius. So my backs are dead.

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nigel

http://www.theluthierblog.com

If I'm reading correctly it should be a breeze.

Laminate the ebony and east indian rosewood together using a cross grain core to add stability, keeping the laminates thin so I can thickness and brace the back as usual.

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Joe Beaver
Maker of Sawdust

I would sand the ebony as thin as I could and laminate it with something cheaper than Indian. Yes, it must have a cross grain lamination. If you laminate it in enough of a curve you won't need to brace it unless you want to.

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nigel

http://www.theluthierblog.com

This could be a good excuse to buy a pump, some tubing, a couple fittings, and a 2'x2' bag, and mesh.



Most - sounds like a pretty comprehensive accounting. The most powerful classical guitar I've played was a double top, double back (nomex both), and laminated 3 ply sides. Not cheap, and the luthier clearly figured out how to make it work with his guitars. But I think we are likely well off Joe's subject at this point.

Andy

"This could be a good excuse to buy a pump, some tubing, a couple fittings, and a 2'x2' bag, and mesh."

Another way to go is get a couple of pieces of melamine coated particle board or some other flat smooth panels (MDF, birch ply, etc) a couple of sheets of wax paper, and a bunch of clamps. To press a back, the panels only have to be about 9 inches wide and two feet long, and you need enough F body or "C" clamps to go all the way around (about 4 inches apart).
I like to leave the lamination clamped up for about a week until the glue (epoxy) has fully cured (I remove most of the clamps after 24 hours).

The plastic tubing is essentially the clamping surface as it's flexible (1") so that even if the dish/surface isn't perfect you will get relatively even pressure from the tubing vs a solid non-flexible surface. I'll upload a pic so that it makes more sense.

I am surprised to hear that people are paying premium money for a laminated back as opposed to solid wood. Nigel, Is this a trend with a particular group of builders? Seems like that would be a hard sell to customers unless there was a large body of work out there. I haven't heard of this before, although I could be living in an envelope...

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Pat

Depends who you are, what you do, what your work sounds like and what your customers' priorities are Pat. If I was making more traditional work, I'd struggle. But no one comes to me looking for conventional work. And my laminated work is rather different from the plywood guitars you can buy in your local store. A bit like the original Selmer guitars - "solid" back and sides isn't automatically "better."

As the new CITES rules start to bite, makers will become more experimental. I doubt those who've invested in "alternative" solid woods will be interested in laminating woods for some time, but those who invested heavily in rosewoods (which for many of us was our pension) may well be in the years to come. Times are-a-changin'.

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nigel

http://www.theluthierblog.com

Laminate in production is often about manufacturing a stable guitar, a cheaper guitar (veneers), et cetera.

In luthiery laminates are used predominately to effect sound (stiff sides, reflective backs), which is not to say that there are not other benefits, like stability, resisting cracks, et cetera.

So laminate is not laminate, so to speak.

Andy

Laminated BRW back - you can still find nice looking veneer.

One piece backs anyone? Well, 5 pieces to be honest...Even when working with solid wood, I'd been making instruments with "dead" backs for years without knowing it. It was Trevor Gore who told me I was!

Dead is dead, so it might as well be pretty.

And yes, these are more stable than solid wood backs for sure.

For me, and for my work, this way of working really suits. It's not for everyone, but then, what is? Also, it's not without issues - binding becomes even trickier - imagine that?

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nigel

http://www.theluthierblog.com

My head hurts...

For me it has opened up a whole new world. I never gave laminated wood a second thought. I always just put it in the category of China using plywood to make cheap guitars.

The wood flooring marketing boys have a leg up on us. They say there is laminated and then there is engineered, I think what we are talking about would definitely be in the 'Engineered' group.

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Joe Beaver
Maker of Sawdust