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I have been reading the discussions about laminated sides being ultra stiff at equal thickness has anyone tried to thin the sides down to make a laminated side that is as stiff as one piece but thinner so it is just as stiff but lighter then a solid one piece?

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Zac

Anchorage Alaska

Finshed my 1st! See #1 here

I dont know if I made one if I would go much thinner than about 70-80 thou .. although I have seen guitars with sides as thin as about 1mm (40 thou) .....

I have seen a DeJonge with double sides, braz rw, and the inner lam was spanish cedar .. cant get much lighter than that - and its cheap.

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Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

There are classical guitar makers that do that. I think the high end ramirez' are made from rosewood+cypress totaling the usual ~2mm.

On the other hand, lets not forget that many great guitars of the past both Spanish and American were made with very thin sides. It may be argued that they have less power but hard to argue they lack beauty of tone.

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Build log

This thread is starting from a common false assumption about the stiffness of laminates. Laminated wood is no stiffer than solid wood of the same thickness (given wood of the same stiffness to begin with). It is more stable and crack resistant. If laminated sides are stiffer than solid, it's because they are thicker or made with stiffer material.

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

Howard, have you tried laminated sides?

My experience is that they are a lot stiffer. I think the aspect of them being a bent lamination may have something to do with it. Also, grain weaknesses are not continuous though the layers since they are different cuts of wood.

The simple fact that the laminates are glued to one another in the bent shape creates a very stable
and rigid side where there is little to no possibility of losing their shape. The layers also present two
different grain structures that sort of work together to create a strong crack resistent piece.

The only trouble that I've had with laminated sides, whether in guitars built by other builders or in
the prototypes and instruments that I've built myself, is that some of the tonal distinction offered by
a solid one piece side is lost and the tone, even though still very good, is not as characteristic of the
woods used as it would be otherwise.

I've built with several different proportionate laminate make ups and have varied the thickness
between .060" and .090" on different projects and have noticed differences in them, but never made
the commitment to using them as a default feature on my guitars just because of the limits on the
sides abilities to contribute fully to the guitar's voice with the distinct characteristics of the outer
layer or what would bne the designated side material in the guitar's spec list. In every instance, the
laminated sides proved to be significantly stiffer across their width than a solid one piece side of
the same or even slightly higher thickness.

I know that several builders are using laminated sides with great results and I've heard their guitars
and liked them, but it's just not a direction that I want to take.

Regards,
Kevin Gallagher/Omega Guitars

[url][/url]http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=15444&p=221015&hilit=laminated+side+strength#p221015

How do you guys get the URL to be a hot link?
Used to work okay......

You need to put the url between the brackets:

http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=15444&p=221015&hilit=laminated+side+strength#p221015

Glenn

You have to paste the link between the bracketed [url]and[/url]

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

stupid question,

I have built 3 boxes and have not finished setting up and finishing any of them. I learn my own way and have fun with this, so please excuse.

Are you guys saying, that you are laminating together 2 sides that are 0.040 each for a total standard thickness of 0.080 after gluing? or are you guys laminating sides thicker in the 0.060-0.080 range for a total thicker side?

Johnfry,
Yes to both questions.
There are some doing it each way and some going thicker and some going thinner.

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"An adventure is only an inconvenience rightly considered. An inconvenience is an adventure wrongly considered." G. K. Chesterton.

If the premise of the question is that theoretically sound and experimentally well-confirmed engineering principles should in general yield to someone's contrary empirically based, intuitive sense of things, then I reject the premise.

But in answer to the question, I have been building with double (and in one case triple) sides for about six years. I think I was pretty early; probably before Ervin. Laminations have many wonderful advantages, some of which I already mentioned. They are more resistant to failure, more stable, can be engineered for greater stiffness by placing higher tensile strength material on their outer layers, etc. But they don't get an increase in stiffness when compared with a solid of the same material. Gluing layers of wood together makes them behave as a solid. Stiffness comes from the compressive and tensile stress/strain ratio of the material. That is not changed by laminating. The resistance of the glue joint to shear failure does not add stiffness (and not much to shear failure resistance if the grain is running the same way in the layers--the shear failure will just occur in the wood itself); it doesn't add to the compressive or tensile strain resistance of the wood. Impregnating wood with certain glues may make it stiffer, but then we are talking about making a composite of wood and another material, which could as well result from impregnating a solid as from laminating.

Aren't you an engineer, Barry? You probably know more about this stuff than I do.

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

Yes, I am an engineer, but I leave my slide rule at work. I try to take a more intuitive approach to guitar building and use it as a creative outlet. Empirical results rule!

I too build in what I'd call an intuitive style. No deflection testing, Chaladni patterns, etc. But that doesn't mean I think guitars are exempt from science. Where they may appear empirically to go against sound engineering principles, I begin from the assumption that there's an error in the observation. That's basic scientific method. It's not hard to see ways in which intuitions about laminated wood can be mistaken.

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

Howard, your analysis of the "sound engineering principles" is overlooking the aspect of bent laminations. When you bend several pieces of wood and then glue them together while holding them in the bended shape, the shear resistance of the glue joints does become a factor in the increased stiffness. At least, that is my story.

I used to share that intuition, until some engineer types convinced my otherwise. The way I now see it is that the shear resistance in the laminate--bent or not-- is still no greater than that of the weakest link. The lignin in the wood is its natural glue, and softening it to bend followed by letting it set again adds as much (at least--because you don't have the laminate layers wanting to spring back between the glued surfaces) stiffness as gluing to a bent shape.

I think this stuff has been worked out and thoroughly tested by the glulam industry, both for straight and curved beams. But a quick Google search didn't find glulam vs. solid wood of the same species stiffness comparisons. Most of the hits are about glulam's strength and resistance to failure, and gains in stiffness by adding outer layers of other material. I did see one or two mentions of glulam behaving as if it were solid re stiffness, but not with numbers.

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

I recently built two spec guitars with laminated sides (BTW Howard, thanks for steering me in the right direction!).
On one, from the outside to the inside, I used EIR .060"/WRC .040"/mahogany .020", all 4sawn except the mahogany which is rift-sawn. The other one has bloodwood .060"/Spanish cedar .020"/bloodwood .040", the bloodwood is perfectly 4sawn and flitch-matched, the Spanish cedar flatsawn. On the EIR guitar I ended up using side braces as the offcuts split easily along the grain like a single layer side, in spite of the laminations. The bloodwood sides offcuts were unbreakable. Needless to say the rims are incredibly stiff. But the added weight is a turnoff for me, and the added mass raises the pitch of the box.
On my last builds, inspired by Rick Turner, I ended up using a hardwood side doubler on the top side, under the linings and the blocks, .080" thick and 1 3/8" wide. For me it is the best compromise as the added weight is negligible, but the rim is really stiff on the top side, which is what I was looking for.
Ah the scientific vs. the experimental… Both are subject to the confirmation bias it seems, we tend to expect what we're looking for…

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Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/

I meant the scientific vs. the experiential, of course…

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Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/

Can I take this off to a slight variation on the topic:

What if I wanted to create laminated sides so stiff that the rims would be capable of withstanding 180 pounds of force without deflecting?

That is, with no back plate or top plate yet glued on, just the rims and the neck block and the tail block and non-kerfed linings attached, a 180 pound ballerina could stand on the end of the guitar. (What, did you think I'd use a 180 pound gorilla?)

I'm in the middle of my second experimental guitar with suspended bracing, and though the suspended bracing does its job well, it is still in the way of the adjustable neck hardware on the neck block. So, I'm thinking about trying to make the sides so stiff, they cannot be twisted or deformed with the full shear force of a set of steel strings.

Any thoughts? Intuitions?

Dennis

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Dennis Leahy
Duluth, MN, USA
7th Sense Multimedia

Have you tried using solid or capped linings? I find that also makes a big difference. I am just doing 2 sides (not 3) but I find that the rims are very stiff alone but once the capped linings go in there is absolutely no moving them. They are rock solid. 0 flexing.

I agree with you on the weight. Mahogany and koa doubles still seem to be very light, but rosewoods, ebonies, etc, tend to get a little heavy. I have been working on trying to find a way to keep the epoxy from seeping though (to reduce the sanding necessary) so I can thin out the sides further and reduce the weight.

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

I thought he was talking about standing the rim set upright, tail block to the table, and putting 180# on top of the head block end.

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

Yep, that's what I meant. Can it be done and still keep the sides *relatively normal* thickness and weight overall?

Dennis

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Dennis Leahy
Duluth, MN, USA
7th Sense Multimedia

You guys doing laminated sides: Are you doing your own resawing and cutting your sides thinner right off the bat, or are you thinning down sides of a "normal" thickness from suppliers, or are you purchasing thinner sides, or what?

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Mike

"The Dude abides. I don't know about you but I take comfort in that. It's good knowin' he's out there. The Dude. Takin' 'er easy for all us sinners. Shoosh." The Stranger

But, she told me she was "Amanda." Oh, wait a cotton pickin' minute! Maybe he was saying "I am a man, DUH!"

Sure could pirouette though. But I digress...

So, you're saying I'll need 3-ply, with titanium as the middle ply?

Dennis

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Dennis Leahy
Duluth, MN, USA
7th Sense Multimedia

Well, maybe fifty-four ply. Using maple veneer, I'd guess that when you had enough layers built up to prevent deflection when the ribs were on an end block, you could dispense with the lining. I've seen this (well, fewer than 54) on thinline AE s, where the plates were glued right to the thick sides. I'd sure hate to have to hand-sand a stack like that on a dish or flat plate.

Dan

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Dan
http://www.acme-archtops.com