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Bogdanovich book and laminated sides
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Author:  davidO [ Fri Jun 29, 2007 5:10 am ]
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I just got the Bogdanovich book "classical guitar making" from the library yesterday. Wow, what a beautiful book. If I were making my first classical I would definately follow it. Instuctions are very clear, thorough, and theres a million colour pictures.

I am not building my first classical however, but am building my first steelstring. I am able to take some of the ideas from this book with me though.

Anyway the reason for my post is that in his book he laminates his sides with the finish wood on the outside and an inner layer of either cypress, Alaskan yellow cedar, or Sitka spruce. The total lamination is the same thickness as a regular side. He uses thickness of 0.065" for finish outside wood and 0.045" inside wood.

He has an interesting thought for doing it this way here is the link with his explanation Bogdanovich on laminated sides (Note: he talks of laminated side starting in the 4th paragraph)

I as just wondering what the thoughts out ther are in using this method for a steel string. It makes sense to me as it would stiffen up the sides instead of installing side braces.

davidO
Author:  Marc [ Fri Jun 29, 2007 5:53 am ]
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I don't do laminated sides, but what I've read in his book and seen it looks like a fine technique. What makes the idea attractive to me is the zero spring back, he claims the sides maintain their shape.
Author:  Dave White [ Fri Jun 29, 2007 5:54 am ]
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[QUOTE=ToddStock] I'm not certain why you would want to install side braces, other than on body shapes that have large, flat areas prone to key cracks. Fabric or veneer tapes work fine for containing side cracks otherwise.[/QUOTE]

If your sides had a certain degree of cupping then side braces could help straighten the sides out. If you use spruce (or even carbon fibre rod pieces) then there is very little extra weight. I'm sure there are other ways to get over cupping though but as I don't really use full moulds and spreaders I find they help.

I use them because I like the look of them and find the process of fitting them very theraputic (it's a pretty cheap and harmless way of getting kicks ).
Author:  Dave White [ Fri Jun 29, 2007 5:59 am ]
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David,

Take a look at these posts here and here
Author:  Andy Zimmerman [ Fri Jun 29, 2007 5:59 am ]
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I do laminate my sides. I LOVE THE TECHNIQUE

1. It makes for a very rigid set of rims (I want this with my thinner tops
and backs
2. No spring back... You could almost build the guitar without a mold
3. No need for side supports

I use lower grade sides of EIR I get from Allied as my inner side.   I go
0.06 and 0.04 or so.
I bend them together (EIR and actual guitar side) on my Hall Bender. Very
easy since both pieces are so thin.
I epoxy them together with West systems
For a cool look, once bent I dye the inside of the rims black.
Author:  davidO [ Fri Jun 29, 2007 8:29 am ]
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Sorry guys I did not mean to bring up an old topic.
Thanks for those links Dave.

I already have my rim done on this build, but I think my next one will have "double sides". Hey, if Ervin is doing it...

davidO
Author:  KenMcKay [ Fri Jun 29, 2007 9:30 am ]
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I agree with Todd.

Bagdanovich laminates a lighter wood inside and that makes them nice and
strong but light.
Author:  LuthierSupplier [ Fri Jun 29, 2007 10:18 am ]
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Todd,
I think that a thin layer of epoxy is much harder and stiffer than wood. But I have no data to back that statement up with. However, I watched Michael Bashkin(Also an Ervin student) do a double side glue up, and it was even stiffer than reverse kerfing. Trust me, it is stiffer.

The biggest drawback of using double sides is extra steps. But most people that do it say it is worth it. I've never done it myself, but have seen the results first hand. I'm a believer, but I just don't have the tools to do the extra processes. So I'll just stick to reverse kerfing.
Tracy
Author:  Brock Poling [ Fri Jun 29, 2007 10:55 am ]
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This reminds me of a story about Richard Feynmann. After the Challenger shuttle blew up he was in a meeting with a bunch of NASA scientists and they were discussion what would happen to the 0-rings at 32F and as the conversation was devolving and going no where... he dunked the sample in ice water and pulled it out and snapped it in half.

That pretty much closed the discussion.

I think it is similar to the double sides. I just couldn't believe how much stiffer they were after I built my first rim. It is really remarkable. Whether or not that is what you want is not the point, but it is clear these are incredibly stiff.

Author:  paul harrell [ Fri Jun 29, 2007 11:33 am ]
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I have never done double sides, but I have done a lot of bent laminations in my furniture work, which is basiclly the same thing. A curved lamiated drawer front is so much stiffer than a straight piece of solid wood, there is no comparison. Bent laminations are an order of magnitude stiffer.

                    Peace, Paul
Author:  davidO [ Fri Jun 29, 2007 1:21 pm ]
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Being a drummer (I know, I know, you are thinking great we have a drummer building guitars. No wonder he's lost ), having looked at alot of drums over the last 25 years, I have noticed good drum shells are built out of laminations and all have solid (not kerfed) rims (linings).

Kind of makes me think maybe they are on to something.

davidO
Author:  Carey [ Fri Jun 29, 2007 3:48 pm ]
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Laminated sides *are* remarkably stiffer than solid sides
of the same thickness. My guess is there are at least two
reasons for this:

1) The woods are typically of different species, hence
(constructively) "fighting each other" a bit, ie they
won't individually be the perfect shape, but together
they effectively will.
2) Not being flitch-cut (necessary consequence of #1)
the path of least resistance is different for the laminated pieces- one is strong where the other is weak.

Laminating the two pieces slightly cross-grain would maximize that effect, and reduce the chance of
long-grain cracking further.

I suspect that the glue per se is not a significant stiffener.

Whether stiffer sides are better is a different question;
imho, if the sides are not causing stress to the top and
back plates, it's probably a good thing.
Author:  Carey [ Fri Jun 29, 2007 4:03 pm ]
Post subject: 
To simplify: Laminating the sides probably effectively creates a
more homogeneous material, more predictable for working
purposes, possibly more practical (eg minimizing cracking)
also, imho.
Author:  Martin Turner [ Sat Jun 30, 2007 7:55 pm ]
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[QUOTE=Hesh1956]

Many builders believe that the sides play very little if any role in generating tone, I agree with this.

[/QUOTE]

Antonio de Torres proved this with his famous paper mache guitar. The top and neck were made from wood but the back and sides were constructed from paper mache.
Author:  Steve Saville [ Mon Jul 02, 2007 2:44 am ]
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[QUOTE=ToddStock] Not to belabor the point, but it would be nice to see something other than subjective judgements on side stiffness - a little engineering analysis goes a long way towards quantifying just how much stiffer and how much heavier, etc. I'm still looking for the mechanism that would significantly increase E by adding a .005 layer of glue on the neutral axis.

[/QUOTE]
Todd,
I'm a mechanical engineer. I respect your call for a less subjective understanding. I wish I had something for you. I was in your shoes a few months ago.
I just built my first laminate side guitar. (Sorry, I don't go for double speak and call it double side, there are not 2 sides, it is one laminated side.) I don't understand why it is significantly more stiff, but there is no question in my mind that it is. It is so obvious that I don't even need to test it.
This might be one of those times that you'll have to try it to believe it.
Author:  Shawn [ Mon Jul 02, 2007 3:38 am ]
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I build only Spanish school classicals and while I agree that a laminated side will be much stiffer would not want to use it as it adds about a 1/3 more weight and thickness than a single side if you use Bogdanovich's .065 and .045 plus epoxy for the laminated side. That leaves the side at .110 or about 2.8mm.

I understand that he is using a lighter wood for the inside layer (cypress, alaskan cedar or spruce) but it is still heavier than a side that is thinned to .075-.080 (~2.00mm) in either Rosewood or Cypress.

A classical guitar is much different than a steel string in that hte player makes very minial contact with the instrument when held so every part of the guitar that can add to the vibration helps. When you make the sides 30 percent thicker it changes the mass of the instrument and its ability to vibrate.

I know there are schools of thought that the back should be a reflector and the top a rigid drum top but when extended to a classical guitar you end up with a hybrid instrument like a Smallman school design in which the rim and sides are MUCH heavier with the top paper thin...you get volume but at the sacrifice of tonal color and range.

The spanish school of classical guitar is know for the instrument being built lightly with every element being as light as practical and contributing to the tone of the instrument. When I build a flamenco, it is under 2 pounds...I attempt to get every bit of sound out of the instrument by building as lightly as possible.

I collect historic guitars and other instruments and have seen spanish guitars with sides as thin as 1mm but have not seen an historic example or precedent for making the sides heavier. I do have historic spanish guitars that have sides that have rosewood veneer on the outside and cypress,spruce, poplar or pine for the insides but that was due to the availability of Rosewood at that particular time, not to overbuild the sides.

Even the Madrid school builders such as Ramirez who build with laminated sides still keep the thickness of the side to around 2mm.
Author:  KenMcKay [ Mon Jul 02, 2007 7:32 am ]
Post subject: 
I agree that stiffer sides are not always an advantage. In making double bass
instruments, the sides should not be made too stiff or the top and back will
split as the instrument seasons. The sides should actually be made knowing
that they will eventually split. Interesting huh?

I have made sides laminated and solid and it seems to make a difference in
the timbre of the instrument to me and both can be interesting.

I don' t know why bent laminatios are stiffer than solid bent wood but they
are. I did the experiment today and here is the results.
[URL=www.upnorthstrings.com/stiffness.html]I put it here on my website. [/
URL]
Author:  KenMcKay [ Mon Jul 02, 2007 7:37 am ]
Post subject: 
Try this here
Author:  John How [ Mon Jul 02, 2007 7:55 am ]
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Has anyone tried using nomex as a center material for building laminated sides? I have not done any side lams but this may be a way to keep the weight down if that is your interest.
Author:  KenMcKay [ Mon Jul 02, 2007 8:10 am ]
Post subject: 
John I have used foam core and thin veneer skins and it is very stiff. Stiffness
to weight is out of the ballpark.
Author:  CarltonM [ Mon Jul 02, 2007 9:16 am ]
Post subject: 
Ken brought a sample of his veneer/foam sandwich to a Michigan Guild meeting, and I can testify to its stiffness. It also weighed about as much as a couple of Cheerios. Interesting idea.
Author:  KenMcKay [ Mon Jul 02, 2007 5:05 pm ]
Post subject: 
Todd, I have made a guitar top with foam core (Airex R63) and I can assure you there is no issue with damping. I would not worry about damping in the sides too much either but I have not actually made a guitar with my composite tonewood (trademark) sides.

P.S. wood is a lot funner
Author:  RobLak [ Tue Jul 03, 2007 12:38 am ]
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Did you ever see the cartoon where there's a herd of cows grazing in a field when one of them suddenly has an epiphany... the cow raises his head and with a startled look says, "Hey! this is GRASS we're eating!" (from "The Far Side" maybe?)

Well... hey! This is PLYWOOD we're using!

Seriously, it wasn't long ago that people used to dis plywood tops (or are they double tops?) as being a cheap ripoff and somethng akin to not being a real instrument. Now double tops (or are they plywood?) are all the rage. Go figure.

Just another example of this technique vs. that technique and neither of them being wrong, just different for different reasons.

You may go now grasshopper...

Rob
Author:  CarltonM [ Tue Jul 03, 2007 3:54 am ]
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I hear ya, Rob, but the systems in use here are quite different from what we think of as plywood. Most important, I think, is grain direction. As I understand it, the grain in each ply is oriented in the same direction, with few exceptions. Apparently this avoids the tone-killing effect of cross-ply construction.
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