How to determine the right thickness for the back?

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How to determine the right thickness for the back?

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Ahmed Flamenco

Posts: 163
Joined: Feb. 22 2014
From: Egypt

How to determine the right thickness...

hello guys,
I was working on a sycamore back and I used the jet plane so as to make it coplanar for bracing, and at the end I realized that the thinnest parts are 2 mm.
I am worried because I've heard that back should not be too thin so as not to have the same resonant frequency of the top that finally results in lower sound.

REPORT THIS POST AS INAPPROPRIATE | Date Sep. 16 2015 10:37:28

Stephen Eden

Posts: 914
Joined: Apr. 12 2008
From: UK

RE: How to determine the right thick... (in reply to Ahmed Flamenco)

This comes down to preference and experience. You should consider how you would like the back to work on your guitars too. I've seen them around 1.5mm and there are probably thinner backs out there too. There are also backs out there that are a lot thicker too.

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Classical and Flamenco Guitars www.EdenGuitars.co.uk

REPORT THIS POST AS INAPPROPRIATE | Date Sep. 16 2015 11:02:00

tri7/5

Posts: 570
Joined: May 5 2012

RE: How to determine the right thick... (in reply to Stephen Eden)

Andres Marvi makes his back and sides at nearly 3mm when using brazilian. He prefers working with a stiff sound box and all the sound forced through the top.

REPORT THIS POST AS INAPPROPRIATE | Date Sep. 16 2015 12:29:01

constructordeguitarras

Posts: 1673
Joined: Jan. 29 2012
From: Seattle, Washington, USA

RE: How to determine the right thick... (in reply to Ahmed Flamenco)

You got it that thin using an automatic planer without it exploding?

_____________________________

Ethan Deutsch
www.edluthier.com
www.facebook.com/ethandeutschguitars
www.youtube.com/marioamayaflamenco
I always have flamenco guitars available for sale.

REPORT THIS POST AS INAPPROPRIATE | Date Sep. 16 2015 15:04:41

Ahmed Flamenco

Posts: 163
Joined: Feb. 22 2014
From: Egypt

RE: How to determine the right thick... (in reply to constructordeguitarras)

at first i used belt sander then jack planer, in the post I said jet but I meant jack

REPORT THIS POST AS INAPPROPRIATE | Date Sep. 16 2015 15:08:20

constructordeguitarras

Posts: 1673
Joined: Jan. 29 2012
From: Seattle, Washington, USA

RE: How to determine the right thick... (in reply to Ahmed Flamenco)

If the back seems too thin, go a little heavier on the bracing. Maybe use 4 or 5 back bars.

_____________________________

Ethan Deutsch
www.edluthier.com
www.facebook.com/ethandeutschguitars
www.youtube.com/marioamayaflamenco
I always have flamenco guitars available for sale.

REPORT THIS POST AS INAPPROPRIATE | Date Sep. 16 2015 15:10:04

Ahmed Flamenco

Posts: 163
Joined: Feb. 22 2014
From: Egypt

RE: How to determine the right thick... (in reply to constructordeguitarras)

I used 3 only but wider than the Santos plan and I glued stripes in the center.It is now stiff. but I'm still little worried what its sound gonna be.

REPORT THIS POST AS INAPPROPRIATE | Date Sep. 16 2015 15:14:53

constructordeguitarras

Posts: 1673
Joined: Jan. 29 2012
From: Seattle, Washington, USA

RE: How to determine the right thick... (in reply to Ahmed Flamenco)

I think stiffness is what matters.

_____________________________

Ethan Deutsch
www.edluthier.com
www.facebook.com/ethandeutschguitars
www.youtube.com/marioamayaflamenco
I always have flamenco guitars available for sale.

REPORT THIS POST AS INAPPROPRIATE | Date Sep. 16 2015 15:15:51

Ahmed Flamenco

Posts: 163
Joined: Feb. 22 2014
From: Egypt

RE: How to determine the right thick... (in reply to constructordeguitarras)

but at some edge where thickness is 2 mm it is flexible.

REPORT THIS POST AS INAPPROPRIATE | Date Sep. 16 2015 15:21:27

constructordeguitarras

Posts: 1673
Joined: Jan. 29 2012
From: Seattle, Washington, USA

RE: How to determine the right thick... (in reply to Ahmed Flamenco)

That sounds good to me for a flamenco guitar. Mine are about 2.5 mm in the center and 2.0 at the edges. Once it's glued to the sides, the edges will be supported by the sides and no longer so flexible.

_____________________________

Ethan Deutsch
www.edluthier.com
www.facebook.com/ethandeutschguitars
www.youtube.com/marioamayaflamenco
I always have flamenco guitars available for sale.

REPORT THIS POST AS INAPPROPRIATE | Date Sep. 16 2015 15:25:33

Ahmed Flamenco

Posts: 163
Joined: Feb. 22 2014
From: Egypt

RE: How to determine the right thick... (in reply to constructordeguitarras)

Ok thanks Mr.Ethan

I hope that this guitar be better than the first one.

REPORT THIS POST AS INAPPROPRIATE | Date Sep. 16 2015 15:40:56

constructordeguitarras

Posts: 1673
Joined: Jan. 29 2012
From: Seattle, Washington, USA

RE: How to determine the right thick... (in reply to Ahmed Flamenco)

You're welcome. The soundboard is much more important for sound quality than the back.

_____________________________

Ethan Deutsch
www.edluthier.com
www.facebook.com/ethandeutschguitars
www.youtube.com/marioamayaflamenco
I always have flamenco guitars available for sale.

REPORT THIS POST AS INAPPROPRIATE | Date Sep. 16 2015 16:26:25

Anders Eliasson

Posts: 5780
Joined: Oct. 18 2006

RE: How to determine the right thick... (in reply to Ahmed Flamenco)

You dont say what kind of wood you are using, so its difficult to say anything about the subject

2mm at the edges is pretty standard for hardwoods. Cypress is normally kept a few tenth of a millimeter thicker.

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Blog: http://news-from-the-workshop.blogspot.com/

REPORT THIS POST AS INAPPROPRIATE | Date Sep. 16 2015 21:39:12

Ahmed Flamenco

Posts: 163
Joined: Feb. 22 2014
From: Egypt

RE: How to determine the right thick... (in reply to Anders Eliasson)

quote:

You dont say what kind of wood you are using, so its difficult to say anything about the subject

2mm at the edges is pretty standard for hardwoods. Cypress is normally kept a few tenth of a millimeter thicker.

sycamore

REPORT THIS POST AS INAPPROPRIATE | Date Sep. 16 2015 22:36:25

Anders Eliasson

Posts: 5780
Joined: Oct. 18 2006

RE: How to determine the right thick... (in reply to Ahmed Flamenco)

Sycamore has a very dead taptone and is structurally stable, so your 2mm near the edge could be reasonable.
But it depends on how well the wood has been cut. If its quatersawn all the way across the width, it should be fine at 2mm at the edges, if its not, then 2mm will be to little.

Ahmed, you always look for the fast and easy answers and guitarmaking (and life) is not like that. It is impossible to give you a good answer without touching the wood.

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Blog: http://news-from-the-workshop.blogspot.com/

REPORT THIS POST AS INAPPROPRIATE | Date Sep. 17 2015 7:12:42

Ahmed Flamenco

Posts: 163
Joined: Feb. 22 2014
From: Egypt

RE: How to determine the right thick... (in reply to Anders Eliasson)

quote:

If its quatersawn all the way across the width, it should be fine at 2mm at the edges, if its not, then 2mm will be to little.

For each half it is quartersawn for edge but flat sawn at the center.

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REPORT THIS POST AS INAPPROPRIATE | Date Sep. 17 2015 12:22:07

Anders Eliasson

Posts: 5780
Joined: Oct. 18 2006

RE: How to determine the right thick... (in reply to Ahmed Flamenco)

Thats what i call a flatsawn set of wood.
I would never use it. Sorry, but I prefer being honest.

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Blog: http://news-from-the-workshop.blogspot.com/

REPORT THIS POST AS INAPPROPRIATE | Date Sep. 18 2015 8:47:44

Ahmed Flamenco

Posts: 163
Joined: Feb. 22 2014
From: Egypt

RE: How to determine the right thick... (in reply to Anders Eliasson)

quote:

I would never use it

that's because appearance , stiffness or being sycamore.

REPORT THIS POST AS INAPPROPRIATE | Date Sep. 18 2015 11:44:45

Jeff Highland

Posts: 401
Joined: Mar. 5 2010
From: Caves Beach Australia

RE: How to determine the right thick... (in reply to Ahmed Flamenco)

I agree with Anders, I would not use it, for a number of reasons.
I would strongly encourage you Ahmed to change your attitude to building from a focus on how cheaply you can build to a pursuit of excellence.
You will never manage to build a guitar cheaper than Asian factories can produce it.
Choosing quality materials is part of the build process, as is being prepared to throw away a component you have cut wrongly, thinned excessively, or cracked when bending.

REPORT THIS POST AS INAPPROPRIATE | Date Sep. 18 2015 21:00:18

Ahmed Flamenco

Posts: 163
Joined: Feb. 22 2014
From: Egypt

RE: How to determine the right thick... (in reply to Jeff Highland)

For the current moment I cannot go to expensive materials for also many reasons, I'm not sure to sell it for high price ,that's because cypress and Indian rosewood are not available in my country and I don't want to ship anything to me right now , I might use cypress and Indian rosewood but not now.

REPORT THIS POST AS INAPPROPRIATE | Date Sep. 18 2015 22:32:46

Jeff Highland

Posts: 401
Joined: Mar. 5 2010
From: Caves Beach Australia

RE: How to determine the right thick... (in reply to Ahmed Flamenco)

I'm not talking about using expensive materials just defect free and appropriate cut, and having an attitude of striving for excellence rather than good enough.

REPORT THIS POST AS INAPPROPRIATE | Date Sep. 18 2015 23:25:53

Ahmed Flamenco

Posts: 163
Joined: Feb. 22 2014
From: Egypt

RE: How to determine the right thick... (in reply to Jeff Highland)

what is the defect you are talking about,being flat sawn is a defect?

REPORT THIS POST AS INAPPROPRIATE | Date Sep. 18 2015 23:38:41

Jeff Highland

Posts: 401
Joined: Mar. 5 2010
From: Caves Beach Australia

RE: How to determine the right thick... (in reply to Ahmed Flamenco)

I am talking about choosing wood in general to be defect free and by appropriate cut I mean quartersawn rather than flatsawn and with minimal runout

REPORT THIS POST AS INAPPROPRIATE | Date Sep. 18 2015 23:48:49

Ahmed Flamenco

Posts: 163
Joined: Feb. 22 2014
From: Egypt

RE: How to determine the right thick... (in reply to Jeff Highland)

but that was the wood available when I went to buy woods, I bought just two pieces for the back.
Do you think I'd better search for a quarter sawn wood?
also I don't use wood with cracks,when I was using paduk for another guitar and it cracked I didn't use it.

REPORT THIS POST AS INAPPROPRIATE | Date Sep. 18 2015 23:59:48

constructordeguitarras

Posts: 1673
Joined: Jan. 29 2012
From: Seattle, Washington, USA

RE: How to determine the right thick... (in reply to Jeff Highland)

Personally, I prefer wood with defects, as on the guitar I have been playing since I made it two years ago:

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_____________________________

Ethan Deutsch
www.edluthier.com
www.facebook.com/ethandeutschguitars
www.youtube.com/marioamayaflamenco
I always have flamenco guitars available for sale.

REPORT THIS POST AS INAPPROPRIATE | Date Sep. 19 2015 0:15:13

Andy Culpepper

Posts: 3023
Joined: Mar. 30 2009
From: NY, USA

RE: How to determine the right thick... (in reply to Ahmed Flamenco)

Ahmed, considering your situation I would try to find some high quality, locally sourced (alternative) woods for your guitar making. I honestly don't know if that's possible in Egypt but if you do some research and talk to wood workers you might be surprised.

Finding high quality wood (quartersawn, resonant, well dried/aged) is much more important than the type of wood you use, and a number of "alternative" species fit the bill just fine. If you source your materials locally they can often be cheap, even free.

Right now I'm building a guitar out of all North American woods: Cherry back and sides, Walnut neck, Hickory fingerboard, Englemann top and I've come to the realization that "tonewood" (e.g. you can only use Cypress and Rosewood) is a myth.

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Andy Culpepper, luthier
http://www.andyculpepper.com

REPORT THIS POST AS INAPPROPRIATE | Date Sep. 19 2015 0:27:58

Ahmed Flamenco

Posts: 163
Joined: Feb. 22 2014
From: Egypt

RE: How to determine the right thick... (in reply to Andy Culpepper)

And that is exactly what I am doing , I am governed by woods I find ,I even contacted with wood suppliers that import woods to Egypt, I am working on a flamenco blanca made of sycamore and IMO it is not bad at all then I will work on a classical made of paduk(I will buy new paduk sides), then after these I will decide what to do.

REPORT THIS POST AS INAPPROPRIATE | Date Sep. 19 2015 0:45:24

alcazaba

Posts: 28
Joined: Jun. 30 2013

RE: How to determine the right thick... (in reply to Ahmed Flamenco)

I have never used flatsawn wood in guitar building, and I hate the idea, but other people do.
If am not mistaken, those high figured woods on steel string guitars are flatsawn. Not sure how problematic they are though.
Still, get the best wood and tools you can!

REPORT THIS POST AS INAPPROPRIATE | Date Sep. 19 2015 1:41:09

printer2

Posts: 54
Joined: Sep. 19 2015

RE: How to determine the right thick... (in reply to Ahmed Flamenco)

Did a search on acoustic guitars built with Sycamore not many made with it but enough where I would not think twice about using it when you are first starting out. Looked at the picture of your wood, yes flat sawn. Much better if it was quarter sawn. Seems that you may not know why quarter sawn is the cut of choice. With humidity changes wood expands or contracts. There is more movement with a piece of wood that is flat sawn than a piece that is quarter sawn.

That being said I made some guitars out of Pine, the quarter sawn back on one cracked while another with flat sawn wood did not. Just goes to show that all wood is not equal. Or I built the flat sawn one when the humidity was low and it had a better chance of staying whole. But given a choice I would build with quarter sawn.

While I am still a new builder I did build an all Walnut guitar (steel string) out of some flat sawn wood. Just used it as I did not know if a Walnut top will sound any good so why waste good wood on an experiment. As luck had it the guitar sounded pretty decent and a year in it survived with no cracks. Recently I built another Pine guitar (nylon), it was just to be a quick build to try out some ideas. I really like how the neck turned out, will have to be real careful with it as it is made out of spruce.

With each guitar I learn something or try something new. They are not worth much but they did not cost me much either. These are my learning guitars, the better ones I will give away. I have a nice stack of wood to make guitars out of but am saving it for when I think I can do it justice (soon). I see no problem learning the skills in making a guitar with less desirable wood. There is enough things you need to learn to do right to build a guitar. I have been asked if I wanted to sell any of these and I declined because I do not want to set the value of guitars I build as low as what I can get for them. They are of value to me as learning tools.

It is up to you to decide what it is you are trying to achieve with the guitars you build. While you have been given some good advice in this forum sometimes you can get some value from coloring outside the lines.

REPORT THIS POST AS INAPPROPRIATE | Date Sep. 19 2015 2:29:58

keith

Posts: 1108
Joined: Sep. 29 2009
From: Back in Boston

RE: How to determine the right thick... (in reply to Ahmed Flamenco)

A lot of companies use Sycamore for lower level flamenco guitars. Cordoba is one that comes to mind. The companies do not specify if the Sycamore is European (a maple) or American (a plane) but many look to have the European type. Most laminate the Sycamore--not sure if is due to economics or the properties of the wood. The wood database reports both types are fairly stable and have a t/r ratio of 1.7 and a tangential shrinkage in the low 8's.

REPORT THIS POST AS INAPPROPRIATE | Date Sep. 19 2015 11:15:38

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