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constructordeguitarras

Posts: 1692
Joined: Jan. 29 2012
From: Seattle, Washington, USA

Neck Reinforcement 

Does everybody use neck reinforcement? I didn't used to, but after a guitar came back with a warped neck and I fixed it with carbon fiber reinforcing material under the fingerboard, I decided I better be safe and use it from now on. It adds a bit of weight, though.



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Ethan Deutsch
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  REPORT THIS POST AS INAPPROPRIATE |  Date Jan. 2 2014 0:17:38
 
Anders Eliasson

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RE: Neck Reinforcement (in reply to constructordeguitarras

I used to build with reinforcements, but i dont do anymore and I havent had any problems. IMHO Its more about quality and storage of the material.

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  REPORT THIS POST AS INAPPROPRIATE |  Date Jan. 2 2014 7:34:43
 
tele

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RE: Neck Reinforcement (in reply to constructordeguitarras

I suppose if the neck is thin/flat it's great idea to use carbon fiber, I thought they used only ebony strips in the middle(which doesn't look too good)

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  REPORT THIS POST AS INAPPROPRIATE |  Date Jan. 2 2014 12:33:15
 
Flamingrae

 

Posts: 220
Joined: May 19 2009
 

RE: Neck Reinforcement (in reply to tele

Seem to be making necks on the thinner side at the mo. Also, with this in mind, I've taken to splicing a strip of rosewood down the middle for a bit of added strength. I turn one side of the neck up the other way too just in case of warping. Anders is right about storage but I just have a thing about this way of making for now. I also like the extra feature in the neck. In an ideal world there would be no movement of wood and if you can buy and store then that is fine. Sometimes I just dont have this luxury and have to use off the shelve.
I'm never going to do again what one maker did and that was to embed a piece of steel tube in there. The arguement was that the routed material v the steel, was a negligable increase in weight - dont believe it - there is.
I like the hidden carbon fibre in Ethan's design - nice and light too I'll bet.
  REPORT THIS POST AS INAPPROPRIATE |  Date Jan. 2 2014 14:39:39
 
Anders Eliasson

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RE: Neck Reinforcement (in reply to constructordeguitarras

remember that the further away from the strings, the better a reinforcment works. There´s little effect in a 6mm deep reinforcement.

Visually I dont like a neck where the reinforcement can be seen on the back of the neck only. If it goes all the way through the head/neck/heel. It can be very elegant.
Good idea to use rosewood and not ebony. Rosewood is a lot more stable.

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  REPORT THIS POST AS INAPPROPRIATE |  Date Jan. 2 2014 15:54:03
 
tele

Posts: 1469
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RE: Neck Reinforcement (in reply to Anders Eliasson

quote:

ORIGINAL: Anders Eliasson

If it goes all the way through the head/neck/heel. It can be very elegant.
Good idea to use rosewood and not ebony. Rosewood is a lot more stable.


good idea, I haven't seen these on nylon guitars though yet., even ones that go thru the heel.

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  REPORT THIS POST AS INAPPROPRIATE |  Date Jan. 2 2014 17:54:39
 
keith

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

RE: Neck Reinforcement (in reply to constructordeguitarras

ethan, did you use a carbon fiber rod or tube? a tube of the same diameter as a rod would obviously weigh less (all things considered equal) but i am not sure though if a tube would be as strong as a rod. a good engineering question? given how inexpensive carbon fiber rods are it seems like something that would have a lot of benefits. i like the hidden rod look (be it ebony or carbon fiber).

question, would a carbon fiber insert reduce the likelihood of future neck angle issues?
  REPORT THIS POST AS INAPPROPRIATE |  Date Jan. 2 2014 18:27:16
 
tele

Posts: 1469
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RE: Neck Reinforcement (in reply to keith

Ovation guitars seem to use maple for strenght, is it used also with nylon string guitars? Might look better than ebony

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  REPORT THIS POST AS INAPPROPRIATE |  Date Jan. 2 2014 18:46:23
 
Andy Culpepper

Posts: 3028
Joined: Mar. 30 2009
From: NY, USA

RE: Neck Reinforcement (in reply to constructordeguitarras

I use carbon fiber rods on my classical guitars (higher action) and when I am making a flamenco with a thinner than usual neck. I have never found them to be needed on my regular flamencos.
Just out of curiosity, why does your reinforcement stop ~ an inch from the headplate? I like to run mine all the way and even under the headplate a little to reinforce the weakest area.
Pretty guitar btw.

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  REPORT THIS POST AS INAPPROPRIATE |  Date Jan. 2 2014 20:50:36
 
constructordeguitarras

Posts: 1692
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From: Seattle, Washington, USA

RE: Neck Reinforcement (in reply to keith

Thanks for sharing, guys.

Keith, I used a rectangular cross-section bar, 1/4" wide and 3/8" deep. I found a place (dragonplate.com) that sells all kinds of tubes--square and round--and beams, such as I-beams, though. But I figure that I might as well fill up all the space I open up.

Andy, I wasn't worried about strength at the head/neck joint as I've never had trouble there. The guitar that had the problem had bowed in the middle of the neck. Also, this carbon-fiber composite is made with carbon fibers (of course) in epoxy resin and I don't know if it sticks to Titebond glue that I use--I suspect not. So I think it might actually weaken the head/neck joint if I made the slot for it go all the way into the head. (Also, I was not completely decided about doing it until I was ready to glue on the fingerboard, so I made a router template that I could screw to the neck around the first and eleventh fret positions--you can see the screw holes in the photo.)

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  REPORT THIS POST AS INAPPROPRIATE |  Date Jan. 3 2014 3:43:55
 
Anders Eliasson

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RE: Neck Reinforcement (in reply to constructordeguitarras

Did you glue it with titebond?

Its pretty common use to use some kind of epoxy glue for neck reinforcements.

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  REPORT THIS POST AS INAPPROPRIATE |  Date Jan. 3 2014 7:26:01
 
krichards

Posts: 597
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From: York, England

RE: Neck Reinforcement (in reply to constructordeguitarras

I used to reinforce but its just not necessary if you use good quality stable cedar. Never had a problem (not yet anyway)

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  REPORT THIS POST AS INAPPROPRIATE |  Date Jan. 3 2014 13:35:29
 
constructordeguitarras

Posts: 1692
Joined: Jan. 29 2012
From: Seattle, Washington, USA

RE: Neck Reinforcement (in reply to Anders Eliasson

Hi, Anders.
Actually, I just shoved the reinforcement into the slot and saw that it hit the bottom and was flush on top, and didn't glue it in except by gluing the fingerboard over it, with Titebond. (Something in the back of my mind told me not to make it so I would have to route it out if there was ever some reason I wanted to remove it.)

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www.edluthier.com
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www.youtube.com/marioamayaflamenco
I always have flamenco guitars available for sale.
  REPORT THIS POST AS INAPPROPRIATE |  Date Jan. 4 2014 19:23:07
 
Jeff Highland

 

Posts: 401
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From: Caves Beach Australia

RE: Neck Reinforcement (in reply to constructordeguitarras

Next time glue it in with good quality epoxy. it needs to be bonded to the surrounding material to be most effective
  REPORT THIS POST AS INAPPROPRIATE |  Date Jan. 4 2014 20:38:47
 
constructordeguitarras

Posts: 1692
Joined: Jan. 29 2012
From: Seattle, Washington, USA

RE: Neck Reinforcement (in reply to Jeff Highland

Thanks for the suggestion Jeff, but I used this method to fix a guitar whose neck had already warped, and it worked perfectly.

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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 Jan. 13 2014 14:23:31
 
Vince

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Joined: Oct. 21 2012
From: Germany

RE: Neck Reinforcement (in reply to constructordeguitarras

I split the neck and glue a reinforcement strip in the middle.
The neck wood is turned over before gluing!

Vince





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  REPORT THIS POST AS INAPPROPRIATE |  Date Jan. 26 2014 11:57:20
 
tijeretamiel

 

Posts: 441
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RE: Neck Reinforcement (in reply to Vince

quote:

ORIGINAL: Vince





What wood is that? It looks beautiful.

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  REPORT THIS POST AS INAPPROPRIATE |  Date Jan. 26 2014 12:03:23
 
Jim Kirby

 

Posts: 149
Joined: Jul. 14 2011
From: Newark, DE, USA

RE: Neck Reinforcement (in reply to constructordeguitarras

Looks like Zebrawood. i wish someone around here thought it looks beautiful - I have about 8 sets that I cut from a board about 6 or 7 years ago.
  REPORT THIS POST AS INAPPROPRIATE |  Date Jan. 26 2014 12:26:17
 
Vince

Posts: 141
Joined: Oct. 21 2012
From: Germany

RE: Neck Reinforcement (in reply to constructordeguitarras

Your right!
Zebra wood, moor oak, Mahagoni









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  REPORT THIS POST AS INAPPROPRIATE |  Date Jan. 26 2014 12:39:54
 
koenie17

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From: España

RE: Neck Reinforcement (in reply to Vince

Congratulations!! Thats a beautifull guitar.

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  REPORT THIS POST AS INAPPROPRIATE |  Date Jan. 26 2014 14:10:55
 
constructordeguitarras

Posts: 1692
Joined: Jan. 29 2012
From: Seattle, Washington, USA

RE: Neck Reinforcement (in reply to Vince

Your guitar looks beautiful. Your reinforcement is wood? Are we sure it is less susceptible to warping than if it were unreinforced?

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Ethan Deutsch
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www.youtube.com/marioamayaflamenco
I always have flamenco guitars available for sale.
  REPORT THIS POST AS INAPPROPRIATE |  Date Jan. 27 2014 23:59:15
 
Vince

Posts: 141
Joined: Oct. 21 2012
From: Germany

RE: Neck Reinforcement (in reply to constructordeguitarras

Theoretically the stiffness of the Neck increase with the modulus of elasticity of the reinforcement part.
When you use a wood like Hardwood it gives you a better strength for the neck:
Cedro/Mahogany E = 10 000 to 12 000 N/mm²
Hardwood (Rosewood) E = 15 000 to 18 000 N/mm²
Stiffness of the neck blank:
I = 60 x 22³/12 = 53240 mm4
E x I = 532.400.000
Reinforced I = 8 x 22³/12 = 7098 mm4 (46141 mm4 rest of the Cedro)
ExI = 127.764.000 +461.410.000 = 589.174.000
f = 1,11
The reinforcement with wood can give you approximately 10 % more Stiffness in the neck!
But when you split the Neck blank and glue them like this, you increase the stiffness too, because the modulus of elasticity depends of the grain orientation (orthotropic behavior of wood)!

But I decide it very freely with the wood that I use, without any calculation!
The basic rule is, use only the best wood and store as long as possible in your workshop before use!
Handle the wood like a baby and the neck will be perfect!



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Vince
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  REPORT THIS POST AS INAPPROPRIATE |  Date Jan. 28 2014 8:37:11
 
Vince

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From: Germany

RE: Neck Reinforcement (in reply to constructordeguitarras

For your interest!
https://www.dropbox.com/sh/d2t4sb8u4hqf814/mslQ914Cgv
I have calculated three different Neck Systems.
One plain System, one with wooden reinforcement and one with a GFK Root.
The surprising result:
The System 2 (Wooden reinforcement) is 13% stiffer than without reinforcement!
The System 3 (GFK reinforcement) is 6% stiffer than without reinforcement!
In the System 3 the parallel axes theorem gives less stiffness than in System 2 because the reinforcement is very close to the stiffness center!
DropBox Link



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Vince
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  REPORT THIS POST AS INAPPROPRIATE |  Date Jan. 28 2014 15:06:00
 
Anders Eliasson

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RE: Neck Reinforcement (in reply to Vince

quote:

In the System 3 the parallel axes theorem gives less stiffness than in System 2 because the reinforcement is very close to the stiffness center!


Exactly. Nicely explained. My vocabulary does not have such fine words.
I think wood reinforcement like you did it is a good approach. It has 2 issues though: Esthetically some dont like it and the schrinking of the hardwood will be very different from that of the cedar and theoretically, that is not the best because it means less stability and more stress in the neck.
On some necks with a ebony centerpiece, you can clearly feel that the ebony has schrunk (spell?)

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  REPORT THIS POST AS INAPPROPRIATE |  Date Jan. 28 2014 15:23:35
 
Joan Maher

 

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RE: Neck Reinforcement (in reply to constructordeguitarras

Thats a lovely guitar - very nice work..
  REPORT THIS POST AS INAPPROPRIATE |  Date Jan. 28 2014 15:28:59
 
Ruphus

Posts: 3782
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RE: Neck Reinforcement (in reply to Vince

quote:

ORIGINAL: Vince

when you split the Neck blank and glue them like this, you increase the stiffness




There is a man named Dr. Thoma in Austria who builds the possibly finest wooden houses out there. ( Me was once thinking of distributing his builds, but could not heave financially.) Especially in terms of dimensional / directional stability and noiseless structure. They are also built exclusively of wood / without any metal.
http://www.thoma.at

Anyway, among the special treatments that he employs there is that grain positioning nearly like in your example. I think to remember that he layers boards with the grain diametrically opposed.

Ruphus

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  REPORT THIS POST AS INAPPROPRIATE |  Date Jan. 28 2014 17:38:28
 
Anders Eliasson

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RE: Neck Reinforcement (in reply to constructordeguitarras

quote:

I think to remember that he layers boards with the grain diametrically opposed.


Thats a standard cabinet maker rule for making solid wood table tops with wide planks. If not, the top will warp. Alternatively you can glue thinner sticks together and hope it wont warp

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  REPORT THIS POST AS INAPPROPRIATE |  Date Jan. 29 2014 7:33:44
 
Ruphus

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RE: Neck Reinforcement (in reply to constructordeguitarras

Gotcha!
  REPORT THIS POST AS INAPPROPRIATE |  Date Jan. 29 2014 17:52:11
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