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Is it crazy to make a 4-ply neck blank?

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Oct 18, 2020 - 2:00:45 PM
4 posts since 3/12/2020

Hello all!

I am starting down my banjo building and woodworking career and with plans to build a few fretless mountain banjos due to the simplicity and the tools that I have available to me. I am going for the simplest possible neck construction (fretless, fingerboardless, and without a truss rod). I have found a source of relatively cheap hardwood lumber, but I don't really have a say in the dimensions that lumber is available in. For necks, I currently have access to 3/4" x 3 1/2" cherry, oak, and walnut. Now, to make a reasonable neck blank out of that lumber I would need to layup a 4-ply laminate resulting in a 3" x 3 1/2" blank which should work with the dimensions of my design. I have seen a lot of 3-ply necks in my research, but I don't think I have ever seen what I have described above which leads me to believe that it might not be a good choice. Most of the lumber I have access to currently is 3/4" thick, so I have designed my plans around that. I am most unsure about the neck and any advice that you might have about laminated necks is much appreciated!

Oct 18, 2020 - 2:36:27 PM
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11132 posts since 6/2/2008

I can't even count the plies in this Martin guitar neck:

I believe USA Fender banjos were technically 5-ply (not counting peghead ears). They were walnut that was ripped and bookmatched with three narrow laminates sandwiched in between to create a decorative dark-light-dark stripe down the middle.

I'm sure your 4-ply will work. And it can look good, too.

Oct 18, 2020 - 2:46:23 PM

3333 posts since 5/29/2011

There is no reason I can see why it wouldn't work. Laminated necks are more resistant to warp than one piece necks so you would have that added advantage. Just because an odd number of plies is more common doesn't mean it is absolutely necessary.

Oct 18, 2020 - 2:58:03 PM
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rcc56

USA

3171 posts since 2/20/2016

Many thousands of banjos were made with laminated necks during the early 20th century by Fairbanks/Vega, and Lange to name just a couple. A lot of those old necks are solid as a rock without any other kind of reinforcement.

Cherry and walnut are both well-tested neck woods.
You might want to consider ripping one or two of your pieces in half. 5 plies would have a more symmetrical appearance.

Oct 18, 2020 - 3:26:56 PM
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1008 posts since 1/9/2012

Down the middle is walnut flanked by maple. The mahogany is glued together 1/2" boards. I made it when I was 15 (56 years ago). (Somewhat paranoid, I put a steel bar where the thin layers aren't -- under the fret board.) The rim, made with hand tools at home, is funky, but the neck is perfect, i.e., was and is.

A Martin rep at the Topanga Banjo & Fiddle Contest once told me you could drive a truck over those laminated necks. (Those bodies are tough, too: formica on plywood -- and they sound just fine.)




Oct 18, 2020 - 3:31 PM
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2945 posts since 2/18/2009
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I make necks with 3 equal plies routinely, three plies at 3/4" makes a 2-1/4" neck blank, which is wider than most necks are at the heel. I then add peghead ears as needed, sized depending on the width of the peghead shape. If you want to do four plies you could put a 1/16" pinstripe of contrasting wood in the center, this can make a nice effect. A 3 ply neck of all matching wood can be oriented in two ways, the center ply can either be parallel with the neck centerline above the 5th fret, or it can be parallel with the truss rod centerline, from the center of the heel to the center of the nut. Either way will work just fine, it's just a matter or how you lay it out.

Oct 18, 2020 - 4:43:52 PM

mbanza

USA

2249 posts since 9/16/2007

Another option you can consider is a scarf jointed peghead and built up heel. 6/8 lumber is all you'd need for this.

Oct 18, 2020 - 5:06:27 PM

2174 posts since 2/7/2008

I have multiple guitars with 5 piece necks in various configurations. Beautiful and stable.




Oct 18, 2020 - 6:33:53 PM

13346 posts since 10/30/2008

Even Gibson made some 5 ply banjo necks in the 1970s.

Oct 18, 2020 - 6:40:09 PM

77 posts since 12/29/2009

FWIW, wood laminated constructions are typically an odd number of laminations. I was told even numbers tend to warp but an odd number will balance around the center lamination.

Oct 18, 2020 - 7:10:37 PM

hbick2

USA

262 posts since 6/26/2004

You could always do this:


 

Oct 18, 2020 - 7:14:46 PM
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7733 posts since 8/28/2013

I absolutely agree with John Hunter. I've been told the same thing, and I've never seen any quality laminated pieces made with an even number of plies.

Since you can't get the size you need with three plies, use five.

Edited by - G Edward Porgie on 10/18/2020 19:17:41

Oct 18, 2020 - 8:18:04 PM

Bart Veerman

Canada

4727 posts since 1/5/2005

Ì just counted the number of plies of my early 70ies 5-string Framus neck: 22

Oct 18, 2020 - 8:41:16 PM

mbanza

USA

2249 posts since 9/16/2007

Regarding the number of plies, many of us have seen necks with two plies, they aren't uncommon. Two pieces glued together to form a neck blank with a central joint.

Oct 19, 2020 - 5:40:16 AM

13207 posts since 6/29/2005

Generally, two symmetrically opposed 3/4" pieces with a center strip of 1/4" will work just fine—you don't need three.  The center strip takes it to the desired width (usually 2"), and can be whatever you want it to be—one 1/4" piece or a multiple lamination.

Oct 19, 2020 - 5:58:35 AM

Helix

USA

12935 posts since 8/30/2006

Not one person mentioned flipping and rotating your pieces so the pieces push together
If you don’t do that you won’t have a neck for long

All cabinet fronts, tabletops , and such have the pieces flipped rotated

You can make all the 5-pc necks you want
The “A” presentation looks like an A, the B looks like a V. At the heel

Here’s a photo 


 

Edited by - Helix on 10/19/2020 05:59:21

Oct 19, 2020 - 8:03:16 AM

7733 posts since 8/28/2013

quote:
Originally posted by Bart Veerman

Ì just counted the number of plies of my early 70ies 5-string Framus neck: 22


Framus necks are an exception. The wood is actually compressed and will behave differently because of that. I'm suer that not all Framus necks had even numbers of plies; the plies were more a function of the needed thickness and depended somewhat on the quality (or lack) of the wood that was squished; woods used would squeeze to different thicknesses depending on their densities.

That same type of laminating was popular among piano technicians for a while for replacement pin blocks. Drilling the holes for the tuning pins was more like drilling masonry than drilling wood. It was miserable stuff to work with, and although it didn't usually warp, there were sometimes other issues that caused its use to be dropped for piano purposes. I hated the stuff, and only did a few at another's request. 

Oct 19, 2020 - 5:58:22 PM

2174 posts since 2/7/2008

I've never seen nor made a layup with an even number laminations. The logic is that if the center is a glue joint, it won't be as strong as if the center were the middle of the center lamination.

However, I have read several accounts indicating that the need for an uneven quantity of pieces is more tradition than engineering.

Oct 19, 2020 - 9:00:11 PM
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mbanza

USA

2249 posts since 9/16/2007

"The logic is that if the center is a glue joint, it won't be as strong as if the center were the middle of the center lamination."

That logic is flawed: A properly prepared joint will be stronger than the adjacent wood. It's easily demonstrated by properly jointing some scrap wood, gluing it, allowing the glue to cure, then breaking the pieces apart.

woodworkingnetwork.com/best-pr...er-strong

Oct 20, 2020 - 4:55:21 AM
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13207 posts since 6/29/2005

Another thing worth mentioning is that the center strip can be made to the same width as the truss rod, and glued up in such a way as to eliminate having to cut a dado in the neck blank. 

I used to do that with the classic Gibson one-way tension rods, where the slot has to be cut at a long arc. 

Oct 20, 2020 - 6:01:51 AM

2945 posts since 2/18/2009
Online Now

quote:
Originally posted by Ken LeVan

Generally, two symmetrically opposed 3/4" pieces with a center strip of 1/4" will work just fine—you don't need three.  The center strip takes it to the desired width (usually 2"), and can be whatever you want it to be—one 1/4" piece or a multiple lamination.


If what you have is 3/4" wood then you either need three layers or a 1/2" center stripe to reach 2" in width.  If you have 7/8" wood then a 1/4" stripe is enough.  I personally prefer to keep contrasting neck stripes in banjos to 1/4" or less, since as they get wider the asymmetry of the neck becomes harder for the brain to ignore.  

Oct 20, 2020 - 7:15:20 AM

7733 posts since 8/28/2013

quote:
Originally posted by Quickstep192

I've never seen nor made a layup with an even number laminations. The logic is that if the center is a glue joint, it won't be as strong as if the center were the middle of the center lamination.

However, I have read several accounts indicating that the need for an uneven quantity of pieces is more tradition than engineering.


I've never heard that "logic," and although it may have been true back when glues were not as strong and stable as they are today, it is no longer the case. The story I've heard is that an even number of plies has mare of a tendency to warp one way or the other; the odd ply is added to help counter this tendency. There are, however, other things that are done to also help keep things straight, such as the "symmetrical opposition" mentioned by Ken and others, and cross laminating, where the grain of the center ply is oriented in a perpendicular direction to the others.

Although some may believe that this has been done as "tradition," I would say that there are usually reasons for such traditions, especially the ones that hold for centuries. I'd also point out that I've had experience with warped and twisted laminated products that were done improperly with an even number of plies. The key frames of early Pearl River pianos were done this way, and every single one I've ever encountered was warped. (Thankfully, the company learned their lesson, and no longer do this.)

Oct 20, 2020 - 7:35:26 AM

2174 posts since 2/7/2008

Yeah, I guess a lot of those traditions are steeped in experience although modern materials may change that.

Even after reading that the odd lamination tradition wasn’t really a concern, I still make odd number laminations. I t may be just because it’s more visually appealing, even if the lamination is all the same woods.

I’ve been experimenting a little bit with using a carbon fiber strip as one or more laminations. It glues up nicely, but it hasn’t finished well.

Oct 20, 2020 - 8:31:16 AM

13207 posts since 6/29/2005

quote:
Originally posted by Zachary Hoyt
quote:
Originally posted by Ken LeVan

Generally, two symmetrically opposed 3/4" pieces with a center strip of 1/4" will work just fine—you don't need three.  The center strip takes it to the desired width (usually 2"), and can be whatever you want it to be—one 1/4" piece or a multiple lamination.


If what you have is 3/4" wood then you either need three layers or a 1/2" center stripe to reach 2" in width.  If you have 7/8" wood then a 1/4" stripe is enough.  I personally prefer to keep contrasting neck stripes in banjos to 1/4" or less, since as they get wider the asymmetry of the neck becomes harder for the brain to ignore.  


Darn, Zach—you caught me!  I use 7/8" wood, which I forgot about, so disregard all the pictures and everything I wrote.

Ken

Oct 20, 2020 - 12:21:03 PM

Helix

USA

12935 posts since 8/30/2006

Symmetrical opposition is standard cabinet making

Oct 20, 2020 - 2:38:43 PM

49 posts since 5/27/2019

quote:
Originally posted by G Edward Porgie
quote:
Originally posted by Quickstep192

I've never seen nor made a layup with an even number laminations. The logic is that if the center is a glue joint, it won't be as strong as if the center were the middle of the center lamination.

However, I have read several accounts indicating that the need for an uneven quantity of pieces is more tradition than engineering.


I've never heard that "logic," and although it may have been true back when glues were not as strong and stable as they are today, it is no longer the case. The story I've heard is that an even number of plies has mare of a tendency to warp one way or the other; the odd ply is added to help counter this tendency. There are, however, other things that are done to also help keep things straight, such as the "symmetrical opposition" mentioned by Ken and others, and cross laminating, where the grain of the center ply is oriented in a perpendicular direction to the others.

Although some may believe that this has been done as "tradition," I would say that there are usually reasons for such traditions, especially the ones that hold for centuries. I'd also point out that I've had experience with warped and twisted laminated products that were done improperly with an even number of plies. The key frames of early Pearl River pianos were done this way, and every single one I've ever encountered was warped. (Thankfully, the company learned their lesson, and no longer do this.)


It might be that part of the traditional "reason" for symmetrical opposition, in something like an instrument neck, is the appearance of the grain.  It's more likely to have an attractive symmetrical pattern if you do it that way, and attractiveness is highly important when selling expensive instruments.

I'm not convinced that if the individual laminations are stable by themselves (i.e. all sufficiently dried to similar moisture content at time of construction, reasonably well-behaved grain, absense of defects, and didn't have internal stresses such that they got all wonky when cut out of a larger board), I'm not sure the "flip and rotate" convention is always meaningful or necessary to the stability of the project.  For example, if you were using two equal laminations of straight grained wood, then it probably wouldn't matter as long as the grain was oriented the same way.  If the grain is significantly running off the edge of both, it might be prudent to have those opposing each other, but it might not matter as much as we think it does.  It might matter more with wood that isn't as stiff, and/or thinner neck profiles, and/or necks without any reinforcement, where the neck isn't as able to resist the unequal tensions of the strings.

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