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Horizontally laminated neck, yes or no?

MPU

MPU

Sep 21, 2004
3,703
10,692
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Valkeala Finland
#1
I'm planning to make a headless fivestringer. I've searched TB for parallel or horizontal laminate necks. I'm somehow liking the idea of making a neck that way. I have wenge and maple for the neck, both quartersawn. I'm planning to make the neck 3-piece laminate with separate fretboard (propably ebony). I'm also planning to taper the center laminate so that the front and back laminates will be equal thickness all the way. I'm going to use a double action truss rod.
Now for the laminates, maple-wenge-maple or wenge-maple-wenge? Or is there any reason why the neck shouldn't be made like described up there?
All input and opinions are welcome.
Marko
 
#4
obaka-san said:
I'm guessing you would need a fairly beefy trussrod and probably some stiffening rods with a neck laminated like that. From my experience (non-bass) laminates like you've described tend to flex alot
Click to expand...

From what I read about parallel laminate I have to disagree. It should be less flexible than say one-piece neck. And they seem to work too. I think parallel-laminate as a kind of a sandwich-structure.
Marko
 
#5
conical johnson said:
I remember JP was really into that idea; Suburban too as I recall. They seemed to think it was stronger than alms perpendicular to the fretboard. Here's some info from Suburban:

http://www.suburban.se/Bassic_Physics/Bassic Physics.htm

There's a lot there, but the relevent information is near the end.
Click to expand...

Yes, I've read all from JP and Suburban. And Linc luthier too. It's a pity there's no pictorial info about JP necks on the net anymore.
Marko
 
#10
Moro, Marko.

I haven't done it that way, but from pure engineering standpoint the vertical is the way to go. You can test that by sawing a quality hardwood plywood (koivu on ok, havu EI) to square dimensions and bending that to both directions. Twisting it when bending should reveal yet another problem.

The main problem is how the different forces are transferred to the glue joints and their directions.

If You go with it, and why not, It can work with a little planning, the glues used must be choosen well to avoid separation.

Lykkyä tykö.
Samuli
 
#11
I disagree. If you're worried about the fact that you're introducing a shear force through the glue plane of the horizontal laminations, this is true, but consider that this is also the way it is on every guitar ever built that has a glued-on fingerboard. It doesn't seem to cause a problem, does it?
 
#12
Benavente has also done necks like this.

These necks are as strong as vertical laminated necks. The glue joint is irrelevent in this instance as wood glue "disapears" within the pores and makes the wood laminates bond mechanicaly to each other. The different densities and grain orientations of the different woods used in the laminates will play against each other to stabilize the whole neck. At least, that's the way I understand it. ;)

I also plan on building a few necks like this. :D
 
#14
I think it all depends on how long you want your instrument to last in a playable fashion. Contrary to what Phil said above, the glue joints do not disappear. (Not knocking you Phil) All glues have a creep factor including epoxy, pva and hide glue. In tests hide performs very well, Titebond OK, and Titebond II not so well. Epoxies are all over the map.

If you laminate three pieces perpendicular to the FB you have three pieces of +-9/16" material with two "tall" glue joints oriented to advantage against the pull of the strings. A lamination of three pieces parallel to the FB would result in three thin pieces (+-3/16") laminated with the glue joint at it's weakest against the pull of the strings.

Now imagine the two scenarios above without the glue. The individual pieces in the first example have a good chance of resisting the pull of the strings individually. None of the individual thin laminations have a chance. You are completely dependent on the glue joint which is under constant stress even as you sleep at night. Over time which one do you think will perform better?

Actually, if you use the same 3/16" laminations but orient them perpendicular to the FB you would have an extremely stiff neck. Each piece would strengthen and gain strength from the others and the glue joints would be multiple and "tall enough" to actually combat the stress from the strings.

Just my opinion. Perhaps it is arrogant to imagine my instruments being played long after I have passed, but that is my goal.

Greg N
 
#15
I'm sorry, Nelson, but you are misapplying principles, and coming up with incorrect conclusions, or incorrect reasonings.

Correct assertion: the horizontal glue plane is subject to shear stress due to the string-induced bending moment. The vertical glue plane is not subject to this stress.
Incorrect assertion: the horizontal glue plane must therefore creep to a significant degree.
Evidence to the contrary: thousands if not millions of string instruments, with the same bending moment, with the same shear stress plane between fretboard and remainder of neck shaft. It is not normal for this to have resulted in the two signs of permanent shear strain (creep) in this manner: permanent forward bow, coupled with a noticeable dislocation of the board at either end of the neck, producing a slight step with the FB protruding axially.

Correct assertion: In a vertical lamination, the individual lams add to each other's strength and stiffness (two very different things, BTW) in resisting the bending moment
Incorrect assertion: vertical laminations add strength to a neck
Proper analysis: starting with the comparatively highly reduced stiffness of a single layer, the layers do add to each others' properties--until they equal the characteristics of the original, undivided solid beam.
 
#16
HI.

Nelson Guitars said:
I think it all depends on how long you want your instrument to last in a playable fashion. Contrary to what Phil said above, the glue joints do not disappear. (Not knocking you Phil) All glues have a creep factor including epoxy, pva and hide glue. In tests hide performs very well, Titebond OK, and Titebond II not so well. Epoxies are all over the map.

If you laminate three pieces perpendicular to the FB you have three pieces of +-9/16" material with two "tall" glue joints oriented to advantage against the pull of the strings. A lamination of three pieces parallel to the FB would result in three thin pieces (+-3/16") laminated with the glue joint at it's weakest against the pull of the strings.

Now imagine the two scenarios above without the glue. The individual pieces in the first example have a good chance of resisting the pull of the strings individually. None of the individual thin laminations have a chance. You are completely dependent on the glue joint which is under constant stress even as you sleep at night. Over time which one do you think will perform better?

Actually, if you use the same 3/16" laminations but orient them perpendicular to the FB you would have an extremely stiff neck. Each piece would strengthen and gain strength from the others and the glue joints would be multiple and "tall enough" to actually combat the stress from the strings.

Just my opinion. Perhaps it is arrogant to imagine my instruments being played long after I have passed, but that is my goal.

Greg N
Click to expand...

Well said, just what I was trying to say, but couldn't quite put in words ;). Could've done much better in finnish :p.

pilotjones said:
I disagree. If you're worried about the fact that you're introducing a shear force through the glue plane of the horizontal laminations, this is true, but consider that this is also the way it is on every guitar ever built that has a glued-on fingerboard. It doesn't seem to cause a problem, does it?
Click to expand...

The fret-/finger-board has the largest gluing area and the plane of force is rather near to the pivot points. The last lamination would have the least area and is farthest from the pivot points and also has the truss rod channel to weaken the things a bit. I've repaired quite a few separated fret-boards, never a separated vertical laminations. For me the less than optimal grain orientation would pose some problems also.

I'm not saying that it can't be done, that's just not the way I'd ever do it.

Regards
Sam
 
#18
We will just have to agree to disagree.

Yes, thousands of single piece necks that warp over time, and thousands of vertical laminations as well. The tension is there, and I believe that even space age materials like Kevlar and carbon fiber are subject to the same issue. Water on a stone as it were. Not too many horizontal laminations from what I have seen, even though it would be easy to do. Why? I don't think this is a new idea and only being tried now. I am not saying that it can't be done, only that I believe there are better techniques.

I believe Martin has a laminated neck out right now that has the laminations perpendicular to the fret board. "Stratabond" A company as serious about it's long term warranty doesn't put an item like that into production without a lot of research. If laminating the other way was a "better" detail then I am sure that would be what they would produce.

I respect your opinion but I stand by my previous post.

Greg N
 
#19
Would you mind explaining what carbon fiber and aramid (Kevlar) have to do with creep in the the discussion? Are why anyone would even suggest aramid, as it has rather low stiffness, making it unsuitable for structural applications such as this? Joe Zon does use it as one layer, in a group of layers where it is relieved of any structural "responsibility." Otherwise, to my knowledge, unused in luthierie, and rightfully so.

Martin doing necks with standard vertical laminations may be an endorsement of this method (I also have an 80 year old banjo built that way), but it is not therefor a knockdown of the other method. They would not do horizontal laminations, simply because their conservative market doesn't want them.
 
#20
pilotjones said:
Would you mind explaining what carbon fiber and aramid (Kevlar) have to do with creep in the the discussion? Are why anyone would even suggest aramid, as it has rather low stiffness, making it unsuitable for structural applications such as this?
Click to expand...

Certainly. The discussion is regarding a question about the viability/quality of a horizontal glue lamination and not just glue creep. I brought up traditional solid neck construction and alternate high tech materials in support of your comment "Evidence to the contrary: thousands if not millions of string instruments, with the same bending moment, with the same shear stress plane between fretboard and remainder of neck shaft." This shows that even my position is not a silver bullet. Glue creep is something that is not often considered or tested for given it's glacial time frame. That is why I suggested considering the systems with no glue at all. Not a 100% fair theory, but one that puts my thoughts on the subject into a perceivable time frame.

Why would anyone suggest Kevlar? Kevlar is used as a composite in many applications where weight to strength ratios are important. Boat hulls, bicycle frames, snow boards and skis to name a few. It has been used for acoustic steel string bodies and I do believe as laminations in necks. Cellos and violins have been built from it as well. It is an innovative field we are in and many things have been tried and failed either due to structural or market driven reasons. Carbon fiber is the latest material that shows promise and is actually being accepted in the stodgy world of classical music. I am floored.

Again, just my experience and opinion.

Greg N
 

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