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norm barrows

frets on a narrow wood spine + truss rod. how? whats the best neck wood?

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frets on a narrow wood spine + truss rod.   how?  whats the best neck wood?

so my ongoing design experiments are leading to a neck design consisting of a very thin (3/4") and narrow (1")  "spine" for a neck, with 3/16" (5mm) rod stock glued on for frets.   similar to heavily scalloped and sculpted necks.

Bizman62 put me onto the idea.  i think he was being facetious, but i found it to be a perfectly sound concept, worthy of further investigation.

at a minimum, a truss rod would need to be attached to a fret board at three points to work: the middle, and the two ends.

a 3/4" x 1" "neck"  is rather small to cut a truss rod channel into.   a larger "neck" would be required to yield the same strength.  and bigger necks usually mean more material in the way between the player's hand and the frets.  so the strength of neck material becomes an issue.

so what are desirable characteristics in a neck material, and what are the best woods for necks?

strength, and stability under changing climatic conditions come to mind as desirable features.  perhaps stain grade and look as well.

maple, mahogany, ebony, and rosewood seem to be the most common neck and fret board woods.

 

Edited by norm barrows

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21 hours ago, norm barrows said:

i think he was being facetious

Actually not. Although I must admit that many of your ideas have their roots firmly in thin air they are inspiring. Trying to find a way to create something impossible keeps my brain young!

A facetious idea would have been to use small nails and individual mountings (similar to what they use to attach rails to the ties) to attach the stubs of rails to the fingerboard.

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1 hour ago, Bizman62 said:

Although I must admit that many of your ideas have their roots firmly in thin air they are inspiring.

My Boss at Wright Patterson Air Force Base said i was an "outside the box thinker".      At the time, i'd never heard the term before.   

when i approach a new subject, i don't take conventional; wisdom as being gospel. i prefer to think things out for myself. if i reach the same logical conclusions as the rest of the world, fine.  but many times,  things are the way the are by happenstance, not logic, reason, or science, or the laws of physics.  and the laws of physics are the only rules we really need to worry about.

question everything.       

trust no one - humans are imperfect - they may be wrong - if you trust them and they'r wrong, you're screwed.       

trust - but verify.

that's the only real way to avoid being led down the garden path by conventional wisdom or relying on the word of others. 

also, take advantage of cross-disciplinary knowledge.  many activities share similar tasks - finishing guitar bodies has many things in common with both furniture finishing and auto body repair.   but tricks from one seldom find their was to another activity.  

apparently luthiers have discovered the beauty of bondo for painted surfaces.  so that's something from the automotive world that's made the transition to guitars.

being an engineer, i like to build stuff. so i've taken a lot of shop classes, and other classes related to building stuff  and when i get into building some new kind of stuff (like guitars) i bring to bear all that knowledge about building stuff. 

so i don't just consider using luthier techniques. i consider all of wood shop, metal shop, foundry and forge, plastics shop, electronics shop, hot rodding, race car building, auto body repair, and aerospace tech, materials, and methods - and primitive technologies to top it all off  (one of the PC games i make is a paleoworld sim with an emphasis on realism - so i had to learn all about primitive tech).    

 

 

so, what does conventional luthier wisdom say about preferred characteristics and therefore woods in a neck?

it just has to be "strong enough" ?

and climatic stability is nice?

if one were to keep the fretboard and truss rod, but minimize the neck as much as possible, what would be the strongest most stable wood to use for the neck?

maple?

oak - despite being hard to work ?  red is stronger than white right?

maple and mahogany seem to be the most common neck woods.

i wonder what a google search will reveal......

 

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well, it would seem that there are different types of "strength" for woods

http://workshopcompanion.com/KnowHow/Design/Nature_of_Wood/3_Wood_Strength/3_Wood_Strength.htm

hardness, bend strength, compression strength, etc.

odd are most folks think about hardness - Janka hardness rating (resistance to pitting and gouging) .

but for a guitar neck, you want bending strength (able to handle a large force perpendicular to the gran before failing).

for Janka strength, black ironwood, black african wood, and snake wood make the top 10, and are used in guitars sometimes. 

Hard maple got a mention on another less scientific site  (they rated it 5 out of 5 for hardness).

but for bending strength:

bubinga - whatever that is -  22,600 psi

hickory - 20,200 psi

purple heart - 19,200 psi

brazillian rosewood  -  19,000 psi

indian rosewood - 16,900 psi

yellow birch - 16,600 psi

hard maple - 15,800 psi

white oak -  15,000 psi

ash - 15,000 psi

everything else looks to be less than 15,000 psi bending strength, including cherry, red oak, walnut, mahogany species, teak, and all your other hardwoods, and all softwoods.

note: that website may not have exhaustive data on the subject. there may yet be other options out there.

 

purple heart is expensive - i think.

hickory, yellow birch, hard maple, white oak, and ash might be good cost effective options - at least in the region i'm located.

 

 

  

 

 

 

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34 minutes ago, norm barrows said:

it just has to be "strong enough" ?

and climatic stability is nice

Those are good. Stiffness is also considered a desirable trait.

36 minutes ago, norm barrows said:

maple and mahogany seem to be the most common neck woods.

Traditionally perhaps, but there are many that are as good or better at the job. I have never used either, although sapele is in the family I suppose. I have probably used jatoba for more necks than anything else, but along with those two, I've also used black limba, zebrawood, Osage orange, katalox, walnut, macassar ebony and East Indian rosewood for necks. All have been good.

SR

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14 minutes ago, ScottR said:

I've also used black limba, zebrawood, Osage orange, katalox, walnut, macassar ebony and East Indian rosewood for necks. All have been good.

but those were more conventional neck profiles, where maximum strength due to minimal material was not a potential issue, correct?

And most were selected primarily for aesthetic purposes - correct?   Indian rosewood is the only high bend strength wood ( > 15 Kpsi )  in that list.

i've found that a softwood spine type neck 3/4" thick and just 1" wide is strong enough for a six string with 8's on it. 

i'd like to fit a truss rod into that, while enlarging the dimensions of the "neck" as little as possible.  

so that would seem to call for a "strong" wood for the neck.

but perhaps i'm jumping the gun, once again. 

perhaps wait til it breaks before you come to the conclusion that a strong wood is required.

after all - pine got it done for no truss rod.

its dangerous to make assumptions like that - "pine won't work, it'll have to be stronger".   but people do it all the time.    i'm guilty of it myself.     

 

 

so all this would seem to lead to "i need to order a truss rod from ebay and do some testing" 

 

Edited by norm barrows

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4 minutes ago, norm barrows said:

And most were selected primarily for aesthetic purposes - correct?   Indian rosewood is the only high bend strength wood ( > 15 Kpsi )  in that lis

Yes and rigidity.

I'm surprised Osage orange didn't make the high bend strength list. It was prized for bow making wood by the Osage Indians, and Osage Indian bows were prized by many of the plains tribes.

Or so I've read.

OF that list it also tops this list for tactile feel once highly sanded and oiled. Really silky.

SR

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26 minutes ago, ScottR said:

Yes and rigidity.

 

interesting....

yes, i guess we're more interested in deflection strength of a neck (stiffness in mega psi), than in cross grain failure strength of a neck ( bending strength in psi).

you make a good point.

 

ok, for stiffness, we have:

bubinga again - 2.48 Mpsi

purpleheart - 2.27

hickory - 2.16

yellow birch - 2.01

yellow pine - 1.98

bazilian rosewood - 1.88

hard maple -1.83

red oak - 1.82

everything else is  < 1.8 Mpsi.   a number of woods like alder and ash come in at 1.7 something,

however....

take yellow pine for example.   high stiffness, but low bending strength.  so it wont defect or bend much, it will just bend a little bit, then quickly snap and break.

so maybe we need to worry about bending strength, not stiffness, after all.

we want necks that don't break. not necks that tend to stay flat, then suddenly snap under heavy load.

the reed sways with the wind or earthquakes or airliner collisions - the skyscraper tumbles.  rigidity can be a bad thing.         

eastern design philosophy, one might say.

rigid = brittle = a type of weakness in a material.  

material sciences was one of my best and favorite subjects. if you're going to build stuff, it helps to know about the lego blocks you're using <g>.

 

Edited by norm barrows

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33 minutes ago, ScottR said:

I'm surprised Osage orange didn't make the high bend strength list.

or Yew for that matter.    english long bows - you know.   

like i said, probably not an exhaustive list.

this site has a poster with hardness for 500+ woods, but not bending strength....

https://www.wood-database.com/wood-articles/top-ten-hardest-woods/

 

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37 minutes ago, ScottR said:

OF that list it also tops this list for tactile feel once highly sanded and oiled. Really silky.

ah!    now there's another universally desirable neck feature - tactile feel - IE smooth for faster and more comfortable playing.

i don't know anyone who likes a rough guitar neck.

but neck drag coefficients are really about the finish, not the underlying material   -   assuming you start with a relatively level surface in all cases.       

so smooth should not influence wood selection, as finishing (including filling and coating particularly nasty woods) should be able to make all woods more or less equal when it comes to smoothness.

so necks should have a high break strength, and finishes should be smooth.   no major surprises there.   but theory backs up assumptions - always a good thing.

now its a matter of how high a break strength is high enough, and how smooth a finish is smooth enough.

well, the neck has to stand up to string tension, and a fall from a height of say six feet to the ground, without breaking or cracking. maybe only a 4 foot drop.  

how far would you drop your most prized axe onto concrete at the worst possible angle with no fear of braking or cracking the neck ?   maybe 4 feet?    much past that and i'd start to worry....

then again, i now know how to spline headstocks.   <g>.  not that i want to try......

 

 

 

 

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10 hours ago, norm barrows said:

for a guitar neck, you want bending strength

As you've noticed with your pine neck the wood species doesn't matter that much. You're not the only one having used pine: The '60's Tele of Bill Kirchen is made of pine with no truss rod and it's still working fine!

Charts can be studied and they give some general ideas or directions to go. However, trees are living creatures and thus affected by many things starting from the soil they're growing in. Aspens are a good example, depending on the calcium level of the soil the wood will rot either fast or never!

There's other things to consider as well. First, if the growth rings are very tight the wood is harder and stiffer. It has grown slowly in a rocky ground, having created resistance for winds and other climate conditions. Tight end grain makes the best woods.

Second, the way it has been sawn makes quite a difference especially with tight grained wood. Quarter sawn wood is stiffer than slab sawn, meaning that the growth rings should be vertical if you hold the neck blank horizontally flat.

Third, you can knock and tap the blanks. If the sound is clean and ringing there's no voids inside the wood. The same method can be used for metals, ceramics etc. I remember an old Don Camillo novel where a Russian-Italian car mechanic listened to the flywheel to hear if it's balanced; the salesperson at a ceramic factory shop did the same for second-rate pots to tell if they were oven safe or prone to crack.

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On 1/16/2020 at 3:00 AM, Bizman62 said:

The '60's Tele of Bill Kirchen is made of pine with no truss rod and it's still working fine!

i saw him play live. a crab house bar in maryland. late 80's - early 90's.

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