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Matthew Noykos

Carbon fiber rods in the neck

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Matthew, you are talking about arbon rods in cello necks right? This is interesting, I believe David Burgess said he builds them in to prevent projection from falling, (maybe he can join the discussion?) but you are the first I know of who claims to hear an improvement of the sound of the instrument. It interests me, because the projection on my cello came down about a centimetre over the first year I had it, but the maker sais it still is within an acceptable range. However, you state that the tone of the bass side is improved, and this is very interesting to me, because my cello has developed a nice sound especially on the a string and also on the d string, but the lower two strings are not so great, especially the c string is weak. Playing it I also have the feeling that energy is disappearing, exactly as you describe, that a part of what I am doing is not translated into sound. Light gauge strings somewhat improve this, but not much. I am wondering, considering that the projection did come down, wether the wood of this cello neck is not as stiff as would be ideal. So in your opinion there could be a good chance that the decreasing power from top to bottom strings could be fixed with a stiffer neck? I am also wondering to what extend a simple lamination with wood under the fingerboard could help, it seems to me that that could already be adding a lot of stiffness.

Maybe this should be a new topic? it drifts away quite far from the original topic...

Baroquecello, I hope you don't mind that I copied and pasted you onto the new topic.

To answer your question Baroquecello, I do hear a better response in the lower strings on instruments that have had a CF rod installed but it would be a lot for me to recommend that in your situation without seeing the instrument. For example, you may have lost some of that power in the low end due to a soundpost that is too short since it's a new instrument. Also, it's not uncommon for necks that are new to lose some of their projection. A centimeter is quite a lot though. Did you have a new bridge cut? I think you possibly lost some power due to a projection drop. If you had the neck reset, I would guess that the neck is done settling and would probably hold the projection better.

You asked about Burgess's solution. I'll let him expand if he likes, but I don't think he uses CF rods at all. His solution, as I understand is to put dowels through the heel of the neck. That might be over simplifying, but I do think it is pretty effective.

One thing I would like to try is L shaped CF rods. I visited Jim Ham's shop in Victoria a few years ago when I was there for vacation. He had some rods made that were shaped in an L shape and the fibers were continuous. This would act sort of like Burgess's method with a rod going into the heel instead of a dowel, but also have it go up the length of the neck too. Some guitar makers will do this with two separate rods. Guitar makers tend to be much more experimental than violin makers.

I would be interested to hear other opinions about carbon fiber reinforcements in the neck. Have any of you tried it? And what was your experience? Does anyone have any thoughts on the fact that it's pretty non traditional and does that bother any of you makers?

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I believe Joe and Sigrun employ them.  I used a rod in an English 'cello neck that had been thinned to fit the player's hand, then proceeded to warp.  Holding up quite well so far.

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The sound changed... and the player liked it... though it's difficult to tell what really caused the change.  I straightened the neck and set the 'cello up properly (to reflect that change).  How much can I attribute to the carbon fiber?

 

Certainly did not seem to be a detriment (and fixed the problem), however, which is about as much as I feel I can really ask.  :-)

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I'll paste myself here:

 

Can stiffening the neck stop the relaxation of the plates; the twist and settling of the rib structure? I have only seen a couple of necks actually twist, or warp, but those soundposts become too short pretty regularly. Is the system of age-related warp really centered on the stiffness of the neck itself?

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When CF bars are used in classical guitar necks it tends to make the instrument brighter. The neck and headstock give off a bit of sound, and neck stiffness a sustain have a relationship. Also the neck has a frequency which goes up as it gets lighter and stiffer. There's no formula, but many people use them simply because they don't want trouble with the neck moving forward or tension to bend too much relief in the neck. Usually its a good consideration if a customer asks for a thin neck.

When I began thinking about making a cello it did cross my mind to include a CF bar. solid bar 3/16" X 3/8" would work. Lots of people use two parallel bars 1/8" X 3/8" in guitar necks.

You could make a cello neck with scrap maple, flex it under a set amount of weight and measure the deflection. Then rout a slot and epoxy a CF rod in an measure it again. You could get an idea of resistance. The CF needs to be set in tight with glue, I wonder if epoxy is the best glue, due to the ida that you want to build bowed instruments with reversible glues.

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Stephen, you said neck stiffness and sustain have a relationship in guitars. Do you mean the stiffer the neck, the more sustain? This would make sense to me. I would think with a stiffer the neck, less vibration would be absorbed by the neck and more transferred through the string. This would give a greater sustain, would it not?

I found cf rods increased the power in the lower strings with viola, cello, and bass. Do find this with guitar?

I'm trained under a classical system of restoration and making that employs hide glue for most everything, but in the case of necks with cf rods, epoxy doesn't actually bother me. I want the rod to be permanent, but I don't necessarily consider the neck itself to be permanent. Does anyone else have thoughts on that?

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It seems that stiffness in the neck leads to good tone. 

Hi Michael,

 

Do you have an opinion on mass and damping too?  From a tone point of view (forgetting distortion over time problems) any guess what's the best neck?

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I'll paste myself here:

 

Can stiffening the neck stop the relaxation of the plates; the twist and settling of the rib structure?

No, but it can significantly reduce neck and heel deflection, which is a major contributor to the neck projection dropping, particularly on cellos.

 

I was in the habit of setting cello necks about 1 cm high, because that's about how much they would come down over time. But you couldn't count on that number. It would vary. Doweled my first neck, not really expecting it to work, and it went out into the world. A few years later, I get a call from Rene Morel:

 

"Daveed, you do good work, but zees time you make meestake and set zee neck too high? I make a breedge for your cello, and need to add wood to zee bottom of zee bridge to make eet high enough".

 

That was my first strong clue that it was really working.

 

 

Carbon fiber glued with epoxy would work fine too, probably even better than the cross-grain wooden dowels I use. I've stuck with wood just because when some unsuspecting fiddle repairman cuts into it someday, they won't curse me for furnishing a surprise which trashed their finely-honed cutting tools. I get cursed enough already. :lol:

 

Or maybe not, and I need to try harder....

 

Jeffrey, yes, it's my understanding that Joe and Sigrun have used carbon fiber in all their cello necks for many years now.

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 Do you mean the stiffer the neck, the more sustain? This would make sense to me. I would think with a stiffer the neck, less vibration would be absorbed by the neck and more transferred through the string. This would give a greater sustain, would it not?

 

I am of the opinion that if the neck is weak, the strings will try and set it in motion, robbing valuable energy that could otherwise be driving the bridge. If the neck is strong, then the energy is reflected back to the strings.

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When CF bars are used in classical guitar necks it tends to make the instrument brighter. The neck and headstock give off a bit of sound, and neck stiffness a sustain have a relationship. Also the neck has a frequency which goes up as it gets lighter and stiffer. There's no formula, but many people use them simply because they don't want trouble with the neck moving forward or tension to bend too much relief in the neck. Usually its a good consideration if a customer asks for a thin neck.

When I began thinking about making a cello it did cross my mind to include a CF bar. solid bar 3/16" X 3/8" would work. Lots of people use two parallel bars 1/8" X 3/8" in guitar necks.

You could make a cello neck with scrap maple, flex it under a set amount of weight and measure the deflection. Then rout a slot and epoxy a CF rod in an measure it again. You could get an idea of resistance. The CF needs to be set in tight with glue, I wonder if epoxy is the best glue, due to the ida that you want to build bowed instruments with reversible glues.

 

So the two bars are left exposed on the back of the guitar neck?  When I first saw that I wondered if that was just a nice lamination feature on the guitar neck.  It was CF rods.

 

Is that the same approach you all take with CD in a cello neck?  Or is it hidden?

 

Seems to me CF seems like a much friendlier symbiotic solution to neck reinforcement than a repulsive heavy alien steel rod.  Same repulsion that I have when surgeons put metal plates in people to support broken bones.  Seems like CF would be a better material there as well.  Metal just seems cold and foreign when dealing with acoustic instruments.  Nice thing about bowed instruments is we can get away from steel strings too.  Although they do sound nice on an acoustic guitar.

 

BTW although most joints in a violin or cello should be reversible, unless the CF would ever need to be replaced, permanent glue is probably best.

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NPR's Science Friday, Just did a program on Les Paul.... inventor of the electric guitar , aparently his motavation was not for volume but for sustain, His first was made from a section of iron rail and they said the sustain was incredable. essentialy standing waves.  the "log" his first real electic guitar was built out of a hard wood post.

   I suppose the wood should be on the dry end of the MC spectrum in order to avoid cracks as shrinkage occurs. would placing the nect in a drying box for a week or so before instaling one be good? or work with normal ambent wood.

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No, but it can significantly reduce neck and heel deflection, which is a major contributor to the neck projection dropping, particularly on cellos.

 

I was in the habit of setting cello necks about 1 cm high, because that's about how much they would come down over time. But you couldn't count on that number. I would vary. Doweled my first neck, not really expecting it to work, and it went out into the world. A few years later, I get a call from Rene Morel:

 

"Daveed, you do good work, but zees time you make meestake and set zee neck too high? I make a breedge for your cello, and need to add wood to zee bottom of zee bridge to make eet high enough".

 

That was my first strong clue that it was really working.

 

 

Carbon fiber glued with epoxy would work fine too, probably even better than the cross-grain wooden dowels I use. I've stuck with wood just because when some unsuspecting fiddle repairman cuts into it someday, they won't curse me for furnishing a surprise which trashed their finely-honed cutting tools. I get cursed enough already. :lol:

 

Or maybe not, and I need to try harder....

 

Jeffrey, yes, it's my understanding that Joe and Sigrun have used carbon fiber in all their cello necks for many years now.

 

Hi David,

 

My next project is a cello for myself and I have a potential customer lined up for cello #2.  I am interested in the details of reinforcing the neck using wooden dowel.  Do you recommend maple, poplar, or oak?  I would opt for 1/2" diameter oak, perhaps?  Are you just routing a channel down the of the neck under the fingerboard or is this a further into the body of the neck?  I was considering setting the neck a little high based on this discussion.  I'm sure I'll be returning to this topic next year after I'm well into the project.

 

Thanks for any additional details you are willing to share.

 

:rolleyes:

Joe

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In addition to the neck being solid, I feel the other end of the strings is equally important, in that the lower block should be solid and be of sufficient mass to avoid robbing string energy too.

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Joe,

 

David had an article in the Strad about his heel reinforcement a while back, worth checking out. It's not a longitudinal stiffening of the neck like your thinking, it's about strengthening and stabilizing the heel vertically. The heel is the weak point, lots of seasonal movement and long term creep there, particularly on cellos where the overstand is high.

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Joe,

 

David had an article in the Strad about his heel reinforcement a while back, worth checking out. It's not a longitudinal stiffening of the neck like your thinking, it's about strengthening and stabilizing the heel vertically. The heel is the weak point, lots of seasonal movement and long term creep there, particularly on cellos where the overstand is high.

 

Ah, thanks!  That makes more sense now. I was wondering about my initial concept of the reinforcement rods.  Since I would have thought the the lamination of ebony fingerboard of the maple neck should be pretty strong in a cello.

 

I would assume the rods are at some "diagonal" angle like the angled bracket holding up a bookshelf?

 

Cheers,

Joe

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Sorry, I can't find the article on the Strad website any more. Maybe I have a PDF of it somewhere.

 

Grubaugh and Siefert do the heel, and also a second carbon fiber piece in a large groove cut under the fingerboard. They lay a thin piece of maple over the carbon fiber so the gluing surface for the fingerboard isn't corrupted, and it can still be planed easily. I just reinforce the heel.

 

The extra area they reinforce will distort too, but it doesn't tend to be much, unless one uses a very curly wood, an unusual wood like pear, or the customer wants an uncommonly thin neck. I seem to recall that they first had a problem on a pearwood cello neck, and eventually decided just to do it on everything for good measure.

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Joe, David's article is in the first "Best of Trade Secrets".  

 

-Jim

 

Thanks!  I see if I can find it searching with "The Strad" android app.  I found a number of good Strad articles and issues to buy and read while on vacation in August.  Available issues only go back a couple years.   Do you recall when it was published?

 

:D 

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David, I'm trying to visualize your dowel. Is it down through the f.board gluing surface into the heel, or doweled through the block into the heel? I understand the truss-rod style going down the length of the neck, and am trying to figure how one reinforces the heel.

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Hi All - let me copy/paste this post here...

 

Hi All

 

I have fitted 16 mm dowels into 4 cello heels - excluding No 3 which was a new cello - I received pleasant report backs that the other three cello all sounded better.  No 3? It proved to be the finest cello I have ever played. Of course it might still have been that without the stiffening dowel...

 

I fitted a 8mm dia. dowel to my Violin no 1 - the fingerboard settled about 0.9mm over 11 months - I'm tempted to remove the f/b, drill out the dowel and fit a 10mm dia. dowel and see what gives.

 

As to using carbon pultrusion bars for stiffening the neck - I've watched a couple of necks being routed and fitted with c/f inserts. I wasn't convinced that they achieved anything and couldn't see the sense in fitting it there. It's just about on the neutral axis of the beam - where nothing much moves when the beam is flexing! (which is why it's called the neutral axis).

 

I would rather rout a 12mm wide by 3mm deep slot into the underside of the f/b and glue in a 12mm x 3mm section of c/f pultrusion. This puts the stiffer material as close to the outer fibres of composite beam (maple/carbon fibre/ebony) - where the compression loads are the greatest  and where the stiffer material would do the most good.

 

cheers edi

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