carbon fiber instead of truss rod

[labraid]

It's unfair to say I'm trying to win a pissing contest by arguing my point, IMHO.

[Dave Cohen]

Brian, first, foam is a really terrible model for a beam made of an elastic solid - like, say, wood or a CF composite beam. Wood and CF composite bars are also very anisotropic, whereas your foam is pretty isotropic (means properties are the same in all directions). And with foam, the moduli in all directions are so small compared to wood or CF composite that you get all kinds of distortions that render your experiments wacky. Second, "proof" lies entirely in the domains of mathematics and logic. Scientists never claim to "prove" anything.

Bryce, you can mill your slots for the CF to follow the plane of the back of the neck by gluing a sacrificial piece of wood or something to the area of the nut. I glue a little sacrificial piece of wood to the nut area with CA, then just chisel it off after I am done cutting the slots. Measure the thicknesses your neck will be at the first and eighth frets, subtract out the thickness at the first fret and you have a triangle. Calculate the sin or cos or tan function of the angle at the nut, and use substitution to figure out how much the back of the neck drops over the length from nut to the end of the neck nearest the heel. By similar triangles, that will also be the thickness of the little sacrificial piece that you temporarily glue on at the nut. Works well, and makes a big difference.

http://www.Cohenmando.com

[labraid]

I swear, ISTJ, you remind me soooooooooo much of my paps. That's part compliment, but the man isn't worth arguing with, cause he'll always find a technicality to completely divert the argument to where he knows he'll win, away from where he isn't sure.
Nothing was solved today then. You haven't won the point without some sort of well, anything more than that... I'm not letting you off. See you at CMSA (bring paper)

[Nick Triesch]

Hey, I found 3 more makers that use the truss rod.....Monteleone, Paganoni, Zeidler. I will buy a mandolin with the adjustable truss rod!

[labraid]

The status quo is such, Nick, that it doesn't need folks to defend it.

[peter.coombe]

I have been away from this thread for a while and I think my earlier statement that some customers are just stubborn has been well illustrated.

[Rick Turner]

Like I said, it's not either/or unless you make it that way. You can wear a belt with your suspenders if you like...

All I know is that CF is really wonderful stuff, and for me, it makes for better sounding instruments by helping drive more energy into the body as the neck robs less energy from the strings.

And I do use both a dual acting truss rod and CF in my guitar necks...

[mandozilla]

Oops!...My Bone!

[mandozilla]

"Can't we all just get along?"

Now if someone could make an adjustable truss rod out of CF...Hmm...

Say, do fiddles have neck reinforcement of any kind? Or don't they need it?

[Stephanie Reiser]

Say, do fiddles have neck reinforcement of any kind? Or don't they need it?



[/QUOTE]

No, and no.

[markishandsome]

"I think it could cost a lot more than a hundred bucks if your non truss rod neck needed an adjustment. "

Maybe, but not much. While the instrument is in for a routine refret, the board is replaned to correct the relief. A common procedure, even on truss-rodded instruments. An additional couple hundred bucks on top of the base cost of the refret. Still only a few percent of a 10k purchase price (ie less than sales tax). Not something I'd like to have to do very often, but if I had that much money to be spending on instruments, i wouldn't consider it a big deal. If i spent 10K on a dog, i'd still have to buy its food.

Violin necks don't usually have any reinforcement. They have an enormously thick fingerboard and a very stubby neck. If the relief needs to be tweaked, it's carved into the fingerboard (just like a mandolin ).

[Dave Cohen]

Brian, I'm not trying to win anything, nor am I trying to divert the discussion away from whatever it is. Your understanding of beam statics is just crazy. I'd like to help you out.

Remember that physical Laws are constructs that have never been observed to be violated. That doesn't mean that they can't ever be violated. Nothing save falsifiability is doctrine in science. Everything in principle must be falsifiable. But if one ever does come up with evidence for overturning a Law, (s)he had better be ready with some mighty good data and explanations. Now to the point. Your understanding of beams and neutral axes violates Laws. I really appreciate the spirit of your foam experiment. I wish that more people would think analytically and empirically like that. But, you have to take your analyses to the next level. Whenever we investigate a problem, we go to the literature both before and after doing our experiments. Before, we have to ask things like "what is the current thinking on this?" and "Do I have reason to think that the current thought is wrong?...or right?...". After, we have to ask things like "What could I have done wrong here?" and "Are there artifacts?" and How will others criticise my hypotheses and work?", and most important, "How do my results either fit with or contrast with whatever is currently accepted?". That is one of the reasons why we have anonymous peer review; it automatically initiates some of those questions. And last, you have to thoroughly understand existing formalism in order to be prepared to topple it.

In your case, you can find some starting places in Fletcher & Rossing's "The Physics of Musical Instruments" (2nd Edition) in section 2.15, pp 58-60. A text on statics would be the next place to look. Maybe Pap has one?

Btw, are you in Cape Breton yet? & if so, do you like it? House hunting?

http://www.Cohenmando.com

[Nick Triesch]

I don't think I am being stubborn Peter, Heck, I'm just going along with the great masters of mandolin construction. Come on, that alone has to say something. Most of those guys have been building for many years. They have it wired! They know what works for them. And they also do not want their mandolins to come back to the shop. I say keep up the good work and keep on building your experiments. Nick

[man dough nollij]

I've been following this thread from a distance, intrigued by the heat generated. I'm far from a builder (not even close...), but I have kind of a tinkerer/engineer mentality so I often follow these threads.

I'm curious about something... Maybe Rick and Dr. Dave and others can chime in on this. I've heard lots of stories where luthiers removed the fingerboard with an iron, using the heat to loosen the hide glue that holds it on.

If you put a CF tube or rod in the neck and used epoxy to hold it all together, wouldn't that greatly complicate any future repairs? I couldn't bear the idea of whackin' the whole neck off of a nice custom mandolin, steaming the neck joint apart and building a whole neck from the joint up, just to replace a fretboard. Wouldn't epoxy create that scenario? Hmm?

[j. condino]

Rough crowd out there in mandolin world for this thread....

I sure wish Peter Mix would add a few comments on carbon fiber and mandolin necks. As a musician, luthier, and engineering grad school dropout, I'll add that that I can agree with and find value in almost all of the comments posted here.

Given the fact that I can use anything commercially available or that I need to custom fabricate to stiffen the neck of my personal mandolin, my preference is for non-adjustable carbon fiber. Field testing them from the bottom of the Grand Canyon in August to the Himalaya in the winter, they've always sounded better and held up better for me.

Most builders I know are generally very accommodating to whoever writes the final check; if you prefer an adjustable Gibson style rod, that's what they will build for you. If you really want it, I know one mandolin nerd who will even cut funny holes all over the sides and paint the thing green for you...

j.
www.condino.com

[Rolfe]

I've heard lots of stories where luthiers removed the fingerboard with an iron, using the heat to loosen the hide glue that holds it on.

If you put a CF tube or rod in the neck and used epoxy to hold it all together, wouldn't that greatly complicate any future repairs? I couldn't bear the idea of whackin' the whole neck off of a nice custom mandolin, steaming the neck joint apart and building a whole neck from the joint up, just to replace a fretboard. Wouldn't epoxy create that scenario? Hmm?

I use epoxy as my primary building glue; so, not only is the neck/truss bar installed with epoxy, the fingerboard goes on with it too. Removing the fingerboard with heat works just as well with epoxy. You heat the knife or wedge used to pry the fingerboard up; you don't heat the whole fingerboard. We just recently removed the fingerboard of one of my mandolins built ten years ago without harming the fingerboard, the inlays, the binding, the neck, or anything. We had pulled the frets already, so when we reinstalled it, we leveled it, refretted, and away it went---nice and original. There is a myth out there about epoxied parts not being repairable. I will say that it is CHEAPER for me to whack off the whole neck (after salvaging fingerboard and parts) and put on a new one than trying to undo the truss bar system, but I've had to do that only once in my career.

[labraid]

If there was any heat it is the result of frictions and not an open flame. Dave's a friend, we just like to grill each other from time to time. He gets me, I get him. All good fun.........

My position on the topic is that the church, in this case, does not want to prove what it believes. I'm happy to continue building necks "glass" flat with approaches to CF that are very mainstream, with only small doubts, perhaps, that the mainstream is 100% spot on in its theory. Still, my results are consistent with other CF users because that is an area I do not wish to take risks in. I may be wrong in my theories, but as Socrates said, "the univestigated life, et caetera, et caetera". Building is my addiction... Questioning, my nature. I'm pretty confident that's the right way to go, and will result in deeper understanding in the long run. Afterall, one does not truly know who they are, until they know who they are not. Same goes for building I think. Get the disease into the sunlight, it'll cure faster than under a wet bandage.

[Dave Cohen]

Glues let go when the "glass transition temperature" is reached. For hot hide glue, that is up around 400-450 degrees F. For epoxy, it is down around 200 degrees F, and it is slightly lower for PVA glues such as TiteBond. Quite a number of luthiers are now using epoxy for gluing fingerboards. Fingerboards glued with epoxy are easily removed by removing the frets and heating with a household iron. I removed an epoxy-glued fingerboard from an archtop guitar a while back That guitar neck has CF reinforcement and a truss rod. The fingerboard came up cleanly, and the rest of the neck was unharmed.

Actually, you need heat plus moisture to separate hot hide glue seams. Hot hide glue seams do come apart cleanly, but not without quite a bit of effort.

http://www.Cohenmando.com

[Rick Turner]

Another epoxy user who has no problem taking fingerboards off with heat. They come off cleanly, easily, and with no fuss or muss. I don't even always take out the frets to do it.

The great thing about epoxy is that it doesn't induce water into the wood, and so glue lines stay nice and stable.

With regard to fix it or replace it...folks who only repair tend to be very leery of replacing necks. Those of us who build may often find it easier, cheaper, and better to simply replace a broken neck. Making necks just isn't that big a deal if you do it all the time.

[Rick Turner]

Oh, one more thing...there are epoxies that cure with heat and can handle up to 500 degrees F before they let go. These are used in aerospace for satellite parts which are cured in autoclaves. The first carbon fiber necks were done with hi temperature epoxies because the parts were made at Ford Aerospace in Sunnyvale, CA, and that's what they had. The materials cured at 350 F.

[John Bertotti]

Oh. No you didn't! I see it now, mando magic and superior tone acheived through baking your tone woods! I have to call OldWave now! Bill just has to bake mando!

[Rick Turner]

I froze a Derrington/Gibson F-5 once; I sent it to a company in LA that does cryogenic treatment of (usually) metals. Had that sucker taken down to minus 360 F for 72 hours. The binding didn't like it at all... The mando was in the white and had been left under Charlie's bench when he left for a few years in the late 1980s. Since I was el queso grande of Gibson Labs West, I could raid the factory for bits and pieces. This was supposedly due to be a factory second, and I made well sure of it!

[Rick Turner]

Oh, the Kulesh Mastertone banjo tone rings that we cryo-treated came out great, and now that has become kind of a fairly normal thing to do to high end tone rings. I still have one of the rings that Rich Sr. made for me. Just have to build a banjo someday.

[j. condino]

"El queso grande", your are my favorite! Nobody else around here has been brave enough to ship out a Derrington F5 to Walt Disney in LA for the weekend.

j.
www.condino.com

[Rick Turner]

I guess I'd better not tell Frank Wakefield about it...

Actually, I'd gotten into cryo treating of strings in the mid 1980s with my old pal Lowell (Banana) Levinger now of Players' Vintage Instruments fame and a guy who has a couple of nice Loars and a pile of Loar ViviTones. We dabbled in a little mail order cryo treated string business for a little while. We were having Tom Vinci make the strings for us, and then we were sending them out for treatment. This is one of those things that I maybe should have patented, but didn't. Now, of course, there are several companies offering cryo-treated strings with Dean Markley being the most obvious.

So when I wound up doing R&D for Gibson, circa '88 and '89, I was quite happy to try just about anything...and did...that being the era of Jim Triggs and Greg Rich in the Gibson Custom Shop... It did get a bit crazy at times...