Which is why I went on to say I’d use woods known for stiffness and add a carbon fiber backstrap.
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Necks without truss rods
- Thread starter ardgedee
- Start date
I took a composite course once when they had some 1 X 6" test strips, probably 0.050" thick, that were a laid up using different carbon fibers directions - some "bent" easily, some resisted bending but "twisted" easily, some resisted twist in one direction but allowed twist in the other (those were most impressive to me), one sample was we we call "black aluminum", which pretty much had the same strength in all directions (equal layers of 0/90/45/135 fibers).
I would guess that laminated wood could also be engineered to improve properties in certain directions, and might be more stable, but the overall "strength" wouldn't be more than an equivalent "block" of the same wood, so have to side with Zooberwerx on that point.
I would guess that laminated wood could also be engineered to improve properties in certain directions, and might be more stable, but the overall "strength" wouldn't be more than an equivalent "block" of the same wood, so have to side with Zooberwerx on that point.
The trick with lamination is not just use thin wood at any orientation - if you can cut up a wide, thin sheet, and then glue them back together with every other piece flipped (not as simple as it might seem - you have to keep track of things), you can get the wood to "warp-buck" itself -half of the pieces will want to warp one way, the other half will pull it the other direction, so the net is that it stays put - that is where laminating really helps.
In the case of a neck, you want all the wood fibers going the long dimension of the neck - that maximizes its stiffness in the direction where it needs it. If you start to do layers in different directions, you will reduce the stiffness in that direction.
The directionality of wood is important in a lot of places it's used. One notable music example is in things like violins. Wood is much stiffer if you're trying to bend fibers than it is at right angles to that - if you look at the shape of a violin, it's not a circle or square - it's elongated. As the stiffness is greatest when bending fibers, the velocity of wave propagation along the length of the top is much faster than it is across the width. The shape of a violin uses this - the width is shorter, so that a certain vibrational mode (the lowest one, actually) gets the whole tope moving together - the waves moving in different directions come back in phase with each other. If you made a square violin with solid wood, it wouldn't do this - for that shape, plywood (which alternated fiber direction) would actually make more sense. And it would look odd as hell.
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Modern wood glued are stronger at bonding together wood fibers than natural lignin. If you put force on a piece of wood such that you are stressing the bonds between the fibers, the wood will break somewhere besides the glue joint, assuming the glue joint was done well.
I the case of the stiffness or strength of a neck, it’s the fibers themselves that are being stressed, not the glue holding them together. The fibers run the length of the neck, not across it. The strength and the stiffness of that structure depends on the fibers’ characteristics and the cross section of things - adding or subtracting glue changes neither the strength or stiffness.
If you orient the fibers across a thin beam, it’s a different (much weaker) structure. If you ever see folks break boards with karate chops, the real secret is they have the board oriented so that they’re breaking bonds between fibers. If you can impregnate that board so that all the fibers are bonded with good modern glue, the strength of that board would be greater - you could injure someone doing that and wreck the demonstration.
I disagree with that, Gary. I can think of three:
- Light weight
- Low cost, much simpler construction
- Deliberately make the neck more flexible and springy, to add percussive attack. Such as an acoustic-only bass where it's designed to have the action high and be plucked very hard. On a bass designed to be set up with high action, fine adjustment of relief isn't important.
Most wood glues are softer or more brittle than wood when dry. They're not contributing stiffness.
Glulam beams have places where the fibers end. Bass necks don’t. There are some non-trivial differences due to that.
They achieve stiffness that same way a solid beam would - with considerable thickness. A glulam is a good idea for a couple of reasons - first, you can make a very long beam from shorter pieces, and second, you can make a thick beam from skinny pieces.
There are plenty of old lodges and such that have big single beams, but most of them were cut from old growth trees. Glulam allows the same performance from newer, smaller trees. The strength and stiffness is in the wood and the dimensions, the glue (so long as it holds things together) is not the critical piece of the puzzle.
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Kramer made aluminum necks that were very solid - built with a tiny bit of relief, they were very easy to setup to whatever playing height you wanted. If you wanted to put a truss rod in there, you would have to take away a lot of the structure - they were so stiff that a normal truss rod would not have been able to bend them. The net result of doing that would have defeated the point of those necks - they were so solid they had incredible sustain; and diminishing their strong point would have been a big loss.
Yes, they neck dived. But i was in my youth, and that was fine. Then.
Now I rely on Warmoth Roasted maple/graphite reinforced necks. Less sustain, for certain, but still more than most, and they don't neck dive at all - even on a 7 pound 5 string bass.
But there is a claimed increase in strength, size for size, so I think the glue is an important piece of the puzzle, particularly when we're talking about resin glues.
I'd like to hear more some time about building necks with fiberglass. That's not something I've seen before.
Building a neck from fiberglass is about the same as building one from carbon fiber. Woven cloth saturated with resin. Carbon fiber cloth is stronger than fiberglass cloth, not as brittle, and cooler looking. And more expensive. But the build technique is about the same.
I don't remember seeing fiberglass much in musical instrument structures, but it was very popular in cars and sporting gear. These days, fiberglass has mostly been replaced by carbon fiber. Because it's so much cooler looking.
I was about to ask if they had truss rods. I've seen them but only ever played one once, when I was literally just starting on bass and didn't even think to ask questions about set-up, etc..
Perhaps a headless aluminum neck would be a good way to go.
Who is claiming a strength increase, and in what situation are we talking about? If it's a bass neck being solid versus laminated (using the same wood and profile) then the claim is a claim, not something real.
The headless Kramer was called "The Duke" - short scale, small body - kind of a Steinbergerish vibe to it.
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My fiberglas necked instruments were DIY specials. The ones with the solid fiberglas necks were short scale guitars. One had a neck made from fiberglas, the other the whole thing was one big layup. One interesting point on that instrument was the cable routes from the pickup cavity to the controls and output jacks - I use cardboard tubes to hold the place for those, did the layup around them, and then...I put the whole thing into a bathtub filled with water, which softened the cardboard so I could yank it out. It was an odd feeling dropping a guitar I'd just built into water.
Here's just one example (still talking about glulams)
I've had a look for tests or data on bass neck sized pieces but I can't see much, perhaps you can point me to some?
Design Properties
Glulam bending members are typically specified on the basis of the maximum allowable bending stress of the member. For example, a 24F designation indicates a member with an allowable bending stress of 2400 psi. Similarly, a 26F designation refers to a member with an allowable bending stress of 2600 psi. These different stress levels are achieved by varying the percentages and grade of higher quality lumber in the beam layup. Use of different species may also result in different stress designations.
Yes, if you use different wood (note the "higher quality lumber" part) , you get different properties - putting stronger wood in the layers with the most stress gets you more strength in the beam. If you used that "higher quality lumber" for a solid beam, it'd actually be a bit stronger, as the whole thing would be better wood. Glulam allows you to use better wood only where it matters most, and keep the cost down. But.....
Again, using the same wood, and laminating layers of it does not gain strength or stiffness over a sold beam of the same wood. That is, as I've said before, is a common misconception.
Yes, if you use different wood (note the "higher quality lumber" part) , you get different properties - putting stronger wood in the layers with the most stress gets you more strength in the beam. If you used that "higher quality lumber" for a solid beam, it'd actually be a bit stronger, as the whole thing would be better wood. Glulam allows you to use better wood only where it matters most, and keep the cost down. But.....
Again, using the same wood, and laminating layers of it does not gain strength or stiffness over a sold beam of the same wood. That is, as I've said before, is a common misconception.
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