Graphite Neck Laminates; Tell Me Your Experiences.

[SwedishLuthier]

If you want good resistance to bending, you need to place the material that shall withstand the bending as FAR away as possible from the centre line of the construction.

this is not practical....they are placed under the fretboard because that is the most practical way to do it,and it adds just the stiffness needed,no more,no less...it isn't an engine hoist after all,it is a guitar neck

I agree, its not practical. That is why we are all in this discussion. We are trying to find out the best possible compromise

or thin laminates between wood, going all the way trough the neck.

hmmm...much like the web of a beam?i thought you said that was bogus?just a few posts ago you were arguing that was not "efficient".

You're right, it isn't the most efficiant way to place the reinforcement. But it means that you place a lot more reinforing material far away from the centre line of the neck. Compared to rods in the middle of the neck I think the strength will increase more with the laminates.

Still, this is all in theory. I'll try to da real experiment and test this. I'll get back about this as soon as I can precent some sientific facts. I'll just have to order some square graphite rods...

Edit: I' setting up for the tests right now. I'll report back as soon as I have some results

Edited August 12, 2005 by SwedishLuthier

[erikbojerik]

Tangent coming from an old thread...

this is how i make a living.installing the iron that the engineers and architects dream up.

←

OK, now I KNOW that Wes is more metal than Perry.

Resume carbon chat...

[SwedishLuthier]

I think that some of the postings in this tread have had a very hard edge to them. Can we please stop this and go on with the task of finding better ways to build guitars. If some of us actually think that the references to different kinds of structural beams make sense, it shouldn’t be put down by other participants.

So, I’ve finished the tests. This is what I did:

I don’t like the idea of using expensive tone woods and graphite rods for a possible destructive test, and I wouldn’t like to place an order at my supplier for graphite rods only. So instead of quite hard and strong tone wood and super strong graphite reinforcements, I used a very soft and flexible wood (I had some straight grained pine laying around) and a very hard and strong wood (oak) as reinforcement. It should work just the same way by means of strong reinforcements embedded in a more flexible surrounding. I used three different neck blanks for the test, all of them laminated to avoid differences created from the fact that I had to laminate one neck blank for “my method”. The first reference blank is pure pine (let’s call it #1). The second is reinforced with square oak rods, parallel to an imaginary trussrod (#2). The third had thin laminates of oak sandwiched between the pine (#3). All measurements are of cause identical, and the rods in #2 are a little wider apart than the laminates in #3

I did three different tests on the blanks

For the first test I simply put the blanks on dual supports. Then I stood on the blanks and measured how much the blanks bent. This test equals the resistance against bending caused by the static string pull on a real neck.

For the second test I first tried the same thing with the blanks standing on their side, but the deflection was too small to get good readings. So I clamped the end of the blanks to my work bench (equal overhang) and hang a heavy motor onto the end of the blanks and measured the deflection. This test shows us how the blanks will resist sideways bending. BTW Sideway bending is NOT primarily caused by gravity as Wes thought I meant, but more likely caused by weaker parts in the wood being close to one side of the neck, thus making the neck bend from the compression put on the neck by the strings. They can bend both up or down. I have had customers that have had this problem with some Fender necks (high volume = poor quality check).

For the third test I clamped one end of the blanks to my work bench. On the second end I clamped a straight, strong piece of oak as a lever. Then I placed my dial indicator at the end of the lever and hang the motor in the middle of the lever. This test gives us the neck blanks resistance against twisting.

Test results:

Test1
Object # Deflection (in 1/1000”)
1 178
2 155
3 145

Test 2
Object Deflection
1 70
2 64
3 61

Test 3
Object Deflection
1 644
2 476
3 484

So what conclusions can we make out of this?

- A neck reinforced with method #3 will resist bending caused by string pull better than a neck reinforced with method #2 or a neck without reinforcements. This is because the reinforcement goes all the way thru the neck, thus taking on both compression on one side and stretching on the other side. With reinforcements placed like in method #2 they will only compress on the string side. No help against the stretch on the back of the neck.
- A neck reinforced with method #3 will withstand sideway pull better than a neck reinforced with method #2 or a neck without reinforcements. That was a little bit of a surprise. I thought that #2 with the more wide spread reinforcements would handle this better. I cannot explain this.
- A neck with square rods will withstand twisting better than the other two methods. This is because a square rod per se resists twisting better that a thin strip.

Any problems with my test? Of cause! Let me give you a few:
- I have not used real tone woods and graphite, but I think that we can use this test as a guidance of what would happen with the real thing.
- Only one test blank of every type was made, so all the results can be caused by variations in the particular pieces of wood used.
- I could not plan the oak reinforcements all the way down to the thickness that the graphite sheets would have in #3, so I gave them a slightly smaller cross section area compared to the square rods. The relationship between the strips and the rods areas are as close as possible to the relationship between the GR0 and the GR7 that LMII sells.

But I think that the test shows us a couple of things:
- It is HIGHLY POSSIBLE that reinforcements like #3 helps the neck withstand the string pull and sideway bending BETTER than if method #2 is used.
- It is HIGHLY POSSIBLE that reinforcements like #2 helps the neck withstand twisting BETTER than if method #3 are used.

But the most important conclusion is this:
ANY graphite reinforcement WILL make the neck stronger, regardless of were it is placed in the neck. We all have assumed that this is that case, but I have NEVER seen anybody actually proving it like in this test.

Have I contributed with some practical information this time, Wes???

Peter

[nollock]

the only practical,implementable ideas to come out of this topic have been proposed by tirapop(graphite exoskeleton)and myself(use as directed...not even my idea...)

Parker guitars use graphite to cover the back of their necks, iirc they also use graphite fretboards.

chris