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Double Bass 'cleating rules'

#21
'Difficult to tell what technique the bass in hand requires from photographs; sitting on the bench everything seems much more obvious. As ironic as it sounds, I've seen several old basses with what looked like Levis soaked in hot hide glue. Are you going for skinny jeans, classic fit, or the droopy old man a$$ fit???
 
#22
Thanks for this background info Matthew; I did not know this was a common approach with the Martin's, so not just for this case.
Matthew Tucker said:
But in the scaled-up world of double bass luthiery, cross grain shrinkage is several orders of magnitude more of a problem.
Click to expand...
My slide ruler tells me the tension / stress is proportional to the lap length, while x-grain unit strength is of course fairly constant. So yes, the problem is much bigger in the DB world, where everything is much bigger.

But what I cannot see from the pics, and what I do not know, is if their brace-like cleats have the grain running purely length-wise. While the 'cleats' are placed at 90° with the top grain, if the 'cleat' grain runs at an angle, so that the angle between the 'cleat' grain & the top grain is substantially less than 90°, it would be much less of an issue. Is that so?

CF should be glued with epoxy or the like, not HHG, and under pressure (vacuum?) to achieve low weight objectives. But even then it may not be desirable in a wooden top (may act as LPF).
 
#23
Ortsom said:
My slide ruler tells me the tension / stress is proportional to the lap length, while x-grain unit strength is of course fairly constant.
Click to expand...

Whatever. That. Means.

Ortsom said:
it may not be desirable in a wooden top (may act as LPF).
Click to expand...

Dunno about it being a LPF, but from a practical viewpoint it PTWF and becomes ITR, making future repairs VFD, in other words it is a PITA!
 
#24
Matthew, the LPF part was a reply to fdeck, who raised the CF. LPF = Low-Pass Filter. But I'm happy to hear that we, once again (yee-hoo) agree that such a repair may not be desirable.

And the first bit means: do the calculation.

Good, with that out of the way: do you know the answer to the question I asked? That would be far more relevant.
 
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#27
Anyway, I'm not going to haggle with you, I'll share my opinions freely. Unlike my question to you, it is of course quite irrelevant for this thread, but as you ask...
Compressional sound velocity in CF is much higher than in wood, which leads to the rays following different paths becoming out of phase, and this effect is strongest for higher frequencies. Hence LPF. Shear will be a next instalment.
 
#29
Nah, your Strauss or whisky have nothing to do with it, this one sits much deeper.
fdeck's CF question, and your remark on using Levi's were very much to the point of the thread, which was fixing cracks, and I too am still on the same track. Ever since my #22 I'm just trying to find out if maybe it is due to the grain direction in the long cleats that this can work, which is very much aligned with the OP's original question. Matthew seems to know the answer, but rather than replying we get silly diversions & less relevant counter questions.

To re-focus, the question was: what I cannot see from the pics, and what I do not know, is if their brace-like cleats have the grain running purely length-wise. While the 'cleats' are placed at 90° with the top grain, if the 'cleat' grain runs at an angle, so that the angle between the 'cleat' grain & the top grain is substantially less than 90°, it would be much less of an issue. Is that so?

(Might have an Irish one tonight though.:thumbsup:)
 
#30
"the question was: what I cannot see from the pics, and what I do not know, is if their brace-like cleats have the grain running purely length-wise. While the 'cleats' are placed at 90° with the top grain, if the 'cleat' grain runs at an angle, so that the angle between the 'cleat' grain & the top grain is substantially less than 90°, it would be much less of an issue. Is that so?"

My answer is still yes; I believe that would be so, if that is what they did. :rollno:

"Compressional sound velocity in CF is much higher than in wood, which leads to the rays following different paths becoming out of phase, and this effect is strongest for higher frequencies. Hence LPF."

The compressional sound velocity is not significant in this application; the CF is being proposed as a cleat repair material, not a fabrication material. But it is not at all irrelevant to discuss the use of carbon fibre cloth that Fdeck raised; woven CF cloth composite is used for its stiffness and impact strength, not for its flexibility. So if stiffness is being increased, as I said before, i believe the effect - if detectable - would be more akin to a HPF (high pass filter, if we must use these electronics terminologies) Stiffness is proportional to frequency; the stiffer the element, the higher the natural frequencies of that element. In my experience if you are after increased low frequency response, you make the salient element more flexible. I understand that the inverse is Ortsom's opinion without warranty, but both science and empirical experience does not bear this out as a fact.

The use of epoxy in bass repair has its place, but there are some applications where I believe it should never be used; for example, in most cases, crack repair.

I have seen how the Thomas Martin workshop work is done; i have had basses restored by them in my workshop. And I have explained my personal beliefs on cleating in some depth, while accepting that there are many schools of thought. Make whatever inference you like. So with regard to their workshop methods, perhaps, as Ortsom wrote "Why is for him to answer":)
 
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#31
james condino said:
'Difficult to tell what technique the bass in hand requires from photographs; sitting on the bench everything seems much more obvious. As ironic as it sounds, I've seen several old basses with what looked like Levis soaked in hot hide glue. Are you going for skinny jeans, classic fit, or the droopy old man a$$ fit???
Click to expand...
Just don't use stretch Levi's. ;)
 
#34
Are your jeans made from linen? I thought they are made from cotton and as I know linen is the preferred cloth for bass repair, not cotton.

HPF and LPF are terms from acoustics or more general the sience of vibration in general. It could be mechanical vibration or any other type like electrical. So this is not a term used exclusively in electronics, even if it is what we bass players mostly think of.
 
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#36
Excellent. So then Matthew you have answered the OP's question, it seems: the Martin's can use these long cleats because the grain in the cleats is at an angle to the cleats. And you can say this because you have seen it in basses restored by them which you had in your workshop. Out of interest: what would roughly be the angle between the grain in the long cleats & the grain in the top?

As an aside, a clarification. Like Matthew, I maintain that IF the stiffness of a bending element is increased, the resonance frequency will increase (this is easily shown), but equally important is the mass of a moving element; if the mass (or weight) increases the resonance frequency reduces. Yet I believe the two cannot be separated meaningfully here; it is pointless to consider stiffness without mass (and mass without stiffness is a fluid). It is beyond the scope of this thread, but Matthew does not depict my opinion correctly. More here.

Indeed, LPF & HPF are not restricted to electronics, but foolishly I choose to use it because of fdeck's background. (Nobody expects the Spanish inquisition...)
 
#37
Ortsom said:
Excellent. So then Matthew you have answered the OP's question, it seems: the Martin's can use these long cleats because the grain in the cleats is at an angle to the cleats.
Click to expand...

LOL no, that is not at all what I wrote.

I wrote - answering your hypothesis - "My answer is still yes; I believe that would be so, if that is what they did. :rollno:"

IF

 
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#39
Whilst I am happy to respond to the OP about my cleating methods - and did so - I am not prepared to write about theirs.

Is that clear enough for you?

If you can simply put your slide rule down for a minute and go look at the pictures on their site, and try to think like a woodworking luthier, you will discover all you need to know.
 

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