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Double Bass 'cleating rules'

bassedsouth

bassedsouth

Dec 2, 2004
418
110
Johannesburg
#1
It is general 'rule of thumb' to not use one cleat to cover more than one crack .... I see on the Martin site what appears to be strips of wood that are reenforcing several cracks simultaneously

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Any insight would be great
 
#2
I'd be curious as well. What impact would all of that have on the sound? That looks like a lot of wood!

From what I understand acoustic guitars have varying patterns for bracing, or scalloped bracing depending on how they want the tone to be affected. Does the same hold true for the top of a bass?
 
#6
SAlcott said:
I'm guessing they are meant to help maintain the integrity of the arching of the top as well as repairing the cracks.
Click to expand...

Agree. I think it's for both purposes, but maybe more so for arching. My Pfretzchner has disastrous sinkage on the lower BB side. Last time the top was off my luthier replaced a huge crude brace with two delicate S shaped braces. Now the bass is maybe louder in the bottom (E to A) fourth, but doesn't speak as well. If I have the top off again I will lobby for something like the Martin repair. I'm surprised though that you would need this kind of intervention on a Pöllmann. Those things are tanks!
 
#7
bassedsouth said:
why ?
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I suspect it is because wood shrinks & grows (under varying humidity) a lot more perpendicular to the grain than along the grain. Therefore tensions can develop in the presence of long cross-grain braces, or x-grain dowels. Now this top is old, hence thoroughly dry & should not shrink further, so I suppose nothing will happen soon.

Furthermore, I too suspect that this much long cross-grained new wood may change the elastic properties of the top noticeably (and more so than the weight distribution). Wood has very different properties along the grain as perpendicular to it (and even perpendicular, there are differences in the 2 directions).
And yes, they should help maintain the arching & combat subsidence, IMO.

Thanks for sharing this restoration!
 
#8
Interesting observations ...... but it still begs the question.....
If this style of repair technique is in general not recommended by highly respected
luthiers then why is a world renowned luthier endorsing it ..... it would appear
that it could be an effective and efficient way of dealing with multiple cracks
 
#9
bassedsouth said:
Interesting observations ...... but it still begs the question.....
If this style of repair technique is in general not recommended by highly respected
luthiers then why is a world renowned luthier endorsing it ..... it would appear
that it could be an effective and efficient way of dealing with multiple cracks
Click to expand...
To which "highly respected luthiers" are you referring? Were their opinions relevant in situations like this? I agree with the principal, but sinkage on a bass top presents a special case.
 
#10
'endorsing' Is a big word. All we know is that Martin did it, in this case. Why is for him to answer, or maybe any of the resident luthiers has insights to share. I know from experience that cross-grain can give problems as I outlined above, in young wood (not an instrument).

Rob, out of interest & not wanting to derail, but do you know if your Pfretzchner BB was pre-sprung?
 
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#12
Of course the integral bar was not pre-sprung, but the problem might have come from the second BB being pre-sprung. What you describe is what pre-sprung bars can allegedly cause. Maybe for discussion w/ your luthier; thanks for the info & my learning.
 
#13
Well then. I had no idea that integral bars were not pre-sprung. I guess it makes sense:rolleyes:. Not wanting to comment on the wisdom of springing the bar, I think that sinkage is quite common on integral bar basses, and I imagine it was already there on this bass before the rebuild.
 
#16
Ortsom said:
'endorsing' Is a big word. All we know is that Martin did it, in this case. Why is for him to answer, or maybe any of the resident luthiers has insights to share.
Click to expand...

R: the Martin shop method ... that method is used in almost ALL restorations coming from that shop, and as far as I know, he pretty much invented the technique. And MANY luthiers systematically use square, oblong and cross-grain cleats and patches.

Personally I subscribe to the diamond school - which I first learned from Arnold Schnitzer, well before Traeger's book came out - which i understand to be; reinforce along the crack/join, keep things flexible, fit and glue well, don't have 90 degree grain orientation, and don't create new stress lines. In most cases this means diamond shaped spruce cleats with grain at an angle, properly fit and neatly feathered on all facets. I don't think cross grain gluing is wise in basses, and in most cases it can be avoided. The only cleats I have seen to fail, are ones where the grain runs perpendicular to the wood grain, or ones that are not well fit in the first place, or ones where there is insufficient glue, or chalk under the cleat.

It was David Brownell in Traeger's book who wrote, in recent history, about not cleating more than one crack with one cleat ... and with the cross-grain cleats he advocates, I totally agree. However, with the diamond cleats, not only is it much easier to avoid doing this, but the shape and grain orientation don't cause the problems he outlined. For what it is worth, even Hans "God" Weisshaar allows for cleating two or more cracks with one crossgrain cleat; and in the violin world this is probably acceptable. But in the scaled-up world of double bass luthiery, cross grain shrinkage is several orders of magnitude more of a problem.

I have become rather a zealot in regard to avoiding cross-grain glueing wherever possible, and yes, I am starting to apply this in my designs for flatback braces, as well as in all my restorations and repairs.
 
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#19
KUNGfuSHERIFF said:
Should I land the Prague Juzek wreck I'm angling on, I may just repair the multitude of major cracks with scraps of old Levi's soaked in hide glue, just to see what happens.
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I wonder if strips of carbon fiber cloth in hide glue would be the thing these days. Very strong, but minimal mass. Of course there are probably some necessary precautions to avoid breathing dust from the fibers.
 

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