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Double Bass prophylactic patch

Matthew Tucker

Matthew Tucker

Commercial User
Aug 21, 2002
2,686
387
Sydney, Australia
www.bresquebasses.com.au
Disclosures
Owner: Bresque Basses, Sydney Basses and Cellos
#1
a soundpost crack can be one of the most devastating things to happen to a bass, requiring an expensive top-off repair.

But if a bass's top needs to come off for other repairs, what do you think of the idea of putting in a prophylactic soundpost inlay patch at that time, even though there may not be a crack at that time?

or even, at time of manufacture?
 
#2
Matthew Tucker said:
or even, at time of manufacture?
Click to expand...

Wouldn't this just be an anticipation of a tragic accident? Most of my expertise is in repair/restoration rather than building basses like you. However wouldn't it logically make more sense just to adjust the graduations? Perhaps moving the center where the top is thickest over to the sounpost area? Perhaps modern makers are already doing this? I'd be curious as to what is said here. I could learn something from this thread for my coming bass build..

edit: Recently I've been doing soundpost patches without taking the top off. When you have a thick chinese varnish that will look like crap no matter what you do to it after taking off the top, this method really makes my customers happy. After gluing the crack, I will thin out the patch to 2-3mm, soak it in really dilute hide glue and water to soften it, then clamp the crap out of it to profile to the top. This isn't as pretty on the inside as a good chalk-fitted inlay but it's every bit as functional.
 
#4
Changing the graduations when building would not obviate a soundpost crack later, unless you make the centre stupidly thick. And changing graduations is not an option on a pre-existing bass that is otherwise fine. A soundpost patch is a couple of hours work, and I am not convinced (because I have not done hundreds, and it is difficult to compare anyway) that there is a sonic disadvantage to having one there.

So I'm wondering how people feel about paying for some preventative medicine? If I was going in for bowel surgery, I'd pay a bit extra to "take the appendix too while you're at it".
 
#7
I have no expertise to add, but I wonder if two questions might help to focus the discussion.

First, is there a sonic disadvantage to the patch?

Second, how common are sound-post cracks on carved basses?
 
#8
Matthew Tucker said:
a soundpost crack can be one of the most devastating things to happen to a bass, requiring an expensive top-off repair.

But if a bass's top needs to come off for other repairs, what do you think of the idea of putting in a prophylactic soundpost inlay patch at that time, even though there may not be a crack at that time?

or even, at time of manufacture?
Click to expand...

Matthew, I asked myself that very question when I was building my [only] double bass and I saw your picture documentary of making a chalk-fitted SP patch, right here on this forum. I decided to do it, and followed your instructions to the letter:)

I oriented the patch grain at about 30 degrees from the top grain. The patch is about 9cm in diameter.

George
 
#9
drurb said:
I have no expertise to add, but I wonder if two questions might help to focus the discussion.

First, is there a sonic disadvantage to the patch?

Second, how common are sound-post cracks on carved basses?
Click to expand...
I don't think there is a sonic disadvantage. My objection is this: Firstly, why remove original wood from a fine instrument? You can't put it back. Secondly, no glue joint is perfect, and all glue joints eventually fail, especially if the grain direction of the patch wood is angled to that of the top wood (or if the moisture content of the two pieces is dissimilar). It is also common for soundpost patches to suffer from glue starvation, as the end-grain of both the patch and the top wood will tend to soak up too much glue (sizing helps). If/when that patch fails, now you will have a big problem. Some modern violin makers glue a thin, slightly angled hardwood veneer over the soundpost area of the top table to help avoid cracks and dents there. To me that is a much less invasive way to go (though not something I do).

As to your second question; soundpost cracks are quite common on basses. I'd say 1/3 of the older basses I see have one. Movers of basses are clumsy, and when a bass takes a whack in the back, the placement of the post and the high tension on the softwood of the top conspire to cause such a crack. A well-made bass that is properly looked-after and carefully moved about should never develop a soundpost crack. Of course, in the real world accidents happen.
 
#11
Thanks Arnold for your angle.

but I'm curious - how often you see a failed soundpost patch? How do they fail? I can't envisage it being anywhere near as common as a soundpost crack, and I can't imagine how a post patch could suddenly fail of its own accord (ie not as a result of major trauma) resulting in serious damage.

I CAN imagine that after opening a bass after a bad knock, you can see that some post patches are cracked or coming away or starved of glue. But these are usually, presumably, patches done on a top that has already had a bunch of repairs.

Even though "no glue joint is perfect, and all glue joints eventually fail" - surely this applies to every other joint in an instrument, and there are many other opportunities for end-grain glue starvation, so I don't see why this is relevant, really.

So, given the reality outlined in your last paragraph, I still do feel that there is a category of instrument where, if the top is off for other repairs, a properly done preventative sound-post patch would not really have a down-side and would be a really good and economical idea.

I do take your point also about the hardwood veneer. But actually, my hunch is this is more likely to fail/crack/buzz than a proper inlay patch.

but i could be wrong :)
 
#12
The guy I work for always does the "hard wood veneer" style patch on all of his new instruments, including his latest bass. I think the world of the sound of every instrument of his I've heard, but I'm biased. We never do it prophylacticly on repairs, my take is that it would be a legit thing to offer a customer if you felt strongly about it.
 
#15
arnoldschnitzer said:
Perhaps we should have our childrens' appendixes removed. After all, they may cause trouble in the future.
Click to expand...

In fairness, that would be analogous to opening up a trouble-free bass just to put in the patch. The risk/reward calculation there is not quite favorable. There are plenty of medical surgeries in which, once you're in there, you do do something prophylactically. I'm just noting this as a matter of logic and am enjoying reading the opinions regarding the patches. :)
 
#16
As a non-luthier furniture-maker, I'm really on thin ice in this thread -- which is going so well -- but let me offer up an example from my life in which Arnold's analogy works well.

I work for a large energy utility. We have billions of dollars worth of stuff, hundreds of engineers, thousands of technicians. The stuff is a mix, from the very old to the very new. Maintaining all that stuff is a gargantuan, multi-faceted process that's been going on for maybe a century or so.

We used to use schedules for maintenance -- you know, every thousand hours change the oil, that sort of thing. And every maintenance episode was a chance to do other stuff "while we're at it."

However, a little more than a decade ago, our engineers had a change of maintenance philosophy. They noticed the reliability data strongly showed outages much more likely after service instances. There was a lot of analysis that went on, and there was a bit of a general movement in this direction anyway, but in short what we learned was that it wasn't always a good thing to interfere with a device functioning perfectly within spec just "to maintain it". Every time you do that, you alter the device in ways known and unknown. You also give the technician an opportunity to leave a nutdriver in the oil tank, over-torque a fastener, that sort of thing. The maintenance philosophy now is centred on monitoring equipment, to assess its performance continuously and to predict when failure is imminent. That monitoring is coupled with economic analysis to determine whether it's smart to fix the thing or to let it burn down. Sometimes it's cheaper to let it fail and replace it.

More than a decade down the road, our forced outages are the lowest they've ever been. "Reliability centred maintenance" is working very well indeed.

Now -- that's billions of dollars worth of electricity utility hardware, not individual basses in the hands of individual build/repair artisans, and not a medical situation either. Just a (rather long-winded, I'm afraid) story that would tend to support Arnold's point of view here: don't mess with something that ain't broke. In the long run, over a huge number of cases and a lot of time, and with respect to my company's case, that philosophy works.

I'm not going to get involved in any philosophical talk here -- just offer the story for interest's sake. I'd like to hear more luthier talk, for sure!
 
#18
Matthew Tucker said:
Thanks Arnold for your angle.

but I'm curious - how often you see a failed soundpost patch? How do they fail?

I have seen a few. Usually, the ends peel away from the top table wood.


Even though "no glue joint is perfect, and all glue joints eventually fail" - surely this applies to every other joint in an instrument, and there are many other opportunities for end-grain glue starvation, so I don't see why this is relevant, really.

Why create the opportunity for another joint failure?


I do take your point also about the hardwood veneer. But actually, my hunch is this is more likely to fail/crack/buzz than a proper inlay patch.

but i could be wrong :)

One of the top three violin makers on the planet uses this method with no failures to date.
Click to expand...
 
#19
Damon,

That's an interesting story and approach and it makes good sense. Again, to be fair, no one was suggesting that a functioning bass be opened up just to put in the patch. Still, once a bass is open it may not even make sense to do it and I certainly do defer to Arnold on such matters.

With basses, machines, and most things, the devil is in the details. When it comes to a timing belt, well, you don't wait for it to fail. When you do go in and change it, it makes good sense to grab the water pump.

For any of these things, experts are the ones to evaluate what is the risk/reward. As you point out, the simple action of messing with something that is functioning well has inherent risks. Your experts certainly seemed to have been dead on in their choice of when to and when not to do maintenance and what were the criteria. In the same way, I trust master luthiers to say whether "preventative" actions make good sense on a bass.

Just another reason I defer to those with expertise. :)
 
#20
drurb said:
When it comes to a timing belt, well, you don't wait for it to fail. When you do go in and change it, it makes good sense to grab the water pump.
Click to expand...

The difference is that the timing belt and water pump (along with the idlers and the tensioner) are wear items, designed to be replaced at regular intervals. The top isn't. :eek:

The reason for a soundpost crack in the top is trauma, whether from an over-long post or impact damage, neither of which can be 'planned for'.
 

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