I BET NO ONE KNOWS WHO MADE THIS CONGA

Let's discuss about the origin and history of this beautiful instrument...

Re: I BET NO ONE KNOWS WHO MADE THIS CONGA

Postby jorge » Thu May 14, 2015 9:45 pm

Careful with glue choice. I have just read all that I could find on the internet about wood glues for musical instruments. The consensus seems to be that Titebond 2 and 3 cure up softer (although with slightly higher tensile strength) than the original Titebond and have much more "creep" than the original Titebond when the joint has continuous shear force on it over time. This could happen due to the force from tuning lugs when the drum is left tuned up for long periods. Titebond 3 is also the first to lose most of its strength with heating even as low as 150 degrees F, like if you leave a conga in the trunk of a car on a summer day. Also, the more flexible Titebond 2 and 3 dampen vibrations between the staves (and different parts of violins and guitars) and reduce the musical resonance of the instrument more than a harder glue like Titebond original or hide glue. For those reasons, Titebond original and hide glue are preferred by luthiers and other instrument makers and repairers. Franklin (maker of Titebond) recommends original Titebond over 2 and 3 for musical instrument repair. I have just glued up a large crack in a cherry drum using Titebond original.
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Re: I BET NO ONE KNOWS WHO MADE THIS CONGA

Postby RitmoBoricua » Thu May 14, 2015 11:56 pm

Jorge,

That's some good information on Titebond and glues in general and
their applications when dealing with wooden musical instruments.
I will keep that in mind, thanks for the tip.
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Re: I BET NO ONE KNOWS WHO MADE THIS CONGA

Postby blavonski » Sat May 16, 2015 11:57 am

@ Macho123,
I live in Berlin,Germany and having any skins shipped here would be cost prohibitive. Besides, I can get quality skins here in Germany, however for a bit more money. I wanted to keep all the components to the drum as original as possible not only for ramnanticism, but also to get an idea of how the drum originally may have sounded. I'm sure you can understand that sentiment.

@jorge

Thanks for the tip. I'll be using a German product UHU, water resistant glue that I have used for years for building cabinetts, furniture as well the Bongos I made a while back, that I'm very satisfied with. In the US, back in the late 80's & 90's when I worked as a interior finish carpenter and in shops building and repairing Furniture we used titebond mostly. But also GorillaGlue and even Elmers wood Glue,which was a bit more Flexible when cured). What I don't like about Titebond is that I find it too labor intensive to remove the spreadout after it cured without a lot of scraping and sanding as well as the yellow color. When you have machine sanders and lathes it's not a big deal. The UHU Glue dries transparent and remains a bit more flexible after about 8 hours, so excess spreadout at the joint is less brittle and cuts away easier in my opinion. It suits my needs and most of if not all quality professional glues have the same or very similar chemical properties to do what they are meant to do. It mostly comes down to personal preferences for the things I mentioned above, clean up, working time, flexibility etc.. And Titebond is much more expensive.

By the way, flexibility in a joint is actually an advantage, particularly with Furniture or even drums, which are exclusively under compression strains, for there's not much pulling goin on with regards to a drum shell. When a joint has some room to flex when under stress and strain it reduces the probability of cracks occurring which, when not headed off at the pass so to speak, lead to distruction. And "creep" has its advantges as well. If not, your shoes for example would never conform to the shape and movement of your feet to become comfotable over time. That's why cheep furniture and shoes break and fall apart, the joints and material properties are too stiff & rigid.
Good Vibrations,
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Re: I BET NO ONE KNOWS WHO MADE THIS CONGA

Postby Mike » Sat May 16, 2015 2:53 pm

FWIW I have used the German brand "Ponal", an equivalent of Titebond I to reassemble staves that had fallen apart, and
they joints have remained strong ever since. There had been a period of 20min in which I could adjust things before strapping.
Peace & drum
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Re: I BET NO ONE KNOWS WHO MADE THIS CONGA

Postby Psych1 » Sat May 16, 2015 5:34 pm

Lots of debate about glues. One thing almost everyone agrees on is that different glues are appropriate for different applications. Glueing a top on a string instrument, that you may want to remove later, calls for a different glue than you would use when building a house. From everything I have read, for what we here do, regluing conga and bongo staves, that we want to stay glued, Titebond 3 is the clear winner.
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Re: I BET NO ONE KNOWS WHO MADE THIS CONGA

Postby jorge » Sun May 17, 2015 3:09 am

Conga staves are not under much tension per se, but there are a lot of shear forces, which can cause creep if the glue is not right. The way this works is that as the tuning lug pulls upward on the lug plate bracket it forms a lever arm of an inch or more from the center of the stave. This causes an inward force on that stave above the lug attachment and an outward force below the lug attachment. The staves have some flex and the glue is part of the structure that resists this movement of the staves. This is called shear force and if the glue has much "creep" it will cause the staves to move permanently so that they pop out a little below the lug and are pushed in a little above the lug. I have seen this happen on quintos especially, where there are higher forces on the lugs. For this reason I would avoid Titebond 2 and 3 and other higher creep, more flexible glues for quintos and congas that are tuned up high, although I do agree there is some trade-off with resistance to cracking.
Incidentally I was at JCR today and noticed the bottle of Titebond original they were using to repair a drum.

We may want to move this discussion to another thread where this issue has already been discussed to some degree:
viewtopic.php?f=14&t=8671&hilit=titebond&start=90
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Re: I BET NO ONE KNOWS WHO MADE THIS CONGA

Postby blavonski » Sun May 17, 2015 3:15 pm

@ Mike,
That’s true, and I also use Ponal, but UHU is equal in quality and less expensive.



@ Jorge,
we had this discussion a while back. So, I’ll keep it brief here.
What you describe here as Shear force is somewhat missleading.
Shear force is tension and compression forces working together, acting as stress and strain on any structure that,(depending on both the strength of a given structure and or the material that it is built with), can or will result in destruction if any of the two are not counteracted equally, to keep a thing standing or intact. It is the hardware and the skins that are under actual shear forces, (tension & compression), not the shell itself.
The shell of a conga or Bongo is under negligible tension forces. This means that, the wood or fiberglass fibers are not being pulled in any way. The shell is practically exclusively under compression stresses and strains. Yes, the stave joints are theoretically under tension forces when the skin is tightened, however that force, (no matter what wood glue you use, in my opinion), has minimal effect on the staves due not only to the glue as you state, but in most part due to the convex shape of staves that form the belly of the drum. Because of this shape, a stave cannot be pulled upward, into and pbeyond the narrower space between adjoining staves to any detrimental effect; it is compressed against the other staves. And that is why these forces, (work Looad), are able to be tranferred to the hardware and skin to be able to tune the drum. And this is why these drums can be built as a solid, as well as a stave constructions. Bongos don't have bellys, so they need the steel Hoop at the bottom to carry the bulk of the compression load when tuning. Quality, professional bongos that is!

Creep in the glue at these joints? Well, you would have to leave a drum highly tuned for a very long period time to have actual creep be relevant here. But, since we know that the skin is the weakest component in this construction, it will do the creeping, stretching, thereby reducing the load on the staves and hardware. However, this unlikely probability of staves creeping is actually a good argument for useing an adhesive that is not so rigid when it is cured; So that, if a joint should want to move out of position when under tension or compression loads, it has the ability to move back in position when the loads are removed or reduced.


As far as the glue used, as I mentioned above, any quality Polyvinyl Acetate Adhesive that is rated as water and heat resistant to varying degrees will do the job here and last many generations to be sure. How the drum holds up over time is as much if not more dependent upon the design, type of wood and construction quality of the joints and not the glue as such. One could for example use Elmer’s wood glue to build a drum with if the use of that drum was limited to being played exclusively indoors. And there are other advantages to water soluble adhesives. For example, it was only possible for me to disassemble my old Cuban Tumbadora in the manner that I did for its restoration because the glue, (maybe a hide glue, that's why the metal bands were there in case it got wet or to much time in the sun, humidity etc.), was water/plant acid soluble and could be softened to a jelly consistency to be able to get the staves apart in one piece. Unfortunately the glue I'll be using will prevent someone in say another 50 years from now to be able to do that. They'll have to use extreme heat, but I highly doubt that it will be necessary.
Good Vibrations,
Mr. Blavonski
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Re: I BET NO ONE KNOWS WHO MADE THIS CONGA

Postby jorge » Mon May 18, 2015 12:56 am

Your concern about inability to take the glued joint apart with water is correct. Your understanding of tension, compression and shear forces and your resulting conclusions about the mechanics of the staves and which direction the staves would tend to move due to forces exerted by the tuning lugs are incorrect. This words-only forum is not a good medium to have this discussion about physics since we can't easily make vector diagrams in our posts. Illustrations that may be helpful in our agreeing on basic definitions are these wikipedia articles on shear, tension and compression forces.
http://en.wikipedia.org/wiki/Shear_force
http://en.wikipedia.org/wiki/Tension_%28physics%29
http://en.wikipedia.org/wiki/Compression_%28physics%29
If you want to continue this discussion, let's move it to the other thread, since this one is completely inappropriate for this topic.
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Re: I BET NO ONE KNOWS WHO MADE THIS CONGA

Postby blavonski » Mon May 18, 2015 10:41 am

Hi Jorge,
I agree, this discussion would belong under the topic of the mechanics of Congas and Bongos. but that doesn't exist here.
And since we had this discussion, as well as the same disagreements a while back, I'll refrain from writing much more about it.
However, my understanding of Tension, Compression, shear stress & strain, resiliance etc is not incorrect.
It may be that I have communicated my thoughts on it in an un clear way, or that you simply can't grasp the concepts?
Afterall, they are complex and can't be integrated into ones way of thinking by simply googling, posting links on a topic and passing that off as knowledge.
It takes diligent theoretical reading along with practice over years with building things.

At any rate, simply put: When any physical object undergoes compression stress & strains, the opposite side of that object or material, to varying degrees is likewise subjected to tension Stresses & strains and vice versa.
These are all, as I understand them, individual and separate physical characteristcs. And dependinging on the material and construction; when one or the other becomes too much to be balanced by the other, the material and or structure will distort to benneficial or non desired results.
Shear is no more than tension and Compression working at more or less at 45°.
Take your conga skin for example. When it is being tuned, this material, (which is also a structure), is being pulled by the lugs. As it is being pulled,(Tension), it is also being pushed, (compressed), against the drum bearing edge which in turn is pushing back up into the skin with preferably equal and opposite force for the desired result. In this process, the atoms of the skin begin shearing,(sliding) past one another in order to be stretched. When the atoms lose there elasticity and become too weakened over time by the shear= tension&compression stresses to move back when detuned, then as you well know, the skin needs to be eventually further strained to get it properly tuned. This is known as Hookes law
I will leave it there. However, I would welcome any example of a properly constructed and intact conga that has staves, (joints) being pulled out of position for the reasons as well as in the direction that you claim. Besides, your concerns about creep in conga shells is, for all intent and purposes, a moot point.

My next post will be in the appropriate category with updates on my Restoration project. I promise!
I had too much unplanned fun this weekend to glue the drum as planned, so til then...
Good Vibrations,
Mr. Blavonski
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Re: I BET NO ONE KNOWS WHO MADE THIS CONGA

Postby MACHO123 » Fri May 22, 2015 6:58 pm

Blavonski;

Well said; I totally understand what you're talking about, although I have no experience with physics. What Jorge is saying makes sense as well, but I don't think it applies to what is being discussed. Well, unless you tune your congas to an unreasonable tension (Requintos), then leave them that way for long periods of time, then what Jorge is saying applies. That's common sense though, you don't need physics to figure out what happened. You only need physics to explain WHY it happened.
I've restored many Congas (approx. 30) using Titebond II with great results and no creeping. But I always de-tune my congas when I'm done playing them.
I guess if you're lazy, and don't de-tune them, well then you would have to worry about what Jorge is saying no matter what glue you use. Eventually with time and force the staves will pull apart.
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Re: I BET NO ONE KNOWS WHO MADE THIS CONGA

Postby blavonski » Fri May 22, 2015 8:05 pm

MACHO123 wrote:Blavonski;

Well said; I totally understand what you're talking about, although I have no experience with physics. What Jorge is saying makes sense as well, but I don't think it applies to what is being discussed. Well, unless you tune your congas to an unreasonable tension (Requintos), then leave them that way for long periods of time, then what Jorge is saying applies. That's common sense though, you don't need physics to figure out what happened. You only need physics to explain WHY it happened.



Hello Macho123,

yes, I agree to a certain point. One doesn't need physics to figure what happens when a structure fails, because one can see the result. However that what is also the how and why of it failing. And often common sense isn't enough. And one can apply physics to figure out how and why it can’t happen inspite of what it appears to be able to do. This is the reason, in my opinion, why Jorges argument, that Conga staves will creep up and out of position makes no practical sense. And to prove any physical fact one has to have examples.

MACHO123 wrote:
I've restored many Congas (approx. 30) using Titebond II with great results and no creeping. But I always de-tune my congas when I'm done playing them.
I guess if you're lazy, and don't de-tune them, well then you would have to worry about what Jorge is saying no matter what glue you use. Eventually with time and force the staves will pull apart.


I disagree, for the reason I mentioned earlier.
In order for this to happen, there would have to be, along with the constant stress & strain of being left highly tuned under tension, active lateral, push & pull movement, forces acting on, (between) the individual staves against one another to loosen them. Like if you are trying to retrieve your wallet that is tightly stuffed in your pocket, for the right reasons; well simply pullin on it isn't always enough, you have to wiggle it from side to side. Because as you are pulling, your jeans pocket is likewise pulling to keep in inside.
At any rate, eventually with time, a conga skin and or it's lugs will creep to find a balance of reduced tension stress that they both can live with, a compromise so to speak. Or, as an example of no compromise, and as we have seen often with skins on bongos and less often on congas because they are thicker, the skin will tear. Or on congas the lug hooks will bend backwards, increasing its radius, or the threads will strip. The movement that is taking place among the staves, (and there is movement, everything moves and deflects under external forces), is microscopic and extremely minimal. And this is why creep is, in my humble opinion, an irrelevant factor here in deciding what type of quality, PVA ,rated D3 wood glue to use in such a construction, and especially when it's only about repairing cracks.

Also, I would like to add that, the old Cuban Quinto that I'm restoring (and that is taking longer than I planned), was stored tuned in a basement here in Berlin, Germany for well over 20 years. And as mentioned in my opening post regarding that drum, the bearing edge and lug- plate area Stave Joints were all still in perfect alignment with one another. And this drum was most certainly played outdoors and definately not treated with kid gloves and most likely even left tuned most of the time when not being played. The separations that were there in the staves were due to the glue becoming brittle and deteriorating over time. And even with those seperations, (which were mostly at the bottom where it took the most abuse), there was no evidence of the staves pulling out at the lug-plate areas or being pulled up and beyond the adjoining staves. However, although the skin was still in tact, it had surface tears all around the rims bearing edge.

I know I broke my promise. :wink:
Good Vibrations,
Mr. Blavonski
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