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View Full Version : Purpose of notching lining for tone bar ends?



HogTime
12-27-2017, 03:26 PM
Why notch the lining vs. not making the tone bars long enough to reach the lining? Is this structural strength related?

I'm working on a StewMac concert kit now and it requires the linings to be notched out. The first StewMac kit I built about 3 years back was a soprano and I don't remember notching it.

Thanks,

saltytri
12-27-2017, 04:03 PM
Others may use terms differently, but to me tone bars are the longitudinal braces that are also called fan braces and extend from the lower transverse brace to the tail. I've never seen a tone bar notched into the lining. The usual practice as far as I know is to sand them down to nothing just short of the lining. The transverse braces that are just above and below the sound hole are notched into the lining by most builders, though there are exceptions. This helps to discourage splitting of the top since they go directly across the grain.

HogTime
12-27-2017, 04:49 PM
Thanks for the reply. Improper use of "tone bar" on my part. :)

I see now that it's only the horizontal braces (on both top and back) in my kit that will require lining notching.

Sounds like the notching is more for tradition than something actually needed. Although, it looks like it would help keep the top/back from sliding around when gluing. I'll find out if that is true later. :)

Thanks,

saltytri
12-27-2017, 04:55 PM
Good, I'm glad that clears it up. The conventional wisdom seems to be that tucking the transverse braces is structurally important. I've heard of, though haven't actually seen, failures of tops on which the braces weren't tucked but maybe that's just a bad rumor.

Enjoy your build!

sequoia
12-27-2017, 07:29 PM
This is a good question. I asked the question a couple years back about whether it is good to cut through the linings and butt the transverse braces to the sides (To Butt or Not to Butt: That is the question?). As I remember there was no real consensus except from Howlett that it was probably "good lutheries practice" to tie off the transverse braces to the sides. I tend to agree. Since then I do tie them off and when the binding is cut in they glue to the binding creating a stronger structure. Does it decrease the flexibility of the sound board and effect response and volume? Frankly I don't really know but I suspect it does. Again it comes down to flexibility versus stability and therein lies the conundrum of design. I've never really come to a conclusion on this question, but I think it is important.

Timbuck
12-28-2017, 01:57 AM
The problem I've seen on some old vintage island ukes that I've repaired is that the tops and backs shrink across the grain (especially on old dehydrated Koa) and the spruce braces push on the sides sometimes pushing through or pushing the bindings off.... I believe it's best to just have them half way into the linings leaving a small 3mm gap from the sides to allow for shrinkage.

mikeyb2
12-28-2017, 02:25 AM
I seem to remember seeing a YT video where Mya Moe stated the don't notch into the linings. They've made many quality ukes, so maybe Aaron Keim(forum member) from Mya Moe might chip in here to tell us if they have many failures.

HogTime
12-28-2017, 09:53 AM
Thanks for the additional comments.

I'm going to notch the linings per the instructions. Will be good training, if nothing else. :)

The soprano kit I made came with a Mya Moe video, so I'm assuming the kit came from them, too. Since it didn't use notched linings, it confirms the comment by mikeyb2.

sequoia
12-28-2017, 06:28 PM
The problem I've seen on some old vintage island ukes that I've repaired is that the tops and backs shrink across the grain (especially on old dehydrated Koa) and the spruce braces push on the sides sometimes pushing through or pushing the bindings off.... I believe it's best to just have them half way into the linings leaving a small 3mm gap from the sides to allow for shrinkage.

I do think about this little join a lot and I've come to the conclusion that in the end it probably doesn't mean much either way. The ends of the braces are going to be scalloped (or should be) and the area of contact is minimal. Plus it is just a crappy little butt joint and just made to fail as the instrument moves over time rendering it pointless from a structural point of view and possibly a point of buizzing which could be a disaster. So now I don't pay that much attention to the area and just get it close leaving about a millimeter or bigger and moving on. What ev. I got bigger problems elsewhere.

Graham Greenbag
12-28-2017, 11:54 PM
From the stand point of a little knowledge (a little knowledge is dangerous) it was ‘obvoius’ to me that the transverse braces should sit into the kerfing because it’s structurally stronger and neater, etc. However, I’m now thinking that gaps are ‘essential’. Reading this thread reminds me that Wood is different from other materials in ways that effect how it can be used. It’s a living material in that it expands and contracts with humidity and it does so at very different rates relative to cut and grain orientation, etc.

The brace and top are different woods and have their grain running in different orientations. For my education how do you match such features such that the woods expand and contract (equally) together, if they don’t then surely (depending on changes in relative humidity) the joint must fail, be prone to it or give in some way?

Pete Howlett
12-29-2017, 02:00 AM
Best practice is caĺled such for a reason.

Allen
12-29-2017, 11:16 AM
From the stand point of a little knowledge (a little knowledge is dangerous) it was ‘obvoius’ to me that the transverse braces should sit into the kerfing because it’s structurally stronger and neater, etc. However, I’m now thinking that gaps are ‘essential’. Reading this thread reminds me that Wood is different from other materials in ways that effect how it can be used. It’s a living material in that it expands and contracts with humidity and it does so at very different rates relative to cut and grain orientation, etc.

The brace and top are different woods and have their grain running in different orientations. For my education how do you match such features such that the woods expand and contract (equally) together, if they don’t then surely (depending on changes in relative humidity) the joint must fail, be prone to it or give in some way?

You choose timber that is 1/4 sawn first. You build at a moderate RH so that the timber has some leeway for movement in both drier and wetter enviroments.

Building with a radius in the top and back further allows for them to expand or contract with changes to the RH. Though this certainly complicates the build of the isntrument, especially when it's the soundboard.

Pete Howlett
12-29-2017, 12:04 PM
I think it would be fair to say that we build today to a much higher standard because of the way we now live. One dud instrument and your reputation is shattered as it is broadcast all over the internet what a useless builder you are.... Anyone building would do well to heed the advice given here - all of it good regarding notching. I do it for structural purposes and the bars rarely reach the limits of the ribs. However it is common practice in the guitar making world cut the notches through the sides to accommodate the oversize top, rout off and fit the bindings. All the big guns do this with confidence.

Beau Hannam Ukuleles
12-30-2017, 09:18 AM
Yep.
What David said. I'd also add that by notching in the upper transverse bars and all teh back braces, it helps the braces from popping off due to knocks etc, and (2) it really stabilizes the upper bout area (im only talking transverse bars here) from movement.

also, i havent notched the linings in this vid yet, but id recommend doing this.

https://www.youtube.com/watch?v=0xQ5ZRPf9Oc


Others may use terms differently, but to me tone bars are the longitudinal braces that are also called fan braces and extend from the lower transverse brace to the tail. I've never seen a tone bar notched into the lining. The usual practice as far as I know is to sand them down to nothing just short of the lining. The transverse braces that are just above and below the sound hole are notched into the lining by most builders, though there are exceptions. This helps to discourage splitting of the top since they go directly across the grain.

Michael Smith
12-30-2017, 05:33 PM
If I'm binding I blow all the way through the sides. Easier and I believe stronger. When I play I'm prone to giving the instrument a violent slap every now and again. I figure some other players are too.

sequoia
12-30-2017, 07:42 PM
Thanks Beau. I tend to butt that upper transverse brace to the neck block and then back it off a tiny bit (1/8 inch) to leave a gap so that the top isn't tied to the neck block when I glue things down. I really think that butting the top brace to the block tends to stiffen up the top too much. It is a small thing sure. I think we must resist the temptation to tie off everything to make everything as strong as possible. Hello little tank. Hello dead ukulele.

Beau Hannam Ukuleles
01-01-2018, 08:37 AM
If I'm binding I blow all the way through the sides. Easier and I believe stronger. When I play I'm prone to giving the instrument a violent slap every now and again. I figure some other players are too.

If you make the braces go all the way through, they can push out the binding if humidity gets too low. I try to leave a little gap.

Beau Hannam Ukuleles
01-01-2018, 08:39 AM
My entire upper bout (from the transverse bar directly below the soundhole) doesn't move, so I lock it all in. WOrks for me.


Thanks Beau. I tend to butt that upper transverse brace to the neck block and then back it off a tiny bit (1/8 inch) to leave a gap so that the top isn't tied to the neck block when I glue things down. I really think that butting the top brace to the block tends to stiffen up the top too much. It is a small thing sure. I think we must resist the temptation to tie off everything to make everything as strong as possible. Hello little tank. Hello dead ukulele.

sequoia
01-01-2018, 05:31 PM
I have been thinking about my statement and thinking it might be wrong so I've decide to flame myself:


I tend to butt that upper transverse brace to the neck block and then back it off a tiny bit (1/8 inch) to leave a gap so that the top isn't tied to the neck block when I glue things down. I really think that butting the top brace to the block tends to stiffen up the top too much. It is a small thing sure. I think we must resist the temptation to tie off everything to make everything as strong as possible. Hello little tank. Hello dead ukulele.

Sequoia writes: That is a stupid way of doing things. Everybody knows that you butt the upper transverse to the neck block extension. This allows the instrument to become one piece and lets the neck become part of the resonating whole resulting in a fruitier tone. You are an idiot!

Sequoia responds: Your mother worked in a flip-flop factory ukulele boy! Any idiot knows the neck plays no part in resonance of an ukulele. I think this thread should be locked!

(self flaming)

Beau Hannam Ukuleles
01-02-2018, 05:18 AM
Any idiot knows the neck plays no part in resonance of an ukulele.

haha- well, all i can say is that i bet that two otherwise identical ukes, but one with a neck attached and one with a neck that isn't attached, would sound different- maybe better, maybe worse...probably worse.
I think necks contribute to more overtones rather than in your face, 'direct' tone (for lack of a better term).

aaronckeim
01-02-2018, 07:09 PM
Sorry to be late to the party, haven't been on the site lately. I totally see how notching the linings is a good idea. I think that Beau, Allen, Pete, et all are doing top work and whatever they say is worth listening too. At Mya-Moe, we have never done it. I do all the warranty and repair work for Mya-Moe, so I have seen it all. When a uke takes a hard hit to the top, we do sometimes get a loose brace end. But in that case, the top is usually cracked anyway and I'm not totally sure that notched linings would have solved the problem. I have noticed that feathering the brace ends down to paper thin, instead of leaving them square or stocky, makes the brace end more flexible and less likely to pop loose under pressure.
Cheers
Aaron

Graham Greenbag
01-03-2018, 03:27 AM
My experience of working in metal rather than wood encourages me to believe with Maya-Moes practice is the better of the options - though the alternatives obviously work well enough too - it’s better both for ease of use and in load distribution. With metals a sudden change in thinkness causes localised stresses to increase which, without other care, leads to parts breaking. I can’t see why wood should be any different in that respect.

Thoughtfully building flexibility into structures makes them more resilient and overly stiff structures are more likely to fail than those with a degree of give built into them. Though it might be counterintuitive flexibility can, dependant on the circumstances, be a very good thing: I find pneumatic tyres are far more fit for purpose than sold ones and trees that bend in the wind are the ones that break less often, etc.

saltytri
01-03-2018, 07:24 AM
I can’t see why wood should be any different in that respect.


Uh, because metal is homogeneous with consistent structural properties in any plane through the material (in the absence of manufacturing defects) and wood isn't?

What Pete said about best practices, with due respect to MyaMoe's excellent record.

Graham Greenbag
01-03-2018, 12:34 PM
Uh, because metal is homogeneous with consistent structural properties in any plane through the material (in the absence of manufacturing defects) and wood isn't?


So what you are saying is that a sudden change in wood thinkness does not cause localised stresses to increase and therefore there is no danger of those parts breaking. If so then that’s rather interesting, I would agree that wood and metal can fail in different ways - some properties are common and some are not.



What Pete said about best practices, with due respect to MyaMoe's excellent record.

What are best practices and who decides? Is best practice something that you do because you have discovered that that is the best way for you to do something or is it something that you do because you copy others? Often we use ‘best practice’ when you’re not certain how something else might turn out. Tradition is a form of best practice but should always be questioned. I understand that Pete’s ideas on many things have been challenged, changed and evolved over the years; isn’t that true of forms of best practice too? Anyway, why does something have to adhere to ‘best practice’ - what ever that might be - when another way of doing something can deliver perfectly satisfactory results?

All that aside you’re the Luthier, you build fine stuff so your beliefs are working right for you.

The counterpoints have been answered and I made my main comments in #22, no point in debating further and I too (see #19) think that this thread would be best locked, too much dispute coming out of it.

saltytri
01-03-2018, 01:05 PM
What are best practices and who decides?


In the case of an arcane and traditional craft like instrument building, hundreds of years of success is more helpful in identifying best practices than is a Gedankenexperiment about what might be. Just ask Schrödinger's beleaguered cat. :)

sequoia
01-03-2018, 06:36 PM
I don't think the thread should be locked at all. I was just joking in reply #19... I think this is an important question and not trivial. For what it is worth, I've done it both ways and no longer notch and butt mainly because it is a lot of extra work and just taper the thangs up to the linings. I think maybe a good point that was missed is that butted braces can expand under certain conditions (i.e. high humidity) and push against the binding (weak point) and cause them to fail (i.e. come unglued). Not a good thing. I forget who pointed out this potential failure and I'm too lazy to track it down, but it is certainly a point to ponder.... Oh and I looked up Schrodinger's cat; not sure how that applies to building ukuleles, but it is a cool thought. Poor cat. Or not.

Schrödinger's cat: a cat, a flask of poison, and a radioactive source are placed in a sealed box. If an internal monitor (e.g. Geiger counter) detects radioactivity (i.e. a single atom decaying), the flask is shattered, releasing the poison, which kills the cat. The Copenhagen interpretation of quantum mechanics implies that after a while, the cat is simultaneously alive and dead. Yet, when one looks in the box, one sees the cat either alive or dead not both alive and dead. This poses the question of when exactly quantum superposition ends and reality collapses into one possibility or the other.

BlackBearUkes
01-03-2018, 08:35 PM
I always tuck the transverse braces into the linings. Having repaired many vintage instruments, a transverse brace seems to curl up on the ends over time if left untucked. As far as cutting the ends of the braces so they do not make contact with the sides, rarely have I seen the brace push out the sides, only in very thin sides and very old have I seen this happen, and only in Koa ukes. I have never seen in happen in a guitar of any age. Just my observation as a repairman.

saltytri
01-04-2018, 03:32 PM
This post has to do with x-braces on guitars but is instructive nevertheless:

http://luthiersforum.com/forum/viewtopic.php?f=10101&t=50143

Sequoia, the cat "experiment" has some relevance to thought processes but doesn't directly bearing upon wisdom in ukulele building. The point is that thinking doesn't necessarily get you there. After all, we're more than a century into quantum mechanics and can't tell if the poor kitty is dead or alive. ;)

Pete Howlett
01-10-2018, 03:57 PM
Best practice is attached to current thinking that is articulated by common experience. This is sometimes static and some times evolving. It is nevertheless an established paradigm. Those of us who work at this business in a professional capacity often have to take positions because the luxury of experimentation is for those who already have an income. If you have anything about you, you will do the research, make your mistakes and arrive at something that works consistently without failure - hence best practice.

Side bar - it always amuses me how much hair splitting goes on here...

Michael Smith
01-10-2018, 06:14 PM
One can only hope the cat won't eat the poison and scratch the creep who put him in there eye out when he looks in the box.

The braces don't expand in length. Humidity will not lengthen quarter sawn wood in that direction though the top or back wood can shrink having the same negative effect.

sequoia
01-10-2018, 07:01 PM
Side bar - it always amuses me how much hair splitting goes on here...

Well amusement is half the fun of the forum isn't it Pete? Glad to hear you are amused...


The braces don't expand in length. Humidity will not lengthen quarter sawn wood in that direction though the top or back wood can shrink having the same negative effect.

This is a good point and I agree... I guess my hairsplitting point is that perhaps this join is trivial and ultimately weak and of no consequence either way so why put in all the work of making it in the first place other than it is "standard practice"? I just don't see the structural gain and I do see possible acoustic loss. Sometimes simpler is better?

Briangriffinukuleles
01-16-2018, 08:42 PM
Sequoia, you may be right, May not make much difference. I have always made the notch thinking it added strength, but I have just finished making three Kasha tenors and the soundboards have no transverse braces, just twelve smallish tone bars, none of which reach to the sides or under the linings. It can't be as strong a top as a traditional two transverse brace tenor, but boy do they sound good. More of the soundboard is vibrating. I'm not planning to play tennis with that uke so I think it is strong enough.