Why do we tie the strings to the bridge on a ukulele?

greenscoe

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When we pluck a uke string, the vibration is transferred via the saddle and bridge to the soundboard which then vibrates and amplifies the sound.

To make this process efficient, we try to make the soundboard and bridge as light as possible. However, this is compromised by the need of the soundboard to be capable of withstanding the forces exerted by the strings. Depending on the means of attaching the strings to the bridge, they either want to rip the bridge off the soundboard or else pull up under the bridge, in both cases distorting the top.

If the strings were not attached to the bridge as in a mandolin, a violin, a dulcimer etc the soundboard on a uke could be so much lighter.

Can anyone offer an explanation? Are there disadvantages acoustically of not fastening the strings to the bridge? Why is it that instruments such as the guitar, lute, uke normally attach the strings to the bridge unless an archtop is used, then a tailpiece comes into play?
 
The shallower string break angle afforded by a tail piece will cause less downward force applied to the saddle, so won't drive the top as well. Less of an issue with things like mandolins as they've got bags of string tension regardless. Ukes are low string tension instruments, probably need an arch top to get near to the requisite tension for decent transference. A lot of complaints about arch top ukes are around soft sound and poor volume regardless.
 
The shallower string break angle afforded by a tail piece will cause less downward force applied to the saddle, so won't drive the top as well. Less of an issue with things like mandolins as they've got bags of string tension regardless. Ukes are low string tension instruments, probably need an arch top to get near to the requisite tension for decent transference. A lot of complaints about arch top ukes are around soft sound and poor volume regardless.

Thanks for that reply, although it's one that I expected. I use a classical guitar style tie on bridge. I could anchor the strings on the end of the box (no tail piece), feed them through the holes on this bridge and still have the same break angle as before ie same downward force at the saddle/bridge but there would be no force trying to pull off the bridge. So its the same question, why isnt this a common arrangement?
 
As I understand it, with the strings attached at the bridge just behind the saddle, the string vibration causes a rocking/twisting motion of the bridge on the top. Whereas attatching further back, as with a mandolin or archtop guitar, causes an up and down, pumping action on the top. Each results in a different mode of vibration (dipolic in the case of ukes and acoustic guitars, vs monopolic on archtops). The dipole gets nicer overtones and mixture of frequencies that we associate with instruments with a round sound hole. Monopole accentuates the fundamental frequency more and punchy mid range sound more suited to f-hole instruments.

At least that's my simplified interpretation.. I'm sure there is much more to it.
 
I did string through once with the idea that it doesn't put as much pressure on the bridge and that it might even put more downforce on the saddle. I did a tailpiece only for the look on a mandolele. I also used beads instead of tie. In every case, I don't hear any difference.


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I've did string through once with the idea that it doesn't put as much pressure on the bridge and that it might even put more downforce on the saddle. I did a tailpiece only for the look on a mandolele. I also used beads instead of tie. In every case, I don't hear any difference.

Thanks for your reply. However you didnt design the soundboard with lighter bracing specifically for this arrangement. If you had maybe there would have been a noticeable difference. Thats the root of my question.
 
As I understand it, with the strings attached at the bridge just behind the saddle, the string vibration causes a rocking/twisting motion of the bridge on the top. Whereas attatching further back, as with a mandolin or archtop guitar, causes an up and down, pumping action on the top. Each results in a different mode of vibration (dipolic in the case of ukes and acoustic guitars, vs monopolic on archtops). The dipole gets nicer overtones and mixture of frequencies that we associate with instruments with a round sound hole. Monopole accentuates the fundamental frequency more and punchy mid range sound more suited to f-hole instruments.

At least that's my simplified interpretation.. I'm sure there is much more to it.

Thanks for that! This is the sort of answer I am seeking. Can anyone expand on this?
 
I use a string through bridge for the reasons you say-
They are better in every way (technically) - The worst place to put all the tension on a bridge is right at the back. Sure there isn't much tension on a uke but uke bridges still pull up/off. The other "best" technical way is to use bridge pins, like on a steel string guitar.

My string through bridges have a permanent gem stone (which is what the store calls them) glued on the inside, which is just like using a bead, but it can't be lost.

Making a traditional tie bridge is far easier (just two rips on the table saw and 4 holes)-

 
I use a string through bridge for the reasons you say-
They are better in every way (technically) - The worst place to put all the tension on a bridge is right at the back. Sure there isn't much tension on a uke but uke bridges still pull up/off. The other "best" technical way is to use bridge pins, like on a steel string guitar.

My string through bridges have a permanent gem stone (which is what the store calls them) glued on the inside, which is just like using a bead, but it can't be lost.

Making a traditional tie bridge is far easier (just two rips on the table saw and 4 holes)-



Beau, you misunderstand what I am saying. I am asking why we don't attach the strings to the end of the box and then run them over the saddle/bridge so that the soundboard only takes the downward force and not the pull of the strings. I mention using a classical guitar type bridge only so that we still get the correct break angle (strings through but not tied to this): it was suggested that using a tail piece would mean an insufficient break angle.

I mentioned mandolins, violins, etc where the strings arent tied to the bridge in any way. Not attaching the strings to the bridge would result in a soundboard which would be much lighter braced and therefore sound differently presumably.
 
I will follow this thread with interest. My observation is that tailpieces are usually used for instruments with arched tops and f-holes such as from the violin family, some mandolins, archtop guitars, but also banjos I think. These instruments also use floating bridge saddles. I think that the fixed flat top bridge approach is more simplistic and associated with more affordable instruments used for folk and simple music. The ukulele fits nicely with this design.
 
I will follow this thread with interest. My observation is that tailpieces are usually used for instruments with arched tops and f-holes such as from the violin family, some mandolins, archtop guitars, but also banjos I think. These instruments also use floating bridge saddles. I think that the fixed flat top bridge approach is more simplistic and associated with more affordable instruments used for folk and simple music. The ukulele fits nicely with this design.

You mean like the Harmony Stella Guitars?
Stella.JPG
 
It is important to understand that it is difficult to isolate a single design element of an instrument and use it on another instrument of a totally different design. For example, the floating bridge on an arch top instrument. To understand how it works, you have to have some knowledge of the total design of an arch top instrument. It has been mentioned that the primary vibrational mode of an arched top is up and down. To facilitate that motion, the top is carved in an arch AND graduated in thickness from very thick in the center to the thinnest part in the recurve area, about 3/4” from the edge. The back is carved in a similar manner, but slightly thinner overall, because it is not subject to string tensions. The sides are narrower than flat tops, placing the top and back closer together, so they can vibrate in harmony. The back in an arch top instrument produces about 50% of the sound. You will see occasionally a flat top instrument with a floating bridge, but they are not usually great sounding. The one exception I know of are the Maccaferri jazz guitars, but they have their own distinct design elements.
Brad
 
In the pre-internet days, I recall a journal article on the benefits and origins of bridge type design.
The only points that have stuck in memory are that tail anchored systems were primarily suited for instruments that were bow driven, not plucked/picked. This system keeps the bridge under constant compression which only varies uni-directionally.
Apparently, bridge anchored systems simulate a suspended pendulum effect, where the pendulum moves in an immeasurable arc. The tension of the strings varies with the plucking force, simulating a slight shortening/lengthening process and imparting an additional rotational or rocking movement. I guess that implies a more complex movement in a tied string bridge?

I measured the string break angles of the only instruments that I can access at the moment ... the tied bridge measured at ~140 degrees with the floating bridge at 165 degrees, so the difference of ~ 25 degrees may be significant in the context of this thread.
 
Mandolins and archtop guitars have steel strings and are often driven by thick flatpicks which aren't commonly used on ukuleles. A banjo uke with a floating bridge might use them but the sound is much different. An ukulele which isn't an archtop could have a thinner top more like a banjo uke but I think it would suffer in the long run. A lot of ukuleles are already minimally braced with a 1.5mm top. I'm wondering what the upside would be of a thinner top more lightly braced. I made a latticed braced ukulele once with a top about 1.3mm. It was a little too punchy for most of music I like to play. But I think you should create something so we can have a better idea of what it might sound like. Doesn't take too long to make an ukulele.
 
Floating bridge instruments (i.e. with strings anchored at the tail) work differently, as has already been explained.

Also archtop floating bridge instruments (like bluegrass mandolins and arch top guitars) work differently, and are constructed differently, from flat top instruments with floating bridges. The downforce point about the break angle is only relevant for arch top instruments - for example, bowl back mandolins have a tiny floating bridge, maybe 1/4 inch high, and though they're not as loud as bluegrass mandolins they are still plenty loud.

I've built flat top guitars and flat top ukuleles with floating bridges. They all sound quite good, to me and to those who've played them. But they sound different - as someone else wrote above, they have a strong focus on the mid-range and less in the way of overtones. Bracing has to be different too - I build light and use ladder bracing, and there is a brace pretty much under the bridge position to stop the top sinking in under the downforce of the bridge. And of course, in construction the fact that the top depresses, rather than raises, under string tension means the neck angle setting is a little different.

The original question was about why we don't see many of these. I'd say it's a mixture of tradition, which is very strong in eyes of buyers, and that over time players have preferred the traditional fixed bridge sound.

But if you like the different floating bridge sound, there's nothing in the physics which stops them working well if you build them right.
 
Mandolins and archtop guitars have steel strings and are often driven by thick flatpicks which aren't commonly used on ukuleles. A banjo uke with a floating bridge might use them but the sound is much different. An ukulele which isn't an archtop could have a thinner top more like a banjo uke but I think it would suffer in the long run. A lot of ukuleles are already minimally braced with a 1.5mm top. I'm wondering what the upside would be of a thinner top more lightly braced. I made a latticed braced ukulele once with a top about 1.3mm. It was a little too punchy for most of music I like to play. But I think you should create something so we can have a better idea of what it might sound like. Doesn't take too long to make an ukulele.

I have made an archtop uke, a couple of banjo ukes, and about 40 other assorted ukes. It may be that I will build a tenor uke with strings that are not fastened at the bridge. I was simply wondering whether such an instrument more lightly braced (perhaps with only a bridge patch) would have more volume and a different tone or whether it would lack that essential sound that is associated with a uke.
 
Floating bridge instruments (i.e. with strings anchored at the tail) work differently, as has already been explained.

Also archtop floating bridge instruments (like bluegrass mandolins and arch top guitars) work differently, and are constructed differently, from flat top instruments with floating bridges. The downforce point about the break angle is only relevant for arch top instruments - for example, bowl back mandolins have a tiny floating bridge, maybe 1/4 inch high, and though they're not as loud as bluegrass mandolins they are still plenty loud.

I've built flat top guitars and flat top ukuleles with floating bridges. They all sound quite good, to me and to those who've played them. But they sound different - as someone else wrote above, they have a strong focus on the mid-range and less in the way of overtones. Bracing has to be different too - I build light and use ladder bracing, and there is a brace pretty much under the bridge position to stop the top sinking in under the downforce of the bridge. And of course, in construction the fact that the top depresses, rather than raises, under string tension means the neck angle setting is a little different.

The original question was about why we don't see many of these. I'd say it's a mixture of tradition, which is very strong in eyes of buyers, and that over time players have preferred the traditional fixed bridge sound.

But if you like the different floating bridge sound, there's nothing in the physics which stops them working well if you build them right.

I think you have raised some interesting points here, especially confirming the different tonal response. Can you explain why instruments with the strings attached at the tail have a floating bridge-why cant it be fixed?
 
A banjo uke has an extremely thin top and fairly good bridge string break angle due to the bridge being somewhat taller than a wood top ukulele. And so the bridge string angle on a wood top ukulele with strings anchored with a tail piece could be maintained by using a taller floating bridge and raising the fret board to match and maintain action.
 
One of the advantages of floating bridges is the ability to adjust the intonation of the instrument by moving the bridge slightly. Because the primary motion of a floating bridge is up and down, you are not likely to gain anything by gluing it to the top.
Brad
 
After reading Ken Franklin’s post, I am reminded of the Tahitian ukulele, which has a thin wood top, floating bridge and tail piece.
Brad
 
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