A floating bridge tenor with segmented soundboard

greenscoe

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This is the third in a series about using a floating bridge on a uke. In the first post I asked why we don’t see ukes with a floating bridge:

https://forum.ukuleleunderground.co...we-tie-the-strings-to-the-bridge-on-a-ukulele

In the second, I showed a tenor instrument made using an Ammoon kit, replacing the top with one made from Engelmann spruce and braced for a floating bridge:

https://forum.ukuleleunderground.co...78-A-flat-topped-tenor-with-a-floating-bridge

Here’s another floating bridge tenor, again based on a cheap Ebay kit, but with a new top. I’ve also introduced a second element. Instead of starting with a soundboard that’s stiff along the grain and weak across it, I’ve made a soundboard that before bracing is equally stiff in all directions. Since the strings apply only downward force at the bridge, the bracing is designed to support the soundboard equally in all directions.

The soundboard is constructed from 8 segments, all with their grain pointing to the centre of the soundboard, directly under the bridge. Scraps of sapele were used which were mostly not perfectly quarter sawn. The soundboard was thinned to 1.8mm.

2 curved spruce braces and a go bar deck were used to introduce a slight dome to this soundboard. The 60mm diameter bridge patch is in 4 pieces set around these braces but note the grain on each is across the grain of the segments to strengthen and unify the centre of the soundboard. The segment joints were reinforced with a single cleat.

In order to put the bridge at the centre of the soundboard, the lower transverse brace was moved towards the neck, necessitating the use of 2 smaller soundholes.

So how does the instrument sound? It’s possibly the loudest conventional shaped tenor I’ve made. Comparing it with 6 other conventional tenors with sapele tops I’d say it sounds similar but it definitely has a lot more bass. Sustain is also similar. It has a quick percussive response great for strumming but needs a gentler touch when picking. I’m not claiming it to be the best sounding uke I’ve ever made, but it’s certainly no lemon.

As always this was fun project. I wonder whether anyone else has tried a segmented soundboard on either a uke or guitar?

Summarising the 3 posts, I reckon there’s no reason not to make a uke with a floating bridge. There is enough downward force on the saddle to produce a loud instrument using a normal thickness soundboard. Based on the 2 floating bridge instruments that I have produced, for me the difference is in the way they play rather than the way they sound.

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Nice work, Greenscoe.
You have gone to a lot of trouble and care in making that segmented top for an experimental exercise.

The nearest thing to this, that I have seen, is a complex radial bracing system under a conventional top, and I'm not aware of the outcome of that.

My biggest commitment to bracing experimentation was tacking different (second grade) flat-braced soundboards to an old guitar carcase with HHG, jerry-rigging a high and low string, and plinking away indiscriminately.
I then made dubious changes to the bracing material, geometry and mass .... but never came close to any breakthrough theories or revelations.
There was always something that needed tweaking, and a lot of the time I was unsure of the right direction to take. Asking others' opinions led to further confusion.
As there were no personal computer sound spectrometer programs in those days, it was all down to subjective hearing, tonal preference and perseverance, … but that is not really a valid excuse for my mediocre/inconclusive results.
In the end I became perpetually frustrated, and threw in the towel without learning too much of real practical value.
 
Greenscoe - You've inspired me to try this concept. This weekend I put together a lutz spruce top with the intention of building a parlor guitar. I've thinned it to .085". When I flex it I can see the segments flexing in all directions from the center (like a speaker cone) rather than just one direction like a traditional top.

Guitartop.jpg
 
Greenscoe - You've inspired me to try this concept. This weekend I put together a lutz spruce top with the intention of building a parlor guitar. I've thinned it to .085". When I flex it I can see the segments flexing in all directions from the center (like a speaker cone) rather than just one direction like a traditional top.

View attachment 127951

Well its great to see that you have followed my lead though you may regret it later!

I've just checked your posts to date and I see you are very new to uke making. You mentioned making mandolins and guitars so that explains why you seem to have done a good job of joining all the segments.

My segmented top felt very different from any other soundboard. As you say it flexed in all directions and didn't have any particular strength along any axis. It therefore clearly needed a patch at the centre to unify it.

To repeat what's already been stated, I made this as an experiment for a uke with a floating bridge since there are only light down forces on the soundboard. I would never have thought about doing this for an instrument with a conventional bridge.

You don't say if you are intending using a floating bridge or how you intend bracing this. It will be interesting to see what you produce and more importantly whether you like the way it sounds.

I have been playing my uke for 10 days or so now and getting used to it. It is quite different from all my other ukes, as I said, it's loud and has lots of bass. I suspect I'll have to try a second segmented soundboard to see if I can improve on the first.
 
I won't regret it. I enjoy just trying a new idea...even if it's a failure.

Yep, I'm new here in the uke world, but not new to building stuff. BTW, fitting all eight segments was a little time-consuming, but I was pleased with how it turned out.

I'm going to use a floating bridge and a tailpiece. It seems to me that a traditional bridge with its twisting force would defeat the purpose of making a soundboard that flexes equally in eight directions.

I'm going to base my bracing on what you did. Maybe beef it up a little. I'll put my usual radius in the top and see how it feels.

One concern I have is that the flexing might loosen the joints over time so I'm going to have to think about how to handle that.

I'm interested to see if the "loud and lots of bass" characteristic carries over to a guitar. That would make a parlor guitar sound bigger than it is.

I'll let you know how it goes, but it may be a while. I tend to build in spurts and have several projects going at a time.
 
"One concern I have is that the flexing might loosen the joints over time so I'm going to have to think about how to handle that".

That was/is my concern. When bookmatching I always add a reinforcing strip so just adding a cleat seemed risky. However I wanted to add as little to the soundboard as possible. I used Titebond original and wondered whether there is a better adhesive for such a situation. I have no experience with HHG which some may suggest.

It's an experiment and the instrument is mine so if the joints fail, it will get repaired.
 
I used HHG on mine. The amount of flexing when playing is way less than the amount of flex I was giving it by hand to test, so it may be a non-issue and hold up fine. I'm planning on a removable neck and no binding on the back/side edge so that I can remove the back and repair if needed. I'll also just put on a coat of shellac and let it prove itself before I french polish it.
 
Well, I finished the bracing today. I'm really pleased with the tap tone - it's very even as I tap in circles around the central point and I can hear a distinct change to a lower note when I tap outward of the center spruce patch. The whole thing seems very lively. Now to see how it sounds and if it will hold up to six steel strings.

If you have any suggestions let me know.

At this point I'll stop hijacking your thread with my guitar build. This isn't the Guitar Underground so I'll refrain from posting more and then post back with the results after I'm finished.

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I can only repeat what I said earlier-it's good to see someone trying this and once again it looks well executed.

I'm eager to know what you think of it when its done. It doesn't matter to me that its not a uke: I'm interested in any instrument that anyone chooses to build.
 
Okay, I'll post periodical updates.

My next challenge is to make and fit a dovetail neck joint. I've never done one before, but the sound holes location keeps me from having a way to bolt on the neck.
 
Hey greenscoe - I have the rim finished and need to get the neck/body/top relationship figured out so that I get the proper action and string height over the bridge.

So my question is, are you using a standard height bridge/saddle, or do you increase it slightly to account for the reduced string angle due to attaching at the tailpiece?

Thanks.

Current pic:
 
This is the third in a series about using a floating bridge on a uke. In the first post I asked why we don’t see ukes with a floating bridge:

https://forum.ukuleleunderground.co...we-tie-the-strings-to-the-bridge-on-a-ukulele

In the second, I showed a tenor instrument made using an Ammoon kit, replacing the top with one made from Engelmann spruce and braced for a floating bridge:

https://forum.ukuleleunderground.co...78-A-flat-topped-tenor-with-a-floating-bridge

Here’s another floating bridge tenor, again based on a cheap Ebay kit, but with a new top. I’ve also introduced a second element. Instead of starting with a soundboard that’s stiff along the grain and weak across it, I’ve made a soundboard that before bracing is equally stiff in all directions. Since the strings apply only downward force at the bridge, the bracing is designed to support the soundboard equally in all directions.

The soundboard is constructed from 8 segments, all with their grain pointing to the centre of the soundboard, directly under the bridge. Scraps of sapele were used which were mostly not perfectly quarter sawn. The soundboard was thinned to 1.8mm.

2 curved spruce braces and a go bar deck were used to introduce a slight dome to this soundboard. The 60mm diameter bridge patch is in 4 pieces set around these braces but note the grain on each is across the grain of the segments to strengthen and unify the centre of the soundboard. The segment joints were reinforced with a single cleat.

In order to put the bridge at the centre of the soundboard, the lower transverse brace was moved towards the neck, necessitating the use of 2 smaller soundholes.

So how does the instrument sound? It’s possibly the loudest conventional shaped tenor I’ve made. Comparing it with 6 other conventional tenors with sapele tops I’d say it sounds similar but it definitely has a lot more bass. Sustain is also similar. It has a quick percussive response great for strumming but needs a gentler touch when picking. I’m not claiming it to be the best sounding uke I’ve ever made, but it’s certainly no lemon.

As always this was fun project. I wonder whether anyone else has tried a segmented soundboard on either a uke or guitar?

Summarising the 3 posts, I reckon there’s no reason not to make a uke with a floating bridge. There is enough downward force on the saddle to produce a loud instrument using a normal thickness soundboard. Based on the 2 floating bridge instruments that I have produced, for me the difference is in the way they play rather than the way they sound.

View attachment 127720View attachment 127721View attachment 127722View attachment 127723View attachment 127724
I like what you have done there...and I know from experience, how difficult it is to glue together accurately those segments so that the points all come together in the middle.:bowdown:
 
Klr, once more I have to comment on how tidily you have carried out the work to date-much better than I usually do things. I also like your use of laminate linings and side stiffeners, I use both quite often.

I am clearly no expert when it comes to floating bridge geometry. On my 2 instruments the string height at the bridge is as for standard instruments, though the top of the saddle is higher because it is notched for each string. This does mean the break angle is lower than normal but both my instruments are loud. The neck angle to the body was therefore also unchanged.

A lot is written about the break angle at the saddle in order to get decent volume. I have never found this to be a big issue. Likewise head angle is often considered important: I have never been too concerned about it.

If you have any doubts about the way to proceed, I can only suggest that you consider various string heights at the saddle and what would be the resulting break angle and the required neck/body angle. You can then take a stab at which to use. This is what I did when I made my archtop uke which did have a high saddle and therefore did need an angled neck in order to give the correct action along the fretboard.

stringheight.jpg
 
I like what you have done there...and I know from experience, how difficult it is to glue together accurately those segments so that the points all come together in the middle.:bowdown:

Hi Ken. Glad you like what I did! It wasnt as difficult as I thought and you will see klr probably did a better job on his instrument. I expected lots of members to tell me it was a waste of time or that it would soon fall apart (perhaps they are being polite?) but I thought it was an interesting thing to try.

I play this instrument every day at the moment. It sounds very different to my conventional tenors. Its hard for me to tell whether its mostly because it has a floating bridge or whether the segmented soundboard really added something. Because of Covid 19, I have been unable to met my uke playing friends to get their impressions on the sound of this instrument.

Its good to see that you are also back to building the occasional tenor. (I have a couple of Martin style sopranos stalled until I am in the mood to make their necks).
 
Hi Ken. Glad you like what I did! It wasnt as difficult as I thought and you will see klr probably did a better job on his instrument. I expected lots of members to tell me it was a waste of time or that it would soon fall apart (perhaps they are being polite?) but I thought it was an interesting thing to try.

I play this instrument every day at the moment. It sounds very different to my conventional tenors. Its hard for me to tell whether its mostly because it has a floating bridge or whether the segmented soundboard really added something. Because of Covid 19, I have been unable to met my uke playing friends to get their impressions on the sound of this instrument.

Its good to see that you are also back to building the occasional tenor. (I have a couple of Martin style sopranos stalled until I am in the mood to make their necks).
I know what you mean about “ it wasn’t as difficult as I thought” I made some banjos resonators with 12 segments like that ..I glued them together first in 3s to make 4 quarter sections made sure they were all at 90 degrees square then glued them up into halves..then fitted the two halves together..one was a bit out in the centre so I drilled a hole and fitted an ebony dot to hide it. ;)
D884A66F-EE4A-42F7-B23C-4662EA8D41F8 by Ken Timms, on Flickr
 
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Klr, once more I have to comment on how tidily you have carried out the work to date-much better than I usually do things. I also like your use of laminate linings and side stiffeners, I use both quite often.

I am clearly no expert when it comes to floating bridge geometry. On my 2 instruments the string height at the bridge is as for standard instruments, though the top of the saddle is higher because it is notched for each string. This does mean the break angle is lower than normal but both my instruments are loud. The neck angle to the body was therefore also unchanged.

A lot is written about the break angle at the saddle in order to get decent volume. I have never found this to be a big issue. Likewise head angle is often considered important: I have never been too concerned about it.

If you have any doubts about the way to proceed, I can only suggest that you consider various string heights at the saddle and what would be the resulting break angle and the required neck/body angle. You can then take a stab at which to use. This is what I did when I made my archtop uke which did have a high saddle and therefore did need an angled neck in order to give the correct action along the fretboard.

Thanks for the compliment. This is my first time to use solid linings. I didn't intend to when I started, but I tried something new while bending my sides and scorched a couple of spots. I tried to sand out the spots, but couldn't, so I cut the sides into strips and bent a new set of sides. I really like how they worked out. The rim feels very solid.

Thanks for the input. I'll shoot for my normal bridge height and see how that works out.

When I joined my top I glued together the three pieces of the upper bout. Then I clamped that assembly and the lower tailpiece segment to a piece of plywood. Then I sanded and dry fit the remaining pieces until they were all tight. Then I glued them.

Ken - How did that banjo resonator hold up? One concern I've heard about using segments is that they expand and contract more at the edges than at the center and therefore don't hold up over time.
 
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I have read your posts on alternative builds as shown in the Bas’nBari pictured. That concept was started several years ago and has gone under some changes in the pickup configuration and choice of strings these past years. Having somewhat more time on my hands due to drastically curtailed shopping trips. I will have another go at this concept.

I’m considering ached tops, narrower sides (35mm), f-holes, rounded edges (not square) and string anchors though the heel block. That’s just the body. The offset necks would be some what thinner and probably asymmetrical to accommodate the thumb. The bridge placement could be more pronounced if I go with a Tenor scale instead of a baritone. The top of the heads pivot point is changed to eliminate the need for a long D string on the bass, and accommodate a traditional slot head configuration. And oh the color scheme would be more traditional.
 
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