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Thread: A flat topped tenor with a floating bridge

  1. #1
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    Default A flat topped tenor with a floating bridge

    On 19th May I asked why we all build ukes with the strings tied to the bridge.

    https://forum.ukuleleunderground.com...e-on-a-ukulele

    After this forum discussion, I set about to build a flat top tenor with a floating bridge to satisfy my curiosity. Regular readers of this forum will know that I have previously used a cheap Ammoon tenor kit from Ebay to test a soundboard. The laminate top is removed and replaced with the test top.

    So once more that’s what I have done, again using Engelmann spruce.

    Since the soundboard takes only vertical loading from the strings at the bridge and no string pull forces, the bracing needs only to consider this.

    If the soundboard were round and wood had equal strength in all directions, then thinking of a loudspeaker, I would have simply added a circular patch under the bridge. But wood is strong along the grain and weak across the grain, so the soundboard needs additional strength across the grain.

    An obvious bracing scheme would therefore use 1 or 2 ladder braces with or without a bridge patch. The location, dimensions and orientation (parallel or skewed) would need to be determined by experiment.

    My thoughts however were to use 1 ladder brace under the bridge and a patch either side of this. These patches taper from 2mm to almost zero at their edges, giving more support across the grain than along the grain and most support closest to the bridge. The soundboard is 2mm thick.

    The strings are attached to a maple ‘bracket’ on the butt of the box in mandolin fashion. I tried a short bridge (60mm) but think the instrument sounds and feels better with a longer (110mm) bridge which spreads the downward force over a larger area (the notched saddle is a scrap of acacia). There is no noticeable soundboard depression.

    I don’t have a particularly good musical ear so characterising the sound is always difficult. Its loud with a percussive quality, it sounds like a spruce topped instrument with that quick and clear response. It has lots of sustain, bass is good, maybe treble is a little weak. I prefer it as a strumming instrument rather than a picking instrument. I am not disappointed with it but its not as warm or rich sounding as my best tenor to date. It's not so different from my other Engelmann instruments and it raises the question of how it could be improved given it's my first stab at a floating bridge instrument.

    I am a hobby builder. As always, I post this to encourage others to have a go at your own ideas. I have tried to outline my thought processes, but of course I may be heading in the wrong direction-so follow at your own risk!

    If you have made a floating bridge instrument, I for one would be interested in seeing how it was braced and your impressions of the way it sounds.

    flt1.jpgflt2.jpgflt3.jpgflt4.jpgflt5.jpg

    If you are interested in this thread, there's a follow on thread on a tenor with a floating bridge:

    https://forum.ukuleleunderground.com...ted-soundboard
    Last edited by greenscoe; 06-20-2020 at 06:14 AM.

  2. #2
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    Default

    What a great post! Meticulously done and researched. I only wish we could hear the instrument in an A - B comparison with a standard reference ukulele...

    A couple of thoughts after looking at the pictures:

    - The bridge patch looks rather large. Is this necessary to distribute the downward forces?

    - The saddle appears to be made of wood. Why not a bone saddle?

    - The bridge itself appears to be quite narrow. Why not a wider bridge to distribute the downward forces and the energy from the strings?

    Anyway very well done.

  3. #3
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    Default

    Nice work.

  4. #4
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    Default

    Here is a Maccaferri style ukulele I built a few years ago. It has ladder bracing and a crease in the top, as in some Maccaferri instruments. I am not thrilled by how it sounds, as both my arch top and flat top instruments sound considerably better, so I have not pursued the project any further

    https://photos.app.goo.gl/7jnaaJPivghnryRx9

    Brad
    Last edited by BuzzBD; 05-30-2020 at 04:51 PM.
    Bradford Donaldson
    Kekaha, HI and Cannon Beach OR
    bradfordj48@outlook.com

  5. #5
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    Default

    [QUOTE=sequoia;2229355]

    - The bridge patch looks rather large. Is this necessary to distribute the downward forces?

    - The saddle appears to be made of wood. Why not a bone saddle?

    - The bridge itself appears to be quite narrow. Why not a wider bridge to distribute the downward forces and the energy from the strings?

    /QUOTE]

    The 2 patches do seem quite large. It was difficult to guestimate their size, but they are thinned removing almost half their weight.

    I have several tenors with an ebony nut and saddle. I dont think using wood affects volume and I suspect it results in a mellower tone.

    I was trying to keep down the weight of the soundboard and bridge to increase volume. I chose to beef up the soundboard a little with the patches but keep the bridge as light as possible. However I did move from a 60 to 110 mm long bridge to spread the load across the board. I am not sure what a wider bridge would achieve.

    I should add that overall I don't think I am structurally so far away as the soundboard has not deformed under string load nor does it feel too tight when picking as does an overly braced soundboard on a fan braced instrument.
    Last edited by greenscoe; 05-30-2020 at 08:25 PM.

  6. #6
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    Quote Originally Posted by BuzzBD View Post
    Here is a Maccaferri style ukulele I built a few years ago. It has ladder bracing and a crease in the top, as in some Maccaferri instruments. I am not thrilled by how it sounds, as both my arch top and flat top instruments sound considerably better, so I have not pursued the project any further

    https://photos.app.goo.gl/7jnaaJPivghnryRx9

    Brad
    Thanks for your response Brad. You dont say how many braces you used or where they were positioned. However since you say it didnt work out well I dont suppose it matters.

    Before I joined the forum 6 years ago, I know you were involved in encouraging makers to try producing an archtop. When I made mine you were not active on the forum and my attempts at seeking advice were not successful. Initially I was happy with the way it sounded but over time I came to find it rather weak sounding. I suspect I left the soundboard too thick. I have subsequently tried to improve it by further thinning but its mostly now a rather attractive wall hanger. I did buy several sets of maple/spruce violin wood to pursue archtops but I have never felt the urge to try again. This flat top is far better sounding than my archtop!

    https://forum.ukuleleunderground.com...hlight=archtop

  7. #7
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    Default

    I made a mahogany-topped parlour guitar with a floating bridge.

    Parlour guitar front (small).jpg

    The bracing was just two ladders across the lower bout, one angled. I didn't use a bridge patch, because the bridge is placed above the lower brace.

    Top bracing (small).jpg

    One important difference, which you can't see here, is that the braces are curved so that the top has a side-to-side arch, rising maybe 5mm after string tension. That let me brace lighter, and I also think it might improve the tone (but that's a guess!).

    It sounds like a mahogany-topped guitar, but I think it emphasises the mid-frequencies more than all the others, perhaps more so than a conventional design mahogany parlour. It's very responsive indeed, so it needs care when playing not to sound "boomy", but it can be very loud and not boomy if you control it carefully.

    I've made a few ukes along these lines, though not always angling the bracing, but I can't find pictures. They, too, emphasis the mid-range more than their conventionally-bridged cousins.
    Last edited by ProfChris; 05-31-2020 at 01:33 AM.

  8. #8
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    One more thought - my tenor guitar which I made is floating bridge, and just uses a standard banjo bridge. Sounds very good, not at all banjo-like, though the top is yew which will change things.

    This is so completely different from what you have that it might be worth a try. Whittling up a banjo bridge should be a very quick and simple job.

  9. #9
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    Beautiful job!
    Too many ukes, but I can't stop buying!
    https://www.catskillukulelegroup.com/

  10. #10
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    Quote Originally Posted by ProfChris View Post
    One more thought - my tenor guitar which I made is floating bridge, and just uses a standard banjo bridge. Sounds very good, not at all banjo-like, though the top is yew which will change things.

    This is so completely different from what you have that it might be worth a try. Whittling up a banjo bridge should be a very quick and simple job.

    Thanks for your 2 responses. Your ladder bracing is sort of what I would have expected since I have a couple of ladder braced parlour guitars not of my making and both with pinned bridges. I also realised that the top should be slightly curved and put a curve on my lower transverse brace and the brace under the bridge: they were glued in place in my domed go-bar deck. The dome was barely noticeable before the strings were added-the top is now flat and not sunken.

    I took a banjo bridge off one of my banjo ukes and tried it on this instrument. It made the action a little higher but I dont think the sound was significantly different.

    You mention your instrument being very responsive: I think that's probably what I mean when I say my instrument is loud and has a percussive quality.

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