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Thread: A flat topped tenor with a floating bridge

  1. #11
    Join Date
    May 2018
    Location
    Kekaha, Kauai
    Posts
    251

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    Aloha Greenscoe, thanks much for the links you provided, now that I have a much better idea of your knowledge and experience, I have a much better chance at providing you with some useful information. I will start with your arch top and do some more on my Maccaferri later.

    Unfortunately I ran into some health issues before you started building your instrument, so I wasnít able to supply you with any details. Benedettoís book is a great source for general information on arch top construction but is about steel string guitars. Here are some specific dimensions that I use on a tenor arch top ukulele.
    Top thickness recurve area - 1.8mm
    Top thickness center - 3.5mm
    Back thickness 10% less than top
    Rib depth 35mm
    It looks to me from the picture of your instrument, the rib depth may be the problem. It looks to me like it may be in excess of 50mm, which means it is too far away from the top and is unable to support the topís vibrations. You can measure to make sure, but if I am guessing correctly, I would consider popping the back off, reducing the rib depth to 35mm and putting the back on again.
    Brad
    Bradford Donaldson
    Kekaha, HI and Cannon Beach OR
    bradfordj48@outlook.com

  2. #12
    Join Date
    Dec 2012
    Location
    Sheffield, England
    Posts
    104

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    I haven't built a floating bridge instrument. But thinking of similar instruments e.g. banjo I would think the aim is to get the rim/sides to be as stiff as possible to resist the pull of the strings from one end to the other. Then the top should be as thin as possible, relying on the rim/sides to take all the string tension. Otherwise I wouldn't expect there to be enough downward movement of the soundboard. Just my opinion.

  3. #13
    Join Date
    Feb 2014
    Location
    Cumbria, NW England
    Posts
    582

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    Quote Originally Posted by Red Cliff View Post
    I haven't built a floating bridge instrument. But thinking of similar instruments e.g. banjo I would think the aim is to get the rim/sides to be as stiff as possible to resist the pull of the strings from one end to the other. Then the top should be as thin as possible, relying on the rim/sides to take all the string tension. Otherwise I wouldn't expect there to be enough downward movement of the soundboard. Just my opinion.
    Thanks for your response. I have made 2 banjo ukes and it is important that the rim is stiff for the reason you state especially if the instrument is open backed. For that reason banjo ukes often have a 'stick' running through the hoop. Some uke makers consider that thick sides and solid linings both contribute to keep the energy in the soundboard making for a better response. I often use laminated linings and sometimes side stiffeners.

    When it comes to wooden soundboards on ukes of all sizes there is an optimal thickness, too thick and there is low volume, too thin and the instrument sounds more like a banjo than a uke. By this I mean it sounds tinny or trebly, has no sustain and may make popping sounds when some notes are played. This is not just my opinion/experience but one that is regularly stated on this forum.

    I have 6 tenors with Engelmann spruce tops all initiall thinned to 1.8mm. On this floating bridge uke, I thinned to 2mm because I knew I would be using less bracing and didn't want the soundboard to dip under the bridge. This instrument is very loud and punchy.

    So again, I thank you for you contribution. This is a discussion forum, so I encourage all to dip in, that's the way we all learn.

  4. #14
    Join Date
    Feb 2014
    Location
    Cumbria, NW England
    Posts
    582

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    Quote Originally Posted by BuzzBD View Post
    Aloha Greenscoe, thanks much for the links you provided, now that I have a much better idea of your knowledge and experience, I have a much better chance at providing you with some useful information. I will start with your arch top and do some more on my Maccaferri later.

    Unfortunately I ran into some health issues before you started building your instrument, so I wasn’t able to supply you with any details. Benedetto’s book is a great source for general information on arch top construction but is about steel string guitars. Here are some specific dimensions that I use on a tenor arch top ukulele.
    Top thickness recurve area - 1.8mm
    Top thickness center - 3.5mm
    Back thickness 10% less than top
    Rib depth 35mm
    It looks to me from the picture of your instrument, the rib depth may be the problem. It looks to me like it may be in excess of 50mm, which means it is too far away from the top and is unable to support the top’s vibrations. You can measure to make sure, but if I am guessing correctly, I would consider popping the back off, reducing the rib depth to 35mm and putting the back on again.
    Brad
    Thanks for that Brad. The sides are 45mm deep and I think all the other dimensions were roughly as you have stated. The soundboard was of lime not spruce so that may be a factor. I cant remember whether I used 2 or 3 braces on the top so it may be that it was over braced. I have moved on and dont intend further work on this one.

    One day I'll wake up and decide its time to make another archtop. Its just unfortunate that with no examples of builds to see its hard to get a handle on how to get the best from an archtop and to rekindle my interest. I like to try alternate types of uke which normally take less time than a standard uke. The archtop took a lot more time than any other uke I've built.
    Last edited by greenscoe; 05-31-2020 at 11:28 PM.

  5. #15
    Join Date
    Aug 2018
    Location
    Australia.
    Posts
    236

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    Greenscoe,

    I really enjoy reading posts on unconventional builds.
    From the respondents' ideas and comments, and your wondering of how to move forward, some ideas you could consider. Most have already been touched on:

    Eliminating the bridge patch, as there are no rotational forces.
    Placing a slimmed down single ladder brace directly under the floating bridge.
    Increasing the upward curve in the ladder brace … (you mentioned that it pretty well straightened out).
    Reducing the top thickness slightly.
    Reducing the mass of the bridge.
    Anchoring the strings a little lower, at the top/butt plane (even if slightly) to increase the string break angle. A degree or two of neck set would raise the bridge height a bit to accommodate this as well. A small difference here should have significant influence on the string down force presented to the soundboard.

    OR, perhaps, none of the above :-)

  6. #16
    Join Date
    Feb 2014
    Location
    Cumbria, NW England
    Posts
    582

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    bazuku:

    It's always good to know that there are forum members who are interested in alternative builds.

    I make ukes purely as a hobby: I have a house full of instruments which I play rather badly. My interest is therefore in making something different, not one more of something I already have.

    As for your list, I have no problem with compiling such a list, it's all about which factor(s) to select. I'm often inclined not to choose proven methods just to see where the alternative takes me.

    However I'm always interested to see and hear what others are doing and what they find to be successful

  7. #17
    Join Date
    Dec 2012
    Location
    Sheffield, England
    Posts
    104

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    Quote Originally Posted by greenscoe View Post
    Thanks for your response. I have made 2 banjo ukes and it is important that the rim is stiff for the reason you state especially if the instrument is open backed. For that reason banjo ukes often have a 'stick' running through the hoop. Some uke makers consider that thick sides and solid linings both contribute to keep the energy in the soundboard making for a better response. I often use laminated linings and sometimes side stiffeners.

    When it comes to wooden soundboards on ukes of all sizes there is an optimal thickness, too thick and there is low volume, too thin and the instrument sounds more like a banjo than a uke. By this I mean it sounds tinny or trebly, has no sustain and may make popping sounds when some notes are played. This is not just my opinion/experience but one that is regularly stated on this forum.

    I have 6 tenors with Engelmann spruce tops all initiall thinned to 1.8mm. On this floating bridge uke, I thinned to 2mm because I knew I would be using less bracing and didn't want the soundboard to dip under the bridge. This instrument is very loud and punchy.

    So again, I thank you for you contribution. This is a discussion forum, so I encourage all to dip in, that's the way we all learn.
    Very happy to contribute.

    But I think you have missed the point. You described the uke as lacking treble, yet have noted that banjos sound trebly due to their thin tops. So there is probably a trade-off on this design. Go thin and sounds trebly (like a banjo). Go a bit thicker and it lacks treble. That is presumably a consequence of less upwards or twisting force on the bridge.

    There may not be a way of getting both to be as you want them with this design. Others I'm sure may disagree.

    I've restored a few bowl-back mandolins with very similar floating bridges. Very thin tops, less than 2mm. And much more tension through the strings.

  8. #18
    Join Date
    Aug 2018
    Location
    Australia.
    Posts
    236

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    Quote Originally Posted by greenscoe View Post
    I'm often inclined not to choose proven methods just to see where the alternative takes me.
    Your attitude is commendable and deserves support.
    I have spent an inordinate amount of time, not trying to reinvent the wheel, but trying to modify it too often.
    However, after many more failures than successes, there came a stage in life when time became more precious, so I decided to defer to the long-established status quo of building.
    I learned to appreciate that generations of sharper minds than mine had laid down lifetimes of hard-fought ground work that I was not using to advantage.
    This led to a complete reversal of thinking and I started building traditional, rustic style instruments, where deviation from the mean was regarded as frivolous at best, or blasphemous at worst.
    This style of building has the added bonus of not requiring the kind of sophisticated skill set displayed to perfection by the elite of our fellow forum members.
    I do not mean to discourage or trivialise experimentation, as there can be no progress without it, but from experience, I feel that time is short, rabbit holes can be deep, and it is sometimes easier to just skirt around them.
    Regardless, I really admire your enthusiasm in your search for answers.
    Last edited by bazuku; 06-02-2020 at 01:35 AM.

  9. #19

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    Thanks for the posting Greenscoe.
    I have been working on an experimental tenor project and am nearing the end with making the nut and bridge/saddle. My top is spruce and has a 25’ radius and is about 2.3 mm thick in the middle tapering at the edges to about 1.8 and is skin braced only in the center at about 1.2 mm. After seeing your success with this type of set up, I plan to do something similar. Still trying figure it all out. I¬’ll post results when finished.

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