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Thread: radiusing a soundboard?

  1. #1
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    Default radiusing a soundboard?

    I've been doing some reading here in the Luthier's Lounge and have come across a few mentions of creating various radiuses of soundboard (25', 18', etc).
    I've tried to do some googling on this subject but have only found fuzzy answers.
    How does one radius a soundboard? Is this done in the clamping/go-barring stage? I ran across a few sites that say the soundboard is placed on a concave base plate of a go-bar deck but there weren't any other details other than that.
    Do the tone bars have to be shaped to accomodate the radius of the soundboard (or will this occur naturally under the pressure of the go-bars)? And after the glue on the tone bars has dried how does the soundboard keep it's radius?

  2. #2
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    Yes to all of your questions. Keep in mind that when you are beginning a new craft everything is fuzzy at the start. Even the clearest information doesn't make sense until you've got some experience down. You're not supposed to learn everything at once. One source is not going to give you all the information you seek but rather will be found in small increments here and there.Comprehension doesn't occur until you get you hands on the materials and practice the procedures for a while. It's part of the journey.

    A radius dish or board is used for building and bracing the tops and backs. I believe I use 25' for the tops and 15' for the backs. Braces are sanded to the curve of the radius you want. Your glued-up sides (with kerfing attached) are also sanded in a radius dish. This is what helps to keep the domed shape. I use a potter's wheel with radius dishes mounted on it for this purpose but there are other, less expensive ways of doing it. There is lots of information on this topic on the Internet in guitar builder forums and sites if you do a Google search. You'll also find information on how to build dishes, soleras and forms as well.
    BTW, radiiusing isn't absolutely necessary but I find it makes for a better instrument. Because of the physics of the domed shape, it allows you to build stronger and thinner as well. Some builders, especially beginners, will choose to keep their sound boards flat and simply bend the backs over the curved sides. As with anything, there are many ways and many degrees of doing things.
    Good luck.
    Chuck Moore
    Moore Bettah Ukuleles
    http://www.moorebettahukes.com

  3. #3
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    Thanks for the advice, Chuck. I'll check out those guitar building forums.

    Mahalo!

  4. #4
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    I did a tutorial article for Uke Talk a while back explaining the process I use for making my domed dishes. I learned from Mike Chock at Hanalima and basically used his information modified to suit my needs.

    http://uketalk.com/luthier-tutorials/domed-dish.htm
    --------------------------------------
    Dominator

    Dominator Ukulele Tabs
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    Practice Makes Practice Perfect

  5. #5
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    Yes! That article was a real find for me when I did my dish two years ago. The warning at the end about the dust is not a joke - try doing it outdoors.

    I still build with flat tops though, haven't got around to put a radius in my solera (a fact that I guess makes it not a solera).

    Sven
    Building blog - http://www.argapa.blogspot.com
    Music and atrocities - http://www.goodcopbadcop.se

  6. #6
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    Awesome tutorial Dom! I'll have to do a little more research but as I'm an uber-noob when it comes to woodworking, let alone luthery I'll have to plan it for a couple ukes down the line. Maybe one day I'll be building smooth sounding ukes like Luthier Vandross... yeah, I said it! Hello? Is this thing on?

  7. #7
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    We had an old boy at college who headed up the CDTdepartment. He had formerly worked for Rolls Royce and was an incredible machinist. One prject in the plastics department was making metalaphones. This old boy used to do the metalwork side and always insisted that 'stressing' the bars a little produced a better tone. That is the principle behind doming the front - as Chuck said you can build thinner but also, you have a stronger structure, and in my opinion, a btter tone. I'm just doing a video of a true hand build - it's a concert Vita Uke for which I do not have my standard high tech form. I'll be doing the first part tonight and you can see how I've domed the top...

  8. #8
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    I'm looking forward to seeing that Pete

    I was just talking about this with Rob and Chy in Hebden Bridge the other night. There were three Howlett sopranos in the same pub. You'd have loved it.

    A few years ago there was a small piano factory close to me that I was given a tour of. They had an interesting way of putting the crown on a soundboard. There was a tall narrow box with a heater at the bottom that the new soundboard went into for several days until the wood was totally dry. While it was completely dry they glued the ribs on in a flat go bar deck. The crown appeared when the wood reabsorbed moisture from the atmosphere. The side where the ribs were glued was unable to expand but the other side could. He claimed that this produced a better sound due to different tensions in the wood. Anyone fancy doing a uke like that?

  9. #9
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    I believe that Martin on their guitars originally glued the radiused braces on a flat board and if they sprang back, then hey, curved front...

  10. #10
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    Dom - I would have made the arc by attaching a router to an 'arm' the length of the radius and cutting a 1/4" template. That's how I did it and then followed your protocol. However I would make one suggestion - glue 2 pieces of 3/4" ply together. I found that over time, my 3/4" board bowed....

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