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Thread: Rib assemblies too small?

  1. #1

    Default Rib assemblies too small?

    Question: If an F5 body is roughly 3/32" smaller all around its edge than a traditional F5 (based on replicated Loar plans), is it still an acceptable F5 mandolin?

    Let me explain:

    I made an outer mold for my rib/block assembly. I bent my sides, placed them in the mold, cut my blocks, glued them in and then glued my kerfed linings in to the soundboard side of the rib assembly. Then I went to work rough out my spruce top plate...

    With the top plate cut to shape (right on the outside of my template pencil line) and the arch and scroll carved, I placed the top on the rib assembly (still held in the mold)...only to find what I believe to be an unacceptable amount of overhang for the top.

    I took out my original top plate template and held it over the outer mold shape, and sure enough the mold was smaller than the template. (I really have no idea how this happened because I used that template to make the mold in the first place...but anywho!) At any point around the edge of the mold it is between 1/16" and 1/8" smaller than my top plate template depending on where you measure. This means that if I were to use the rib assembly as held together by this mold the resulting body of the finished mandolin would be an average of 3/32" smaller all around than what is a "standard" F5 based on my template, which is based on a set of replicated plans for Loar F5s...

    The mold is going to be corrected. I have already traced the line of the template around the mold's line and will be using my bandsaw and spindle sander to bring it to a more acceptable size.

    What I want to know is whether I should toss out the rib assembly. Is it a lost cause because of the discrepancy in size? Is an F5-style mandolin body that is smaller by about 3/32" at any point on its edge still considered an F5 mandolin? Or is it...something else?

    Thanks for your input.

    -Mark

  2. #2
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    Default Re: Rib assemblies too small?

    Of course it's still an F5. However, there's a couple of things to consider on this particular build. First, with your overhang, is the edge of the top going to be the thickness you are shooting for, or when you trim it to fit the rim, are you going to be going into your recurve? That, I guess, depends on how far you've taken the recurve at this point. I never finish my recurve until the top (or back) is on.
    On another note, you know that it's "off" from what you intended and what the plans call for. Will that be lurking in the back of your mind whenever you show your mandolin to someone forever into the future? Will you feel compelled to explain to each and every person that it's off by that little amount? If so, I'd write it off to experience and do a new rim. It's not that big a deal. Considering how much total work is going to go into the end product....

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  4. #3

    Default Re: Rib assemblies too small?

    3/16" smaller will not be noticed by anyone other than a serious connoisseur and the change in chamber volume isn't going to affect the sound to any degree you'd be able to hear. I would go with it and chalk it up to experience. On every build you learn something new. Just my opinion.

  5. #4
    Registered User Schneidly's Avatar
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    Default Re: Rib assemblies too small?

    What if you kept the plates oversized and made these to have more of a violin construction appearance like a Campanella?

    https://themusicemporium.com/mandoli...5#&gid=1&pid=6

    Just a thought.

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    Default Re: Rib assemblies too small?

    Quote Originally Posted by Schneidly View Post
    What if you kept the plates oversized and made these to have more of a violin construction appearance like a Campanella?

    https://themusicemporium.com/mandoli...5#&gid=1&pid=6

    Just a thought.
    That's what I would do and was just going to suggest that. I love the looks of a fiddle top mandolin.
    THE WORLD IS A BETTER PLACE JUST FOR YOUR SMILE!

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  9. #6
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    Default Re: Rib assemblies too small?

    Like Dale said, as long as your recurve fits, it should be fine. I've collected drawings and plans for F5's over the years. What I've found is the body sizes on each one is different.

    That said, if there was anything that you didn't like about your ribs for this one, maybe the scroll split at some point? Then I would use this as an excuse to start over.

  10. #7
    Registered User sunburst's Avatar
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    Default Re: Rib assemblies too small?

    Extra work, but the glue joints at the corner points could perhaps be released, "slipped" and re-glued thus expanding the rim.

  11. #8

    Default Re: Rib assemblies too small?

    Quote Originally Posted by sunburst View Post
    Extra work, but the glue joints at the corner points could perhaps be released, "slipped" and re-glued thus expanding the rim.
    Brilliant, that would be my choice.
    Richard Hutchings

  12. #9
    Registered User j. condino's Avatar
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    Default Re: Rib assemblies too small?

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  13. #10

    Default Re: Rib assemblies too small?

    You can take out the tail block and cut the rib to expand the circumference. Inlay with contrasting wood and a new block.
    You can pull the linings and apply a variation of the "Jimmy Rogers Weymann" guitar external banding and binding.
    Burning will be the last of the learning for that one.

  14. #11
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    Default Re: Rib assemblies too small?

    my plates are always oversized and are then fitted to the rims.. then are final thicknessed .. it's a great luthier that can cut a plate exactly to a rim --- I'm not even close to being there.....
    kterry

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