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Thread: Octave Mandolin fixed bridge compensation?

  1. #1
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    Default Octave Mandolin fixed bridge compensation?

    Hi everyone, I'm building an octave mandolin with a guitar shape similar to the Pono models. 21" scale length so what would you add to this as compensation, to the leading edge of the saddle.
    I know this will spark lots of scientific and technical responses, regarding types of strings, tensions etc, but I'm after a ball park figure to cover most general situations, with minor adjustments being made to the saddle if necessary.
    I asked a similar question regarding guitar compensation a while back, and the general consensus was that a particular figure could be used to cover most scale lengths. Technically this isn't true, but in practice it does work. As a result I made something like the Stewmac bridginator , to place the bridge in the right position. Without changing the amount of compensation on the bridginator , I have used it to make several guitars with great intonation.
    The different calculation tools available online, seem to be contradictory.
    Your thoughts would be appreciated thanks. Mike

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  3. #2

    Default Re: Octave Mandolin fixed bridge compensation?

    I was taught to use a trial string up. I use a block of wood to make a temporary tailpiece and position the bridge blank with the strings on and at at full tension, then add one millimeter to compensate for the top rising when the strings are pinned to the bridge. Fine tune by shaping the saddle.

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    Registered User j. condino's Avatar
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    Default Re: Octave Mandolin fixed bridge compensation?

    This ^^^^^exactly.

    Don't look for answers in books or pretty photos or complex formulas or tapping on unicorns and fairy dust. Build your instruments in a way such that you can string them up for important critical areas and use you ears to tell you when they respond in an appropriate musically pleasing manner.

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    Default Re: Octave Mandolin fixed bridge compensation?

    Thanks, and whilst this might be a valid answer, it's not the one I was hoping for. I do believe there are easier ways, without all the added work of stringing up with false tailpieces. I might have to use your method in the end so I won't rule it out, but in the meantime hope that there may be more replies that answer my question more directly.

  8. #5

    Default Re: Octave Mandolin fixed bridge compensation?

    Quote Originally Posted by mikeyb2 View Post
    Thanks, and whilst this might be a valid answer, it's not the one I was hoping for. I do believe there are easier ways, without all the added work of stringing up with false tailpieces. I might have to use your method in the end so I won't rule it out, but in the meantime hope that there may be more replies that answer my question more directly.
    If you are going to build more than one the easier way comes when you have refined your design and can duplicate your proven measurements. The trial string up also gives you an idea how the neck is going to behave which is a big factor. The temporary tailpiece can be very simple. Here is what I use for a Mandolele
    Click image for larger version. 

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    Default Re: Octave Mandolin fixed bridge compensation?

    Quote Originally Posted by mikeyb2 View Post
    Thanks, and whilst this might be a valid answer, it's not the one I was hoping for. I do believe there are easier ways, without all the added work of stringing up with false tailpieces. I might have to use your method in the end so I won't rule it out, but in the meantime hope that there may be more replies that answer my question more directly.
    The people who answered your question know of what they speak. James in particular has a lot of experience. You may find a formula but unless it is simplified it will be very complex to take into account, string height, neck angle, relief, and the physical characteristics of the strings. By the time you work through such a formula you could have followed the suggestions given and gotten something you know is right. If the formula is simplified it won't be right.

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    Default Re: Octave Mandolin fixed bridge compensation?

    Quote Originally Posted by MrMoe View Post
    If you are going to build more than one the easier way comes when you have refined your design and can duplicate your proven measurements. The trial string up also gives you an idea how the neck is going to behave which is a big factor. The temporary tailpiece can be very simple. Here is what I use for a Mandolele
    Click image for larger version. 

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    Thanks again, I can see that the tailpiece is quit a simple set up, but what I wonder about is the tuner end. Do you somehow attach temporary tuners or fit the real ones, which would involve fitting the shaft bushes. This would mean they would have to be forced out again so the neck could be "finished", or do you finish the neck first? Mike

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    Default Re: Octave Mandolin fixed bridge compensation?

    Quote Originally Posted by Nevin View Post
    The people who answered your question know of what they speak. James in particular has a lot of experience. You may find a formula but unless it is simplified it will be very complex to take into account, string height, neck angle, relief, and the physical characteristics of the strings. By the time you work through such a formula you could have followed the suggestions given and gotten something you know is right. If the formula is simplified it won't be right.
    Hi, i'm not looking for a formula, I have it already. All I need the value to add to the bridginator. Once I have that value it will take 2 minutes to set it up, as opposed to the many hours involved with a trial string up. And as you say the people who answered my question know what they're talking about, of this I have no doubt and have every respect. I'm sorry if it appeared I was being dismissive, it wasn't intended. Their suggestions are the right and proper ones, but not the easiest for me.
    I was hoping that somebody out there has built instruments using my method and would come on here and say "yes, I use x" and it works". Like I said earlier, I've used this to build guitars successfully.

  12. #9

    Default Re: Octave Mandolin fixed bridge compensation?

    At Franklin the instrument is brought to full tension several times during several stages of the building process. Tuners do go on during these steps.

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    Default Re: Octave Mandolin fixed bridge compensation?

    Quote Originally Posted by MrMoe View Post
    At Franklin the instrument is brought to full tension several times during several stages of the building process. Tuners do go on during these steps.
    So what happens about the tuner shaft bushes, or is the headstock finished at the stage the tuners are attached?

  14. #11

    Default Re: Octave Mandolin fixed bridge compensation?

    Some times before finishing, always after. Nick has "shop tuners" that are modified to be easily installed and removed. If your tuners have knurled bushings they can be tapped out with a dowel. When I build a regular octave I do not do all of these steps. Mine are not high end instruments. When I bulid for a fixed bridge I always do the trial string up (with finish on). Then create the bridge.
    Last edited by MrMoe; Mar-31-2021 at 8:06am. Reason: ps

  15. #12

    Default Re: Octave Mandolin fixed bridge compensation?

    mikeyb2 I started my learning by studying this book for several years. I have also followed Dan Eriewine for many years. I am very much an amateur builder.

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    Default Re: Octave Mandolin fixed bridge compensation?

    Quote Originally Posted by MrMoe View Post
    Some times before finishing, always after. Nick has "shop tuners" that are modified to be easily installed and removed. If your tuners have knurled bushings they can be tapped out with a dowel. When I build a regular octave I do not do all of these steps. Mine are not high end instruments. When I bulid for a fixed bridge I always do the trial string up (with finish on). Then create the bridge.
    Once again thanks MrMoe, it looks like I will be trying your method after all, so as my body joint is a M&T bolt-on, I have now started to finish the neck and as soon as it's done, I'll install the tuners and continue from there.
    This is not my normal way, as I usually mark out and tape off the bridge once I'm happy with the fit, then I'll pore fill etc and spray a few coats of finish. When it's all cured, I'll remove the tape and glue on the bridge. Attach the neck, then do a set up. Works for me, but as I don't have the values I need for my normal bridge placement procedure, I'll find the value by using your advice.
    Cheers Mike

  17. #14
    Mandolin tragic Graham McDonald's Avatar
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    Default Re: Octave Mandolin fixed bridge compensation?

    In general, you should add 1.5-2mm to the theoretical scale length to locate the front of the saddle for the string which will need the least compensation. On most guitars/ovtave mandolins/bouzoukis this will be the highest open string, E4 or D4. On an octave mandolin, using a wound second course tuned to A3, because of the thin core wire, this course may have to have its contact point closer the nut by 1-2mm to that of the first or third course. Here is a pic of how I would start the shaping of a saddle for a five course cittern with a 22" scale, more or less what you are building with an added higher course. Hope this helps.

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    Default Re: Octave Mandolin fixed bridge compensation?

    That's just the kind of answer I was looking for Graham, and round about the figures I was expecting, but now, as the previous contributors have persuaded me to use a trial string up, I'll continue with that and see where it takes me.
    Many thanks Mike

  20. #16

    Default Re: Octave Mandolin fixed bridge compensation?

    Mr. McDonald is next on my list of must reads.

  21. #17

    Default Re: Octave Mandolin fixed bridge compensation?

    The Mandolin: A History arrived today via I.L.L. from our county library. I can see right away that I will be buying my own copy before it is due.
    Thank you Mr. McDonald! I enjoyed the images and text regarding Mr. Gilchrist. I had the honor of spending an afternoon with him during the time that he had a workspace in Fulton MO.

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    Default Re: Octave Mandolin fixed bridge compensation?

    As MrMoe has just reminded me of this thread, here's an update. The bridge position (and saddle slot angle determined)has now been located using the trial string up method as suggested above. I had to modify my building process to do this, but everything's worked out ok. So, many thanks to all who contributed. Mike

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  24. #19

    Default Re: Octave Mandolin fixed bridge compensation?

    I would like to confirm Graham McDonald's advice in his post above. I built my first octave mandolin with a fixed bridge about a year ago (building number three now). I set the compensation based on the info in his book entitled The Bouzouki Book. The saddle diagram Graham posted above is in that book. It worked like a charm on the first try without the need for any sort of trial string setup. I highly recommend his book.

  25. #20

    Default Re: Octave Mandolin fixed bridge compensation?

    Mike has little if anything to learn from me. Here is his update and his realy nice octave.
    https://www.mandolincafe.com/forum/t...dolin-finished

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    Default Re: Octave Mandolin fixed bridge compensation?

    Quote Originally Posted by MrMoe View Post
    Mr. McDonald is next on my list of must reads.
    I already have Graham's books on both Mandolin and Bouzouki. Great reads and much useful information. My go-to source for data.

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