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Thread: Conversion: Harmony Master H945 to Octave Mando

  1. #1

    Default Conversion: Harmony Master H945 to Octave Mando

    I spotted a dirt cheap Harmony H945 Archtop guitar with a warped neck at Root Note in New Paltz, NY, and decided that I would sacrifice it in the name of attempting my first build of an Octave Mandolin. I figured that given the little amount I paid for it, it wouldn't be worth it restoring it to playable guitar status, especially since I'm not a guitar player myself.

    I've never built an instrument or done any heavy repair work, so this is very much going to be a crash course, learn-as-I-go kinda deal. I will plan what I can, but my goal here is to not break the bank, but learn what I can on a build that won't have me crying over every small mistake.

    I have a few initial questions that I'm hoping to get some info on:
    1. A place to find octave necks. Preferably as finished as possible.
    2. Scale length. The H945 has a 25"1/4 scale length, and I'm hoping to reduce that as much as possible. How short of a scale length can I get away with for an octave? Obviously it would also mean some bridge movement, and I'm wondering if the bracing of the top would be significantly affected based on the relocation of the bridge.
    3. Tension. I know tension between a guitar and an octave would be different, and I'm wondering how much that will affect the structure, sound, and playability of the instrument.

    Again, this is something I'm not planning on losing much sleep over. More of a way to get my feet wet in the building, repair, and conversion world. So I want to keep the cost down while still learning as much as I can from the process. I have access to a decent amount of tools, but by no means do I have any specially designed luthiery implements.

    Link to Harmony's archive page on the H945: http://harmony.demont.net/guitars/H945/251.htm

  2. #2
    Registered User PT66's Avatar
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    Default Re: Conversion: Harmony Master H945 to Octave Mando

    First: Good luck. Moving the bridge is a bad idea. It will alter the sound and upset the structure. You could still do a shorter scale but the number of frets clear of the body will be reduced. Tension can be address by adjusting string gauge, not to difficult. The neck will need to be custom made to fit the existing dove tail joint (costly). You could stay with the 25 1/4 scale and try to straighten and reshape the neck. String gauge would start with .011 for the high e, about .018 for the a, a standard guitar D string for the D and medium to heavy gauge A string tuned down to G.
    Dave Schneider

  3. #3

    Default Re: Conversion: Harmony Master H945 to Octave Mando

    Quote Originally Posted by PT66 View Post
    Moving the bridge is a bad idea. It will alter the sound and upset the structure. You could still do a shorter scale but the number of frets clear of the body will be reduced. Tension can be address by adjusting string gauge, not to difficult. The neck will need to be custom made to fit the existing dove tail joint (costly).
    I appreciate the heads up. There's gonna be a lot of drawbacks to doing this the way I'm doing it. I knew that moving a bridge at all is gonna mess with the sound, so what I'm hoping at the very least is that the bracing can even handle it, let alone sound good.

    As for the scale, I might just look for an equally cruddy half-size acoustic guitar and lop the neck off. This thing is gonna be an uglier than Frankenstein's monster, and I'll be lucky if I get it even close to the functionality of Dr. Frank's creation. I'm not particularly optimistic, but I'd rather make a lot of mistakes now and be that much more prepared when I go about doing this the right way.

    If there really isn't an online resource to order an octave neck from without burning a deep hole in the wallet, then this is going to get a lot more interesting.

  4. #4
    Certified! Bernie Daniel's Avatar
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    Default Re: Conversion: Harmony Master H945 to Octave Mando

    Quote Originally Posted by PT66 View Post
    First: Good luck. Moving the bridge is a bad idea. It will alter the sound and upset the structure. You could still do a shorter scale but the number of frets clear of the body will be reduced. Tension can be address by adjusting string gauge, not to difficult. The neck will need to be custom made to fit the existing dove tail joint (costly). You could stay with the 25 1/4 scale and try to straighten and reshape the neck. String gauge would start with .011 for the high e, about .018 for the a, a standard guitar D string for the D and medium to heavy gauge A string tuned down to G.
    I'm not so sure. The OP said the neck wrapped so it sounds like it might be pretty much history? Straitening guitar necks is iffy at best right?

    So assuming the neck is shot you might as well go for a shorter one that fits octave tuning -- in which case the bridge will need to be moved.

    One problem with just solving the matter by adjusting string gauges is that then you'll have an octave mandolin that is just as hard to play as a mandocello (same fret spacing).

    Believe me after you play on a mandocello for 30 minutes then pick up your octave it seems like a toy. Huge difference.

    I've taken old Harmony necks off before and it is not too hard to do. But finding new shorter neck will be problematic.

    There are actually guys out there who do custom builds of necks and other parts and you could send the old neck along with the request to make sure that you get the tenon part of the dove tail cut right. Generally a custom neck should not set you back too much $$.

    Problem with finding the neck on a smaller guitar is the dovetail most likely would not match up?
    Bernie
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    Default Re: Conversion: Harmony Master H945 to Octave Mando

    Since you don't want to spend money you will have to make your new neck (not rocket science). You will have three steps to follow in sequence to help keep the process as simple as you can:
    1. select your scale length
    2. get your fingerboard slotted
    3. figure out your parts placement and make your new neck.

    To really help keep things on track make a side view drawing at full scale, and put everything in the drawing (strings, machines, frets, nut, bridge, body, and obviously the neck.) From this drawing you will make your neck.

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    Registered User Tom C's Avatar
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    Default Re: Conversion: Harmony Master H945 to Octave Mando

    Ive thought about doing something like this, but realized the neck should also be narrower. I was lucky to find and old arch top body that has a good dovetail joint. I'm having somebody make a new neck.

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    Certified! Bernie Daniel's Avatar
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    Default Re: Conversion: Harmony Master H945 to Octave Mando

    Here is a link to a builder in Ohio who makes acoustic guitar necks. I think I talked to him a few years ago and he does make a custom necks if I recall correctly. His prices seem reasonable to me and if you are wondering I have no financial interest in his company.
    Bernie
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    Default Re: Conversion: Harmony Master H945 to Octave Mando

    Depending on how bad the warp is you may be able to do a re-fret after sanding the fingerboard straight. Even if you have someone else do it, it should cost a lot less than a new neck.

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    Certified! Bernie Daniel's Avatar
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    Default Re: Conversion: Harmony Master H945 to Octave Mando

    Quote Originally Posted by Nevin View Post
    Depending on how bad the warp is you may be able to do a re-fret after sanding the fingerboard straight. Even if you have someone else do it, it should cost a lot less than a new neck.
    Excellent thought and you could narrow the neck at the same time!
    Bernie
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    Due to current budgetary restrictions the light at the end of the tunnel has been turned off -- sorry about the inconvenience.

  10. #10

    Default Re: Conversion: Harmony Master H945 to Octave Mando

    Quote Originally Posted by Bernie Daniel View Post
    One problem with just solving the matter by adjusting string gauges is that then you'll have an octave mandolin that is just as hard to play as a mandocello (same fret spacing).

    Believe me after you play on a mandocello for 30 minutes then pick up your octave it seems like a toy. Huge difference.

    I've taken old Harmony necks off before and it is not too hard to do. But finding new shorter neck will be problematic.
    I certainly would want to avoid the giant spacing and width of a mandocello. I'd like to shorten the scale length as much as I can to improve ease of play, but I wonder what the shortest scale length is that I can get away with. I've seen some builds as short at 19" or 20" but placing a 19" ruler up against the body results in pretty hilarious results. I'm looking at either a comically short neck or a bridge that's so close to the neck that it would be completely clear of the space between the F-holes.

  11. #11

    Default Re: Conversion: Harmony Master H945 to Octave Mando

    Quote Originally Posted by Nevin View Post
    Depending on how bad the warp is you may be able to do a re-fret after sanding the fingerboard straight. Even if you have someone else do it, it should cost a lot less than a new neck.
    Unfortunately the neck is pretty bad, and the lack of truss rod and my lack of resources necessary to straighten it make the neck a lost cause. I was content from the start to work with a new neck, especially since I want to shorten the scale length.

  12. #12

    Default Re: Conversion: Harmony Master H945 to Octave Mando

    Quote Originally Posted by Bernie Daniel View Post
    Here is a link to a builder in Ohio who makes acoustic guitar necks. I think I talked to him a few years ago and he does make a custom necks if I recall correctly. His prices seem reasonable to me and if you are wondering I have no financial interest in his company.
    I'll look into that. Thank you!

  13. #13

    Default Re: Conversion: Harmony Master H945 to Octave Mando

    Quote Originally Posted by Tom C View Post
    Ive thought about doing something like this, but realized the neck should also be narrower. I was lucky to find and old arch top body that has a good dovetail joint. I'm having somebody make a new neck.
    Definitely looking for a narrower neck. Let me know if you have any luck!

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