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Thread: Martin OM Style Acoustic Guitar

  1. #1
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    Martin OM Style Acoustic Guitar

    Here we go...

    I'm using plans from LMI. The guitar is based on Martin's OM model.


    Two sitka spruce soundboard pairs were purchased from Alaska Specialty for $8@


    I also bought some sitka splits for the braces


    The tools I have been using so far


    Rather than making templates and forms from plans like I've done in the past, I took the lazy way out


    I milled the sitka splits on the tabla saw to the dimensions shown on the plan. To rough cut the sweep on the brace tops, I used a jewelers saw then went to planes, rasps and sandpaper to finish.
    “Travel is fatal to prejudice, bigotry, and narrow-mindedness..." - Mark Twain

    Diapers and Politicians need to be changed often... Usually for the same reason.

  2. #2
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    This is going to be fun to watch!
    --

    The most expensive tool is the one you buy "cheaply" and often...

  3. #3
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    After spraying the final coat of poly on the kitchen cabinets, I rewarded myself with some time on the guitar. The brace thing and "voicing" the soundboard is, from what I have heard and read time and again, a kind of voodoo magic combined with throwing darts and some serious engineering, all reliant on how the guitar sounds in the hands of different people. Easy peasy.

    After getting my hands "conditioned" to making braces, things started looking up


    I have absolutely no idea what kind of sound this will bring but at least the braces are shaped according to the plans.


    Before I can glue them to the soundboard I have to rout out for the rosette. For this soundboard I opted to buy some pre-made rosettes. For now, I want to concentrate on learning the fundamentals.


    Awaiting the rosette arrival...
    “Travel is fatal to prejudice, bigotry, and narrow-mindedness..." - Mark Twain

    Diapers and Politicians need to be changed often... Usually for the same reason.

  4. #4
    Hello! I'm in the middle of building my first guitar as well. I am following Kinkead's book and using his plans (kinda). If you are following his procedures, you might want to look into the neck joint and neck angle somewhere else. I've found that Kinkead sort of glosses over those parts. Depending on what you decide and which system you follow, it might be important to address the shape of the sides near the upper bout before you glue the top on. I think this is something I wouldn't have looked at if I'd only been looking at Kinkead's book.

    I was also pretty bamboozled by shaping the braces. I made a guess just like you did. Mine was based mostly on watching a video where Dana Bourgois voices a guitar top. It's a cool video even if you feel more confused after watching it than before. Also I get the impression that the way he looks at voicing a top is only his way and others may disagree. There don't seem to be too many other free options on youtube though....


    Hope it goes well! I'll be watching with great interest.

  5. #5
    Just realized you might be the same person I responded to on OLF. If so, sorry for the flood of similar advice!

  6. #6
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    Thanks, Adam! I've kind of conceded to the fact that voicing the soundboard is as much voodoo as it is science, if for no other reason than the fact that even within the same tree, there is no reliable consistency in cell structure from one spot to another. I'm thinking there may be a lot of completed soundboards that never made it into a guitar and probably some guitars that ended up as El Kabong! guitars (see the video below). In his voicing video, Dana Bourgois used a soundboard he said was a reject yet it looked perfectly fine.

    The Gore & Gilet book sounds interesting and some say it will help understand the science sufficiently to be able to turn out a good guitar on your first attempt. The GAL videos I've seen are also pretty interesting and have, at the very least, given me a real appreciation and deep respect for those who have mastered the art.

    The rosettes have yet to arrive so the soundboard work hasn't progressed, making this a good time to cross some things off the procrastination list.


    “Travel is fatal to prejudice, bigotry, and narrow-mindedness..." - Mark Twain

    Diapers and Politicians need to be changed often... Usually for the same reason.

  7. #7
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    This is going to be fun to watch.

    The OM is a nice little guitar. All I have are Dreadnoughts and an old Brazilian Craviola. Voicing is art, not science. But it isn’t as daunting as it seems.
    Shawn

    "no trees were harmed in the creation of this message, however some electrons were temporarily inconvenienced."

    "I resent having to use my brain to do your thinking"

  8. #8
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    I don't think voicing is something to be too concerned about at first, though maybe I don't know what I'm missing. If you follow the plans and practice good joinery and have good materials you'll end up with a good sounding instrument. Voicing reportedly enables those who can do it to fine-tune the parameters of the sound they want to get, or to have more repeatable results, but it's not like an 'unvoiced' instrument won't still sound good.
    Zach

  9. #9
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    I was reading an article in American Lutherie about Olivier Fanton d'Andon, a French luthier. He said, "bracing is the most difficult part, the most fastidious part. It is long work and I have to adjust and carve each bar very slowly." As he works the bracing, he listens for harmonics. Something else he said stuck - "The purfling has to be as thin as possible: it is very important for the sound." His purflings are 3mm thick.

    Still waiting on the rosettes...
    “Travel is fatal to prejudice, bigotry, and narrow-mindedness..." - Mark Twain

    Diapers and Politicians need to be changed often... Usually for the same reason.

  10. #10
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    The rosettes finally came. I used my homemade Dremel circle jig to rout out the soundboard. It came out perfect.


    I have to make some dished bases for the top and back, at 15' and 25' radii, respectively. I figured the best way to do that is with the router as opposed to carving or sanding. I used the LMI radius sanding tool to mark up some plywood and took the plywood to the bandsaw for the concave cut then took an oak board from the old kitchen cabinets and made convex radii on either edge. From there it was a lot of sanding to get the final shape.


    Yesterday I was resawing some 6x8/4 rough sawn cedar into 3rds so the bandsaw had the resaw blade in it so why not resaw for the backs and sides? I have a couple of 12"x9'x8/4 sipo so I cut off 36" and resawed, planed, etc until I had (6) 9"x36"x0.125" pieces.


    It doesn't seem like much but it sure took a long time to do!
    “Travel is fatal to prejudice, bigotry, and narrow-mindedness..." - Mark Twain

    Diapers and Politicians need to be changed often... Usually for the same reason.

  11. #11
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    Got the rosette glued in and leveled out. Had to fill in the gap under the fretboard, too. The back halves are glued up and flattened. Next was making a Go-Bar deck. The 1/2" threaded rod was stiff enough to stand on its own. The fiberglass rods I found at HD. They have plastic caps on them and are half the price StewMac charges. The whole thing ran me about $30.


    Jigs for routing bindings and profiling the sides are pretty pricey so I fashioned up a jig.


    I noticed on the underside of those jigs they had something to help ease the guitar body underneath the router. I took a piece of HDMW to the lathe then fit it into the underside of the router base.
    “Travel is fatal to prejudice, bigotry, and narrow-mindedness..." - Mark Twain

    Diapers and Politicians need to be changed often... Usually for the same reason.

  12. #12
    Thanks for sharing - looking good. This is def on my bucket list.

  13. #13
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    Thanks, John. This has been on my bucket list for years.

    I went to glue up the braces on the soundboard. I'm using hot hide glue. Once the glue was hot, I applied it to the X brace joint and found it gummy. It wasn't hot enough. Then it hit me. I FORGOT TO PUT WATER IN THE KETTLE!!! That dumb move cost me one heater. A new one is on the way.

    In the meantime, why not glue the back braces with PVA? They usually don't need to be replaced.


    Next is doing some shaping on the braces and pinging the board to see how it sounds. My homemade pinger is at the top right. It seems to get better results than a fingertip or knuckle.


    Pinging it resulted in some notes but pretty much no sustain. If the soundboard is similar, this may be a guitar for hard playing.
    “Travel is fatal to prejudice, bigotry, and narrow-mindedness..." - Mark Twain

    Diapers and Politicians need to be changed often... Usually for the same reason.

  14. #14
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    Julie, I have no intention of building a guitar, but am really enjoying your build thread. Always interesting to me to see how things are done. I’m impressed with your ingenuity and skill. Thanks for sharing.

  15. #15
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    Thanks, Phil. I'm plodding my way through this as best I can. Still trying to figure out what to do to get the best sound out of it.

    Yesterday I glued up the braces for the soundboard. After the glue set, I did some tap testing and the soundboard was completely dead! Not even a hint of sound, just a short thunk. So I got out the planes and started carving the "marimba bars" (braces).


    I'm getting something now but it still doesn't sound very good. The back, having done nothing to it, still sounds better. I'm dancing the delicate dance of removing mass from the braces while keeping the necessary structural rigidity necessary to withstand the 180 pounds of pull the strings apply to it.
    “Travel is fatal to prejudice, bigotry, and narrow-mindedness..." - Mark Twain

    Diapers and Politicians need to be changed often... Usually for the same reason.

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