Martin D-18-ish Acoustic Build

Discussion in 'Project Depot' started by terryward, Jan 31, 2020.

  1. terryward

    terryward Well-Known Member

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    So, this is still a work in progress and has been shelved for the winter months until its warm enough to start building again. For now, I'll start catching everyone up on my progress from last year, and then I'll start putting some real time updates come spring time.

    After taking an acoustic building course in late 2018, I started prepping my shop with some of the jigs and molds I'd need to make a go of this on my own. It took me till about July to get going on an actual build.

    I'm undecided as to whether this will be for me, or if this will be the first build I actually try sell. Depends on the finished product. To play it safe and try make something that could attract a buyer I decided to go with a classic - a Martin D-18 style build.

    I bought plans for a D-28 as a general building guideline for a dreadnought but I decided against rosewood (thanks CITES!) and even mahogany was a bit pricier than I'd hoped, so I settled on sapele back and sides, with a sitka spruce top. Neck wood is somewhat up in the air. Sapele would be the obvious choice but its generally heavier than mahogany and I don't want this to be neck heavy. I may spring for mahogany for the neck instead. Fretboard, bridge and headstock plate will all be ebony.

    First step was to joint the pieces of my back and soundboard and get them glued up. Here's the pieces, joined, glued and ready to go.

    20190713_083303(0).jpg

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  2. terryward

    terryward Well-Known Member

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    Next up was side bending. This was an ordeal. I whipped up my own bending jig, and experimented with both light bulbs and silicone heat blankets. My preference was to use light bulbs, after some bad times with a Chinese heat blanket involving toxic smoke and too high temperatures. It was user error more than product failure though, and the seller was kind enough to front me a replacement blanket. That turned out to be necessary.

    After doing a few practice pieces to break in my light bulb driven bender, I steeled my nerves and set about bending the good wood.

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  3. terryward

    terryward Well-Known Member

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    After letting the bender warm up for a good 20 minutes or more, the first side went in, and all went smoothly. After about 15 minutes in the bender, it came out beautifully, and went into the mold to cool off.

    While prepping the second side, I heard a sudden pop, and looked to see what happened. Lights off in the bender. Checked the breaker box, all good, then noticed the breaker on my power bar tripped. I unplugged the bender, reset the breaker on the power bar, plugged it back in - instantly the breaker trips again.

    Unplug it and do some investigating. This seems to be the problem:

    20190712_175049.jpg

    Rookie mistake, and I know better than this. I put the wiring for my light bulbs inside the bender, underneath the bulb sockets. Bravo! Seems like an obvious design flaw in hind sight. Lucky for me I wasn't in contact with the bender when it shorted out.

    Did I mention my second side has already been sprayed with water, sealed in foil, and curling up like a potato chip?
     

  4. terryward

    terryward Well-Known Member

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    Chaos ensued at this point, and I didn't stop to take any pictures throughout this debacle. I was too busy trying to salvage my second side and get it bent somehow.

    I had no choice but to fall back on my replacement silicone heating blanket. This is a fine way to bend sides normally , but my particular blanket had a heat range of - 20 degrees from the target temperature. That is, if I set it to 120 degrees (Celsius that is), it heats to 120, but falls back to 100 before kicking back on and heating to 100. Not ideal. You need more consistent temperature than that.

    Having no choice I throw the heat blanket in and hope for the best.

    20190712_163625.jpg
     
  5. jam

    jam Well-Known Member

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    I love this! Thank you for showing us the steps. I'm just as keen on the jigs and tools as the guitar (maybe more!).
     
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  6. OMB

    OMB Well-Known Member Supporting Member+

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    Dreamers...gotta keep on Dreamin'!
     
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  7. redman

    redman Well-Known Member Supporting Member+

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    That's great I would love to try my hand at building an acoustic I've built a few electrics from kits but that's it. I have sanded a lot of nuts and saddles on acoustics for people over the years but no structural work. I am however definitely a luthier fanboy I admire you guys that build instruments from the ground up. Many moons ago when I was in my early 20's I worked at a local music store called Dunhams Music House I was an electronics tech and a dude named Randy Hughes was our guitar tech he later opened his own shop and now his son and him work together and they build some really nice guitars.
    His web site is ***here***
     
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  8. MichaelR

    MichaelR Well-Known Member Supporting Member

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    This is great, Ill be watching this thread.
     
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  9. terryward

    terryward Well-Known Member

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    Swamped with work today and tomorrow, but more to come soon!
     
  10. terryward

    terryward Well-Known Member

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    So after struggling with the wide temperature range on the heating blanket, I managed to get the other side bent. Coming out of the bender though, there was a lot more spring back than there was with the first side.

    Hoping for the best, I started clamping the second side into the form. As I tightened the clamps into the upper bout curves, I heard a sickening cracking sound. My heart sunk, but I had to let it be and leave it clamped up over night.

    The next day I unclamped the sides, only to find this.

    20190713_084323.jpg
    Ugh. Not that you can tell, but on the bright side, this crack coincides with the location of the binding between the sides and the sound board. Not enough to completely remove the crack, but it will minimize it.

    It also isn't cracked all the way through, just on the outside. I decided to brush glue into the crack and clamp it.

    In hindsight I should have waited on the glue and clamp. It worked, but I still had to deal with the spring back in this side.

    I fiddled with the control box on the heating blanket, and managed to get the temperature range down to 3 degrees. With that, I put the side back into the bender.

    Success, but the heat obviously softened the glue and reopened the crack, which I expected. Shoulda rebent, then glued and clamped.

    In the end, I cleaned the crack up a bit, injected CA glue in there this time, and reclamped. That seems to have done the trick.

    After trimming off the excess from the sides, here's what I had.

    20190713_083350.jpg
     
  11. terryward

    terryward Well-Known Member

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    After that initial bit of drama, things went fairly smoothly. Here the sound hole has been cut, and the rosette installed. For the rosette, I used the off cuts of sapele from the back, joined them together, and cut a circle with my circle cutting jig. I also added some BWB purfling rings as well.

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  12. terryward

    terryward Well-Known Member

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    Here I've added heel and toe blocks to complete the rim.

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  13. terryward

    terryward Well-Known Member

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    Here's the soundboard cut to rough shape, resting on the rim.

    20190801_123606.jpg
     
  14. uwmcscott

    uwmcscott AGF Survivor Champ

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    I am always amazed at the level of patience and craftsmanship that a project like this entails. I am skilled in mechanical and logic/technical areas but am not sure I have the patience required to complete this kind of endeavor, although as I get older that is improving somewhat.

    I would imagine that playing a guitar you know inside and out is very satisfying on a whole different level, thanks so much for documenting the process.
     
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  15. terryward

    terryward Well-Known Member

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    At this point it was time to start on bracing. I'm using a homemade go bar clamping deck with DIY go bars made from fiberglass driveway markers and bolt thread covers. The deck itself is made from 3/4" scrap plywood and MDF and some 1/2" threaded rod. I can take down the deck for storage, and adjust the height as needed for whatever I'm trying to clamp.

    The x braces and upper transverse braces were pre-radiused using a 25 foot sanding dish. You can radius the tone bars too, but I chose not to.

    I'm also using the 25 foot radius dish to clamp the soundboard down against to achieve, you guessed it, a 25 foot radius on the soundboard.

    Here I'm installing the x braces and transverse brace.

    20190808_101652.jpg

    Followed by the tone bars.

    20190808_125827.jpg

    Here I'm clamping the upper bout webbing strip and the bridge plate. For the bridge plate I'm using a custom made radiused clamping caul for this specific bridge plate. It will come in handy again later when I install the bridge. I've already installed the finger braces at this point too.

    20190808_193605.jpg
     
    Last edited: Feb 1, 2020
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  16. terryward

    terryward Well-Known Member

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    Here's the fully braced soundboard, ready for carving. I've added the final "popsicle stick" braces around the sound hole for support, as well.

    You might also notice the cleats running down the center joint. The instructor at the course I took suggested doing this, as in his experience, a soundboard is most likely to split within a few grain lines of the joint, not on the joint itself. This is cheap insurance, so I'm carrying on his tradition.

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  17. nomadh

    nomadh Well-Known Member

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    Very cool. Thanks for posting. Both my kids went to a hs that has an acoustic guitar making class sponsored by taylor with wood supplied free. Good pr for them and they're local so they hire some of the kids.
    Neither of my kids took the class.
    I dont want to talk about it anymore or I'll need to go over and kick them.
     
  18. idiotsdelight

    idiotsdelight Well-Known Member

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    I was reading the posts with glee, having a question for when you got to the bracing. You're already there, but i'll wait until I see the (kerfing) steps I'm inquiring about.

    Thanks for the thread terry! This is a nice change.
     
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  19. terryward

    terryward Well-Known Member

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    Speaking of kerfing...

    Here's the kerfing going onto the soundboard side of the rim. D'ya think maybe I could have squeezed some more clamps in?

    For spreader clamps to hold the rim into the mold, I'm just using turnbuckles and some DIY MDF cauls. Cheap and effective.

    20190816_115216(0).jpg

    Its probably worth mentioning, I'm obviously skipping through a fair amount of work in relatively few pictures. I wasn't really trying to document the process in detail at the time, just snapping a few pics as I went. I'll try get a little more detail when I pick the build up again.
     
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  20. terryward

    terryward Well-Known Member

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    Kerfing complete. The next step, not shown, is the radiusing of this side of the rim, to prepare it for the soundboard.
    Just imagine a heavy, two handed sanding block, and two hours of boredom.

    20190816_163601.jpg
     

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