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LMII Acoustic Steel String Build

Discussion in 'Acoustic Heaven' started by pypa, Apr 21, 2021.

  1. guitarbuilder

    guitarbuilder Telefied Ad Free Member

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    Consider how long that flat top guitars have been around vs domed tops. Not that there's anything probably wrong with domed tops, but the longevity of flat tops proves that there isn't really a need for a domed top if you ask me.


    True, domes are stronger than non- domes according to the Romans or Greeks, whoever came up with it first, but the flat top does become a dome under string tension. Put a straight edge on your flat top tuned to pitch.

    I've been experimenting with neck angles via the mortise and tenon joints of my last 3 guitars. My angle is hovering around .5 degree for a flat top. The fretboard then falls away from that pivot point without having to sand in fall away. 2 degrees is what Gibson calls for for a bridge that is 5/8" high. Perhaps a dome calls for that. I don't know.


    For a newbie builder, I'd just be aiming for a guitar that looks, plays, and sounds nice.

    Those are my goals for number 14 because it's like starting over only doing one every couple of years. :)
     
    Last edited: Apr 24, 2021
  2. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    Pypa, you will learn that there are many ways to build an acoustic guitar and good reasons for all of them. I will tell you what I do and why, but feel free to do as you want. I told you about the "bible" for acoustic guitars builders (and told you that most of us don't do what they describe) and I suggested you get a copy of Cumpiano and Natelson for reference. They discuss domed tops and describe how they build the traditional domed solera for their Spanish style construction. Another way to skin the cat.

    I'm going to make another humble suggestion before you go too much farther. Get ahold of a nice fairly new acoustic guitar that you think plays well. Measure everything about it - lay a straightedge across the lower bout behind the bridge and see if there is a gap at the rim. Measure the neck angle, height of the bridge and saddle, look at what the upper bout is doing with respect to the neck. Measure the back in every direction you can think of. Measure the action parameters so you know what you think feels and plays good.

    You mentioned your plans don't show any dome. I told you that the Antes plans often come under criticism and that we could discuss these things as you progress. Many people feel his top braces are too stiff and that there should be an arch to them. The tone bar is shown bass-ackwards and depending on the scale you have chosen you might need to move the braces a tad.
     
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  3. pypa

    pypa Tele-Meister Ad Free Member

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    I'll revert when I get a little more accomplished. I think I'm giving the impression that I'm not reading or noting all of your advice. I think I'm just asking my question the wrong way. Regardless, I have the answer I need: reference to the top. The arch of the top does not scare me. Even though the plans show it without, I will likely do it with. Thank you everyone!
     
  4. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    I took a couple of pictures of my little parlor. This was built in 2015 from the Antes plans - I play it a lot. It has a sponge/baggie in its case and is well humidified. Here is the top

    IMG_6691.JPG

    IMG_6692.JPG

    and back

    IMG_6694.JPG

    IMG_6693.JPG

    The neck angle is right at 2 degrees (protractor reads 88, just the way I zeroed it)

    IMG_6697.JPG


    and the fret plane just hits the top of the bridge

    IMG_6696.JPG

    Action is my normal medium low fingerstyle action.

    One more thing to remember about the top - when you put 150 pounds of string tension on your 24.5 scale you are going to get both shear and rotation at the bridge. The rotation wants to pull up the lower bout and push down the area between the bridge and the sound hole. That in itself will provide a little bit of a dome - the braces are there to control it.
     
  5. pypa

    pypa Tele-Meister Ad Free Member

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    A67C1CEC-D8E7-40A8-A013-8AD8562B1A2C.jpeg I have sanded the end and heel blocks to match the form, and am ready to glue up.

    I realize that the vertical positioning of the blocks is already determined for me because my sides are already tapered. I am setting it in the form with the flat side down, so the taper is on the up (back) side.

    I will cut the heel joinery after glue up. I am undecided between a straight m and t or dovetail.
     
    Last edited: Apr 25, 2021
  6. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    The tapered angled dovetail is an elegant joint and if you have the tooling and understanding it is a great way to join the neck. The bolted M&T joint is simple and works very well, takes a lot less tooling to make and is infinitely easier to adjust ("set"). I struggled with dovetails on my first couple of guitars, got them to work but changed to M&T on following guitars unless I can't get into the body to install the bolts (for example an archtop).

    John Hall at Blues Creek guitars did one of the best videos on not only how to make a dovetail but exactly why you do it the way you do - it was only after seeing that I felt I understood the actions involved. I have a few pictures of mine by I won't be posting them because I don't feel I'm very good at this.
     
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  7. printer2

    printer2 Poster Extraordinaire

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    Now to complicate things, I would advise you to do the 28 foot radius on the top, more or less. It is something that is worthwhile to protect for humidity changes. As said, it is more something that effects the with of the guitar than the length. As far as where the center of the dish should be when putting a radius in the sides, it does not matter. You are going to sand the arc in with the neck and end blocks being the points that the arc is referenced to. As long as they are sanded down to the right point the rest of the sides will get the arch.

    But there is a but. But you do not want to put an arch into the block where the fretboard sits. You want it flat otherwise you will have a gap underneath the fretboard. Some people leave the whole upper bout flat above the sound hole. I keep the area under it flat and put a bit of arc in. I do this by sanding the sides on the dish except where the fretboard is by having the neck block overhang the sandpaper on the dish. I am assuming you will be radiusing your braces on the dish and gluing them onto the top while in the dish also. The cross brace above the sound hole will have a radius to it except where the fretboard goes. That is it for words of wisdom for now. It just makes life a little easier.
     
  8. pypa

    pypa Tele-Meister Ad Free Member

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    Thank you Printer; I missed your post. I am confused by the caveat not to radius the upper block. I have not heard that warning before. In fact since the fretboard runs along the top to the hole, shouldn’t that whole surface be flat? That is, does anyone radius the top and then flatten the upper bout above the sound hole?

    I received my radius dishes today. I am reluctant to just stick paper to them because it will be hard to remove it. I am shellacking the surfaces. Is that what you guys do?

    also I see a lot of experienced folk build a jog and use the disc on top of the guitar instead of placing the guitar on top of the discs.

    I had the idea of gluing the 2 discs back to back in order to make them more rigid if I do the disc-on-top model. How do you guys do it?
     
  9. printer2

    printer2 Poster Extraordinaire

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    Sorry, did not mean to confuse the issue. What I meant was that the portion where the fretboard runs is to be flat rather than arched. From the edge of the guitar at the neck joint to the sound hole you can lay a straight edge on the top and it will be flat. You do not want to put a radius underneath the fretboard. Just wanted to say some glue up the top with the radius even everywhere, some flatten the soundboard in the upper bout lengthwise.

    I am not too sure of gluing them back to back, I would almost get a piece of MDF and glue it to either back. Sure, coming from the guy who routed out his own dishes and the 15' one is getting a little thin in the middle. I just do not abuse them too much and put them away when done. I clamp the sheets to the top, I do not like the idea of gluing onto them, but mine are still raw and not coated.
     
    Last edited: May 3, 2021
  10. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    As far as sandpaper and the dishes, I just hold a piece of 8x10 against the dish and sand against that. Once the kerfing is on the sides the rim can be removed from the mold and it will pretty well hold its shape while you sand (be careful). Your mold is much smaller than mine, you might be able to leave it in.

    IMG_4918.JPG

    I simply flatten the top where the fretboard extension rests to be the same plane as the top of the neck. I set the neck and then lightly sand the top where the extension goes. My top is domed, it just this area is slightly flattend.

    IMG_5017.JPG

    Ideally the top just continues the neck plane with neither a drop off or a ski jump. If you have to have one or the other, fall off is better.
     
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  11. printer2

    printer2 Poster Extraordinaire

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    Said much better than me by Freeman. Just wanted it not to be an issue later saying, "I should have done this."

    I was following the instructions in a book on how to disassemble a 1911 handgun. It said to ".....", I did "..." and the small spring jumps out onto the carpet. The next sentence in the instructions is, "Be careful as the spring can jump out and go flying."
     
  12. pypa

    pypa Tele-Meister Ad Free Member

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    My blocks are too tall. I need to bring the top one down about 3/4” and the bottom about 3/16”.

    I probably should have done this beforehand. I don’t have a choice but to grind this down. I can’t get a saw in there and am afraid to chop it down with a chisel.

    79BB9A52-5143-4AE5-A04E-066AE4720AEA.jpeg
     
  13. pypa

    pypa Tele-Meister Ad Free Member

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    Duplicate post
     
  14. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    Have you decided on the neck joint you will be using? Are you using a pre-routed block or do you plan to route the mortise after the body is closed up (both methods are valid).

    If you find 1bad914's first build thread he closed the box and then routed the dovetail pocket using a fairly fancy jig. The few times I've done dovetails I bought pre-routed neck blocks and made necks to fit them. If I'm doing a bolt on neck I buy the LMII block and fit the neck.

    The reason I ask is that you need to consider where the bottom of the mortise will be - how close to the back of the guitar. That will determine how much you need to cut off. If you plan to route after assembly it doesn't matter.
     
  15. pypa

    pypa Tele-Meister Ad Free Member

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    Thanks, Freeman. My blocks are glued on already. I will cut the mortise after assembly.

    I was thinking to do a mortise and tenon with LMI bolts. I think all of this can be cut and installed after assembly.

    I got Cumpiano's book ($9 on ebay ;) I have some reading to do.
     
  16. pypa

    pypa Tele-Meister Ad Free Member

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    A736959E-35BE-40AC-8C98-AB8F47A882D1.jpeg I was able to hack down the blocks. Next time I would cut them closer to final height before gluing in.

    I mounted a dowel in a dog hole in my bench and centered and clamped the form about this dowel. The disc will ride on this dowel.

    I have quite a bit of the sides to take down. I am using a plane but checking progress with the disc.

    6335168D-2654-46DF-9066-70A27A98810D.jpeg 24FEE43B-8506-4968-B7E0-081D64ADA1DE.jpeg
     
  17. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    All of the guitars that I have built with bolted on necks I used LMII's premade neck blocks - they have the two bolt holes and the truss rod hole drilled and the mortise routed. No reason not to do it with the block in the guitar as you are doing. I make the tenon on the band saw to fit the mortise - there are pictures of that in the build threads that I've given you.

    On all my bolted necks so far I have used the LMII inserts screwed into the end grain of the neck. It scares the heck out of me, but has never split (knock wood).

    IMG_1030.JPG

    IMG_1031.JPG

    IMG_1035.JPG


    The last picture shows the neck bolted in place and I'm checking to make sure I can access the truss rod adjuster thru the sound hole.

    Dave Higham uses a type of toggle bolt in his necks - I might consider that next time.

    https://www.tdpri.com/threads/how-to-fit-threaded-inserts.1070269/#post-10638410
     
  18. pypa

    pypa Tele-Meister Ad Free Member

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    Thanks.

    I brought the back down to radius.

    The dowel jig works very well. Also adhering 9x11 80 grit sheets to the disc worked without issue too. Way more economical than getting the larger sheets. 5 sheets did this disc.

    I’ve been chalking, sanding a bit to find the high spots, then planing them. It has been fun work. But I have to police myself to go slow and check progress often with the level.

    Next time I will spend a lot more time prepping the end blocks. Thank goodness they are pretty soft, but it’s a relatively lot of material to sand down. I will certainly pre cut them close to height and profile if I do this again. There is still a little bit more to go.

    I've been reading the Cumpiano book. From that and all the comments I wonder if the dishes (especially the top) would be better off as a caternary curve instead of a circle radius. The caternary is flatter at its ends, and also a more natural bend for wood. It would result in marginally less tension vis a vis a circle radius where the top meets the sides. Also, it would create a flatter surface above the rosette for the neck to lay upon.

    99CA9C4C-2C81-4302-8392-FC2405800274.jpeg D775F2F8-C159-4F6F-9D26-862348DFDF61.jpeg

    0E5BF104-7399-4553-8952-4225AE0FCC9E.jpeg 2FC8E774-90E1-4A9A-ABD5-6CB1479D7643.jpeg

    B2F28D12-8C61-4E5B-AFCB-B22349C988BA.jpeg
     
    Last edited: May 5, 2021
  19. trapdoor2

    trapdoor2 Friend of Leo's Gold Supporter

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    Catenary curves...these are fun "thought exercises" but they are often difficult to implement and/or provide marginal change. A catenary would be a complex 3D surface, like an archtop.

    Back when I was 14, I was flying R/C sailplanes in local competition. I had a flying buddy who's Dad was a NASA meteorologist. We were always designing "the best" sailplanes. His dad hit on caternaries for the wing's dihedral. The jig took a month to build...and the wing was beautiful. It flew like a pig.
     
  20. pypa

    pypa Tele-Meister Ad Free Member

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    No, in fact caternaries are sometimes easier to produce. When I make furniture I do curves often by pinning the ends of a flexible stick and pushing in on the center to the apex of the curve.

    a router sled to produce the dish would be just as easy to make as a circle radius. I don’t mean to throw out high falutin terms. It is genuinely an easier curve to construct.

    As an aside, these curves usually look better and more natural than try circle arcs.
     
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