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  #46  
Old 08-03-2016, 04:04 PM
dekutree64 dekutree64 is offline
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Originally Posted by emmsone View Post
I'd also like to find a way to 'reference' the tap-tone of my soundboard just before its glued in (other than using memory) so when my next build comes along i'll have a point to work from as I don't have any point of reference for this one, its just hoping the bracing and soundboard thickness dimensions given in the plans work out good.
Any ideas how I can do this without investing xxx thousands of dollars of sound analysis equipment? would an iPhone recording be good enough? i'd say no, but its my only idea right now.
iPhone recording is certainly better than nothing. Should be enough to get a frequency plot in Audacity, and a general idea of what it sounds like.

But even more than the tap tone, flex it with your hands and memorize the feel of the stiffness. Thumbs on braces so you don't risk splitting it or popping brace joints. The total stiffness of the braced soundboard is one of the primary differences between a cardboard box and a fine guitar.
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  #47  
Old 08-04-2016, 08:13 AM
emmsone emmsone is offline
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Quote:
Originally Posted by dekutree64 View Post
iPhone recording is certainly better than nothing. Should be enough to get a frequency plot in Audacity, and a general idea of what it sounds like.

But even more than the tap tone, flex it with your hands and memorize the feel of the stiffness. Thumbs on braces so you don't risk splitting it or popping brace joints. The total stiffness of the braced soundboard is one of the primary differences between a cardboard box and a fine guitar.
That makes sense, although I have have no reference of stiffness to go against until i make the next one.


On another point. I have some graphite strengthening rods that I never used in my bass build as I couldn't get the right router bit and decided to go without instead of wait 6 weeks for the bit to arrive.
I might use them on this build now but my next question is, these things seem super strong (which is the whole point of them) but if I put these in, does that mean the truss rod cannot create a neck bow so easily? won't this just create much more pressure on the underside of the fretboard when I turn the truss rod key and make it likely the fretboard could pop off? or will the graphite bend, just not very much?
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  #48  
Old 08-04-2016, 08:46 AM
dekutree64 dekutree64 is offline
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Originally Posted by emmsone View Post
That makes sense, although I have have no reference of stiffness to go against until i make the next one.
Yeah, that's the unfortunate part. Best I can tell you is that if it feels stiff as a board, then keep carving The tone bars and lower X ends can be carved down to zero at the perimeter. Unless you're building with an exceptionally thin soundboard, the plate stiffness alone is plenty for the perimeter. Connecting braces in there is an effective way to raise the resonant frequency, which is often a good thing for the back but not the soundboard.

Quote:
On another point. I have some graphite strengthening rods that I never used in my bass build as I couldn't get the right router bit and decided to go without instead of wait 6 weeks for the bit to arrive.
I might use them on this build now but my next question is, these things seem super strong (which is the whole point of them) but if I put these in, does that mean the truss rod cannot create a neck bow so easily? won't this just create much more pressure on the underside of the fretboard when I turn the truss rod key and make it likely the fretboard could pop off? or will the graphite bend, just not very much?
It's mostly a non-issue. The truss rod does have to work harder to bend a reinforced neck, but so do the strings, so the truss rod pressure should be more or less the same as usual.

But if you're wanting to use the permanent pinned M&T joint that Kostal uses (which he learned from Somogyi), the carbon rods aren't necessary. As long as the neck is made from good straight grained wood, it should last indefinitely. The soundbox is what you have to worry about. As an integral neck builder, I've done a lot of pondering on it, and wrote a spiel about it here a while back (DennisK is me) http://www.luthiersforum.com/forum/v...=10101&t=47103
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  #49  
Old 08-04-2016, 09:43 AM
emmsone emmsone is offline
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Originally Posted by dekutree64 View Post
Yeah, that's the unfortunate part. Best I can tell you is that if it feels stiff as a board, then keep carving The tone bars and lower X ends can be carved down to zero at the perimeter. Unless you're building with an exceptionally thin soundboard, the plate stiffness alone is plenty for the perimeter. Connecting braces in there is an effective way to raise the resonant frequency, which is often a good thing for the back but not the soundboard.
Ok cool, thats good to know, i'll see where its at when I start working on it again next week.


Quote:
Originally Posted by dekutree64 View Post
But if you're wanting to use the permanent pinned M&T joint that Kostal uses (which he learned from Somogyi), the carbon rods aren't necessary. As long as the neck is made from good straight grained wood, it should last indefinitely. The soundbox is what you have to worry about. As an integral neck builder, I've done a lot of pondering on it, and wrote a spiel about it here a while back (DennisK is me) http://www.luthiersforum.com/forum/v...=10101&t=47103
Well I was going to go for the dovetail option until I read that Kostal thread, I do like that Kostal/Somogyi method, because it means in my case for someone who hasn't done a dovetail before, my neck is much more likely to remain in a straight line!

Actually, some of the earlier posters were not convinced on the straightness of grain in my neck, 1 piece of walnut and the maple centre strip are just about right, but the other piece isn't on the same grain line. I'm kinda thinking its going to be ok, but those who have more knowledge then me seemed to say otherwise. This time round I have access to a table router which will make routing these channels a simpler task and if thats the case I may put the graphite rods in "to be safe". I'll grab another picture of the neck grain on monday.

Thanks again, i'll read that article right now.
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  #50  
Old 08-04-2016, 10:56 AM
dekutree64 dekutree64 is offline
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Yeah, carbon is a good idea if you can't find ideal neck wood.

But if you go out hunting for neck wood again, keep in mind that you only need around 2x6x45cm of perfect grain for the shaft itself. Or actually even just 40cm, since there can be minor flaws in the headstock end. The rest of the heel and headstock can be glued on from lower quality stuff.
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  #51  
Old 08-05-2016, 09:24 PM
LouieAtienza LouieAtienza is offline
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Originally Posted by emmsone View Post
Ok cool, thats good to know, i'll see where its at when I start working on it again next week.




Well I was going to go for the dovetail option until I read that Kostal thread, I do like that Kostal/Somogyi method, because it means in my case for someone who hasn't done a dovetail before, my neck is much more likely to remain in a straight line!

Actually, some of the earlier posters were not convinced on the straightness of grain in my neck, 1 piece of walnut and the maple centre strip are just about right, but the other piece isn't on the same grain line. I'm kinda thinking its going to be ok, but those who have more knowledge then me seemed to say otherwise. This time round I have access to a table router which will make routing these channels a simpler task and if thats the case I may put the graphite rods in "to be safe". I'll grab another picture of the neck grain on monday.

Thanks again, i'll read that article right now.
More so with a dovetail, it takes a "knack" to leave enough to trim while still ensuring a tight fit and ensuring the neck is pointed straight. Otherwise there will be gaps that need to be shimmed. On a mortise joint, the tenon on the neck is made straight relatively easily, then the mortise made straight via a jig, which just leaves trimming the shoulders to the body.
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  #52  
Old 08-10-2016, 08:23 AM
emmsone emmsone is offline
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Managed to get a few more hours work done this morning, this finished the back bracing, pretty much finished the soundboard bracing, I still have not sanded them clean as i may tweak the braces slightly during voicing it when I attach the top to the rim (although the voicing procedure is just going to be complete guesswork so I might just leave it and hope that its good as it is now) and did some sanding work on the edges of the rim and glued the maple bridge plate in.

finished bracing on the back
Untitled by David Emm, on Flickr

closer view of the bracing on the back
Untitled by David Emm, on Flickr

during the bracing triangulation process
Untitled by David Emm, on Flickr

soundboard braces carved after the bridge plate was glued in
Untitled by David Emm, on Flickr

did some "bus driving" in the radius dish to get the back edge of the rim as it needs to be. I did have a clamp in place holding the sides into the spreaders. My mould is too big and too heavy to use that to hold the rim steady while sanding so I had to find an alternative.
There is still a several millimeter gap at the bottom of the curve of the cutaway (the corner right by the neck block) which I forgot to take a picture of. Not sure if I cut the side profile wrong or not, or if this gap will be a problem and I have to sand more off the neck block to get it all 'level' (not level as its in the radius but yea)
Untitled by David Emm, on Flickr
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  #53  
Old 08-16-2016, 06:39 AM
emmsone emmsone is offline
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Finally got back into the workshop yesterday afternoon and this morning and got some good work done.

Sanded a 1 degree (or pretty close) slope on the sides onto the area between where the first horizontal brace is and up to and including the neck block. Chiselled away the the linings to create some pocket cutouts, trimmed the ends of the braces to fit into these pockets, trimmed the edge of the soundboard a bit closer to the outline of the guitar, and finally glued the soundboard to the sides!!!!! and after that cut the neck much closer to the required dimensions. I plan to shape the headstock next time.

just about the only way to show the 1 degree-ish angle i sanded onto the neck block ends of the sides
Untitled by David Emm, on Flickr

A terrible picture but this is one of the pockets i cut into the linings. The linings were from the outside edge of the Walnut piece i cut the neck from. Turns out this wood chips out very easily, i'll have to pay attention when shaping the neck.
Untitled by David Emm, on Flickr

The sides sitting on the the soundboard before the soundboard was trimmed closer and the soundboard was glued on
Untitled by David Emm, on Flickr

I used a 6-8mm thick flexible board under the guitar to give myself something to clamp to when gluing the soundboard on, also added a few extra clamps after this picture was taken
Untitled by David Emm, on Flickr

cut the sides of the neck pretty much to dimensions
Untitled by David Emm, on Flickr
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  #54  
Old 08-16-2016, 09:26 AM
dekutree64 dekutree64 is offline
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Careful there... that bracing still looks like cardboard box territory at the moment. But at the same time it could really use some soundhole braces. Higher up, more stiff. Lower down, less stiff.

As I said before, carve the ends of the lower X legs, tone bars and fingers down to nothing at the perimeter. Tap and listen as you do it. This is one place where having the soundboard glued to the rim is very useful, to hear the effect of perimeter stiffness. Should be more audible if you take some height off the lower X legs first.
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  #55  
Old 08-16-2016, 02:28 PM
emmsone emmsone is offline
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Quote:
Originally Posted by dekutree64 View Post
Careful there... that bracing still looks like cardboard box territory at the moment. But at the same time it could really use some soundhole braces. Higher up, more stiff. Lower down, less stiff.

As I said before, carve the ends of the lower X legs, tone bars and fingers down to nothing at the perimeter. Tap and listen as you do it. This is one place where having the soundboard glued to the rim is very useful, to hear the effect of perimeter stiffness. Should be more audible if you take some height off the lower X legs first.
Thanks dekutree,
Actually this is one reason I glued the soundboard to the rim first so i would have a better idea of what any adjustments actually do, not that i have a clue in a first guitar what adjusting anything gains/loses.

What am I actually listening for? I can hear it makes a tone when I tap it, and it makes different tones when I tap it in a different place, but what tone does it need to be? once i've carved more off the bracing, how do i know if i've gone to far? what are tell-tale signs i've done something right/wrong?

The plans I have don't include soundhole bracing, but i had previously thought maybe i needed some as those areas look mighty empty compared to other guitars. Any suggestions as to what type of soundhole braces I need? similar to the finger braces? or taller like the main ones? Perhaps flat wide ones a la the 'brace' in the upper bout?

thanks

Dave
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  #56  
Old 08-16-2016, 06:37 PM
dekutree64 dekutree64 is offline
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I'd go with about 1cm high, 6-7mm wide, shaped something like this /ŻŻŻŻŻŻŻŻŻ\ and roughly triangular cross section.

"Opening up" is a good term for what you're trying to hear. It really is hard to describe in words.

You never know for sure if you've gone too far structurally until it has strings on it and you can measure the deflection. If it starts sounding flabby or the tap tone duration gets shorter instead of longer as you remove material, then you've probably gone too far tonally.

Another thing I'd recommend is taking a chisel to that bridge plate and tapering out the thickness toward the front and back edges. Looks very large and stiff and heavy for what's needed at this soundboard thickness.

What is the exact soundboard thickness, actually? I'm guesstimating the stiffness from the edges I can see in the photos and the average Young's modulus of spruce. At least a number can take one of those variables out of the equation

Last edited by dekutree64; 08-16-2016 at 11:16 PM.
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  #57  
Old 08-16-2016, 09:28 PM
LouieAtienza LouieAtienza is offline
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Well you're looing pretty darn good so far!

I agree with dekutree64 that you will need soundhole bracing. I prefer the tall and narrow variety to the low and thick. This is one area that will deform under string tension. My thoughts go so far as to postulate that deformation and vibration in that area can be an energy sink.

As to the bracing it's tough to say since we don't know how stiff the bracings were to begin with. There is a fine line between open versus tubby, and full and rich versus thin. You can go too light and lose the bass that so many seek. While I've come up with methods I feel get my bracing stiffness where I want them at different areas of the top, it's not too hard to adjust these after the guitar is built. But what I normally do is notch the X bracing in, and taper the tone bars and finger bracings down to zero.

I would check that angle at the upper bout area, looks more like 4-5degrees to me...
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  #58  
Old 08-17-2016, 05:05 AM
emmsone emmsone is offline
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Default damaged sides :(

Thanks again dekutree and Louie.
Dekutree, my top was thicknessed to 2.8mm, Louie, it looks much more extreme then it actually is, it was hard to get a picture of it to even show the angle, when i'm in close and at an angle it looks extreme, its probably closer to 2 degrees than 1.

I'll likely add some soundhole braces at some point.

HOWEVER

this is now waaaaaaaaay down my priority list as this morning I went to check how well my top got glued on and i found a nice surprise after taking the clamps off, the sides in the waist area have buckled and split. One side has a slight wavyness to it, the other side has a giant lump, corresponding dent next to it and the top of the lump has a crack in it. I have no clue how this happened, I thought I was careful with my clamping pressure, but I can only it was far too much.
I don't know if it can be repaired/fixed/corrected. Its so bad (at least one side) that i have a feeling i may have to remove the top which I guess can be saved, and get some more wood and remake the sides.
If someone knows if its repairable, and can tell me how i can do that, and if its possible to get it looking "normal" or at least close to normal, that would be appreciated. Otherwise it looks like the project might be over as I can't afford to buy more sides and then pay for an extra 20ish hours in the workshop that it took me to get the sides ready the first time round.

Here are some pictures of the damage. This is actually all the worst side as the pictures of the "less bad" side came out too blurry

Untitled by David Emm, on Flickr

Untitled by David Emm, on Flickr

Untitled by David Emm, on Flickr

Untitled by David Emm, on Flickr

Untitled by David Emm, on Flickr
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  #59  
Old 08-17-2016, 08:05 AM
charles Tauber charles Tauber is offline
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emmsone,

Fret not, for it can be repaired. Early in my guitar making, I did something very similar, gluing an ebony back onto its ebony sides, using "the rubber band method", with one-too-many rubber bands. I watched in horror as the sides collapsed. I did repair it and it went on to be a fine instrument.

Having the sides buckle at the waist is the most difficult area to fix, but it is doable. (It should also have been the strongest area.) Generally, what I would do to repair it is to create a second, short, partial side that is glued to the interior of the existing side. It does not have to be the same wood type, but is less obvious if it is. Cut and thickness an oversize piece for each side. Bend it to match the interior of the existing sides, trim it to fit, then glue it to the interior, using appropriate gluing cauls that will both flatten the existing sides and clamp it to the second side. At the same time, apply glue to the crack. Use wax paper, or similar, to ensure you don't glue the cauls to the sides. (This is made much easier if using a traditional outside mold, since you have ready-made exterior cauls.)

It is a bit of work, for sure, but it can be saved. Soldier onwards. It's just a minor setback.
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  #60  
Old 08-17-2016, 09:58 AM
emmsone emmsone is offline
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Thanks Charles,
I'll investigate if i can make something approximating your idea tomorrow. My first thought was to steam it, or heat it in some way with some water to be able to bend/push it back into shape because the lump seems pretty solid right now but obviously this is going to undo the gluing of the linings and the top thats just been glued on so is not really a useable option.

Interestingly I was planning on gluing the side support braces on at this point as I had thought they would be mostly for side rigidity for sound purposes, i didnt realise how structurally handy they could have been had i done that before gluing the top on.

Thanks again

Dave
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