Who doesn´t do anything can´t do any mistakes, right? 🙂
First mistake on the prototype I should mention: For design purposes I decided to use a layered stack of colord veneer wood under the indian rosewood headplat on the headstock as you can see on this picture.
Doing this is quite straight forward. You glue the first sheet of veneer on the bare cedar headstock top (before cutting the tuner slots that is, so very early in the building phase of the neck), and immediately after the second (as many as your design requires) and finally you cover the with a thin plate of wood, typically the same wood you used for the back and sides. So far so good. Then you align things, and clamp it all down to let it dry.
To be really cool, my top rosewood plank of wood is not plain rosewood, but I decided to inlay a leftover purfling stripe of wood (the same I used to seperate the “2 halves of the back”. Nothing wrong so far.
What I didn´t realize or should I say what I didn´t think was important (even so John Bogdanovich mentions it clearly on his dvd like in his book) is that these veneers like the top plate have a tendency to skew or slide around once you put clamp pressure on the stack. This due to the glue in between. To avoid this John recommends to drill tiny holes in the area where the tuning slots go later, and to use locating pins to anchor everything so that it cannot slide on you. Well, I didn´t do that….
The sliding movement is minimal, and since your veneers and top plate are still a bit oversized in all directions at that time, you don´t even notice since the cedar headstock is still covered all around…. It´s when everything is glued tight and you remove the clamps that you get that impression that something is not quite right… 🙂 and indeed, the sliding becomes really noticable because of the center purfling stipe, which ends up not being straight anymore 🙂
You may be able to see that on these 2 pictures:
Ok, its not dramatical, but not perfect either. Next time I´ll use location pins or sure 🙂
Second mistake happened on the blanko (my 2nd build):
For playability reasons and more precisely to achieve optimal string action without jeopardizing saddle hight during the fine setup of the instrument you want the strings to have a given hight where they will reach the saddle, by keeping a correct action all over the fretboard. To do that I built myself a solera which incorporats a minimal neck angle. Since the guitar is assembled on the solera, once you glue the back on the otherwise assembled instrument, that neck angle gets locked in, and everything from there on should be ready and aligned. As a last step you glue your properly thicknessed fretboard on the neck, and if all is correct, it all ligns up. Since strings under tension form a straight lign from nut to saddle, the saddle (inserted in the bridge slot) needs to be at about 8 mm above the height of the fretboard at the 12th fret. (This will give you an average string action of about 4 mm above that same 12th fret, which is what you want before doing fine setup and nut like saddle intonation work).
So far so good. Did I mention that I dome my tops to a 25´´ radius? Well if not, that´s what I do. it adds further stiffness to the top thus allows me to keep top thickness to a minimum which helps the sound quality and responsiveness… bla bla bla. off topic.
Important: the doming will reduce the hight of the lower bout of the top by about 4 mm, which is what I want in order to make sure that the bridge (given its own height) will sit at the right height, so that by adding the saddle, and having it still about 3mm over the bridge I achieve that height of about 8 mm I mentioned before. So, to make sure the top will be curved down towards 4 mm at a continous 25´´ radius, I sand the sides at the tailblock (back end of the guitar) 4 mm down, and gradually continue this sanding until I reach 0 at the area of the sandhole level.
It might sound complicated but is actually pretty straight forward once you do it. So where did I do something wrong?
Hmmm I said “sand down the sides for about 4 mm. Since the goal is to have to top curved downwards in the direction of the back of the guitar, that means that you need to be removing wood from that side of the “sides” where the top will be glued on 🙂 If you are in a rush and remove wood from the opposite side, well then you´re screwed 🙂 hence need to repeat the process on the other side as well.
Result: in stead of reducing the overall height of your guitar body at the back by 4 mm, well, you end up reducing it by twice that much. So the blanko model turned out with a thinner guitar body depth than initially planned. Since we´re talking half a cm you can´t go without noticing. However this unwanted design change also has an impact on the sound of the guitar since the reduced body depth reduces the amount of air volume in the guitar (smaller overall body size), which has a notable impact on overall bass response (whith, all other things remaining equal it will have less bass than it could have).
You should be able to appreciate her overly thin waistline here:
However since I did not want to run that risk I decided to slightly change the design of the top (which wasn´t glued on at the time and was barely finished, and luckily even so the rosette was installed I had not yet cut out the soundhole yet). My opportunity to see whether I had properly understood Ervin Somogyi´s explanations on the Helmholz resonance theory and its application to modern guitar design, like the air-cavity response etc. My decision: make the soundhole a little smaller than originally planned, and try pushing the monopole mode by losening up the stiffness of the top at and around the lower bout. So I did remove some material from the fan braces at the very low end, and thinned the top more where it would eventually be glued to the sides at that same lower bout.
Why? A smaller soundhole will increase the potential of bass response, and a more predominant monopole mode will favor low frequency vibrations, which again are the basses.
End result of all this: She sounds really really well, and I don´t miss anything in the bass area either. Deep and woody as I love them. But this proved something else: I really think I understand what I´m doing, and Ervin´s book is an absolut must have, unless you have the luxury to learn by doing, something I don´t really possess since my luthier carrer (so to speak) starts at 45. So I´m sort of missing the 20 years to learn from my own mistakes period:) Unless all this is nonsense, and she would have sounded the same without any of my changes 🙂 guess I will never know 🙂 sometimes you have to be a believer 🙂
Wanna hear about a 3rd (and really silly mistake)?
I´ll tell you anyhow :). Same guitar -the blanko- different day. Things came to an end and I was in a hurry since I had planned to bring the ´playable´ instrument to a jamming session at Mike´s that upcoming Saturday. However, I still had to glue the fingerboard on and the bridge, and do the fretting work etc. Given the expected glue time for he fretboard and bridge, and given that I had not cut the fret slots to the target scalelength yet I was a day short…. It was late night already, and all of a sudden I had that terrific idea: what about chaning the order of things around a little…. since the bridge was done, I could still glue that on before going to bed, and it would have time enough to dry while I would be finishig the fretboard slotting, and glue that on the following evening…. (normally you glue the fretboard on first and then the bridge, but there was no way I would finish the slotting that same night).
Quickly said, quickly done. Put my nut placeholder in its position, took my 640 scalelength measure (its a piece of wood which has the shape of the fretboard, but extends all the way to 640 mm, so that it buts staight up and against the saddle that you stick into the bridge slot for the operation. It´s a foolproof way to make sure the saddle is located at the exact and precise distance from the nut given the targeted scalelength. Align everthing, and lock the bridge position in place by surrounding it tightly with sticky tape. That way you can simply remove it and put it back at the exact measured location once the glue is on. Then remove everything, but glue under the bridge take my shopfox (special bridge gluing device -> have a look at the equipment section to see what it´s like), clamp it down through the soundhole…. and …. go to sleep (with a good consdcience still)
The surprise (as often) comes the next morning once you remove the clamps and inspect your work. First however I finished slotting the fretboard and make it ready to be glued onto the neck. The nut placeholder goes first (don´t forget it), put glue under the fretboard lay it on the neck, but it up against the nut (make sure you don´t glue it against the nut because of glue squeeze-out once you start clamping the fretboard to the neck. To avoid that it´s generally a good idea to remove the nut immediately once the fretboard is locked into position. Since the neck at this stage is wider than the fretboard you have room to adjust it sideways to align it properly in line with the bridge and the soundhole. (The idea is for it to be straight and centrally aligned to the middle of the soundhole where they meet. A small offset, be it only 2 mm can be seen on the finished product an will look strange. So I made sure to avoid that. So far so good…. if it weren´t for the bridge that was alreadz glued on and locked in position, so no opportunity to ´also´ adjust its position sideways to keep it perfectly aligned with the fretboard, itself aligned to the center of the soundhole.
Shit…. the bridge as it turned out was off to the bass side of about 4 mm. Something I did´t see the previous night since the bridge locating template or ruler (since its 640mm) hides the soundhole, and I mistakingly thought that everything must be lined-up. Since the neck itself was just a little off, putting the template centered on the neck was a mistake. It is usually not a problem to have the neck a little misaligned since it is larger than the fretboard and you cut it level and flush to the fretboard when all is done. (the final neck shaping is really the last step in the building process). What escaped my attention was the fact that a very tiny misalignment at position 0 can quickly turn out to become 3 to 4 mm 640 down at the other end….
So…. what to do now? Since there was glue in place I didn´t have long to think before the glue would settle in and I wouldn´t be able to any adjustments on the final fretboard position anymore. (One of these stressy moments where you got the time against you 🙂 ) So I decided to cut the damage in half, remove clamp pressure a little and push she fretboard slightly in the direction of the bass-side of the guitar. That would align it half-way to the bridge position, and not decentralize it too much from the center of the soundhole. Clamps back in place…. hope and wait LOL
But, I was still in time for the Saturday night jam session over at Mike´s place.
Then, (8 hours later… would usually leave the fingerboard due to the large gluing surface overnight) but…. 8 hours had to be enough this time around.
Off go the clamps and…. well, only a little misaligned from the soundhole, and since the bridge is too far away to tell, I was confident. It´s hard to tell because its the bridge string holes that need to be aligned to the fretboard, and not necessarily the outer dimensions of the bridge itself.
So, I put the frets on, roughly smoothed them out on the sides and put the strings on. (All of this takes about 2-3 hours max). Unfortunately it was really with the strings on that I noticed my misfortune. A picture says more than a thousand words:
2 mm off center so that the bass string ´falls off´ the edge, and far too much room on first string.
What to do…. in the end (no more stress since I knew this was pretty bad, and that I would miss the jam session…. poor Mike 🙂 Only one solution seemed possible. Remove the bridge and relocate it where it should have been from the beginning….
Now I know why everybody and everything I have ever read or heard about this, well they all tell you to glue the fretboard on BEFORE the bridge. Too late now…
So, next question: how remove a tightly glued bridge from a thin and fragile spruce top? Guess nore John nor Ervin talk about this since they probably couldn´t imagine that somebody would be stupid enough to to what I did 🙂 So… it was googeling time. And there are quite some videos out there where people show you how to do it. The trick is: patience, enough heat, but not too much since you don´t want to loosen the braces under the bridge inside the box, a very thin spatula, and more patience…
This is what it looks like:
My bending iron upside down on the bridge to heat the glue-join (later I switched to a hair-drier) and after about 40 minutes, off it came, and to my surprise with out any damage to the spruce. (guess my patience and overly carefullness paied out this time)
And here the result. The rest is straight forward. reuse my bridge locating device (on top of the fretboard this time) reposition the bridge at the correct lateral position this time, and glue her back on.
Even so I was sure all would be ok, I can´t hide the relief I felt after restringing her the next day noticing that everything was nicely lined-up this time around. Well almost, remember my decision to cut the damage in half by disaligning the freboard about 2 mm from the center of the soundhole…. that misalignment remains, which, down the whole scalelength results in an off-center location of the bridge of about 3,5 mm towards the bass side.
However, this time around it remains purely esthetics, and if you haven´t tead the above, chances are you won´t notice at all.
There were a couple smaller errors that I was able to fix easily and aren´t worth my time documenting them or your time reading about them.
So what do we retain from all of this?
- Concentrate and don´t rush
- Fixing a mistake is risky at times, and will take 10 times longer than doing it right the first time around
- If you buy expensive books and dvds that recommend certains things, FOLLOW them and don´t take shortcuts when you´re lacking the experience to know better
- On the other hand fixing mistakes can be interesting and challenging, and they force you to think out of the box. No book to help, you have to come up with your own solutions….(even though google can help with the ´how´ once you have made up your mind about the ´what´.
- They are stressful moments. If you notice your mistkaes late, you could risk to ruin all the work, which can be anything between 10 and 100 hours wasted work.
- They are overly frustrating
And most importantly: They are usually silly because I could have avoided them all if I hadn´t decided to rush things and if I had followed the information I had available in due time.
This being said, luthery is also about repairing guitars, and I guess this was my first step in that direction as well. So no regrets. You always learn something you will eventually reuse sooner or later. The price that comes with experience I guess 🙂
The good news before closing this chapter: Even me, with my little practical experience have been able to fix any of the issues or mistakes that have come up so far. In other words: A guitar is made out of wood, and many things can indeed be fixed, and really dramatic end final mistakes should really be very rare and unfortunate events. Up to now….. let´s touch wood 🙂
There you go, un homme averti en vaut deux 🙂 as they say in french.