Just closed falcate classical - with tap spectrum

[johnparchem]

I just closed up my first falcate classical guitar. The body is a Hauser 37 shape and depth. Of course modified to be a cut away. I know things change as the guitar is finished with a bridge but I tapped it to see what the top without a bridge is like. It looks sort of wild to me. I see a clear peak at about 87Hz T(1,1)1 the top is at about 187Hz T(1,1)2 and the back was 238Hz T (1,1)3. It looks like the cross dipole was at about 257Hz. I have no idea what the big peak is around 120Hz? Probably something horribly wrong. All though the taps do sound good.

It will be interesting to see the tap after I get a neck and bridge on and string it up.



The Guitar is Lutz spruce with East Indian Rosewood back and sides. The bindings will be Australian Blackwood with bwb purfling (like the back strip). It will have a bolt on, bolt off neck.

[kiwigeo]

Some Chladni testing will help work out what's going on at 120Hz. Do the top and also the back. Nice work by the way.

[johnparchem]

The gain on my mic was cranked too high. there is a new spectrum in the post.

[johnparchem]

I made a bunch of progress on this guitar. I did radius the top rims, but flattened out the upper bout a bit.

The top as a 32' radius, the back has a 10' radius. Although the guitar looks more contemporary all of the final set up will be within the classical guitar range. I put a 20" radius on the fret board. I guess I will make a compensated nut as the nut slot is forward 3 mm.

It is starting to look like a guitar, maybe even a bit more like a classical guitar. Although it is a more contemporary design it still is a classical guitar size and the set up will be within the classical guitar range, for neck thickness, nut width, string spacing and what not.

I am thinking a bit about the final details like adding the closing binding between the neck and the rim and the cutaway. It would provide a clean finish, but it is a bit of a busier look than I really want. I will cut square ramps in the slots as well.

I had a little mishap when routing the extensions truss rod slot so I moved one of the extensions bolts up a bit. Luckily put together nobody notices. I have to say the bolt on bolt off neck for the classical was the hardest thing I have ever done. I am not that good following instructions, but I went back and re read the section over and over again to avoid making mistakes.



All and all it is starting to look like a guitar.

[RobDyball]

I have to say the bolt on bolt off neck for the classical was the hardest thing I have ever done. I am not that good following instructions, but I went back and re read the section over and over again to avoid making mistakes.

How did you go with the tapered neck wedge? That's the only bit that fries my noodle

[johnparchem]

For the neck I followed the lay out in the book for the bolt on bolt off classical. Everything has to work together to get it to come out and it needs to be set before you start. The thickness of the wedge is dependent on angle of the upper bout. The wedge just needs to be tall enough so that the plane of the fret board extends to the right height at the saddle location. The fret board needs to be placed on the neck far enough from the break at the head stock so that an extension of the head stock plane hits the nut position at the height of the wedge. Of course you want the 12 fret to be at the top of the rims. That is why I followed the layout, including the 15 degree head stock angle. The order of the steps are also important to follow. After carving I can not really even see the wedge. I cut a 5mm slice off the same wood I used to make the neck.

Seeing it all in action I could play with my own parameters including changing to a 10 degree head stock. Which would have the fret board start even farther away from where the head stock angle starts.

The individual wood working steps were not the hard to do.

[kiwigeo]

Looking good John.

From the photos the bolt holes in the mortise look a lot bigger than 6mm...what diameter bolts are you using?

[johnparchem]

Looking good John.

From the photos the bolt holes in the mortise look a lot bigger than 6mm...what diameter bolts are you using?

Thanks, They are for 1/4 inch so a bit bigger. I use the brass inserts so I drill a 5/16 hole.

[kiwigeo]

Looking good John.

From the photos the bolt holes in the mortise look a lot bigger than 6mm...what diameter bolts are you using?

Thanks, They are for 1/4 inch so a bit bigger. I use the brass inserts so I drill a 5/16 hole.

Ok thanks John..I assumed you were following the books and using the brass bar embedded in the heel.

[johnparchem]

Looking good John.

From the photos the bolt holes in the mortise look a lot bigger than 6mm...what diameter bolts are you using?

Thanks, They are for 1/4 inch so a bit bigger. I use the brass inserts so I drill a 5/16 hole.

Ok thanks John..I assumed you were following the books and using the brass bar embedded in the heel.

At some point I will when I get comfortable with a mortising bit and chisel, I have never used one.

[johnparchem]

I finished this guitar with Royal Lac shellac from Shellac Finishes. I am really happy with how it is going on. Here is a description I found on line Royal-Lac is a proprietary formulation formed by cross-linking shellac with carefully selected synthetic resins to form new polyester chains that combine the look and feel of shellac with the durability of synthetic finishes.. Also it can be buffed to a high shine. It comes as a 2 lb cut I have been using it as a 1 lb cut. It really builds nicely and stays level. My method is sort of half FP half padding. I use a proper muneca or fad so I can control how much I am applying but I am using almost all with the grain strokes and no oil. At some point I will level sand and buff it out.

This is after two days of applying the product, no sanding.









While waiting until the finish cures of the guitar so that I can buff it out. While waiting I decided to build a contemporary bridge mostly following the instructions from The Book. This is a CF, 2 layers, reinforced Padauk. I used padauk as it is lighter than rosewood by a little bit. A lot lighter than cocobolo. It is a little heavier than black walnut, but at least it has what I hope is the color I want.

Before making the bridge I made a simpler version of the router jig from the book to route the separation between the saddle block and the tie block, the saddle and ledges for bone on the tie block. The jig was simple to make I routed a channel for two pieces of aluminium that were just right two hold the router base guide stable. With the tracks in place I used the router in the guides to route a well for to hold the bridge while I am working on it. The leading edge of the well is perfectly in line with the router track because I routed it using the track.





I sliced a strip of padauk close to the bridge size and resawed it so that I could make a 2 mm, 3 mm and a 4 mm slices to be laminated with the carbon fiber strips.





I used some west system epoxy 105\206, laminated the stack together, clamped it and let it cure overnight









The next step was drilling the string holes. I tried to make I nice reusable jig out of wood and aluminium like in the book, but drilled one hole off center. So I just drilled the holes in the bridge on my drill press. I took a bunch of extra time to make sure that everything was square to the drill bit.



I used my jig to make the first cut to separate the tie block and the saddle block. This cut went to 2mm from the bottom of the bridge. I then shaped the saddle with my luthiers friend remounted the bridge in my jig and cut the saddle and cut ledges for some bone strips on the tie block. I shaped the saddle block a bit with chisels and sand paper.







The bridge ended up at 16.5 grams (minus the bone that is coming)



I am still nervous about the color, as it is different for a bridge. But with a hint of brown in shellac it is not horribly off of the cocobolo head plate.

[RobDyball]

That finish looks quite nice - Would love to see some macro shots!
I've been told the CF bridge laminate can get furry when shaping, did you find that happening at all?

[johnparchem]

Thanks

It will be a couple of more day until I level sand and buff out guitar and I will take pictures then.

I did not have trouble with the CF during the use of my drum sander with 80 grit and my hand sanding to 220 grit of the wings. I used a chisel to do a lot of the rest of the post router shaping. Then the only issue was keeping the chisel sharp.

[johnparchem]

This is not the jig that Trevor uses to machine his compensated nuts. He has a much more elegant jig that allows him to adjust the compensation he needs for each string attach a sized nut blank to the jig and machine the nut using a drill press as a pin router. I could not get together everything I needed to make the jig so until I do I found another method using my new made classical bridge jig that I based off of one in the book It seems to work.

When I made the classical bridge jig I used the rails to make the well so the front edge is parallel to the rails. My bishop Cochran router base adjustment is .8 mm per turn. So 1/2 = .4 mm, 1/4 = .2 and 1/8 = .1. These are all positions that are easy to see. I could probably get close to .05.

I made a nut holder that was the same thickness as the fret board so that I could easily set the depth. I zeroed on the front of the nut and proceeded to cut each slot. I had one that string location that I needed to ease the router into the rails. But it came out ok and pretty accurate. I have them all a tad more compensated so that I can clean the leading edge.









It still needs shaping but the front ledges are very close to where they should be. I will do a bit of clean up and make them just tight.




I glued the bone into the bridge so it was time to glue the bridge down.

I level sanded and polished the guitar so that I could do that without the bridge in the way. I used my ROS at 600 grit light sanding and then micro mesh disks up to 8000, followed by buffing.





Because I am doing all of this fancy compensation, I check and double checked the bridge placement. I used the 12 fret as my home to measure from as the nut edge of the fret board was cut 2 mm shorter. Because I have a compensated nut I need only .8 mm of compensation. I do have a wide saddle for a classical so I can compensated up to 3 mm.







I checked the plans to find a good location for the locating pins and drilled them







I use a scalpel with a brand new blade to outline the bridge. It is so sharp that a light cut cleanly cuts through the finish.



I use a heavy duty utility blade to scrape the finish off the wood. I tape the back end so I only need to keep track of one end.





To get ready for the vacuum clamp I taped some appropriate sized blocks on the wings, I just find it does a better job of clamping the wings, I leave the pins end but I duck taped the slot to get rid of leaks. I applied the vacuum clamp for about 8 minutes, cleaned up the squeeze out and am keeping it clamped for an hour or two.

[johnparchem]

I completed my first falcate classical. This is my best sounding classical guitar. I did miss my target frequency on the top. As seen in the figure below the top low around 178 Hz instead of 190 Hz for the top. This lower frequency puts the top and the Air resonance an octave apart 88.6 Hz. I am not really hearing any horrible weakness around F but I am also not hearing what the guitar could have sounded like if I hit the target. I did put the back about 4 semitones away at 224 Hz. Ultimately I should have had the falcate braces taller. Possible the 7 mm that I used for my SS.

Over all I am very happy with this project. I have good data for my next attempt and a good guitar.

[charangohabsburg]

That turned out very nice John!
Thanks for commenting the build.

I also liked to see the numbers for closed box resonances vs. finished guitar resonances:

87Hz T(1,1)1 => 88.6 hz,
187Hz T(1,1)2 => 178.3 hz
and
238Hz T (1,1)3 => 224 hz

If I didn't miss something in your thread here this is due to binding the box, gluing on the bridge, and maybe a bit to bolting on the neck and varnishing (you know that magic Stradivarius-varnish that improves everything ), but without thinning the rims of the top or adding side mass (I guess that, given the fact that you already were a hair below your targeted T(1,1)2, this wouldn't have made sense to you unless trying to achieve a different balance between two or mode resonance frequencies).
Most interesting to see go up the air resonance, I would not have expected that, on the other hand it is not by much.

[johnparchem]

Thank you Markus,

I was surprised by the change to the top value from before strings and lowering the back resonance.

87Hz T(1,1)1 => 88.6 hz,
187Hz T(1,1)2 => 178.3 hz
and
238Hz T (1,1)3 => 224 hz

[johnparchem]

Thank you Markus,

The guitar has really opend up since I originally posted. It is a very good sounding classical, with the positive falcate characteristics I hoped for. My classical guitar instructor really liked it. He said that it has a great voice, is very quick to follow dynamic changes, great sustain, very consistent across the strings with good separation. The guitar has concert level projection. He also really like the the 20" radius on the fret board He is around 80 years old and has the start of arthritis in his fretting hand index finger. He said for the first time in months his bars sound good.

I was surprised by the change to the top value from before strings and lowering the back resonance to the value with the strings on.
closed => no strings => final
87Hz T(1,1)1 => 89.5Hz => 88.6Hz,
187Hz T(1,1)2 => 185Hz = 178.3Hz
and
238Hz T (1,1)3 => 237Hz => 224Hz (this was me shaving the lower bout brace)


Spectrum right before strings

[kiwigeo]

Nice work John...

[Dave M]

John thanks for posting up the info, I know it takes an effort to photograph as well as to do...

At some point you make the comment that you think you should perhaps have left the falcate braces a bit higher to achieve the higher main top resonance that you wanted. I may have missed it but I don't see what height you actually did use. Particularly interested since you say it turned out a good guitar.

I have just today glued down my curved little darlings and have them at 7 mm. No idea really how the top will perform.

Apart from a practice run it was a first for me using carbon fibre and epoxy. It really is hard to keep it clean isn't it? As Trevor says the trick is for minimal resin. I just had one little brace where the fibre wanted to splay out from under and that was because the epoxy was going very rapidly off and I wanted to finish the job so used too much. Gave in and took it off and redid it with a new mix.

Dave

[lauburu]

Great result and a most informative thread
Miguel

[johnparchem]

Thanks Dave and Miguel,

Dave, I will want to know how yours turns out. I had my brace at 6 mm but with this second one I would at least have them at 7 mm maybe 8 mm I still want to think it over as I was down a bit more than 10 hertz from my target of 190 Hz for the top.

I did post some recording of both my falcate steel string and my falcate classical at http://soundcloud.com/johnparchem.

The guy who played the classical really like the voice, the loudness, the clarity of the notes, all and all he said it was a very good guitar, he said that if I got a bit more on the treble string it is approaching a great guitar. We will see on my second.

[Trevor Gore]

Well done, John. It seems like you got a successful outcome there. If you want a little more treble, you might get there using fluorocarbon strings. Hard to tell from the pics, but what you have on looks more like nylon than fluorocarbon.

Having worked through the whole book pretty well now, did you find that there were any steps missing or not sufficiently explained?

We tried really hard not to leave any gaps, but we might have assumed some things that are not obvious to others.

Thanks in anticipation.

[johnparchem]

Well done, John. It seems like you got a successful outcome there. If you want a little more treble, you might get there using fluorocarbon strings. Hard to tell from the pics, but what you have on looks more like nylon than fluorocarbon.

Having worked through the whole book pretty well now, did you find that there were any steps missing or not sufficiently explained?

We tried really hard not to leave any gaps, but we might have assumed some things that are not obvious to others.

Thanks in anticipation.

Last night and this morning I spent some time trying to come up with any gaps in your build volume and I could not really come up with much. The book is detailed enough that one could follow it using only the pictures or using only the text. The books are very well written. I really have not run into any section that I thought was not well explained. I have enjoy the style of writing where not only the how is described but the why. The early section of the book focusing on home construct-able jigs is really valuable. The build volume is also very good at being able to show the construction of multiple types of guitars and describing alternative build options in a coherent linear process. The only jig that threw me for a loop was the construction of nut compensation jig. (I it understand it now, from a previous post). I made your bolt-on bolt-off classical guitar neck for the guitar in this post. All of the angles were so complicated I followed the book every step of the way, I think my only hiccup was that I narrowed the wedge extension when I tapered the fret board, I needed it to be a little wider as it was under where the head stock started to flare out.

I am still exploring the depths of the design book and have read most of the sections a few times. I am able to get more out of each section as I develop my own intuitive model of the acoustic guitar while applying what I am learning against my guitars. With experience I have gained the context to really understand a point in the book not just accept it. With help from this forum I have the 4 dof model running and have played around with the relevant parameters. The next step I am considering and planning is to calibrate the model to the guitars I am making. So for all of my guitars I am building I am going to make sure I get the mass of the braced top and back and rims. I am already documenting the plate thicknesses and brace heights. It would be fun to get a calibrated model and use it on a new size guitar and see if I could still hit my targets.

I also have some area's rightly or wrongly that I want to explore. For example, combining two bits of information from a couple of sections on bracing in the Book, with spruce braces one really needs to be careful with regard to stiffness/mass with CF vs. no carbon fiber, as spruce already has a good stiffness to weight ratio. , the other point is that when a brace is glued to the plate the neutral axis moves pretty close to the plate. Specifically for spruce, given that the CF between the brace and the plate is close to the neutral axis is it still better to have the CF between the brace and the plate vs having an epoxy free joint. If not does having CF only on the top of the brace still protect against cold creep.

My copy of the two books is pretty tattered, as I use then frequently. I really am hard pressed to come up with a weak section in the Build book. It is hard for me to imagine the amount of work that went into the Books I thank you and Gerard for the books.

[kiwigeo]

A glue, epoxy, shellac and beer proof version of the books would be useful....like those kiddies books with the plastic pages so you can easily clean off the baby shit.