Classical Build (s) - Hopefully falcate!

[mooshalah]

Hello folks.

I'm probably going to be shot down for this long and complicated post, but that's OK, if perhaps even a small part of what follows might be useful to someone. Perhaps I should post it elsewhere.

I'll preface what follows with the statement that I have spent my previous long working life as an Industrial Chemist / Chemical Engineer and have sometimes managed large laboratories, so I know a little whereof I now will speak!

"Alcohol" is just a word that, scientifically, is used to describe a particular chemical structure. There are literally thousands of alcohols - all different, but with this (rather simple) organic chemical structure that contains as one of its parts, an -OH structure (oxygen-hydrogen bonded together). The suffix "-ol" in chemistry always describes an alcohol. So, ethanol, methanol, propanol, isobutanol, sorbitol, menthol etc.

Ethyl alcohol (also known as ethanol, but for hundreds of years as "spirits") is the stuff that people drink the world over. It's in every "alcoholic" drink known on earth. It's not poisonous as such - although it makes you drunk, and will even kill you, if you drink too much!

Ethanol is produced on an amazingly vast scale, all over the world - and not by having to distil beer and wine. It is one of the most common (and cheap) solvents required by global industry. As you'll imagine, governments don't want people to just go and buy pure ethanol and drink it. It honestly costs much, much less than a dollar per litre to produce, and so it would in fact be the cheapest way to get drunk - and all governments want the heavy taxes that they impose on alcoholic drinks, and it's not desirable to have large swathes of the population staggering around drunk on cheap alcohol!

So earlier governments required that ethanol producers (that is, industrial scale producers) "denature" the ethanol by adding methyl alcohol (methanol) to it, to inhibit people from drinking the stuff. Methanol is in fact a known poison, deliberately added so that if you drink it you'll get sick (and if you drink pure methanol you can become blind, and you'll certainly die if you ingest too much!)

Over time, as public safety concerns have changed, so have formulations. It is still permitted to sell Metho in Australia with up to 5% methanol added to it, but suppliers are also permitted to substitute it with chemicals to make the stuff taste bitter, smell bad, and colour it (often purple or blue). For example denatonium benzoate, an extremely foul-tasting bitter material colloquially called a "bitterant" might be added at a level of around 0.1 - 0.2%, either to substitute for, or in addition to methanol.

The problem is that "Metho" is now the generic Australian word for "ethyl alcohol with some stuff added to it to make it undrinkable". In America the expression "denatured alcohol" means the same thing. It doesn't necessarily fully describe the ingredients of any particular bottle.

So, Metho may or may not contain methanol. For example, here in Australia, Diggers brand of "Methylated Spirits" that you buy in Bunnings contains no methanol, while the Recochem brand, also sold in Australia as "Special Methylated Spirits" contains 5% methanol.

Methanol is very closely chemically related to ethanol, so that if it is added to the ethanol, it doesn't change the solvent properties of the material in any meaningful way. Thus, it's usually pointless and expensive to try and buy "pure ethanol" for this purpose (acting as a solvent).

I can't speak authoritatively about which stuff to buy (ethanol with or without 5% methanol) for French polishing, - although I do some of this - but strongly suspect that it makes no difference (and you're welcome to disagree with me!) The presence of water in the Metho might however be worth some discussion.

The commercial production of ethanol yields a material that is 95% ethanol and 5% water. This is not because the producers are sloppy, or want it this way. Rather, commercially, ethanol is produced via a final distillation step, and the purest that one can obtain ethanol by this process is 95% pure. The matter has to do with the formation of what are called chemical azeotropes.

During the process of distillation, 5% of water "clings" to the alcohol during the boiling and condensing process. To get the last 5% of water out of the ethanol, a second (more expensive) process, using sodium metal is required - and for the purposes of it being an industrial solvent, this 5% of water is not an issue.

Likewise, methyl alcohol and bittering agents will not separate from ethanol during distillation, so you can't simply boil up then condense Metho for a cheap drink!

Any cheap ethanol you buy as Metho (or Methylated Spirits, or Denatured Alcohol) will have this 5% water still in it (and if it has in addition an added 5% of methanol, it will thus be only 90% ethanol), and this could just arguably be an issue in French polishing, given that shellac is completely insoluble in water. Again, I don't see this, but others who will know much more about this subject might wish to correct me.

Finally, just to complete the picture, Analytical laboratories require pure ethanol which can be bought from laboratory chemical suppliers - but the Australian government loads such product with a huge tax, so that it's prohibitively expensive. If you have a commercial laboratory and MUST have pure ethanol, you can apply for an exemption from the taxes - but this is a complicated matter, requiring the keeping of careful records that governments periodically inspect - and if you can't account for virtually every drop, the tax is ruthlessly, retrospectively applied.

Cosmetics manufacturers that use ethanol in their formulations that may be applied to the skin have their own set of hurdles to jump.

As a chemist, I constantly rage against the common, inaccurate terms applied to chemicals. For example, methanol is often also called "wood spirit" and chemically (more correctly) as "methyl hydrate". And don't get me started on "rubbing alcohol" aka "surgical spirit" which is usually a 70% isopropanol / 30% water mixture, but the term is increasingly being misused in this age of Covid-19 hand sanitisers.

Thus endeth the sermon.

Frank.

[johnparchem]

Hello folks.

I'm probably going to be shot down for this long and complicated post, but that's OK, if perhaps even a small part of what follows might be useful to someone. Perhaps I should post it elsewhere.

I'll preface what follows with the statement that I have spent my previous long working life as an Industrial Chemist / Chemical Engineer and have sometimes managed large laboratories, so I know a little whereof I now will speak!

"Alcohol" is just a word that, scientifically, is used to describe a particular chemical structure. There are literally thousands of alcohols - all different, but with this (rather simple) organic chemical structure that contains as one of its parts, an -OH structure (oxygen-hydrogen bonded together). The suffix "-ol" in chemistry always describes an alcohol. So, ethanol, methanol, propanol, isobutanol, sorbitol, menthol etc.

Ethyl alcohol (also known as ethanol, but for hundreds of years as "spirits") is the stuff that people drink the world over. It's in every "alcoholic" drink known on earth. It's not poisonous as such - although it makes you drunk, and will even kill you, if you drink too much!

Ethanol is produced on an amazingly vast scale, all over the world - and not by having to distil beer and wine. It is one of the most common (and cheap) solvents required by global industry. As you'll imagine, governments don't want people to just go and buy pure ethanol and drink it. It honestly costs much, much less than a dollar per litre to produce, and so it would in fact be the cheapest way to get drunk - and all governments want the heavy taxes that they impose on alcoholic drinks, and it's not desirable to have large swathes of the population staggering around drunk on cheap alcohol!

So earlier governments required that ethanol producers (that is, industrial scale producers) "denature" the ethanol by adding methyl alcohol (methanol) to it, to inhibit people from drinking the stuff. Methanol is in fact a known poison, deliberately added so that if you drink it you'll get sick (and if you drink pure methanol you can become blind, and you'll certainly die if you ingest too much!)

Over time, as public safety concerns have changed, so have formulations. It is still permitted to sell Metho in Australia with up to 5% methanol added to it, but suppliers are also permitted to substitute it with chemicals to make the stuff taste bitter, smell bad, and colour it (often purple or blue). For example denatonium benzoate, an extremely foul-tasting bitter material colloquially called a "bitterant" might be added at a level of around 0.1 - 0.2%, either to substitute for, or in addition to methanol.

The problem is that "Metho" is now the generic Australian word for "ethyl alcohol with some stuff added to it to make it undrinkable". In America the expression "denatured alcohol" means the same thing. It doesn't necessarily fully describe the ingredients of any particular bottle.

So, Metho may or may not contain methanol. For example, here in Australia, Diggers brand of "Methylated Spirits" that you buy in Bunnings contains no methanol, while the Recochem brand, also sold in Australia as "Special Methylated Spirits" contains 5% methanol.

Methanol is very closely chemically related to ethanol, so that if it is added to the ethanol, it doesn't change the solvent properties of the material in any meaningful way. Thus, it's usually pointless and expensive to try and buy "pure ethanol" for this purpose (acting as a solvent).

I can't speak authoritatively about which stuff to buy (ethanol with or without 5% methanol) for French polishing, - although I do some of this - but strongly suspect that it makes no difference (and you're welcome to disagree with me!) The presence of water in the Metho might however be worth some discussion.

The commercial production of ethanol yields a material that is 95% ethanol and 5% water. This is not because the producers are sloppy, or want it this way. Rather, commercially, ethanol is produced via a final distillation step, and the purest that one can obtain ethanol by this process is 95% pure. The matter has to do with the formation of what are called chemical azeotropes.

During the process of distillation, 5% of water "clings" to the alcohol during the boiling and condensing process. To get the last 5% of water out of the ethanol, a second (more expensive) process, using sodium metal is required - and for the purposes of it being an industrial solvent, this 5% of water is not an issue.

Likewise, methyl alcohol and bittering agents will not separate from ethanol during distillation, so you can't simply boil up then condense Metho for a cheap drink!

Any cheap ethanol you buy as Metho (or Methylated Spirits, or Denatured Alcohol) will have this 5% water still in it (and if it has in addition an added 5% of methanol, it will thus be only 90% ethanol), and this could just arguably be an issue in French polishing, given that shellac is completely insoluble in water. Again, I don't see this, but others who will know much more about this subject might wish to correct me.

Finally, just to complete the picture, Analytical laboratories require pure ethanol which can be bought from laboratory chemical suppliers - but the Australian government loads such product with a huge tax, so that it's prohibitively expensive. If you have a commercial laboratory and MUST have pure ethanol, you can apply for an exemption from the taxes - but this is a complicated matter, requiring the keeping of careful records that governments periodically inspect - and if you can't account for virtually every drop, the tax is ruthlessly, retrospectively applied.

Cosmetics manufacturers that use ethanol in their formulations that may be applied to the skin have their own set of hurdles to jump.

As a chemist, I constantly rage against the common, inaccurate terms applied to chemicals. For example, methanol is often also called "wood spirit" and chemically (more correctly) as "methyl hydrate". And don't get me started on "rubbing alcohol" aka "surgical spirit" which is usually a 70% isopropanol / 30% water mixture, but the term is increasingly being misused in this age of Covid-19 hand sanitisers.

Thus endeth the sermon.

Frank.

With all of that I think I was right in suggesting care with a can of something called methanol.

[kiwigeo]

This is the stuff I use.....I used to get it from a retail outlet here in Adelaide and I think Robert Shines still supplies the stuff. http://www.recochem.com.au/index.php/pr ... industrial

Robert is best contacted via phone call....he's very knowledgeable and helpful. http://shines.com.au/

[seeaxe]

Like most things in life things are often more complicated than they seem as first. So thanks @mooshalah all useful stuff.

I actually purchased some ethanol (it was pretty hard to track down) but have a big tin of this stuff whatever it actually is to use up so that's what I am doing. So far so good as far as i know.

Thanks for all the inputs everyone.

[56nortondomy]

I've bought 100% methylated spirits for FP from paint spot. Not all the paint spot stores sell it.
Wayne

[seeaxe]

Well if you thought the FP spirit was bad you should read the MSDS for the Mirotone. 25 pages. First two pages told me i dont have the correct PPE or ventilation and the other 23 set consequences of using the stuff. Holy crap.

Given im doing this in my garage i would be wafting clouds of this stuff all over the neighbours. Not to mention my son in law.

So the Mirotone is going back and I'm FPing the whole thing. Its probably going to cost me money but that was one of those decisions i knew was right. RTFM...before you buy the stuff.

Anyhoo onwards and upwards.

[seeaxe]

So the bridge is on but I have had a bit of a set back on the FP on the back, either didnt wait long enough before getting stuck in with the fine cut and polish, or getting too stuck in with the fine cut, or both, and went through the FP. Currently sanding it back and starting again.
Such is life. Sides are done though and looking pretty OK

Bridge turned out OK, 17 grams

By the way the nice folks at Mirotone took the lacquer back so all ended well there
And the tuners and nut are done

[lamanoditrento]

Ah don't you hate that. Totally been there!

Is that just a temporary saddle? It looks flush with the bridge?

[seeaxe]

Nope its the final saddle. 11mm off the soundboard. I havent trimmed back the cheeks yet so the saddle is actually flush now but won't be when finished. This is my way of dealing with the lefty righty problem. The saddle has a bit of blackwood glued either side of it. I plane it to get a suitable bridge angle then make the sides parallel. Ends up around 6mm. I cut a 6mm slot and place it in that. If i want to revert to lefty i flip out the saddle and make a new insert.

[lamanoditrento]

Nope its the final saddle. 11mm off the soundboard. I havent trimmed back the cheeks yet so the saddle is actually flush now but won't be when finished. This is my way of dealing with the lefty righty problem. The saddle has a bit of blackwood glued either side of it. I plane it to get a suitable bridge angle then make the sides parallel. Ends up around 6mm. I cut a 6mm slot and place it in that. If i want to revert to lefty i flip out the saddle and make a new insert.

Very cool

[kpcart]

nice red soundboard.

[seeaxe]

I put the strings on this one this weekend, happy with how it sounds. I've got to do the tap testing and tune the back but it is much sweeter and even across the strings than my previous fan braced classical. The bottom E string sounds muddy compared to the rest so need to investigate that. Its not that loud but its early days yet as its only been strung up for 24 hours

I have a long list of things I will do better next time and once this has gone to its temporary home later this week, Ill be starting on number 14. (number 13 being the electric we built during lockdown). The bolt on neck works well but can be improved. While its fiddly to get on and off its a doddle to get the action exactly how you want it. Need to do something about string path if I'm keeping that headstock shape

[Bob_H]

Looks great - really good to be able to follow along!

[seeaxe]

Have now done some tap testing and measured bridge rotation.

Interestingly the top went from 180hz before I put the bridge on, up to 189hz now, which I deem close enough to the target 190, so thats OK
The back is at 250 Hz and if I want it 4 semitones above the top I reckon I need that to drop to 235 Hz. I have had a go at trimming the central back brace but its not moving it much. All of this is frustrated by very unclear VA spectra. I had VA working nicely last time but I'm stuffed if I know why I cannot get clean curves this time.

The bridge rotation is a bit of a disappointment though. It rotated about 1.5mm over 150mm so its way too stiff. I was kind of expecting this as I left the main braces at 10mm at the highest, rather than trim them in accordance with the I value calculation in the "Book".

But I'm puzzled, as if I had reduced the top stiffness to achieve a more flexible top, and more bridge rotation, then how would I have kept its T1,2 up at 180-190?

Any suggestions/thoughts?

[Trevor Gore]

... But I'm puzzled, as if I had reduced the top stiffness to achieve a more flexible top, and more bridge rotation, then how would I have kept its T1,2 up at 180-190?

Any suggestions/thoughts?

Resonant frequencies are proprtional to SQRT(stiffness/mass); so.......

[seeaxe]

Thanks Trevor...will think about that.

[kiwigeo]

The top is Lutz spruce. I bought a lot of this wood off Shane Neiffer back around 2000 and a lot of the sets had these nice red streaks through them.

nice red soundboard.

[Dave M]

That is very nice looking.
A small point, if it is the third and fourth string paths that are a problem you could try winding them towards the outer side of the headstock rather than the inside. Dave

[seeaxe]

Thanks Dave M, and yes I restrung right handed last night and eased the strings over which helps. Was kinda going for straighter strung pull, 4 out of 6 isn't bad. I will try more bevel on the headstock next time.

Of the sets I got from you Martin that one had the best stiffness by some margin. I'm thinking that will fade a bit and as the top ages to the lovely golden spruce colour they will be less prominent but still a feature.

Having posted so many pics here there's not much point putting this in the gallery but for the record It is
Lutz spruce top (ex Martin, ex Shane) final thickness around 2.3mm
Black Heart Sassafras back and sides ex Tim S I think.
Macrocapa lining and side laminates (gotta have a bit of NZ wood in there somewhere!!)
Spruce bracing ex can't remember
Falcate with one strand of 3k tow under and over the braces, West system epoxy
Fijian mahogany neck,
Rosewood fretboard, bound
Aus blackwod laminated bridge
Satin box binding from Tim S (lovely stuff)
Gotoh tuners, Savarez HT strings
French polish finish
Bolt on neck a la Telecaster but with nylock nuts on studs the inside.

As much to cement them in my mind as anything else I'm going to do a fairly thorough lessons learned list on this one, when I get time.
Handing it over to the guitar teacher tomorrow so we will see what he says.

Overall, i'm giving this one a fail (sonically at least) as the main reason to build it was to try out the falcate system and its way too stiff.
It has been an enjoyable build though and when all is said and done its still a nice guitar. I would like to think I can do a bit better though.

[seeaxe]

To close out this thread, after a few hiccups I delivered it on the weekend and the new owner is delighted. I have got the lowest action I have ever managed on a classical and so when you climb into stuff there are a couple of buzzes, so we will lift that slightly after the guitar settles down a bit. Feedback so far is that its better than any of his other guitars so I suppose that's a good start for a first falcate. It certainly looks better.

Ill start a new build thread for the next one.

Thanks for the input and no doubt I will be asking a bunch more questions about the next one. The challenge will be to improve on this one and get the top stiffness and mass down and bridge rotation up. I did make up my list of things to make sure I get right next time but its two pages long so not going to post it here. Its all mostly simple stuff I forget to do when I get excited in mid build anyway.

The major things on this guitar that I am keen to pursue (apart from the falcate bracing of course) are the bolt on neck and the laminates sides.

Cheers all, see you in the next thread!!

[seeaxe]

I thought I was done with this but I'm not.

I noted that the bridge rotation was much lower than expected and over time I have become a bit unhappy with the sound. It doesnt sound as bright and responsive as my previous guitar, built following Cumpiano and Natelson. But as Trevor points out, I shouldnt use the R word without doing some objective measurements.

I have actually been contemplating cutting the top off the guitar and shaving down the falcate braces (to get better bridge rotation) but thought that I should follow through on my attempts to measure monopole mobility before doing something that drastic. So this afternoon I had some time and finished off the testing jig, much the same as the ones posted on here.

The first thing that became obvious was that the falcate top on this guitar is twice as flexible as the one on my conventionally braced older guitar, the one I considered more responsive! So much for that. Having measured the stiffness of the three classicals I have to hand I then had to get the uncoupled top resonance sorted.

Enter my bete noire of the GG universe - getting sensible results out of VA. After 15 minutes of fumbling around I caved in and bought Robbies video of Trevor explaining it all. Its really useful and I heartily recommend it to anyone who is struggling with VA. You can have the video running and your own VA screen set up beside it, copying his tutorial. I soon had my frequencies and off I went. (Note that as Trevor quotes his deflection and weight, and the frequency of the top he measures, before stating his monopole mobility, you can actually use those numbers to check that you are working the formula correctly, solving for m).

I ended up with a monopole mobility of 14.6 for my old guitar and 27 for the falcate. So its not too stiff....

Since I now had the VA plots working I decided to go back and revisit the usual tap testing on the guitars.

The first one I built sounds a bit tinny. It had a T1,1 of just over 100 and a T1,2 around 240 so not hard to see why that is.

My main guitar is the conventionally braced Lutz top, sounds nice.
T1,1 was 111, T1,2 was 224

The falcate was T1,1 104, T1,2 195, so close to the ideal figures if a little high. A bit close to G at 196.

All of which leaves me still a little puzzled as to why I prefer the sound of the older guitar, perhaps I have just got used to it over the ten years I have been playing it. At least I now no longer want to pull the top off the falcate and instead will look at some weights to see if I can get the main top down nearer 190, see what that does to the sound.

I also looked at the effects of the soundholes, but thats for another post.

[seeaxe]

Update. I added some side weights and tap tested as i went. I got the main top resonance to 190 fairly easily. It sounds a bit brighter which is good but i still have a few muddy notes. Unless im imagining things the F#4 dies about twice as quickly as everything else. Doesnt seem to affect F#3. This is a problem as i spend a lot of time in drop D tuning. Ive looked for resonances at that frequency or multiples/divisions thereof and so far theres nothing obvious. The top at 190 should be far enough away i would have thought. Will keep playing with it and post something in the GG forum if i cannot sort it out.