Official Luthiers Forum!

In making a nylon "crossover" style instrument the main feature that makes them different from a classical is the neck, rather than the body size or bracing. More like a steel-string neck in width, profile and action. Maybe 1 3/4 inch at the nut (noting Al's caution not to go any narrower than that), and a thinner profile than a classical.

You can also go for a non-traditional bridge shape - but you want to keep it fairly light. I recently did one with an 18-hole bridge to allow tying of the strings without them having to loop over the lower bridge. It looks very tidy and "more modern". It is another way to mark it as different from a traditional classical instrument. There are some posts here on the OLF about 18-hole bridges if you want to search for them.

Basically, from what I can see, the larger the guitar the more 'bass balanced' it will be. Since treble is the main issue on nylon string guitars, making them bigger doesn't address that. Also, although it seems counter intuitive to some, it's easier to make a loud small guitar than a loud big one. The more Classical guitars I make, the more I tend to move toward the smaller boxes. It's possible to make an OM/000 size Classical that has decent treble and good power, if you pretty much follow the Martin recipe as it was practiced a hundred years or more ago. Anything bigger requires either some more modern technology (such as CF) or the use of a carved arched top and back. Even then, when going larger than the OM/000 size I'd tend to make the box shallower and the hole a bit bigger to boost the trebles. Just my opinion.

Just saw this. Over a year ago, I built my own version of a classical, based on a Taylor Grand Concert form I already had, and a Hauser classical plan. It had East Indian rosewood back and sides, a sinker redwood top, a sound port, an arm bevel, and a 1-7/8" nut width. I think it turned out well, and it sounds good! Take a look, if you're interested (warning: it's a pretty extensive account): http://www.theamateurluthier.com/retire ... aylor.html

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Kathy Matsushita
San Jose, CA USA
http://theamateurluthier.com
Facebook: https://www.facebook.com/kathy.matsushita

Excellent build documentation Kathy! Sweet guitar

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Joe Beaver
Maker of Sawdust

Thank you all so much for the great comments ,advice ,pics etc ,very thought provoking and informative
So The above bracing pattern which I found on Google is the one I've chosen
After looking at hundreds of designs .I googled George Lowden Bracing and the above jumped at me .
The model for this Guitar which will be a one- off for myself ,will be loosely modelled on the Lowden Jazz .
I watched a lot of vids on GL's talks on his building technique and this bracing seems near to what he uses .Also after watching Kathy M's vid I have to have an arm bevel .Hehe!
...Any comments ?

That Lowden pattern is for a steel string with a pin-less bridge - I think there is some advice in this thread regarding the low energy ouput from a set of nylon strings, might be a good idea to review.

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Ken Cierp

http://www.kennethmichaelguitars.com/

I think what everybody here is trying to tell you is that an OM is not a good choice for a first nylon string guitar... While its what you have in hand - its really not well suited to nylon.

If you really want a crossover - start with a larger classical plantilla like Fleta, Hauser, or Ramirez and build around that. The advantage is these are well trod ground and fairly well understood Classical designs that are well worked out, proven designs with bracing patterns that are already sorted out.

Its not much of a stretch to adapt one of these to a narrower neck, pickup, and a radiused fretboard.

I'm going to disagree with truckjohn (which is always risky, I know).

It's interesting that very few Classical makers have worked with a plantilla much larger than the biggest ones Torres used. There's a reason or that, or actually more than one. One is that, as I've said, treble is what's hard to get from a Classical, and making the box bigger gets you more bass. It's also the case that it's easier to make a loud small guitar than a loud big one. Since nylon strings run lower tension than steel, there's less energy available at a given action height which makes the problem of power worse. Classicals usually use higher action than steel strings, and get around the issue that way, at least in part. For a crossover, where you'll probably want the action low, that's not an option.

Each top bracing scheme seems to set something of an upper limit for the width of the box across the lower bout. You can push that a bit, but not too far. When guitars went from ladder braced tops to fan bracing, starting around 1775, tops got wider. Fan bracing is a bit more efficient structurally, and you could use a bigger box and still keep the trebles sounding good. The same thing happened when X bracing came in; it's more structurally efficient, and allows for a wider box. Keep in mind that this was a long time before steel strings became common; those early X-braced guitars were made for gut strings. Martin introduced the 12-fret 000 in 1909, iirc, and didn't start offering steel as a factory option until much later. The OM is the same width, just shortened up to accommodate a 14 fret neck. With the greater treble content of steel strings you can push the lower bout to around 16-17" wide, but not much more than that on a flat top. Arched tops are even more efficient structurally, and the practical limit for lower bout width there seems to be ergonomic. I have built nylon string arch tops 16" wide and feel I could easily go to 17" with them given the right piece of top wood.

Reducing the top thickness and brace heights to suit the lower tension of nylon strings, and using a slightly different neck set to get somewhat higher action without a taller bridge, should give you a good crossover instrument. Don't go narrower at the nut than about 1-3/4": every time I've done that at customer insistence they come back later wanting it made wider. Just be sure to make it obvious that this is not meant for steel strings: use a Spanish style tieblock bridge, a slot head with big rollers on the tuners, and note the restriction on the label, or somebody down the road will put a 14-60 set on it and rip the top off.

But you didn't disagree with me....

Yes I did. You wrote:
"If you really want a crossover - start with a larger classical plantilla like Fleta, Hauser, or Ramirez and build around that."

In my experience it's actually hard to build a larger plantillla Classical and make it coome out sounding good than the smaller sizes. Larger boxes give you more bass and less power, nether of which is what you want from a nylon string guitar. If you really know what you're doing you can make that work, but it's not as easy. X-bracing is enough more efficient structurally than fan bracing that you can make the bigger top stiff enough without adding too much weight. That still tends to give you more bass, but with care you can get plenty of treble and clarity too. It won't sound just like a Spanish guitar, but that's not what you're going for here anyway.

A few years back I showed one of my 12-fret 000 size Classicals to Sharon Isben after a concert. She liked it, but since she'd just gotten a new guitar and was still getting used to that she talked herself out of borrowing mine for the wekend. My own (naturally completely objective... ) impression was that my guitar compared well with her Humphrey. Each had strengths and weaknesses, of course, but over all they seemed pretty well matched, and she seemed to feel the same way. The larger platform can work if you do it right, but I think the X brace is a real help when you get that big.

BTW, Evans and Evans give specs on a number of guitars by different makers. The Hauser 1 they show is only a millimater wider in the lower bout than a Torres from 1859; 354 vs 353. Fleta is larger at 363, and Jose Ramirez is up at 372. By comparison the 12-fret 000 and OM are 381mm wide across the lower bout. Over time they did seem to grow, but the only 'Classical' guitar they show that wide is a Raponi from 1970, and many of the more recent ones seem to trend smaller.

Ok. Now I got what you were saying.

You were agreeing that an OM was a bad place to start if you wanted a nylon string crossover....

But then went a step further that the Hauser, Fleta, and Ramirez were ALSO probably too big for a good first go at it.... Given that our OP probably doesn't want a 1/4" high 12th fret action or a 650+mm scale....

I agree with you there as well with the point you have made.... That to get something sufficiently loud and sweet sounding that also gives you a very wide margin of error building for nylon strings - start with a classical or flamenco pattern that is even smaller yet... And there are plenty to choose from.

I think we have to remember that the original poster, Niall, told us that he has a OM kit already, so I presume that he is committed to that body size and shape (Niall - are your sides bent already?). If so, telling him to use a different shape is not going to be helpful. We need to respond to the question as follows: "I am making a OM and want it to have nylon strings - what would be a good bracing pattern?"

Niall, I think Ken is right in saying that the Lowden picture you posted is a steel-string model, not the nylon jazz model. From the same webpage that shows that picture there is also this illustration - and I think this is the nylon model.

Unfortunately it doesn't show the whole soundboard, but I think we can see that it is an X-brace with some sort of lattice pattern in the lower bout, and the typical Lowden A-frame in the upper bout which runs into the neck block. Also worth mentioning that the Lowden S-shape body is quite small. Closer to a 00 than a OM, but still with 14 frets to the body. The Lowden nylon jazz model certainly has a lot of fans as a crossover style instrument, so it would not be a bad one to take your inspiration from. But your OM will be a bit different again.
Mark

truckjohn wrote:
"You were agreeing that an OM was a bad place to start if you wanted a nylon string crossover...."

NO! I'm saying that while an OM kit might not be a common starting point for a crossover guitar it's a good one if you do it right! IMO it's superior to the larger plantilla Spanish models for this application. It's hard to get a good sound out of the large fan-braced guitars, but when done correctly the X-braced top works well. The main things you'll need to do are to reduce the thickness of the top and height of the bracing by about 15%, replace the hardwood bridge plate with a spruce one, use a tie block bridge to reduce the likelihood of future stupidity, and set the neck a little differently to allow for somewhat higher action. I'm sorry if my penchant for verbosity obscured the message: I keep trying to give complete explanations when a simple assertion might be better understood.

The other possibility is to whack 1/2 an inch off the ends of the sides at the tail block to decrease the lower bout width to 14 inches. The length of the body is about the same as a classical and the upper bout width not much different. Again, a 12th fret to the body joint neck would move the bridge location closer to that of a classical, and with a cutaway would still give good upper fret access. A kit is always just a starting point, what you make of it is up to you.