Hybrid Acoustic

[Mickguard]

Ever since I came across this guitar at Robert Irizarry's ergonomic guitar site, I've become kind of obsessed with the idea of building something similar.

My goals:

I want a 'quiet' acoustic to play late at night and, since my son has been bugging me to let him play my guitars more and more, something he can play too. Not something meant to be a performing guitar in other words, but I'd still hope it would sound nice enough.

The guitar will have a top-mount acoustic bridge (like my Takamine), and an electric-style mahogany neck, which will be easier for him to play. I'd also use a electric-style bolt-on configuration, at least for the prototype.

For the back/sides, I'll probably glue up a multiple-piece blank (at least for the prototype), which I'll route/carve until it's hollow. I'll probably go with birch, since I can find 50- 60 mm boards here and I find it a really nice wood to carve.

I'm also planning to go with Folk Nylon strings instead of steel strings -- my son's still pretty young, so his fingers are really tender and he's not old enough to force himself over the callouses hump. (he takes drum lessons, he's only casually interested in the guitar, this guitar is mostly for me).

From what I understand, the Folk Nylon strings are specifically made to fit steel string guitars, right? I'd want the option of using steel strings though, so I'll use the appropriate bracing on the top (spruce).

Building a hybrid like this would also let me build an acoustic that will actually be comfortable for me to play too, when I'm slouched back on the couch at 2 in the morning...the Takamine's a jumbo...

I'd be able to carve the bacck. And since the sides will be from the blank, it should be easy to build it as a slant top too. The body design will be based on the Klein/Breadwinner family --it'll be the same design as an electric I've been developing, so I'll already have the template prepared anyway.

This one would be only acoustic, no pickup at all. If I like the basic sound of the prototype, I'd then build a second version with a pickup and preamp.

I'm tempted to go without a soundhole, but if I do, it will probably be something in the upper part of the guitar, or even incorporated into the side -- the idea being that the sound/volume of the guitar will be projected at the player first of all. I also like the look of that.

Any thoughts about things to take into consideration? Things you definitely think won't work, or things you think will increase the possibility of getting something that sounds decent acoustically?

I've been looking at the Godin Multiac -- apparently it uses a 'chambered' mahagony body/back/sides --but I haven't found information yet as to whether they're using bracing. Perhaps the chamber walls take the place of the braces?

[fryovanni]

Mick,

I think that sounds like a cool project. I think the idea of carving/ routing seems sensable as an option, given that you are looking for this ergo type shape (and assuming your thickness is going to be reasonably thin compaired to a flatop or archtop. Because of the size of the box I suspect you will get a fairly quiet acoustic. A side soundport may be a good idea to bring a bit more volume to you while you play. As far as the soundhole or lack there of it has ramifications, but it is such a uniquely sized and constructed guitar exactly what to expect would be hard to say (of course there will be no getting in to make any adjustments if you totally close up the box). I might be tempted to attach a back, as opposed to trying to carving the sides and back from one piece of wood. This would make it easier for you to control the thickness, brace, and tune it. I would try to make it as lively as I could (you will need to get all the volume you can with such a small instrument, and bass responce will probably be your big challenge). You are really picking a challenging acoustic to make. Not much information out there to help in terms of bracing, thickness of plates, bridge shape and so forth. I think it is a cool idea though

The bolt style neck is perfect for that body, even if you bent your sides you would have large blocking for the ergo back carves, and you should be able to make a good solid rim by routing/carving. Focus on the top, back, bracing, bridge, and see if you can study smaller flattops if you go with a pinned bridge.

Peace,

Rich

[Mattia]

Honestly? A lot of work for a guitar that's not going to sound great unplugged. Quiet, yes, but there's quiet, and there's pleasant. Pop in pickups (even just an undersaddle), and you've got a guitar that you can go gigging with as well, worthy electrocoustic that'll likely feed back less than the average instrument. At one point in the past, I considered building a 'stage acoustic' following this model, but I've since figured that if I'm going to make a stage acoustic, I'll model it roughly on a Turner Model 1 or similar; WRC core, hardwood top and back, and mostly solid, and get a good pickup system (like the Mamma Bear, for example) to get the sound I want out of it.

Still, fun project, and feel free to post questions and the like for feedback and/or design ideas; this is the kind of thing I really like thinking about!

[fryovanni]

Mattia,

Just to toss a thought around a bit. Do you think a bit of added depth could improve (or maybe provide better potential is a better way to put it) the performance quite a bit? The depth or volume of the body is the one point I am most unsure of on this design.

Peace,Rich

[Mickguard]

Mattia,

Just to toss a thought around a bit. Do you think a bit of added depth could improve (or maybe provide better potential is a better way to put it) the performance quite a bit? The depth or volume of the body is the one point I am most unsure of on this design.

Peace,Rich

I plan to make a fairly thick body --perhaps up to 60 mm (if I go with a slant top--the upper bout would end up as more like 40 mm). Most likely I'll end up layering wood to get to that thickness -- I already have some nice contrasting woods here for that. This will also make it a lot easier to make it hollow, since I'll be able to use a scroll saw instead of a router.

Also of note, that the body will be quite wide --at least 36 cm and possibly up to 40 cm --that depends on what's comfortable.

So between the depth and width of the body, I'll have a volume approaching that of a small acoustic.

Like I said, I'm using the same body for an electric, so building this guitar won't really be effort wasted. The prototype will also feature inexpensive woods and spare parts, so the cost will be fairly minimal.

I've considered using a back, but that eliminates the body carve that I want to do (this is the most fun part of building for me, so I don't like to give it up!).

Good point about the soundhole providing access...I'm not against them, just don't really want a round one. From what I've read, some luthiers believe they should be located on the upper bout anyway.

My main concern is that I'll end up with a guitar with zero sustain and resonance -- I'm just getting started researching that, but it seems to me that if I can get away with less bracing, I'll be able to boost the bass response a bit? The sustain will be a crap shoot. The tone -or lack of it- is not a big deal, since I often practice using an electric to keep things quieter.

I might as well ask here, since I'm curious ---is there any reason I'd have to use wood for bracing? Why not my favorite carbon fiber kite tubes?

Anyway, I'm looking at this as a baby step toward eventually building a true acoustic. I still need to bring up my skill level a lot before then.

[fryovanni]

I plan to make a fairly thick body --perhaps up to 60 mm (if I go with a slant top--the upper bout would end up as more like 40 mm). Most likely I'll end up layering wood to get to that thickness -- I already have some nice contrasting woods here for that. This will also make it a lot easier to make it hollow, since I'll be able to use a scroll saw instead of a router.

That has ruffly half the depth of a more traditional flattop. You will also lose a bit of body volume with the back carves. There is a relationship between the top and back via the air coupling in an acoustic. You could relate it to a drum with a batter head and resonant head, vs just a batter and open shell. Although compairing drum to a flattop is not a perfect comparison. It is probably a good way to kinda get a feel for why top/back/depth(think of deep toms vs shallow) play a role in the sound created.

Also of note, that the body will be quite wide --at least 36 cm and possibly up to 40 cm --that depends on what's comfortable.

That is a fair amount of soundboard surface (getting close to an OM or dread.), which is cool, but I am not sure how the lower volume large surface will play out.

So between the depth and width of the body, I'll have a volume approaching that of a small acoustic.

Again around 50%.

Like I said, I'm using the same body for an electric, so building this guitar won't really be effort wasted. The prototype will also feature inexpensive woods and spare parts, so the cost will be fairly minimal.

Very sensable

I've considered using a back, but that eliminates the body carve that I want to do (this is the most fun part of building for me, so I don't like to give it up!).

Carving is cool of course, if you really want to. To be sure I was clear, I wouldn't suggest deleting the tummy cuts or what have you. Just attaching a back to a rim that has the carves. It can be kinda tricky to route a responcive back, meaning it is not as easy to get just the right thickness by listening and feeling the stiffness of a free plate until it is where you want it. I take my backs bow about .003" per. pass until they feel right, then I move to bracing. Attaching a plate also make it much easier to build a radius into the back, which adds strength when using a thinner more responcive back. To get that you would have to approach the back more like an archtop plate, carved with a rim in your way.

Good point about the soundhole providing access...I'm not against them, just don't really want a round one. From what I've read, some luthiers believe they should be located on the upper bout anyway.

In terms of performance, placement wherever you like or whatever shape you want to try is cool. What I have found about the odd shaped soundhole in the upper bouts, is that you will have a heck of a time getting an arm into the box if you want to adjust a brace. That may not really even be possible with a thin body, so it may be a mute point, and it was just something I wanted to toss out there anyway.

My main concern is that I'll end up with a guitar with zero sustain and resonance -- I'm just getting started researching that, but it seems to me that if I can get away with less bracing, I'll be able to boost the bass response a bit? The sustain will be a crap shoot. The tone -or lack of it- is not a big deal, since I often practice using an electric to keep things quieter.

You can optimise a top for responce, but the size and shape play a huge role in how it will sound. You have probably heard people say a dread will sound like a dread no matter what you do with your bracing and such. This is very true. The bulk of the way it will sound is based on volume and shape of the box. You can certainly refine it and make it more efficient or make small adjustment to adjust the responce a bit.

I might as well ask here, since I'm curious ---is there any reason I'd have to use wood for bracing? Why not my favorite carbon fiber kite tubes?

Spruce has a very good weight to stiffness ratio. You would be very hard pressed to use 100% carbon fiber. Some people have laminated very thin layers of CF into bracing stock with good results. The biggest advantage I see is that CF has no memory issues that wood can have over time, and is not effected by moisture. Big downside is that it takes so little of it to get enough strength it would be very difficult to attach by itself. CF tubes are way too much for bracing the board, I did use them on my last build as buttress braces between the neck block and rim.

Anyway, I'm looking at this as a baby step toward eventually building a true acoustic. I still need to bring up my skill level a lot before then.

I think this will be more challenging than a regular flatop. You have no point of reference to start from. Just my opinion though.

Peace,Rich

[Hector]

I think you should make it like an acoustic guitar, bending the sides and all, If you have a 60mm body, then carve all that, you`re wasting a huge amount of wood, and also the thin sides and back of a real acoustic are there for a reason.

one more thing, 4mm for the top seems too much for me, i`d go for 1,5/ 2mm with an X bracing, you can go thinner if you use a lattice. this will improve the sound of the guitar.

I`m building one based on the dreadnautilus guitar but with a bracing not as complex as carlson`s original... with a bolt on design that lets me remove the neck to travel.

let`s see how that turns out.

[Mattia]

Rich: More depth might help, but it'll add a lot of mass. I'm a little skeptical, honestly, but I don't mind being proven wrong. If I build an acoustic, though, I optimise for acoustic tone.

Mick: the internal volume, even with a 60mm blank, will be less than a quarter of the internal volume of a classical guitar, by my guesstimation.

As for soundholes: very few believe they should be in the upper bout, and while that works, it changes the modes around (although what the modes will look like on a radically asymmetrical body, I really don't know). I've seen little in the way of evidence that it's a 'better' place to put things. The most common guitar with a non-standard soundhole location is...an Ovation. Not what I'd call the epitome of great acoustic tone, but opinions differ on that on

Re: bracing, what Rich said. Spruce is stiff and light, in comparison CF is really, really very heavy for the stiffness it provides. As for sustain, I wouldn't worry too much; a top that's too resonant will likely give you too much sustain, and I wouldn't expect a massive amount of bass from a weirdly shaped guitar the first time around. Also, like Rich said, you're more likely to get a good acoustic sound out of a standard design, even the first time around.

Hector: 1.5-2mm is crazy-thin, not to mention fragile. And lattice bracing (besides being slighly fringe/niche school of building), with all the lap joints, is a much bigger challenge than fan or X bracing, which have been optimised over the past century and have a proven track record. For a nylon string, perhaps 2.0mm (fairly standard), but I don't think you should go too light on a top; loosen the edges (thin them) to increase resonance, but a 3 to 3.2mm center works very well for a standard X-braced steelstring. I'd say try not to improvise too many things before you have a grasp of the basics.

[Hector]

Hector: 1.5-2mm is crazy-thin, not to mention fragile. And lattice bracing (besides being slighly fringe/niche school of building), with all the lap joints, is a much bigger challenge than fan or X bracing, which have been optimised over the past century and have a proven track record. For a nylon string, perhaps 2.0mm (fairly standard), but I don't think you should go too light a top; loosen the edges (thin them) to increase resonance, but a 3 to 3.2mm center works very well for a standard X-braced steelstring. I'd say try not to improvise too many things before you have a grasp of the basics.

sorry mattia I posted the wrong numbers, I meant 2/2,5mm center, 2mm at the edges, but I`ve build 2 guitars that had less that 2mm at the edges.

I`m on my 5th acoustic build right now and none of the previous ones gave any problems. and they sound good! And I think a modified lattice can offer some improvement over the traditional x bracing.

on my last steel string acoustic I made a lattice like on a classical, but with beefier braces. I`m gonna check my notes and then post the dimensions of each brace. worked out pretty good with no top deformations.

works for me, I don`t know about you guys.

Edited February 2, 2008 by Hector

[Mickguard]

Well, you guys are giving me a lot to think about. Looks to me like I really need to study up on bracing, get more clear about how it works and what it can do.

I'm not worried about wasting wood --most of what I'll be using will be 'advanced scrap'.

I can see now that what I'm proposing is closer to an archtop than an acoustic, thanks fryovanni. I'm thinking that it might be easier to pre-carve the back before building up the body. That will make it easier to control the thickness of the back.

I should point out again that I'm not hoping for an acoustic tone with this idea -- what I'd like to achieve is something a little more resonant/full-sounding than an ordinary electric semi. From the description of the Mash guitar I linked too, that guitar achieves that to some extent. He does say that he mostly plays the guitar acoustically.

Also, of the three guitars I've built so far, two are basically hollowed out guitars like this --except the back, sides and top are much thicker in both cases. And neither feature a free-floating spruce top. But both sound pretty nice acoustically, even with electric strings. So what I'm hoping for is to achieve just a bit more. Plus have a cool looking guitar.

But I think Mattia's right, I'll look into equipping it with a pickup system, just in case.

[Mattia]

Hector: 1.5-2mm is crazy-thin, not to mention fragile. And lattice bracing (besides being slighly fringe/niche school of building), with all the lap joints, is a much bigger challenge than fan or X bracing, which have been optimised over the past century and have a proven track record. For a nylon string, perhaps 2.0mm (fairly standard), but I don't think you should go too light a top; loosen the edges (thin them) to increase resonance, but a 3 to 3.2mm center works very well for a standard X-braced steelstring. I'd say try not to improvise too many things before you have a grasp of the basics.

sorry mattia I posted the wrong numbers, I meant 2/2,5mm center, 2mm at the edges, but I`ve build 2 guitars that had less that 2mm at the edges.

I`m on my 5th acoustic build right now and none of the previous ones gave any problems. and they sound good! And I think a modified lattice can offer some improvement over the traditional x bracing.

on my last steel string acoustic I made a lattice like on a classical, but with beefier braces. I`m gonna check my notes and then post the dimensions of each brace. worked out pretty good with no top deformations.

works for me, I don`t know about you guys.

Ah, ok. 2.0-2.5 is pretty standard for acoustic tops; I like 'em a little thicker in the middle, but I do take them down to around/a bit less than 2mm around the edges of the lower bout, pretty much. I'm sure lattice works; my only point is that it's not really the easiest place for someone who hasn't got any acoustic building experience yet to start out with. X-bracing's pretty well established, after all

As for 'benefit', I suppose that depends on what your objectives are; I think guitars are loud enough already, and I like how X-braced acoustic guitars sound. I use modern materials in construction where I find them useful/where I think they'll benefit counstruction (like CF in my main braces right now, to prevent deformation over time rather than add much real stiffness; it's the memory effect I'm after). I also like Larrivee's symmetrically braced stuff, so I will be doing a few double-X guitars, maybe eventually a hybrid X-brace/Lattice top. Did you use traditional spruce braces, or smallman style balsa topped with cabon fibre?

[Hector]

Ah, ok. 2.0-2.5 is pretty standard for acoustic tops; I like 'em a little thicker in the middle, but I do take them down to around/a bit less than 2mm around the edges of the lower bout, pretty much. I'm sure lattice works; my only point is that it's not really the easiest place for someone who hasn't got any acoustic building experience yet to start out with. X-bracing's pretty well established, after all

As for 'benefit', I suppose that depends on what your objectives are; I think guitars are loud enough already, and I like how X-braced acoustic guitars sound. I use modern materials in construction where I find them useful/where I think they'll benefit counstruction (like CF in my main braces right now, to prevent deformation over time rather than add much real stiffness; it's the memory effect I'm after). I also like Larrivee's symmetrically braced stuff, so I will be doing a few double-X guitars, maybe eventually a hybrid X-brace/Lattice top. Did you use traditional spruce braces, or smallman style balsa topped with cabon fibre?

hey mattia,

the first one I built used the larivee symmetrical bracing and it worked out just fine. the second one I used the tradicional x bracing. and now here`s what I`ve been using lately.

It`s a friend's idea to use the lattice on steroids for steel string guitars, he`s a classical builder and came up with this, which works perfectly.

I always use spruce braces, sitka its my favorite. If I can`t find sitka, I use german.

[fryovanni]

I don't think it is hard to get enough strength from braces, I think the pattern you choose can give you different types of control over the stiffness. If you want more strength from a brace, make it taller. I feel like it is best to attach braces that are at least providing 1/4" or so joint surface, but of course a strong taper can allow you to have height and a wide base without being heavy. A person can also remove material from the middle third of a brace with little loss of strength. So you have some basic design elements that can really provide very stiff light braces. CF laminates seem like a wonderful idea, but I am not sure as to the best orientation to make the most of them. Maybe some of the guys with more experince using them could elaborate on this subject.

The X brace system is a wonderful pattern. It offers a very straight forward method for construction, with plenty of documentation to reference. It is easy to control the stiffness of your bracing behind the bridge, because of the elegant placement of your two crossing braces. Double X locks in a point of strength in this area, based on your placement (has plus and minus to it). A modified X / lattice grabs a larger footprint allowing you to adjust the points of strength, but I am not sure yet if that is better or just more complex. Standard X for steel strings is a huge jump in all the right directions for someone who is wanting to use a reliable, good sounding, efficient, controlable system. There are a lot of patterns you can use, but for a first step(or anytime for that matter) into bracing I see X as a natural choice.

Mattia makes good suggestions on top thickness. I think it is important to make sure your bracing and top thickness are in line with each other. Don't try using extreamly stiff bracing with a very thin soundboard (results are sloppy), don't go heavy with the thickness and carve the heck out of your braces (too heavy and not very efficient). Try to strike a good balance. This is where an established pattern and commonly used thickness can really bring you much closer to a refined match, than trying to use a less documented system. Remember if you dream up a new system you may just find out after a few builds (trying to refine it) that it is less effective than a more established pattern (be prepaired for a lot of trial and error, and possible failure).

Peace,Rich

EDIT,

Hector, I just took a look at your bracing. Why are you running bracing under your bridge? I did use a pattern similar to this. I found it to be hard to loosen the top up. I am assuming you have not started to carve down all that tall lattice.

Peace again!

Edited February 2, 2008 by fryovanni

[Hector]

Hector, I just took a look at your bracing. Why are you running bracing under your bridge? I did use a pattern similar to this. I found it to be hard to loosen the top up. I am assuming you have not started to carve down all that tall lattice.

Peace again!

hey rich, this particular guitar has a bridge that doesn`t require the top to be drilled. again, based on a classical guitar bridge.

that allowed the bracing to go underneath it without fear of drilling a brace.

the top is loose, but not so much that the guitar would sound boomy (its a steel string acoustic) and the braces are indeed tall, but very thin. the shadows in the pic makes them look taller.

that guitar is finished and sounds good, better than a friend´s 714 taylor. but that´s just my opinion.

I will try to remove a little more material on the next one. living and learning I guess. but I wouldn`t consider this a bad guitar at all.

the double X bracing is on my mind too. but with some modifications. we`ll see.

[fryovanni]

Hector,

I was just trying to understand what purpose bracing under a bridge could serve. The bridge is such a massive brace in and of itself, that the top is pretty much rigid under it. I think we probably have a lot in common when it comes to thinking about brace patterns, adding height with reduced width, lattice, pinless bridges and so forth. Very cool to hear the project turned out well

Peace,Rich

[Jon]

Seeing different styles of bracing always get me excited for acoustic building. I can't wait till I start.

Very cool work, Hector.

[fryovanni]

This is a pic of the lattice on the build I am finishing up right now.

Not too different in basic pattern concept, although exact placement is different as well as carving. Does really show how playing with a less common pattern can lead people very different directions in search of optimizing that pattern.

This top was right at .100" (pretty stiff Lutzi), the main X is .25" wide and right at 1/2" tall at the main X crossing, The lattice is 3/16" wide and the carves are from paper thin to various peaks(3/16" would probably be a max. height on the tallest peak). It had just loosened up before I attached it to the rim, then I had to refine it a tiny bit more to loosen it back up.

Peace,Rich