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Wanted to get some input on my bracing. I'm following the Natelson/Cumpiano book for this classical. I know its a bit rough in some places, i have yet to go over and really smooth it all up (1 mistake was not thicknessing the bridge pad to what i wanted before gluing the fans on, had to sand a bit in between), but i wanted to get some input on the heights i have on the bracing pattern. upper transvers is 7/16" and both cross struts are 9/16". believe the fan braces are 1/4" and slightly thinner on the outside two on either side. Cumpiano basically says that he thins stuff down after initially gluing and forming the braces to get the stiffness where he likes it. This being my first i have no point of reference point. Just wanted to know if where i have them is "close enough". (top thickness is between 0.100 and 0.110.)

Thanks in advance!

Lots of questions, before giving answers. What's the top wood? How thick is the top? Did you taper the edges of the lower bout thinner than in the center, around the bridge? How thick is the bridge pad? Did you use Coumpiano's doming method? How much doming? Did you spring the braces in?

MY first observation is that you are still way over braced, if you have a relatively stiff top. The pattern you are using is similar to the standard Torres pattern. General size of Torres braces would be 7 mm wide and about 3 mm high, with some variations depending on the wood. So, 7 mm wide would be about a quarter of an inch, but 3 mm high is only about an eighth of an inch. Also, you will want to get rid of some of the heft in the squareness of the braces. You can take off the upper corners, making them more rounded or triangular in shape without changing the stiffness much. If it were my top, I'd be doing some severe wood removal, and tapping as I went. What you are looking for is a good sustaining, musical tone, in a low register whey you hold your top near the edge, up by the #2 TB, or when you hold it at the tail. The tone should be fairly even around the lower bout. Evenness is very important, in my estimation. Those closing braces need to come down with the fan braces, too.

Some other areas where I would be removing wood would be the finger braces above the TB below the sound hole, and the sound hole patches, though I doubt that is critical. The TB's don't look bad, but you'll probably want to take them down closer to the top at the edges, when you use this type of brace. I don't use this type of bracing, so I have no real experience there. How tall are the TB's? You may have said, but I doubt you need anything taller than about 15 to 16 mm in the center. That would be just over a half inch. You should also look at tapering the TB's to a tall triangle. Look at Stephen Boone's build of a Flamenco guitar, on this website, he has some great pictures of brace carving. It'll give you a better idea of what your braces should look like.

Have you weighed your top? How much does it weigh. When I weighed the top of my current build it was in the 165 gram area, but I do use different bracing.

Post some answers to the questions in the first paragraph before you go off making a bunch of changes, and lets see what you really have.

Others may totally disagree with my assessment of your situation, so you might want to wait for some other posts.

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Waddy

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Sound Clips of most of my guitars

Very difficult to tell from images but I'd say if you are following the book closely then you will be ok. FWIW typically I keep the 3 braces in the center full size and taper the outer ones as needed. Your lower braces could probably be feathered a bit more too.

I took a minute to find Stephen's post on the Flamenco build. While the bracing pattern is different, more straight than fanned, for the fans, but the TB's are nicely done, and will help a lot in the weight of the guitar, and the response, overall, of the top. Here is the link viewtopic.php?f=10101&t=27124&st=0&sk=t&sd=a&start=25

And, just for information, here is a picture of my most recent top. Remember, different bracing pattern, so it's not exactly the same, but it'll give you an idea of what I was saying. My braces on this guitar are a fat 4 mm wide and the tallest are about 6.5 mm and the shortest are about 3.8mm on the wings of the lower bout. The closing braces are about 3.5 mm tall. I suppose what I'm trying to say is you don't need to be as heavy as you are, even on your first guitar. I'm not recommending excessive changes, just a lot of trimming and tapering, which will reduce weight and have limited effect on stiffness. The lighter top will be more responsive than a heavier one, even if it is too stiff. I might add that these braces on my #5 are bigger than the braces on my other 4 guitars. This top was pretty stiff longitudinally, but was really floppy across the grain, so I beefed things up by making the braces a bit wider. On all my other guitars the braces were 3 mm wide, instead of 4. The heights vary dependent on the sound of the tap, I get. This one sounds really good right now.

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Waddy

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Sound Clips of most of my guitars

Top is german spruce (LMI kit) which is thicknessed to between .100" and .110" depending on measurment point, you could assume an average thickness of .105. Its fairly stiff with the grain and when thicknessed was in my opinion very flexible perpendicular to the grain. lower bout is not intentionally tapered. the bridge pad was 1/8" (should of been 1/16) i sanded it down abit after the fan braces were glued on (this was a mistake that im living with now). Not sure what you mean by spring the braces in, which probably suggests that they are not. I did fallow Cumpiano's doming technique, i used Pro/e to draw up the radius template i wanted then made a maple template from that and used that to mark and hand plane the radius onto the bottom of the lower cross strut (the only curved brace on the top). the two Cross struts are feathered to 1/4" height while the upper transvers is feathered to about 1/8".

Other than missing the thickness on the bridge pad i've followed the book. I've tried tapping the top and would agree that from the sound its over braced. If I did my conversions in my head right i think we have the same/similar over all height for the LCS UCS and upper transvers braces. I believe my fan braces blanks started at 5/8" overall height and the middle three should be at about that height, the lower ones are maybe 1 to 2 1/8's" lower. I would weigh the top when i get back from work, however i dont have any means to do so.

From what you've said i should basiacally fix the "shape" of the cross section of the fan, finger and v braces and possibly reduce their height a little further. Possibly add a bit more taper to the LCS UCS and upper transvers as well? IE more of a V shape rather than the domed shape the braces have now?

Nate-
Looks like you are doing a good job and making progress!

You've gotten some very good advice already- I'll just chime in here with a couple of comments- just my '2 cents worth' after building a few classicals.

There are two themes to consider - stiffness and mass. For a classical, you want to have an easy-to-drive top which generally translates into low-ish mass. You need enough stiffness to control the sound/tone and make sure the top is strong enough.
Mass: A digital (postal) scale is pretty useful - a lot of classical builders record top mass and especially bridge mass. If you are going to weigh the top, (or do Chladni patterns or other testing), it's a good idea to trim it a bit closer to the final outline.
Shaping the braces ('gable' tops aka pointy, or rounded) affects the mass more than the stiffness, but is mostly in the 'very fine tuning' or cosmetic area - the mass of all the fan bracing is quite small compared to the top plate.

Stiffness- Top thickness and brace height are at work here, mostly. Your top at 0.105 (2.7mm) is plenty thick enough, and leaves some room for thinning (accidental or deliberate!) when you are sanding the top. Lots of classsical tops are in the 2.3-2.3 area when finished. I wouldn't worry too much about the bridge plate at this point, since it does have a 4mm+ thick rosewood 'brace' aka bridge glued to it on the 'other side'.
A lot of classical builders work in mm these days, so a mm ruler and a cheap digital caliper that reads in mm and thousandths of an inch is very handy. Fan braces vary from maker-to-maker, some are wide and 'flat', others more skinny and tall.
Some numbers (in mm) from my recent projects (these are right from the plans)
Barbero flamenco- Fans 6w x 3.5 tall, closing braces 6 w x 2.5 tall, bridgeplate 2 mm thick
Rodriguez classical - Fans 4 x 4 and 5 x 5, closing 5w x 3 tall, bridgeplate 3/32 inch thick

So I do think you could probably take some height off the fans and especially closing (V) braces.

I 'scoop' the ends of the transverse braces the same way I do in a steel-string (so that I can run the braces through the sides and hide the ends with the binding), but this is not the traditional classical way.

Cheers
John

I got distracted and John got a good post in there, with good information.

Good numbers. I think, while I might take my top a bit thinner, that it is within, what I would call a normal range, and probably should be fine. I think, for the most part what you took from my post was right - mostly additional tapering, both at the ends (particularly the tail ends) of the fan braces, and changing the vertical cross section to more of an inverted V shape or a steep sided parabola. Doing this will loosen up the tail of the instrument a bit, and open up the sound of the top. I would also work the closing braces down a bit, as I think they can be lower than the fan braces. I won't comment on the join in the center, as I've seen it both ways (tapered to the center and left at full height at the center). Doing this should make the top much more responsive.

When I asked about doming, as I recall, Cumpiano recommends using 1/8" poster board or cork or something like that, laid in the solera, and cut out in the lower bout so that the edges of the top sit on the raised perimeter, but with the upper bout left at full thickness. The fan braces are then pushed and clamped to the top, which springs the top into a dome in the lower bout. It may be that you left out that step, and it's not critical, but it makes a difference in how a top will act, and increases the stiffness slightly after bracing. If it's not domed, I'd take a little less off the fans. Either way, I think you can take the outboard fans down to about half of what they are now, if they are close to the center ones, and the inboard pair, from those, splitting the difference between the outboard ones and the center three at present height. While doing this, I would pick the top up and tap it frequently, listening for that musical sustaining note when you tap it. You may hear the most difference as you taper along the length of the fans, and lighten them up. Go slow and listen often. You'll probably get a higher tone with limited sustain first, then, the more you take off, the lower the tone will go, and the more sustain you'll get. Stop when you feel comfortable with it and hear a tone you like. You can go too far.

One thing, I'm telling you what I think. Don't do anything you are not comfortable with. If it were me, I'd be looking at websites, and what other people's braces look like. There are lots of pictures out there, on this web site and others. Take a look over at http://www.luthiercom.org, and look at some of the classical builds over there. There must be 10 or more, including mine. One for sure to look at is the classical that Colin Symonds built for Dave White. It has a very similar bracing pattern to the one you are using. His fan braces are pretty standard Torres dimensions of 7 mm wide and 3 mm high, but carved to perfection, and his guitars are astonishing in sound quality.

_________________
Waddy

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Sound Clips of most of my guitars

One thing to keep in mind about weight: most of it will be in the top plate itself, with only about 1/4 of the total being the bracing. Of that, the fans themselves account for very little weight, but, of course, they contribute a lot of stiffness where you need it. What it comes down to is that you could take 3 grams off the fans and go from 'robust' to 'weak', so just keeping track of the wight is not as useful as you might hope.

My handy calculator says that your top is at about 2.7mm, which is about right for an 'average' piece of Euro spruce, at least for the way I build. Here's where knowing the weight of the top might help, particularly if you has the weight without the bracing. The reason is that stiffness along the grain for softwoods at a given thickness pretty much tracks the density. If your bare top was much lighter than say, 125 grams, that would suggest that the wood was pretty low in density (and stiffness), and maybe should get somewhat heavier bracing. If it was much more than 145 grams or so, that wood is probably fairly dense, and thus would be stiffer at that thickness than most wood, and it would need less bracing, or, even better, could probaby be thinned out a bit. Keep in mind that those are 'bare' weights: the braced top will be something like 25-30 grams heavier.

Thanks guys!

Wade, i will definitly look up the guitar you mentioned by Colin Symonds.

It will be difficult to take too much of the fans over the pad because of the mistake i made not taking the bridge thinner, I will try my best to at least fix the cross section of the braces and take the heights to what im comfertable with, after seeing some of your guys bracings, i really think i could thin out the cross and transvers bars a bit as well because i think mine are a bit wider.

Any way, im not married to the idea of getting it right the first time, Rome wasn't built in a day after all, I will be happy if it is playable and i can get the action set up ok, not to mention not messing up the neck angle =P. In the end the tone CANT possibly be worse than the junky cross over nylon string im playing now

I'm guessing you are mistaken here. 5/8th would be way to big for fan braces. 5/16th... maybe?



That's a good attitude. I built my first classical right out of Sloan's book about 18 years ago. It sounded great right off the bat, not the best but whatever, and I still play it till this day, looks like hell but sounds great and has been a great friend.