bracing a tenor top

In following the threads on the forum and going to many websites of makers I have seen tenors with two, three, or sometimes five fan braces. I was wondering if some of you would comment on the reasoning behind the different number of braces. Those who use more exotic bracing tend to explain why they believe their system is worth the effort but I haven't seen much on why those who fan brace use one number of braces or another.

Hi Philstix, let me take a stab at this. First, the bracing pattern of an instrument is part of the overall design and must be considered in that context. I arrived at my bracing patterns by copying designs of instruments that I admired and slowly tweaked the sizes and positions to achieve the sound I was going for. It is a process with me that continues today. My feeling is the modern trend is to go with thinner tops with more, but lighter braces. Most of the luthiers I know have their own method for determining how they brace that may work for them, but not for someone else. For me it is an intuitive process that I can't really explain.

Brad

For tenors I either use 3 fan braces or lattice bracing with carbon fiber laminated top and bottom to balsa. With the fan bracing the tops are somewhere between 1.8 and 1.5 mm thick. Depends on the piece of wood. For lattice bracing the top is 0.8 to 0.9 mm thick.

And just to really confuse you, I've got an Adirondack spruce top for a tenor right now that is just so stiff I'm considering to go with just a bridge patch.

I favour very thin and tall braces as compared to wide short ones. Has everything to do with the cube rule. If you don't know what that is, then you're in for a fun bit of study.

LIke Brad, the rest is just intuitive, and every single top will end up being voiced different in some way than another. That's part of the magic and thrill of building. Don't try to apply a cookie cutter approach to it.

There's lots of theories out there about bracing but it comes down to mostly black magic. Beyond structural duties, braces also transmit vibrations around the top and can establish vibration node points. Its easy to see if the braces do the structural part well or not....but the tone is pretty subjective. There isn't any "right" way to do it because there isn't any "right" ukulele tone.
I'd say the 3 tone bar bracing pattern is the standard on tenor size ukes because that's how the original builders made them and established the popular sound. If the originals were made with X bracing or kahsa style bracing we would think tone bars were exotic.

Its a hazard of uke building.....if you hear a great sounding ukulele you only think of how it was built

I appreciate the input. I'm not really interested in trying to figure out what is best, since as has been said, there are way too many variables to give that any kind of certain answer. I'm interested in what the reasoning is behind a builders patterns. The few ukes I have built have been with three fan braces and the top braces relatively tall and thin tapering off to zero. A uke made with everything else the same but two fanned braces instead of three seemed to have a stronger fundamental but less overtones and a little less sustain. And as Allen said, the variation between one piece of wood and another of the same species, and even from the same tree can very greatly, as the 5 sitka spruced tops I am currently beginning to brace prove. Two are quite stiff, two are a little floppy, and the last one is somewhere in between.

You know what would be really great? If folks could post their bracing techniques and explain why they think theirs is the best route to go. After just a few builds I've come to the conclusion that bracing is one of the most crucial treatments in an instrument. It would be great if those in the know could spread some knowledge.

I'll start with mine. I've only built a few ukes but I've noticed that a slightly taller and somewhat thinner bracing gives a much better volume in a soprano uke of the martinish type, especially when dealing with stiffer woods. And the treble side does seem to need a little more taken off the sides in order for the treble to keep up with the bass. But if you go too thin it seems too much vibration might cause a buzz? Am I wrong?

As many others have posted, I stick with the tried and true methods of the best of the best and tweak from there... it's really the safest way to go. But not the only way.

BTW Philstix, thanks for starting this thread.

Oh, and by the way, thanks to Brad and everyone else who have posted already.

Vic, If you're sticking to "tried and true" methods, why are you bracing your sopranos?

Bracing is something that is always evolving for me, in fact it's changed quite a bit for me in the past few years. For Tenors I go back and forth between three and five braces. Three is usually sufficient and occasionally I'll throw in a couple of tiny finger braces for a total of five. It depends upon what the top calls for. I've done the tall and narrow thing before, but now my bracing is quite wide (1/4") and very short (1/16" to 1/8" over the bridge patch and feathered to zero at the ends). I think the extra width ensures that the braces are going to stay there. Naturally the bracing cannot be considered alone. David Hurd once told me that he relies 80% on the proper thickness of the top and uses the braces for "fine tuning". Like him, I deflection test everything several times during the process.

Like him, I deflection test everything several times during the process.

Click to expand...

Chuck: Could you expand on this, please? What is involved in deflection testing? Do you use the kind of expensive equipment that Roger Siminoff uses or is it a technique that might be more accessible for us hobbyists?

Thanks,
Michael

David has posted some good tutorials of his process on the OLF. I was at a conference in Western Australia where he demo'd for us over a couple of days.

You can view links to his posts here.

Thanks for the link. Allen. Very informative. I am left wondering, though, what one does with the data once compiled and transformed into a colorful chart. What is the luthier looking for in making adjustment either to top thickness or tone bars?

The deflection data is only useful as a way to record and duplicate previous successful instruments. The idea is when you build one that makes you say "WOW", then you go to your notes, check the deflection measurements on that instrument, then build another using the same numbers. Keep in mind that this is only one of the factors that I consider when tuning the tops and I use it as a way to double check my work. You do this long enough and you don't really need measure, you do it automatically, drawing on all your senses. Depending on what mood I'm in, how much sleep I've gotten, how much work I've got to do, whatever, all these things affect my senses and I like to check the numbers. I have to admit though, my thumbs are the deflection testers I use the most.

Just as Chuck said. It's really useless to you without tracking successive instruments and charting what you consider success or failure. The more data you collect, the more useful it can be. But it's only useful if you study it, and then apply what you've learnt to your next build. For too many I think that they are good at collecting data, but taking that information to the next level is more science instead of art.

I'm not much for crunching numbers like David is. I prefer the use of my senses and intuition. I suppose it's the inner artist in me.

I was reading this post and the first thing I thought was "no builder is going to let THAT much out".

I still think that, but, I'll respond anyway. 5 braces. Why? That's what I was taught by my teacher, and by his teacher.

My teacher has since moved to 3 braces, and I've tweaked my bracing to the the point, fortunately or unfortunately, where I can actually install a LRBaggs IBeam. The IBeam was the goal, but I've never installed it. Go figure, I had to do some things to the bracing to make way for the IBeam, and ended up keeping it.

Not unlike Chuck, I can tell you I install 5 braces, and even taper to zero at the ends, but this serves nothing if you don't know what else I do to the instrument - bracing, size, shape, etc., is more like "final touches" and part of the whole, rather than an individual variable. I change the cut of the braces if the instrument is a low g or re-entrant, softwood or hardwood top, etc. It changes per instrument depending on body woods and the sound the client is looking for, a tweak here, a tweak there.

Yes, I can tell you I do all of that, which I do, but if I were to cut and shape braces EXACTLY the same on each instrument, no one would probably notice, including me.

Call it voodoo lutherie (I stole that term from here, Chuck I think), but I know one builder who normally does 3 fan, get a request from a client for a 5 fan (yes, the client requested it). Compared to his 3 fan instruments, the 5 fan lost some volume, but gained in other areas. Yes, there was a difference. There should be with two extra braces on an instrument built for 3. The client loves it, and if he needs volume, he just turns it up, and doesn't even consider the slight volume loss a concession - the overall package wins over an individual insignificant variable.

I can imagine after reading this post, some may say, "okay, volume loss from 5 fan, gotta go with 3," and that's okay, if you play a cheap instrument and installed Aquila's to bring out more volume. I referred to a higher end instrument based of midrange construction, which brings much more complexity to the table as a total package.

Note: I did do an X-brace, twice, but that was for tiples, and you can bet that I adjusted the bracing before gluing on the top of a 6-string.

Aaron