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Just about to close it up and wanted some feedback on the bracing as built so far. The guitar is smaller 13.5 LB 9.5" UB and I obviously can't have any larger braces at this point but want to know if I should go any smaller than what's shown. X is approx. 1/4" x .56" at the X.

The asymmetry is intentional but follows no real experiential data, just something I'm experimenting with. Bridge plate is BRW and the bridge will be walnut.

Thank you

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I'd kind of get rid of the peak on the treble X leg, seems too close to the rim.

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Build log

I agree, I'd take the treble side of your X leg down towards the bottom. I might add that I never liked such a sharp drop off ,like on your UTB. Finger braces looks beefy. It might be just the photo, but how thick is your bridge patch? Clinton

What's the scale length? Will the wings of the bridge overlap the x-brace legs?
I'd make a steady tapper of the lower legs of the x-brace from your 0.56" height down to nothing, than I'd probably remove more material from the sides of the x-brace legs.
This is of course only based on the visual, not having the top in hand to flex & tap really does make giving suggestions difficult.

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I like a stout UTB, helps put off neck resets IMHO but I agree the roll off at the ends is quite sharp. The rest appears quite heavy for a smaller guitar.

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Brian

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If those braces are a quarter inch that must be a pretty small top. They look really beefy to me. On the smaller bodies, just gluing the top to the sides stiffens it up considerably as compared to the larger size guitars. If it's a small enough body you might consider the main x could be 7/32 or even 3/16ths inches wide and a half inch tall. The fingers and fans can definitely be lightened up.

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Thanks so much for the replies.

The top material is Port Orford Cedar. Approx. .090 thick. The scale length will be 24.9" - the bridge plate is approx. .095. Bridge will overlap the 'X' as in the drawing in this link.

viewtopic.php?f=10101&t=38360&start=0

I went with 92 degrees instead of the 90 shown,

The consensus seems to be the bracing is heavy in a couple of spots.

Thanks so much for the input. I'll adjust and post some pics later.

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I agree with the other comments. It looks a little heavy in places.

X/fan hybrid bracing like that tends to lean towards a bright sounding instrument. I've tried it a few times (on various guitar-like instruments). POC - from sound samples I've listened to - also seems to have this tendency. Just something to be aware of. You may want to consider a heavier bridge wood than walnut to balance this.

IMHO, those fans are probably going to telegraph. They seem pretty wide and low, but even so, in my experience, fan braces on steel stringed instruments will always telegraph eventually.

Also, I don't agree with the butt joints between the soundhole braces and the X arms. The string tension is trying to cave in the soundboard in this area, and those butt joints could be pulled apart. Consider scalloping the ends.

For a small guitar it is over braced for my liking, it will probably be very tight sounding and not real loud. Just my thoughts on it, I like real active tops with what Trevor Gore calls high Monopole mobility. The top thickness you stated sounds good for a small guitar though.
Go ahead and build it but keep detailed notes on what you have there so if changes are needed you have a place to start

Fred

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Fred Tellier
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It's interesting that nobody has asked you what sort of sound you're after.

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Trevor,

Being after a sound and producing it are two very different universes at this stage in my building experience but in the simplest terms I hope to build a smaller guitar that does things a small guitar would not be expected to do. Larger sound with more bass than expected, and balanced, bright trebles. Not asking too much eh?

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I do have a BRW bridge that I've been contemplating as an option.



Thanks Greg I'll keep those tips in mind.

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Well, on a small guitar, the difficulty is in getting the bass up to match the trebles. So I'd be suggesting that you match the treble side bracing to the bass side to loose some of the stiffness you have there. If you think the bass side will survive as is, the treble side should, too. Going asymmetric, unless you really know what you're doing, usually just ends up with a quieter guitar, as mostly it is extra stiffness that is added. Also, to help get the bass up, go with a live back and don't stiffen the sides too much. I'd be going with the walnut bridge. If you end up thinking it's too light you can always add mass by using heavier bridge pins. It's much harder to move in the opposite direction if you start heavy and want to go lighter. Final point, consider an arm rest. Not one of those bevel things, but a proper arm rest that will keep your forearm off the top. Makes a huge difference on small, responsive guitars. (Well, it does on mine!)

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Thanks very much for the reply Trevor BUT [Ignorance] I'm not getting this at all. Does stiffening a bass or treble side brace tend to amplify or attenuate that frequency?

Your suggestion to scallop the treble side of the X to match the bass side of the X to bring out more bass would lead me to believe that a smaller or more scalloped brace will attenuate or lessen that tone? I surely need a very basic primer on the acoustics of bracing.[/Ignorance]



Good tips and I'll take them to heart.

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Let me see if I understand this a little better after reading more on the subject. The suggestion to match the treble scallop with the bass X brace was not to change the 'treble' side but more to loosen the entire top and create more bass as, I have earned, there is really no bass or treble side to a guitar. Is that at least a little more accurate? Wow, the more I learn the less i know. Humbling experience.

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That's it exactly, Larry. To get more bass you need to keep the three lowest resonances - the "main air", "main top" and "coupled back" in the low range. The pitch of the main air resonance (which has a fairly significant influence on the bass response) is determined as much by the stiffness of the top, back and sides as it is by the box size and sound hole area.

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http://www.goreguitars.com.au

i'm no expert and in general avoid showing my work on forums but imo the bracing is a bit stout. i think the asymmetry will confuse the rolling motion of the bridge by adding an elliptical component to the top motion. sort of like hitting one wave going towards the beach with one coming at it from the side.

what sound are you after? and how does the plate tap?

here's what i'm doing on a size 2 flat top:



the kerfing on both the top and the back is actually one piece reverse kerfing that i broke through at each piece with a razor saw thereby making them "falsoellones". this should liberate some top freedom. the bracing is actually smaller then it looks. (.25 x .5 or so) and not visible under the clamping blocks is the heel block extension butted against the utg. top is .09 thick cedar and the b/s's are primavera.

One thing I didn't notice at first as I viewed on my iPhone was that the x-brace that runs from left to right (upper bout to lower bout) has LOTS of run out....Don't know if this concerns you at all....

I find if I want more bass response in a small guitar, I want to ensure the top is more flexible at the edges so I'd want very minimal bracing out at the edges, hence tapering the braces down to nothing from the intersection of the X (going south on the braces, not north).

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Thanks very much for the post and the picture Arie. It's nice to see other people's work and yours looks very nice. I would like a large sound with more bass than might be expected from a small guitar but enough treble to balance the bass (who wouldn't I guess) but I really have no idea what I'm doing as this is my 4th guitar and I haven't built for a couple - 3 years so my starting point is very much at the beginning again.

And to answer your question about the plate's tap I really couldn't say and I don't mean to be flippant but I wouldn't know one tap from another or a good tap from a bad one. I'm reducing some of the bracing and closin' her up and will have to see what happy surprises occur if any.

I do intend to build more of this size guitar so I'll take detailed notes re: bracing and other such details and use this thread as a reference for future builds.

On a side note, I just discovered Prima Vera at a local wood supplier and it seemed like a great wood for guitar B/S. Have you used it before with good results?

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Very much appreciate the post Rod and I hope my ignorance and my very beginning knowledge isn't too much of a hindrance here on the forum but I just looked up 'run out' so I could even understand that there might be a problem. The brace will stay for this build but I'll look for it the future. What is exactly the problem with a brace with run out?



Thanks Rod, I'll keep that in mind. I've reshaped the braces and am afraid it's till very random with no clear direction in mind and very little understanding of tap tones and even the dynamics of a guitar and how it makes sound. I intend to build many more of these smaller guitars so at some point I'll have close this one up and see what happens. Taking notes on this build and hopefully I'll learn what works and what doesn't as my skill and knowledge increase.

Again thank you very much for the reply.

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OK, here's the sound I'm looking for - not asking too much eh?

http://www.youtube.com/watch?v=0nbXjpW2 ... _embedded#!

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...i keep hearing the term "telegraph" used as a verb in this forum. can anyone explain what is meant...? thanks

Same as "print through"; i.e. you can see the outline of the braces as deformations in the (usually glossy) outside surface of the top. Most responsive guitars will exhibit this to some degree or other.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

I built several guitars using a similar fan pattern. I did have one top crack along each side of the center lower fan brace. However that guitar resided in a house with very little climate control; and it was quite dry as well.

This top bracing will also distort the top and cause it to (ripple and dip down) on either side of all the fan braces too so be aware of that. After that one top cracked, I went to four fans and straddle the center seam and then did not have any more that cracked. I also added 3 small cross grain diamond patches across the center seam joint at the same time too. BTW, these tops can also have a stronger emphasis on mid range too so be aware of that.

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tim...
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as far as tap tone goes it's your own personal choice but in general you don't want a high metallic ping nor do you want a flubby, tubby, tap either. fwiw i usually go for an even tap across the entire top. for me every square inch must sound equal and clean and i'll take great effort to even out the tap after each piece of wood goes onto the top. i'll tap the plate before it's glued to the top and after. i tend to gravitate toward the lower end of tone just shy of the tubby (but still with a bit of resonance) sound because i know that once the other components and finish are added the top will tighten up a bit pulling me out of the hole so to speak-jmho

first time for primavera for me. my wife bought it for a build a couple of years ago and the size 2 is finally getting it. that guitar is actually made from leftover stuff from the closet. it cuts like a gummy mahogany. the interlocking grain can be an issue regarding tearout as it didn't seem to be as firm as hog or sapele. nice sheen to it even rough sanded with 120 grit. scraping really brings out some super nice silking at least on my pieces.

i tend to agree with tim on the midrange issue because i think that bracing pattern will enhance the cross dipole which is largely responsible for midrange activity.