Should we inlet the X-Braces?

[Allen]

I thought I should start a new thread for this as it's really interesting and has some great points of view on differing construction philosophy. These quotes were taken from comments about my current construction of 2 identically built guitars except for the species of top wood.

You can view the original thread here.
http://www.mcguitars.com.au/forum/viewt ... sc&start=0

Firstly Graham Commented

There are two schools of thought on this (as on most aspects of instrument building). The other takes the approach the locking the end of the X brace in under the linings, even a little bit, helps in preventing the end of the X brace popping loose at sometime in the future. Certainly you want flexibility around the edges, but there are structural considerations as well. I prefer to add a couple of notches a mm or so deep in the lower bout as a bit of extra insurance.

cheers

graham

Then Kim Responded

Graham,

I have done a reasonable amount of repair work over the years and I can say in all honest that I have only ever had to re-glue a popped brace that was not inlet when it had been left too thick on the ends and, in my opinion, anything over 1/32" is too thick.

I have found that if the brace ends are scalloped down to paper thin, they wont normally pop upon impact to the top. Instead, the thin ends will flex with the stress of an impact and act like a shock absorber if you will. I would imagine that this flexing, even minute, would considerably reduce the load on the glue joint.

On the other hand, I have had to re-glue a number of braces that were inlet into the linings. Not only is this a bear of a job, but the noise of a guitar with a loose brace buzzing in it's rebate is unbearable. A popped brace on a guitar that does not have the braces inlet remains playable, even if a little quieter in one frequency or the other.

Anyhow, to each his own. Smile

Oh, must add, great work as always Allen Cool

Cheers

Kim

Grahams reply

I agree entirely that the lower ends of the X braces should be feathered down to a mm or so at the ends, or even to nothing by the outside of the body. I just think it is sensible to lock those ends under the linings. I was stimulated to throw in my comments as I have a friend's Maton here at the moment on which I have had to reglue one of the X braces on the lower bout. It is a well used guitar and has had some 'interesting' repair work done on it previously. Like a Western red Cedar bridge plate. Still trying to work out the logic of that one!

cheers

graham

Kim again

Funny you should mention the Maton Graham, I have had to do a few X brace re-glues on them in the lower bout and I think the reason they are/were susceptible is that they leave/left the ends too thick like is said above. I have seen them an 1/8" even on a double X and at the upper bot end where they were allegedly tucked into the linings, I have seen a rebated to a depth of 3/16 where the brace has been trimmed to just 1/16th"?? Rolling Eyes

Anyhow, my post above was not meant to question you or your methods my friend. I seen what you can do and man you have your chops and are a very skilled craftsman who has my complete respect. I was just pointing out what I have observed in a few repair situations and my thoughts about why it was happening.

And Allen, with the quality of work your putting out mate I would not be hiding in any corners either, that's dancing on the roof top material you got going there mate and I am yet to see a short coming of any kind.

Cheers all

Kim

Craig's comment

Firstly , Happy New Year everyone !

I'll quote this from one of my Piano Building text books ( Wolfenden ), regarding hot glue and braces.

" The most important thing to observe is that the ends should not be made so thin as that the moisture of the air in damp places can easily penetrate to affect the glue ; 1/8th to 3/16 in. is a usual and fairly safe thickness " end Quote

A coat of shellac (may) help thin brace ends stay put. Makes good sense to me. Pianos soundboards are coated both sides B.T.W.

Just thought this may be something some of you guys may want to consider ,especially those feathering brace ends to nothing, and using hot glue. I'm like Graham , and like that little bit of security. so, let the ends in .If the ends are down to about a mm. I can't see them hindering the sound board a whole lot.

Cheers everyone , Craig

[Allen]

I had sealed the insides of my first 4 guitars with shellac but stopped doing it because of many comments about repair issues. If one of the ways of protecting hide glue is to seal it with shellac, what are your thoughts about continuing this practice?

[Craig]

Thanks for starting a new thread on this subject Allen.

As I stated above , air will penetrate through brace ends any thinner than 1/8 " to 3/16 " , and so the hot glue will degenerate over time. A coat of shellac is no guarantee against that , although it may help.

Cloth side braces should be sealed for the same reason. Good reason for builders such as George Lowden and others to continue using yellow glue.

I have been using hot glue for over 35 years and love the stuff . It was my job as an apprentice to mix up our hot glue batch for the other tuners in the workshop when required . I gained a real fondness for it ,but there are certain applications where other glues may be more suitable.

The use of hot glue seems to have become rather trendy of late among guitar builders. Some of these "hot glue snobs" ,who have mostly had little experience with the stuff,should maybe rethink a little.


Regards to all ,Craig Lawrence

[Dave White]

The use of hot glue seems to have become rather trendy of late among guitar builders. Some of these "hot glue snobs" ,who have mostly had little experience with the stuff,should maybe rethink a little.

Craig,

I've taken your advice and done a little rethinking ... it was a very tranquil and peaceful moment. Thanks It's kind of nice to know that my instruments are bio-degradable.

But more seriously, how much "air penetration" (days, weeks, months years) in your experience do you think it will take for a brace end of less than 1/8" height glued with hot-hide glue to have the glue degenerate enough to let go - and (as your piano handbook quote talks about damp air) what are the critical relative humidities? "Hot glue snobs" (or should that be hot air snobs) demand to know these facts as we won't be able to sleep at night and will spend all of our waking ours sucking out the air through the instruments soundhole, soundports and any other orifices we can think of

Would it help if I made my hide glue yellower - I believe pissing in the glue pot was the "old fashioned" method?

[Craig]

G'day Dave ,

I've never pissed in a glue pot as yet , and don't intend to start

The conclusions reached by Wolfenden are based on experience . A whole lot more experience than modern guitar builders. As to how long before your instrument becomes troublesome would depend on the climatic conditions it has endured.

Not trying to be a smart arse here Dave , just passing on what I think should be known to hot glue users.


Cheers Craig Lawrence

[Hesh1956]

Good thread!

One of the things that I see on other forums that I do not agree with is this misconception that HHG is the end all to be all..... It seems as if some users of HHG and how often they can use HHG for different things that in many cases make no sense at all are better builders, have more hair on their chests (this is directed at males....) and are superior and more advanced then others who may use say Titebond.....

Mind you I also use HHG and love the stuff. But I see it's real value in it's ability with a super hard, very thin at the molecular level glue line to be better at transferring/transmitting vibration. So to me where it counts to use HHG is for the top bracing, plate joining, bridge and bridge plate and any place where the plates need to act as a whole and not inhibit the free flow of vibration. I see no value in HHG for gluing the blocks, installing the kerfed linings, installing head plates, fret boards, frets, etc.

Makers in the olden days used HHG where ever they could because this is largely what they had and all they had. Had they had Titebond, a very fine glue, or Fish glue, perhaps a finer glue, would they have used HHG every where?

On another forum the few who attach the plates to the rims and use HHG cite no sonic value nor can prove same but instead revel in how wonderful their chops are for being able to pull this off.

As for inletting I agree with Kim and there are lots of examples of vintage guitars that did not inlet the lower X-brace legs that with proper care over the decades are fine now. The trick as mentioned above is to feather the brace away to nothing AND to use best practices while using HHG i.e. having all the braces and clamps in place in 15 seconds, excellent fit of parts, properly mixed, fresh HHG, and dry runs to be sure that you can pull this all off in a timely manner.

Lastly, and perhaps more importantly is this idea that I will throw out here. All of the examples that most of us have for how to build a guitar come from factories in many cases like Martin, Taylor, Matron, etc. Companies are inherently risk adverse and when given the choice of reducing warranty claims going forward or making better sounding guitars today they of course get conservative and over brace, inlet the world (all braces) and use thick tops etc. Their products go to any one and everyone and will be subjected to the most appalling abuse that any musical instrument could ever hope to avoid.

On the other hand when we price our guitars at $3K plus our market is different. Our buyers are not entry level, leave it in the trunk on a 110F day idiots. Typically, not always, they are much more informed in the care and feeding of a quality guitar and have come to become our customers because the brick shit houses offered by the factories just simply don't flip their switch and generate the excitement of tone and oneness of a fine instrument becoming an extension of the player that factory crap does.

I don't inlet my lower X-brace legs favoring to free up the top more and provide an instrument that sounds great today, and not have to wait 50 years from now..... I also believe that if those of us who will sell an instrument will properly qualify a prospective client AND educate them refusing to sell to anyone with more money then dedication to caring for the instrument that everyone will have a better experience.

Some of the top builders in the world today are not inletting their braces and Somogyi is an example and there are many more. HHG is great stuff when used where it makes sense AND properly in terms of the slightly more complex methodology. I use Titebond for my side tapes exactly for the reason stated in prior post, so the bugs don't eat exposed HHG. But if you wanna use HHG for this and coat it with shellac this problem is solved too.

Remember folks that we ALL have a tendency when newer to building to over engineer and over build. Play an nice 2.9 pound guitar and see, feel, and hear the difference AND be sure to take care of it too. Lamborghinis, Aston Martins, Steinways, and Somogyis all require a great degree of dedication from the owner to maintain peak performance but the pay off is clearly worth it for those who appreciate the finer things in life.

[Kim]

Hi Folks,

First a point in clarification. As far as guitar repairs are concerned, I have worked in the main for experience rather than dollars. I have always turned away any instrument of historic value as I do not feel that I am experienced enough or qualified to take on that kind of risk. When I now say that I have only ever had to re-glue braces that had been installed with yellow glue, this is not meant as a pan for yellow glue in any way, rather it is an indication of my own lack of experience with historic instrument repairs.

However, it remains my opinion that in every instance I have come across where a brace end had popped, regardless of whether that brace had been tucked or not, a contributing factor to this failure was the fact that the ends of that brace had been left too thick. I have concluded that, aside from any other contributing factor, such as glue degradation from excessive heat, upon some form of impact being received to the top of the guitar, these brace ends had been so robust as to resist most of that force completely thereby transferring most of the energy from that impact to the glue joint causing it to fail. So there

That out of the way, I am not sure that I can understand the quote from Craig's piano builders book being applied to guitars, but more on that later. First I would like to share a few points that I think should be considered when looking at this topic. Hide glue is somewhat hygroscopic, but then so is shellac and all of the wood in and around a brace. The up-take of moisture from the air is not restricted to end-grain, however end-grain is indeed more likely to be affected. To my mind, if there is an issue with thin brace ends coming unglued when exposed to "The moisture of the air in damp places", like a canary in a coal mine, it would be an indication of what lay ahead in time for the entire instrument and therefore the instrument should probably be removed from that environment.

Now, back to my questioning the application of Mr Wolfenden's statement to our own situation. In keeping with those points I made above, regardless of how thick or thin a brace is at any given point along it's length, the line of the bond remains constant, it's very thin. Therefore over an extended period of exposure to "The moisture of the air in damp places", it is understandable that a piano, given the hygroscopic nature of all it's components, including the shellac, the thin spruce of the soundboard, the end and sides of the braces and the exposed sides along the length of any glue line, would face catastrophic failure in this circumstance.

The key words here are "extended period of exposure" which is something that a piano, given that it is so big and heavy and generally permanently allocated to it's place within the household, is more likely to encounter than a guitar. Those who have undertaken some furniture restoration would probably be aware that an old lose hide glue joint can be made good again if it is injected with hot water and clamped. This fact not only demonstrates how hide glue can re-absorb moisture, but also how that moisture can then dry out again quite quickly and reform a bond as good as ever.

My point is that a guitar is generally only ever exposed to "The moisture of the air in damp places" for a short period of time. Probably too short of an exposure to cause any real damage. Once the guitar is removed from that environment, any ill affects should be reversed as things dry out a little. There is also the point that a guitar when not in use is generally stored within a case which, to my way of thinking would insulates the instrument, to some extent, against larger swings in moisture levels.

Some food for thought.

Cheers all

Kim

[James Mc]

Hi All
Just a couple of thoughts on this topic… My experience is very limited and the little formal training I had was from a guy who only built and repaired classical guitars. While I know that the fan braces on a classical wouldn’t be subject to the same strain as those of a x braced steel string, it is interesting in terms of the moisture issue to look at how some of the magnificent old guitars were braced.

These pics are from the plans for a Herman Hauser and seem to be the middle ground from the half dozen famous classical guitar plans I have. They all have the cross bracing on both the tops and backs reinforced under the linings or side braces.

Yet the moisture issue with hide glue doesn’t seem to hold true when you look at the fan braces, which are very light on all the plans. On one of the Torres plans the fan braces are triangular 4mm wide at the base 2.5mm high and taper to 1mm. over the last 30mm. I’ve seen a couple of very old classical guitars pulled apart that were made with hide glue and the fan braces seemed fine on both of them after 60 plus years. We had to remove the braces on one of them and it was a chore getting them off.

On the issue of sealing a guitar with a coat of shellac on the inside. The old guy that taught me tried this because he was concerned about the humidity in Brisbane (try North Queensland). But he had stopped doing it because he said it killed the warmth and he thought it would take too long for the top to settle in. These probably wouldn’t be as much of an issue with a steel string.

[Bob Connor]

Dave and I don't inlet any braces south of the soundhole on soundboards.

The X-braces are feathered down to nothing where they disappear under the linings in the lower bout..

We use hide glue for plate jointing, braces and glueing the bridge.

Titebond for glueing the top to the rims and all other back, lining, tail and end block glueing.

We do, however change how we inlet the back braces depending on what we are building.

Here's a pic of the back braces on a Mahogany Dread that we're building for a bloke in Tassie.

The braces were left to 1.5mm and inletted because of the larger spans involved in this style of guitar. We just felt that the 16" width needed a bit more strength and Mahogany is not as stiff as some of the other woods that we use.



This next pic is an 0-18 which is only 13" across the lower bout and it's Ziricote which is much stiffer across the grain. This one had the back braces feathered into the linings in an attempt to free up the back a bit.



When I was down in Tassie for Christmas I got to play the Myrtle OM that we built a few months back (which was the first guitar that we feathered the back braces)

This guitar actually rumbles your guts when you play it. The interplay of the back with the top is considerable which I put down to the feathered bracing on the back.

I had an Indian Rosewood OM (some of you may remember Trev the Parabolic - inletted back braces) with me for comparison. Trev's a very nice sounding guitar but is not in the same league as the Myrtle one.

I believe that feathering the back braces makes a heap of difference but really it depends on your style of building, what woods you are using and what you are trying to achieve tonally from the instrument.

Mind you, Dave and I tend to push tolerances to the limit but that's the only way you will find out how far you can go.

Bob

[Allen]

Great reading here.

As most everything in a guitar is hygroscopic, then shellac is more of a method to slow down moisture getting at the hide glue, at least that is what I'm getting from this discussion. So does an instrument living in the wet tropics probably needs a couple coats of shellac on the inside surfaces?

By finishing the inside with shellac, does it pose much of an issue with repairs that may be required in the future?

[Kim]

Allan,

I think you are on the money, I think the best shellac can offer you is to act as a buffer against extreme changes in RH, and my own feeling as expressed above, is that this buffering affect should be enough unless the guitar was kept in a constantly damp environment.

Will shellac then impede a future repair? To a certain extent I guess maybe it could. But then if the above is true that could be a trade-off well worth the hassle as it may be affective enough to prevent a lot of repairs from being required in the first place. Also, as only those surfaces not actually sealed within a glue joint would get coated, it is difficult to see how shellac would realy cause that much of a problem. Sure it may slow down the removal of the worn or damaged part, but once done the shellac should leave a clearly defined foot print for the replacement component.

My main concerns would be the same as those suggested by James earlier, and that is in the short term the effect that the shellac may have on the guitar tonally and in the long term how this buffering effect against RH swings may also retard the process of the guitar opening up over time.

Cheers

Kim

[James Mc]

Hi Allen
I think a thin coat or two wouldn’t be too bad, it would make it a bit harder to repair but the possible benefit from doing so in our part of the world could well a be a repair or two prevent. I suspect that Barry Kerr for Woodtone Guitars gives his an inner coat of shellac.

I personally won’t be shellacking the inside of the soundboard on the classical/flamenco I’ve just started but I will give the inside of the back and sides a quick coat (just thicknessed the yellow cedar back and sides… eek what a mess, fine yellow dust everywhere).

My compromise on the top will be to give the braces and maybe a small area around them a light coat. From what I’ve read the issues with moisture and guitars go way beyond those of HHG. Expansion and contraction of the timbers can cause all kinds of joint separations, warping and cracking of timbers. Seems to me that moisture and drunkenness are the two top guitar killers, so if a little strategic shellacking can help with one of these issues it can only be a good thing. Unfortunately there’s not much we can do about people getting shellacked and falling on, dropping or swimming with their guitars.

[Kim]

Hi Allen
Unfortunately there’s not much we can do about people getting shellacked and falling on, dropping or swimming with their guitars.

And this causes problems you say James??? Well there ya go

Cheers

Kim

[Allen]

Yes, Berry shellacs the inside of his guitars. I get wood from him fairly regularly, and he's told me he does this to help with wide RH swings.

This is the first time I've heard about hide glue being effected by high RH. I was more concerned with wood moving about with changes in the RH. It would be fairly common for an instrument to travel from here on the coast to up on the Tablelands and experience a drop of 40% in the RH in less than an hour.

I'm going back to shellacing the inside of my guitars.

[James Mc]

Kim
I watched a guy I was travelling with serenading (well trying to) a gorgeous local girl from a boat when we were in Pittsburgh (USA). He was a little shellacked at the time and lost his balance dropping the guitar into the river. Dropping the guitar didn’t help him because he fell anyway, landing on the guitar that he then used as a float to swim to riverbank. From memory it was a Martin so no real harm done, made a nice fire when the timber dried out. The maiden in this story found the whole episode hilarious and agreed to go out with him… proving once again that “make them laughâ€

[Kim]

Nice story James here is an image I used for an early avatar which takes things to the next level



Cheers

Kim

[matthew]

I think sealing the inside of an instrument to slow down moisture absorbtion is a good idea. After all, the outside is fully sealed and this does not hurt the instrument, nor impede future repairs. Shellac, unlike oil finishes, does not soak into the wood and is easily removed if necessary. And other things stick to it really well. I sealed my bass on the inside, ribs and back with one coat of shellac and will continue to do so on other instruments.

Big sudden changes in RH are far more likely to cause plates to bend and split than to cause even thin hide glue joints to fail. And if a hide glue joint does pop, it is probably doing you a favour by being a "release valve" for other unwanted wood movement. If it didn't fail, you could end up with a crack. usually easy to reglue.

[kiwigeo]

Hey there Matthew, no posts from you for ages.... I thought you were dead!

What have you been up to in the shop of late?

Cheers Martin

[matthew]

I thought you were dead!

Dead???

Martin, since when does my life on earth depend on weekly forum posting???? You've watched too many episodes of "Lost" I think ...

I've been in Europe over Christmas.

Workshop has been in hibernation. I'm now back and raring to continue on the cornerless bass and a few other things. But first, a big sharpening session to start 2008 with sharp gouges and planes.

Matthew

[kiwigeo]

Good to hear youre alive and kicking mate and looking forward to progress pics on your latest project(s).

Cheers Martin

[Bob Connor]

Nice to see you back Matthew.

I wondered where you'd disappeared to over the last few weeks.

Bob

[matthew]

I was here:

[Rick Turner]

In the first place, there is a better alternative to "yellow glue", and that is the LMI white glue. It's just as easy to use and it exhibits less "cold creep" than typical yaller carpenter's glue.

Second, this idea that moisture will penetrate wood and degrade hot hide glue joints is just nuts. If it were true, then all the glue joints between tops, backs, and braces or top or back center seams should be just completely falling apart on several million guitars made before 1955 or so. Do you think that French polish or nitro lacquer prevents moisture movement through wood? It doesn't; it merely slows things down a bit.

Most of the degradation of HHG joints is likely due to the glue not being freshly mixed in factory environments, especially at any facilities less careful than C.F.Martin. Gibson, Harmony, Regal, Washburn, etc., etc. were not particularly careful about their use of HHG. Old glue would be reheated the next day, and the day after, and the day after than, ad nauseum (probably literally!). Heat regulation was spotty at best.

As for tucking braces...it all depends on whether you want to free the top to vibrate nicely...

Well glued braces do not spontaneously come loose in any climate I'd feel comfortable sending a guitar into. If your clients are living in the jungle or swamps, they should probably play Rain Song or CA guitars.

[Rick Turner]

One other issue...we shouldn't take too seriously the experience of piano makers or repair techs. Pianos have much broader cross grain distances, and so the stresses built up when pianos go through humidity changes are much worse than we deal with on guitar tops. There is much more shear stress on brace-to-top joinery with piano soundboards, and the much larger cross sectional area and length of piano bracing makes them even less able to move with any humidity changes.

There is no evidence that I've seen that supports this theory of hot hide glue degradation because of thin wood in guitars. This is the over-intellectualization that happens when people spend more time thinking of potential problems than at the bench fixing and building. Some luthiers should turn off the brain every now and then and just build some great guitars.

[Paul B]

Do you think that French polish or nitro lacquer prevents moisture movement through wood? It doesn't; it merely slows things down a bit.

Agreed.

There is a tendency to think that if you put a finish on you are preventing moisture ingress. Slowing it down? Yes, a bit. Stopping it? Not even close.

I spent 4 years in R&D trying to prevent moisture ingress into supercapacitors. I coated these things in every type of polymer you can think of (that are known to have moisture barrier properties). I'd developed a very sensitive method to measure the moisture ingress vs time. Man oh man, I would have been better off smacking my head against a brick wall for 4 years.

Other scientists will tell you that capillary action and osmosis are weak forces. My come-back is usually; "Go away and try preventing them, then come back and tell me how weak they are".