Official Luthiers Forum!

I am a newby to the forum and do enjoy reading all the information about building guitars. This forum is a great source and it certainly has made it easier for me to do my builds.
My question deals with how stiff to make the sides. It seems to me that the stiffer the side the more the energy would stay in the top. My thinking...although it may be wrong... is that the top is like a diving board and to get more energy out of the diving board it needs to be firmly mounted. If this is true why not make the sides thicker than .090 inches, which is the thickness that I have been using. Of course you have to be able to bend the wood. I have been using a heated pipe and I think that I could go thicker. Thanks...and ya'll are a great group of guys.

Your thinking is correct according to many. Another way many of us stiffen the rim is to use reverse kerfed lining or solid liners. As soon as the glue sets on my reversed kerf liners, they're so stiff I no longer need the mold.


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What James said Pete. Thicker than .090 could make it problematic with bending. I take James's approach a step further and make a reverse kerf lining that requires heat to get to shape. Beyond that you would look into double sides.

Yep. Same here, Danny. I still have a few sets of linings from Paul Woolson which require pre-bending.

Thanks everyone.

Double sides is a good approach. I've been doing that for 5 or 6 years now. Also using reverse kerf lining.

They are extremely rigid and the general consensus from players has been that what they have done to the sound is a positive thing. I like what I am hearing as well.

My outer is around .060 and inner .045-.050. I have been using the same species of wood, just a lower grade for the inner.

It also makes bending figured wood or tight cutaways less stressful.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

I have been laminating the sides on my last couple of guitars, I really like the stability and rigidness it gives to the whole assembly, as others have already said. And bending sides at 0.060-0.065'' is much less stressfull, as long as you don't use much water if you're bending on a pipe, thin pieces of wood tend to warp easily with humidity.

Another route to go if you don't want to laminate is to use laminated linings or reversed-kerfed linings, with additionnal side braces.

Many ways to skin a cat.

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Not much but at least it exists : http://jbluthier.com/

Pre-bending reverse kerfed lining, double sides, laminated linings. Thanks for the responses.

Pete

You can laminate backs and sides from several layers of veneer, which can allow you to use some of the most attractive woods and also be very cost effective. "Scrap" veneer shorts can often be had for a fraction of what solid wood would cost.
If you do want to bend thicker solid wood sides then you may want to consider using a veneer softener, such as super soft 2, which many on the forum have reported good results with (I have not personally used it).

All of the above are good and here's one more. Dominique Field (high end French classical guitar maker) glues upright reinforcements across his sides about every 3" from heel to tail. He feels that this adds the desired stiffness while retaining the "natural" sound he is looking for. This would, of course, also have the benefit of protecting against cracks.

I have two related questions which I believe are consistent with the theme of the thread. Do you guys feel this added stiffness is also beneficial to arch tops? ...and...for those of you who may also use vertical side braces, as I always have, do you "inlet" those into CONTINUOUS reversed kerf linings?

Thus far, I've used more conventional kerfed linings. I glue in a short section, then butt a full height side brace, then another lining section and so on. At the end, I go back and cap my side braces with small pieces of lining. When all of that has dried, I pare off the "caps" so the lining is the same width all the way around, with the side braces behind the lining. This gets the job done very nicely, but I'm always willing to consider a new approach.

Thanks to all.

Clay, I'd like to find a local source for. Veneer off-cuts like yours. What type of bugs was should I be looking for? Are you getting that really nice stuff from a cabinet shop? I don't see a lot of rosewood cabinets. . .

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

cphanna: I use continuous reversed linings and side braces. I remove the wood between two adjacent kerfs to the depth that the kerfs show from looking at the face of lining. This allow the end of the brace to not align with the stress riser at the joint of side and lining. Don't have any pictures so hope you can follow my wording.
Tom

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A person who has never made a mistake has never made anything!!!

I have done five archtops with double sides. Hard to comment on tone. I used side supports on the first two but not after. I think you would be OK without.

It sure makes bending the cutaway easier.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

There's a fair amount about this in Trevor Gore's book. If I read it right, it's mostly the added mass, rather than the stiffness, that does the job. Anything you do to make them stiffer is likely to add some mass, of course. Trevor actually bolts weights to the inside of the side, on the 'straight' part below the waist. When I first heard about this I tried mass loading the sides of a guitar using spool clamps, and saw pretty much what he described. You could argue whether that added any stiffness. Be aware that a change like that can alter the timbre, and you may or may not like it.

Couple of things to mention:

First one builder out our way bends sides at .150"...... Until I saw how he does it I would not have believed it... But it works for him and after all that's really all that matters now for each of us isn't it....

Next there are various camps when it comes to the construction of high-end acoustic guitars. There is the Somogyi camp that is keen to use double sides and just as keen to correct folks when they call double sides laminated sides. What ever.... anyway 2 of the top sounding instruments that I have ever had the pleasure of playing for a bit of time were Somogyi double-sided dr*ads and they sounded absolutely superb IMO.

Keep in mind that Somogyi also does lots of other things as per his excellent books and the double sided thing for him is part of a greater system of building that also includes using tops that at times may be only .065" thick.... Ervin Somogyi also has the ability and access to go through hundreds of tops and hand select as he wishes, most of us do not this level of access depending on where we live and who we know.

Other camps are into light weight instruments believing that the energy from string vibration is finite and as such has to be milked to every degree possible. To them less mass overall is a positive thing. You will find some of the US folks who do vintage reproductions keen to also mirror the at times very light weight of some of the vintage instruments that they are honoring with their reproductions.

I'll second the comments of James, when my reversed kerfed linings are in place the rim can come out of the mold. This was not the case with conventional kerfed linings at least for me...

I've never pre-bent my reversed kerfed linings favoring instead to soak them for about a minute only in a bath of hot water. The plastic, disposable trays available at Lowes and Home Depot for wall papering work great for this. Linings are pulled out of the hot water bath, excess moisture is padded off and then they are flexible enough to bend fine IME. Attribution: Hot water bath idea came from our host Lance years ago.

What do I think? I've always agreed with the OP's feelings about stiffer sides but have yet to tool up for and pursue double sides. As such I go the route of being a anti-excess-mass kind of guy.... and am happy with what results, for now and so too are my hernias....

For a new builder though there is a lot to be said for convention, what ever that is... More specifically you will have 1,346.985 things to consider when you get more into this and as such my mission in this thread is to help steer you in a direction where the immediate gratification that you receive from your own personal Lutherie journey is sufficient to keep you coming back for more....

I suspect that if you build a dr*ad (dread, I like to use the * when ever a word offends me to some degree....)(and I really do like dr*ads but have to keep up the convention as I have for 10 years now...) if you build a dr*ead even from a kit and take your time, learn all that you can, remain open to the idea that there is more to learn than a lifetime of time I suspect that you will be thrilled.

Your furniture will then be in peril as that wooden coffee table will never be able to rest with you eying it over and over again wondering what kind of guitar you can make from it.... Downed trees will no longer be obstructions on your way to the store but potential opportunities for WAS (wood acquisition syndrome leading to GAS guitar acquisition syndrome....).

Lastly when I started I had a lot of ideas for doing this and that sometimes radically differently than what I was seeing being done. Over time most of my ideas were off the mark and unsound and not worthy or pursuing. This is not to say that your ideas will be smiliar but what I am trying to say is that time and more experience filled in lots of the blanks for me and all I really had to do to move forward was keep building, be open to repairing as well, and above all have fun.

And really lastly a mentor would be advisable. Someone that you can trust, who's accomplished in the trade and has lots to show for it. Forums are useful and folks are generally pretty generous with their advice.

Welcome aboard!

Bryan. The best source I have found (not local, sorry) is eBay. They have lots of veneer, and if you are selective, you can get some at much cheaper prices than the typical web or brick store. I use Rio Rosewood for the internal and middle layers. I bought enough to make several dozen sets of guitar sides for about $25. Also, I scored a really nice box of Brazilian rosewood veneer for about the same price; unbelievable value.

Thanks Barry. By the way I was asking "what type of business," auto correct supplied the "bugs was." I'll keep looking at eBay, it seams to be a bit hit or miss whenever I look for veneers. Maybe I'm not refining my search terms well enough. I'm actually interested in the veneers for purfling and rosette making so I can use even narrower prices than I would need for sides.

Sorry to hijack the thread. . . FWIW, I use laminated solid linings

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

When a bending wave traverses the top of a guitar and meets the sides, some of the wave is reflected back into the top and some of the wave transmits into the sides. How much of each depends on the magnitude of the mechanical impedance mis-match between top and side. The impedance mismatch theoretically increases with increasing stiffness and mass of the sides, but is also related to frequency. In practice, increases in mass makes most of the difference at the relatively low frequencies where most of the power is.

Others have given their very valid reasons for using laminated sides. My preferences is for single sides, large top linings, side braces and variable side masses. The large linings add both stiffness and mass to the rim so help reflect more wave, the side braces can be tailored to alter the side panel stiffness (worth ~ 3 Hz or so range on the main air resonance) and the adjustable side masses do lots of beneficial things: increase power and projection, can be used to trim the T(1,1)2 resonant frequency independent of other resonances and alters the timbre of the sound, beneficial for most guitar types but not something you'd do on a flamenco blanca.

Why all of this happens is a long (but very rational) story which can be read about in full in that epic publication that Alan so kindly mentioned.

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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

Yes, Tom, I understand. You've described your process very clearly. Thanks!

This seems to be a minority opinion these days, but I often prefer the sound of guitars with thin sides. They usually have a bit warmer bass, and sound better to the player. There are builders out there with oodles more experience than me, but nonetheless it is something I have noticed.

Going with what Trevor Gore has said, I assume what is happening with thinner (and hence lower mass) sides is that the impedance change is less severe, and therefore waves are not being reflected back from the rim as strongly, but are continuing onwards into the sides.

I have posted this before but here is the ultimate technique for isolating the top. Lead lining around the rim, laminated sides with a middle layer of lead mesh. Massive upper bout bracing and minimal lower bout bracing. Fan braces but no bridge plate.
Made by a character named Bennett Tolliver in the 70's
It was LOUD but rather harsh and midrangy

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It's not what you don't know that hurts you, it's what you do know that's wrong.

Greg B. wrote:
"This seems to be a minority opinion these days, but I often prefer the sound of guitars with thin sides."

'Horses for courses' as the Brits say.

I think a lot of the emphasis on 'keeping the energy in the top' has to do with making a louder guitar. There are good reasons for some people to want that, but not everybody likes the timbre that seems to be associated with it in many cases. Sometimes the only way to find out what effect a particular change is going to have in your building is to try it. Sometimes it doesn't work out the way you want or expect. If you can find some guitars that are made like yours but with that one thing changed you might find out without the need for doing the experiment. Usually there are too many differences to be sure.

Yes, that's right. The guitar examples at the extremes are flamenco blanca guitars where the linings are light and the B & S wood is not much different in density to the top wood (total instrument mass < 1.2kg), whereas at the other end of the scale is the Smallman type classical guitar with the "tone well" (AKA "toilet seat") construction, with thick laminated B & S (total instrument mass ~3.0 kg). They sound a bit different!


The impedance mis-match effect and the "heavy sides" effect are different. One effect of heavy sides is that it moves the node line of the T(1,1)2 mode out towards the rim. The T(1,1)2 mode (main top mode) is interesting in that it is actually a concentric dipole, because the area outside the node line moves quite a lot, but obviously 180 degrees out of phase with the area inside the node line. So there is some phase cancellation of the net radiated sound. However, a lot of what the player hears is sound radiated from the outer area, out of phase, part of the soundboard, (as it's closer to the player's ear) whereas the audience tends to hear the sound radiating from the larger inboard area which has the bridge on it, with the out of phase component netted off. So simply put, (absent near field reflections) a heavy sides guitar sounds louder to the audience due to the increase in the sound radiation area of the inner part of the concentric dipole, but not as loud to the player, as the outboard radiating area decreases. The builder gets to choose which is more important for the usage in mind.

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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

Thanks to everyone for all the feedback. I now see that the mechanical impedance between the top and the sides can be adjusted to a degree, and that this will effect the timbre of the instrument. When I started building guitars I didn't realize how engaging, both mentally and physically, the process would be. Looking forward to many years of luthier enlightenment. And, yes Trevor, your books and The Big Red Books are my favorite bedside reading, although I must say that sometime they put me to sleep in short order.

Thanks, Pete