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I'm currently building a guitar with walnut back and sides. In the past I've always used spruce to reinforce the sides. This time, purely for aesthetic reasons, I'm considering using some of the walnut. Any reason why I shouldn't do this?

Thanks,

George :-)

P.S. Whatever wood I use, I will taper the ends to nothing where they meet the linings.

Hey George, walnut will work just fine. I use it for reinforcements often. It is nice and stable like mahogany.

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Any wood should be fine. Instead of tapering to nothing, I would leave as much as you can to butt up against the lining as that is the worst place to get a side crack. The hard part is to make it look nice.

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Pat

I use cherry/ spruce /d. fir for adding strength and loading the sides . Walnut is good . Perhaps trev will chime in.

You could take it one step further and let them into the lining a bit. Just a little more insurance against side cracks.



Pat

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Leaving the fillets high at the edge of the liner is NOT the way to avoid side cracks. We learned that from a restoration expert from the Met Museum at Carleen Hutchins' courses. What that does is to concentrate the stress at the end of the fillet, next to the liner, and that's where the side will crack; right where it's hardest to repair. Tapering the fillets out over some distance to nothing at the liners is better, but the best is to inlet them.

I have seen a couple of side cracks that I believe were _caused_ by side fillets. They were on good quality imported guitars, that used a soft wood for the sides and back, and deep sides. The fillets, being across the grain, would not shrink in length as much as the sides apparently tried to shrink in width, and this caused the cracks IMO. The cracks were in the flat area below the waist, and ran right across the fillets.

I wasn't suggesting leaving them full height. Certainly taper them to reduce stress. In my case, I use triangular linings and I taper the side reinforcements down to about 1/32 to match the top edge of the linings.

Inlet or full length reinforcements are best. Nice clean work Pat!

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Pat

I take my side braces all the way to the edge of the sides. I align them so they tie to the back bracing.

My biggest concern is as Alan mentioned, unequal expansion of the sides and braces. That is one reason I spray a light coat of spar urethane on the inside of the back and sides. I know it won't stop moisture moving in and out of the wood but my hope is it will slow it down considerably. Although time will tell, but after several years of doing this, no side cracks.

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Joe Beaver
Maker of Sawdust

I do mine the same way Pat Foster shows his with the reversed linings. This is another reason why I like reversed linings. Mostly Mahogany, but Walnut would work equally as well. Have a look at how cleanly Pat has inlet the back braces into the linings. Not trying to take anything away from Pat but the reversed linings make this much easier. Still another reason why I like reversed linings.
Tom

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

FWIW, I simply used 1/32" thick walnut strips to reinforce the sides on my walnut super jumbo. This seems to be thick enough to do the trick, and thin enough not to cause problems. Also, they'll easily conform to the side curves without needing to be sanded. I considered inletting them into the linings, but decided it wasn't necessary - or perhaps I was just lazy. If using thicker side reinforcements, I like the idea of letting them all the way through.

Great information. Thanks! I'd read about tapering them to avoid the issues that can arise when butted against the liners, but not the inletting technique. Good to know!

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George :-)

On my most recent I did what Pat and Tom describe above. Just need to use reverse linings and make the side braces roughly the width between two kerfs. I used a chisel to pop out the small pieces of lining between kerfs, which was a piece o' cake, then glued in the braces using a small clamp at each end and a couple of rare earth magnets in the middle. Pretty sure I'll be doing it this way going forward.

In the past I used taller spruce reinforcements and tapered them down and inlet into the linings. They got a "parabolic" cross section and with the tapered and tucked ends, they looked like tiny braces. I began to wonder if having the reinforcements so thick/tall could actually cause the sides to be too stressed, and even split, when the humidity changes (I don't know if it would or not but Al's comments above seem to indicate the same thing). Lately I have been using strips of wood which are the same thickness as the side hoping that the side moving will be able to bend the reinforcement slightly rather than the reinforcement splitting the side. Again, I don't know if my logic is sound or not. It has served to simplify the process. I make them out of my laminated lining strips so the first layer lays down in sections next to the lining and the next two go over them locking it all together.

These are the best pics I have access to at the moment, but they probably explain better than my drivel above. . .

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Bryan Bear PMoMC

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

I found out the hard way, side reinforcements work, I dropped my White Oak Herringbone D on my concrete shop floor, pretty much on the end block, two nice splits in the back, side was unscathed, Coco binding is pretty tough also.

Best is to inlet (reverse kerf) or overlay (possible with wedge kerfed lining) or go through to avoid the stress concentration problem. I've tended to use Silver Ash (an Aus. wood that is neither silver nor ash) or Aus. blackwood, and occasionally Am. black walnut. All work fine. Make sure your sides are dry, though. If they come out of bending wet, give them a few days at ~45% RH before you block them up.

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

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Some folks seem to be worrying about cracks forming due to the sides loosing moisture and shrinking. One has to have confidence that the reasoning that allowes us to glue braces across tops and backs will also work for sides. I stole the idea of using wooden side braces from David R. Young back in the 70's and while the number of guitars to my credit is not large, not one of them has developed a side crack. As long as the RH is maintained in the proper range I don't see any reason for worry. As Alan Carruth has pointed out the real critical area is at the edge of the lining. Simple answer.......inlet in whatever way that works for you. Thus lowering the effect of the stress riser in that area.
Tom

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

+1 on inletting the side reinforcements into the linings.

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Gene

Politicians and diapers must be changed often, and for the same reason- Mark Twain

I always use side reinforcements on my builds as well, but I always wonder just how effective they are in preventing cracks. After all, they are usually spaced a fair distance apart, so it would seem that a bump in the space where there is no reinforcement could result in a crack. Maybe the adjacent reinforcements would prevent the crack from continuing.Anyhow, for me the side reinforcements hopefully?? helps prevent folding and/or cupping. Then again, maybe only in the reinforced areas.

Sent from my GT-P3113 using Tapatalk 4 Beta

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Under Compensated Nut!

Wilb: The main reason for the side bracing is to prevent the spread of a crack that may happen. But of course there are added benefits as you pointed out.
Tom

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

I have wood reinforcements on a few but also have some with 3/4" cotton/polyester tape soaked in hide glue then finished off with a coat of shellac. Linings go over the tape no problem.

I've heard varying comments on the value of the tape approach but all I'm really going for is to stop a crack if it occurs. Does anyone have repair experience on guitars with tape reinforcement - does it work?

I used wood on a falcate dred I made based on Trevor's plans. I do like the way it looks and the way it provided additional stiffness to the sides especially when combined with the solid linings. Structurally this must be good for limiting/preventing cracks but I wonder if, sonically, is this a good approach for all guitars or useful mostly for guitars with live backs?

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Steve Smith
"Music is what feelings sound like"

I use the same approach for both live non-live backs. Side mass makes a difference, as we know. If sides are made rather thin and the reinforcements flexible, it's possible to drop the main air resonance by 1-2 Hz, which can be quite significant in the scheme of things if you are pushing for a lower main air target.

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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 Trevor. I'm leaning more and more towards getting set up to use the wood reinforcements with laminated linings on all my builds. It seems to be worth the extra work.

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Steve Smith
"Music is what feelings sound like"

Tom West wrote:
"Some folks seem to be worrying about cracks forming due to the sides loosing moisture and shrinking. One has to have confidence that the reasoning that allows us to glue braces across tops and backs will also work for sides."

I'm a little confused here. It's pretty obvious from my experience in repair that braces across the top and back don't protect them from cracking with humidity cycling, and not at all obvious to me that cross grain braces don't cause cracks. Furniture makers avoid cross grain braces religiously, and probably for good reason. We can't avoid them on flat plates, and put up with the drawbacks because other systems tend to have even more problems. We also tend to use design features, such as arching the top and back, that help mitigate the problems. I suppose you could arch sides too, but I fear the customers would tend to regard that as a flaw.

If stopping side cracks from running is what you want, side tapes can be very effective. The main advantage I can see to wood fillets is the stiffness they add, and I do believe they come with the drawback of making some types of side cracks more likely in some cases. As usual, there's no 'perfect' choice.

Alan: My intent was not to say that braces on the sides will stop cracking...! What I was trying to say if we used the same diligence in ref. to watching RH during the building process and later in it's adult life there should be no more reason to worry about the sides cracking then we do the back and top. Hope that clears the air a bit. Sides are also a lot less in width then a back which tends to even things out even though the back is arched. It makes sense to me .................Maybe not others???
Tom

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Im fairly new at this and have always used the same material as the sides in question .... thought thats way was supposed to be lol

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