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I would be interested to hear opinions on using reverse kerfing.......where the smooth flat side faces the inside of the guitar. I am hearing from a couple of locals who use it that its supposed to stiffen the sides up more, and is superior. Curious to know what you folks think about it?

Standard on my guitars until I started using laminated linings (3 layers)
It does seem to stiffen sides up, if done one piece, or with overlapping veneers at any joins.
Still not as stiff as laminated linings.
Also tends to lessen squeeze out as the kerfs take glue between them.
I've seen normally kerfed linings described as looking like an acoustic baffle

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

It seems to me that the little bit of webbing between the kerfed saw marks to each individual block is borderline insignificant once the sides are glued to the top. But I've never done the math on it either. Intuitively to me it seems a wash.

I prefer the reverse-kerfed lining because it stiffens the sides. For the few times the sides are handled outside the mold, it makes them easier to handle for me. For ease, I’ve recently been installing them in pieces a few inches long rather than as a complete strip. It doesn’t seem to make much difference in stiffness. I have also used triangular spruce linings in some guitars recently. Those sides were almost as stiff as the reverse kerfed linings. Once the plates are on, I don’t think the side the linings are kerfed makes any difference.

I prefer the reverse-kerf lining to the standard type although for the last four or five guitars I've been using the Ryan A-5 linings - only because they're fast and easy to install plus I think they look good.

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"Music is what feelings sound like"

Yay

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Yay.


Mc

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I use laminated/solid linings be a use they are cheap and easy to make, look nice and stiffen the rim (much like I would think reversed kerf linings would). I don’t throng the benefit of rim stiffening is all that great once the plates are glued on but the rim sure is easier to handle when the plates are off.

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Bryan Bear PMoMC

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Next best thing to solid linings. Stiffness wise they are way closer to solid lings than they are regular kerfed linings.

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Here's a bit of heresy: I use reverse kerfing for the back -- because it looks better when viewed through the soundhole. I use regular, slotted kerfing for the top because it allows me to fill the kerfing gaps with tile grout which adds mass (ala Gore/Gilet) at the rim of the soundboard to maximize the discontinuity of acoustic impedance, reflecting the incident energy back into the soundboard. It results in LOTS of sustain (if that's what you want).

Reverse kerf linings are easier to make and do stiffen the sides quite a bit more, at least until the plates are glued on.
If you make them extra tall they can be resawn to make standard triangular linings and tentalones (from the off cuts)
On the last several instruments I have been making linings from bending ply. They act kind of like a cross between solid and A5 linings - look of solid and flexibility of A5.

Definitely yay. I like how they look and they make the sides way more rigid than standard kerfed linings.

If you install standard kerfed linings and then hold the sides by the head block or tail block hanging vertically and then move your arm up and down, the sides will stretch and contract lengthwise like a slinky because they are so flexible. Reverse kerfed linings completely eliminate that flexibility. If you take hold of the head block in one hand and the tail block in the other and twist in opposite directions, sides with standard kerfed linings will twist easily. With reverse kerfed linings, there is no twist at all. That greater rigidity carries over to the closed up box of course. I like the idea of the body being a lot more solid. I don't know if it makes a functional difference that matters in the real world, but I like the idea of it.

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Yay - I went with reverse kerfed linings early on and never looked back. They make a considerably stiffer rim and I considered them a decent compromise between the wimpy kerfed linings and double sides which are a can or worms in terms of process, ep*xy etc but super stiff.

I soaked mine in a wall paper wetting tray (plastic at Home Depot and cheap) and then they bent much easier. Used Titebond original and put my linings on still damp and flexible never had any issues.

Wanted to add since I always try to attribute what I post to who I learned it from. The wetting them first came from Lance who owns the OLF. Works great.

They do stiffen the sides until you glue on the plates, then I don't see how they could make any difference. I find it easier to cut neat inlet pockets for the braces in reverse kerf liners; the regular ones always seem to chip away on the edge. It doesn't make any difference in the strength, of course, but tight pockets look better.

This one could go in the tips and tricks forum post but if you wet the reversed linings then clamp them to the bend sides on the outside and let them dry over night then they will be bent to shape in the morning.

I have noticed they do make the sides stiffer when the sides are loose but again I cannot see how it would matter once glued to the top. Where it is directly glued to the top there would be no difference between kerfed and reverse kerfed. As you move further from the top (or back) to the edge of the lining then that little bit of webbing might have a very slight stiffening attribute in a twisting dimension. But again, is it really so much that of the thousands of variables that make up a guitar will make an actual difference?

So imho I only use them for looks and as mentioned they are a bit easier to work with.




Interesting idea with the tile grout. How many grams of weight does that add? And do you worry about it popping lose some day?

Why wouldn't the added stiffness of reverse linings still be there once the plates are glued on?

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

I was about to do just that when your post popped up. I do exactly the same thing. Installing the linings after they are bent to shape makes installing them easier and they are less likely to break during installation in my experience.

If you want to add that to the tips and tricks thread, I'll defer to you.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

I feel like the decision to use reverse kerf linings (or solid/laminated, which is even further down the stiffness path) is a decision to take as part of broader design philosophy for the instrument as a whole. If you want stiffer sides, yes use them. If you want even stiffer, more massive sides, use solid or laminated linings.

I get good results making the sides stiff and massive, using laminated linings and a relatively “loose” top. Most sb bracing doesn’t meet the rim, the top is thinner at the edges than the center etc.

Last week I worked on a guitar from a well-known small builder - in contrast to one of my guitars it was light as a feather, delicate, quite thin sides with linings of individually glued “tentellones”. The top was lightly braced but the bracing was very evenly distributed and overall there seemed to be no areas I would describe as “loose”. All the bracing continued through the linings. It was a great sounding guitar.

So there’s many ways to skin a cat. The thing is to decide whether you are aiming for a feline filet or a tomcat t-bone and adjust your approach accordingly

FWIW, we do reverse kerfings exclusively. I feel like it gives me a more consistent contact with the rim, where the opposite seems like it would be creating additional "bumps" that would push the kerfing away from the rim on a majority of the body. Again, I stress this is a perception thing and probably not a critical factor for strength, longevity or tone. But, I like the idea that reverse kernings give me the result of individual tennolins (sp?) without having to place each piece individually.

J De Rocher asked:
"Why wouldn't the added stiffness of reverse linings still be there once the plates are glued on?"

No. Reverse kerf liners help keep the edge from bending in and out before the plates are glued on. Once the plates are on the edges can't move in that way anyway; the plates see to that.

The people I used to work with were both engineers, and what I took from a number of discussions and the building guide we used with students is best quoted directly:



To summarize: absent issues of function, cosmetics dominate. In other words, attractive and functional wins over ugly and functional, although we all have our own ideas as to what that might look like in terms of linings. If a rationale is needed for your choice of linings, it's perfectly OK to prefer pretty things over not-pretty things, although you may want to avoid expressing that sort of opinion in mixed company.

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