Laminated sides questions

[Eric Knapp]

Hi, everyone.

I'm using laminated sides for my next two guitars. How many layers do you use? How thick do the sides usually get? Do you use linings with them? If so, how thick is the lining?

Thanks,

-Eric

[Barry Daniels]

I have used two layers of standard veneer thickness (0.023") with a show layer around .050". This makes for very strong and stiff sides. You could definitely go thinner.

On my latest guitar I also laminated the linings and they were triangular with a max thickness of 1/4".

[Eric Knapp]

I have used two layers of standard veneer thickness (0.023") with a show layer around .050". This makes for very strong and stiff sides. You could definitely go thinner.

Wow, I'm over-building and over-thinking. I have one show layer that is 0.050". I was thinking of using two layers of basswood that are 0.080", and then an inner layer that's also 0.050". I suspect that would make extremely strong and heavy sides that are totally unnecessary. Hm, if the basswood wasn't so white I think I could go with the show layer and one inner layer of the basswood. I've seen videos of very thick laminated sides and also some structured sides that led me on the path to over-building. Time to rethink this before I glue them up.

On my latest guitar I also laminated the linings and they were triangular with a max thickness of 1/4".

I have enough reverse kerfing for a few guitars so I'll probably go with it once I decide on the laminations.

Thanks!

-Eric

[Alan Carruth]

Making the sides heavier can alter the sound; it tends to 'keep the sound in the top', and can increase the power. Gore covers this in his book.

[Bryan Bear]

I only have a very vague understanding of the concept of making the sides heavier and increasing the impedance at the rim. Alan you say 'keep the sound in the top' that makes intuitive sense to me but I struggle with what that actually sounds like. Or maybe the better question to ask is what is the trade off in sound?

I use laminated solid linings so it is very easy for me to increase the mass of my rims by using denser woods and/or making them taller. But. . . I'm not a good enough maker (or make enough guitars) to pretend that I can predict what those changes are doing. . .

I don't mean to hijack the discussion. I ask because if one were to do laminated sides, they could also build that concept into the design by choosing thicker veneers or heavier veneers.

Eric, you mentioned 0.05 show with two 0.08 basswood and one 0.05 inner veneer. That comes out to 0.26. My sides with linings come in around 0.32 so you would be close to not really needing linings. If you were planning to use a wide purfling scheme you could just laminate one more narrow strip of veneer around the rims and skip kerfed linings all together. That is, if the thick heavy rim was something you wanted to explore.

[Eric Knapp]

I only have a very vague understanding of the concept of making the sides heavier and increasing the impedance at the rim. Alan you say 'keep the sound in the top' that makes intuitive sense to me but I struggle with what that actually sounds like. Or maybe the better question to ask is what is the trade off in sound?

I think that would be very hard to predict. To this old rookie there seems to be a lot of factors that determine sound and knowing which ones do what would take far more time than I have.

I use laminated solid linings so it is very easy for me to increase the mass of my rims by using denser woods and/or making them taller. But. . . I'm not a good enough maker (or make enough guitars) to pretend that I can predict what those changes are doing. . .

I hope to make a few good guitars in my time. Good as in playable and sound decent. I just hope they also hold together for a while.

I don't mean to hijack the discussion. I ask because if one were to do laminated sides, they could also build that concept into the design by choosing thicker veneers or heavier veneers.

Eric, you mentioned 0.05 show with two 0.08 basswood and one 0.05 inner veneer. That comes out to 0.26. My sides with linings come in around 0.32 so you would be close to not really needing linings. If you were planning to use a wide purfling scheme you could just laminate one more narrow strip of veneer around the rims and skip kerfed linings all together. That is, if the thick heavy rim was something you wanted to explore.

I think I do want to explore thick and heavy rims. The next few guitars are still in the learning category so it doesn't really matter what I do. This will be fun at least.

Thanks,

-Eric

[Alan Carruth]

If you use Cladni patterns to look at the way the assembled guitar vibrates it's pretty easy to show what happens. The loudspeaker-like 'main top' resonant mode is the most effective radiator of sound on the guitar, because is has most of the lower bout moving in the same direction at any given time. If you sprinkle some glitter on the top and drive it at that pitch you'll see that there is a stationary 'node' line all around the perimeter of the lower bout. It's usually a couple of inches in from the edge, so what's happening is that as the bridge (say) is moving 'up' the rim is moving 'down'. This has to happen because momentum is conserved: if the mass of the bridge is moving one direction there has to be some mass moving the other way to balance it. If you add some mass to they will not have to move as much to balance out the movement of the top; the node line moves outward toward the edge of the top. This gives more top area moving in the same direction to produce sound.

There's no free lunch, of course. The pitch of the top mode will change; most likely dropping a bit, and other modes that are coupled to the top, such as the Helmholtz-like 'main air' resonance will change. How this will alter the sound is a bit hard to predict in the abstract; where you end up depends on where you started out, and we don't know that.

Gore has worked out ways to predict some of these low-order modes with reasonable precision mathematically. He actually builds in 'pads' on the sides, in the straight part below the waist, that have hardware in them, so that he can bolt on weights to tune the modes. He tests the assembled guitar out, and calculates the amount of mass that will be needed t reach his target frequencies. Apparently the mathematics are just within the power of Xcel to compute.

Keep in mind that Gore is focusing on getting the most power out of his instruments: as Calkin said: " Give them power and they'll hear tone".

Note, too, that what we're looking at here is the mass of the sides, not the stiffness. I checked his result out by putting a bunch of spool clamps around the edge of the top, and measuring the movement with an accelerometer, and saw pretty much what he predicted with no change in the side stiffness. Side stiffness could also be a factor, of course, but I haven't looked at that.

It should be possible to check this out on your own guitars by adding poster adhesive to the sides. I'll note that, in some cases, a given mass of poster adhesive has less effect than the same mass of something rigid that is tightly bound; the poster adhesive can wiggle. Still, with enough weight added to the sides you should be able to hear whether it made a change that you want.