Laminating Guitar Sides and Linings
Laminating guitar sides is one of the many of the techniques I use in guitar making that come from my days of furniture making. There are basically two methods guitar makers use to bend sides, steam or heat bending and laminating, and both methods work. And they will work equally well on classical guitars as well as steel string guitars.
I am not the first guy to laminate the sides of the guitar. The old top of the line Rameriz 1A classical guitars had laminated sides. Daniel Friedrich laminates the sides of his guitars as well. There are more now but back when I started doing it these were the only two I knew of. Bending with heat takes time and is fairly inaccurate. Laminating his it beat on both these counts alone. And there are many more advantages. There is more information on the advantages below.
Torres believed that the purpose of the guitar’s sides were simply to hold the to and back apart and had nothing to do with sound production. He made a guitar with paper-maiche sides to prove his point. An optimal set of sides are to be as stiff as possible. They behave much like the rims of a drum. They hold the skin taut and don’t get in the way. That is exactly how your guitar sides should behave.
When I was designing and building furniture I used this method of laminating exclusively to create just about any desired shape. I found it to be very reliable and easily repeatable. I now use this method to make linings and purflings. If done properly this method will produce lasting superior results. I started laminating sides on my second or third guitar. I have not done it any other way since.
Advantages, Demonstration & Details
Laminating Guitar Sides & Linings
There seems to be a mistaken perception that laminated guitar sides are some form of plywood. This is simply not true. If done properly laminated guitar sides still have a thick enough outer skin of rosewood. There is some other solid wood glued to the inside for strength and stiffness. If executed properly laminating will produce lasting results.
Reasons for Laminating Guitar Sides and Linings
- Stiffness – The most important characteristic for guitar sides is stiffness. Laminating the sides of your guitar will produce stiffer sides than a solid piece of wood that is steam bent.
- Repeatability – Steam or heat bending is difficult to repeat accurately and is time consuming. Once the mold is created laminating sides is pretty quick.
- Consistent Shape, Box Volume and Resonate Pitch – Laminating assures a consistent shape and box size from guitar to guitar. If the shape of the guitars sides differs from guitar to guitar, the amount of volume (cubic inches) inside the box changes, and its resonant pitch as well. This may result in inconsistent results acoustically.
- A Way to Bend Un-Bendable Wood – Laminating may be just the trick for bending wood that will break if you try bending it at full thickness with heat. After wood is thinned down to .060 – 070″ it becomes easier to bend without breaking and may be just the solution.
- Sides without Tension – Building any tension into the instrument is also something to avoid where ever possible. This will extend the life of the instrument. Using turnbuckles or other clamping devices to maintain correct shape of the sides during assembly will build unnecessary tension into the instrument. Laminated sides are locked into the correct shape and no force will be necessary to keep them that way.
- Less Weight – If you laminate using the materials I recommend you are removing a heavier wood and replacing it with a lighter wood which will reduce the weight of the instrument. So you have a lighter guitar that is stiffer. Ideal situation for a classical guitar.
- Increased Stability – Laminated sides will be more stable. There will be almost no movement with humidity changes hence less prone to cracking.
Laminating Guitar Sides
The only disadvantage to laminating guitar sides and linings is that it will take time and care to produce an accurate mold. I do not consider this a disadvantage, you only have to do it once. You are then free to bend into perpetuity with that same mold. It may require a few iterations to dial in the proper amount of compensation at either end for spring back. But getting the right results are worthwhile. The more accurate your molds are the more closely your sides will adhere to the ideal shape and desired body cavity volume of your design. Unless you are a pro, one mold is fine. Molds for the classical guitar designs in both the book and the DVD are available in the store.
Lining molds are the most difficult to create. Linings are made in a two piece mold. Getting exactly the correct amount of offset between the two halves is necessary for the linings to fit properly. The two halves of the mold are offset by the thickness of the sides, plus the thickness of the gasket cork on the surface of the mold. This is very difficult to do accurately by hand.
The Caul System
Cauls distribute the pressure and hence create a good seal. The cauls consist 3 pieces of masonite the same height as the mold thinned down to about .090″. Pieces of 3/4″ MDF act as clamp pads. The pieces at the waist, the upper and lower bouts have to be shaped in order to match the shape of the side of the guitar. One surface of some pads may also have to be angled in order to get proper clamp register.
Our caul kits have pads for 16 clamps. Be sure to place a pad in the middle of the waist as shown in drawing above. The caul kit and drawings are included with the molds. Masonite for the cauls is not available at a thickness of.090″. It is best to thin down 1/8″ masonite in a drum sander.
The Thickness of the Laminations
When laminating wood to create a shape the rule is, more and thinner laminations will produce better results. If you are building guitars using the traditional Spanish method of fitting the sides into slots in the heel, it is best to make the total thickness of your sides slightly bigger than the slot. If you are using the side slot cutting sled with a .100″ wide table saw blade, it is best to make the total thickness of all 3 laminations approximately .115″. This way it will be necessary to trim the sides slightly to produce a tight fit.
The outer layer of wood must be thinned down to between .070″ and .065″. I typically pre-bend the outer layer of to make the process go smoothly. At this thickness it will bend easily without water and there will never be a chance of sanding through. The inner laminations are two pieces of .6mm (.022″) thick veneer.
Wood for Inner Laminations
For laminating guitar sides I find that certain woods work well for the inner laminates. On spruce top instruments I typically use Alaskan yellow cedar, or sitka spruce if I can find some. On a cedar top guitar, pear wood is my wood of choice. Alaskan yellow cedar and pear wood side laminations are available in the store. Before laminating lightly sand the inside surface of the rosewood especially if it has been pre-bent in a side bending machine. Apply the glue evenly, preferably with a roller. Sandwich all the pieces together, place them in the mold with the cauls on top, and apply the clamps starting at the waist.