Laminating Guitar Sides - Luthier Tips du Jour Mailbag
In this episode, Robbie O’Brien shows how to laminate guitar sides.
Video Transcription
[on-screen text reads: Luthier Tips du Jour Mailbag]
Mailbag question: Can you offer some advice on how to laminate guitar sides?
Robert O'Brien: Today's Tips du Jour Mailbag question comes to us from Georgia. "Robert, I'm considering laminating the sides of my guitar, but I'm not quite sure how to best go about doing this. Can you offer some advice? Paul, in Atlanta."
Paul, the first question I have is why? Why do you want to laminate your sides? Were you're sitting in your underwear late one night in front of the internet, surfing around and you came across laminated sides and thought, "Wow, this is a great idea. I'll do this?" Well, if so, that's fine. I like for my students, however, to understand why they're doing something. Don't just copy somebody else. It's no fun going through life doing that. Figure out the why behind it, and then move forward if you want to, but do it with an education. Figure out why. Don't just do it. Have a little wisdom behind it, let's say.
Why would you want to laminate sides?
All right. So why would you want to laminate the sides? Two reasons, structural and tonal.
Structural reasons
Let's address the structural, first of all. Some sides are prone to cracking, breaking or rippling across the grain. A lot of times we see guitars have slight ripples in or low spots in the sides. That's not uncommon when bending sides, because we're introducing moisture and heat. And wood doesn't like that, so it tends to cup, and bend, and twist, and break and do all kinds of things.
Perhaps also, you have a high dollar set of sides that you're really worried about bending around that cutaway, the pucker factor's off the charts. So perhaps thinning them down to a thickness that is suitable for bending, and lowering your pucker factor is good perhaps, but then they're too thin so you need to laminate them to get them back to an adequate thickness.
Tonal reasons
So those are some structural reasons of doing it. Tonal reasons of doing it. Now this can get pretty involved, so I recommend if you want to take it a step further, go out and get the books by Trevor Gore, good friend of mine in Australia who actually wrote the books on modal tuning. And he explains the why behind doing laminated sides when it comes to tone. Basically, it boils down to this, and I give this example in my class, I think Trevor also gives this example, is if you have a swimming pool. You jump into it and you create a wave. If the sides or the barrier of the swimming pool are plastic, or rubber, or some absorbing material, then that will absorb, and you reduce some of the efficiency of the waves because they're being absorbed. If you have a side that's made out of concrete or a brick, when the wave hits it's immediately reflected back into the pool.
So a guitar is the same thing. The wave will hit a dense or stiff side and be reintroduced into the soundboard, and therefore you have an instrument that works a little bit more efficiently. Not a lot of energy in these instruments to begin with. So anything that we can keep in the top or in the soundboard is better for their overall sound. Now, obviously not all guitars need that. A flamenco blanca for example, you don't want it to reflect as much sound. You want it to absorb some of it. So you need to know the why behind this, Paul. Don't just go out and do it. Design the instrument with this in mind, or the lamination with the instrument in mind of why you're going to do this.
Options for laminating the sides
So the next problem we have is how? How are you going to laminate the sides? And there's several ways to do that. A lot of people these days are using vacuum pumps. However, a vacuum pump can be expensive. You have to buy some gear. The bag, the pump, accessories, odds and ends to make it happen. And sometimes that becomes a little bit cost prohibitive for some people. However, there is a company called Roarockit, and I believe this company is Canadian if I'm not mistaken. And they started by making vacuum bags with manual pumps. And it was used for the skateboard industry. Guys that wanted to make their own skateboards could do it now, and laminate and form the board using this manual pump vacuum press. So it's a really interesting way of doing things. It's now being used in the furniture industry. It's being used in the luthiery industry and instrument making. So it's a neat way of doing it without having to have a large investment right up front.
The Roarockit vacuum press
And if you like, I'll show you how to do it. Let's go over to the bench, we'll get it done. So Paul, here's a couple of the vacuum bags that I got from the company called Roarockit. One is large enough that you can even do double tops or you can use it to glue your braces to the top or the back. The other one is the size for doing sides, and this is the one we're going to use. So the kit comes with the bag, it also comes with some vinyl tubing that's hooked onto this inlet here, and then it's hooked onto this base. Once you put your materials inside here, there's a reusable seal here. You just peel off this little vinyl strip. And I'll show you how to do all this in a minute and make the seal, then put the pump on there and just manually suck all the air out and pull the vacuum.
Really slick idea. They stayed up overnight to think this up. I think it's going to work really well for us. So let's get started. So here's the pieces I'm going to laminate together. One is a side and I've pre-bent it. I've thicknessed it as I normally do my size down to 1.6 millimeters. And I'm going to laminate that with only one lamination. Some people do two. In this case I'm going to do one. I'm going to do a piece of 0.6. No, actually I think this is 0.5 Indian rosewood veneer. So 1.6 and 0.5 comes around about 2.1 millimeters, leaves me plenty of room having a 1.6 to be able to do my sanding and scraping of the bindings and stuff on the outside if I'm careful. So as the adhesive, I've heard of people just using regular instrument maker's glue from LMI. I've heard of people using fish glue. I've heard of people even using the polyurethane or gorilla glues.
In my case here, what I'm going to use is a two-part epoxy. Now remember, one of the reasons why we're doing this is that introducing moisture into very thin pieces of wood causes them to cup, and warp and things. And that's what we're trying to avoid by doing this. So I'm going to stay away from the water-based glues. However, some people are able to get them to work. I just choose to use the two-part epoxy in this case. So here's a little tip for you. If you want your epoxy to have a little more viscosity to it or a little less viscosity to it, you can put it in a bath of hot water here and get it to soften up a little bit. That way it flows out a little easier. You could also heat it with a heat gun as you're applying it.
Mixing and applying epoxy
And I've got a small cup here to mix with. Be careful with your mix ratio. Make sure you read the instructions. Get the mix ratio right. Also, you're going to want to use gloves when you're mixing. If you decide to do it by volume, that's fine, or you can also do it by weight. Follow the instructions on the back of the epoxy, and make sure you get that mix ratio right. So I'm going to apply my epoxy to the thicker side [Robert applies the epoxy to the inside of the guitar side], and it doesn't take a lot. You don't want this stuff oozing all over inside the bag once you get it inside there. Now to spread it, I'm going to use a credit card. Now I've heard that the rich luthiers, they use the American Express cards. However, I'm just using an old supermarket card here, and that seems to work just fine. And you've got about 30 to 45 minutes to work with your epoxy here. So you should have plenty of time to get done what you need to get done, including rip a hole in your gloves. The important thing is you make sure you get even coverage everywhere.
Now if you want to do a three-ply, which some people do, you probably could get by without even pre-bending one of your sides, because this stuff is flexible enough that it would probably bend without having to heat it. However, since I'm just doing a two-ply and I've left my side a little thicker, I've decided to go ahead and pre-bend it. All right, so now I'm going to take my veneer and just place it inside here [Robert sets the veneer on the inside of the guitar side]. Notice I have not pre-bent the veneer. What I'm going to do though is take a piece of tape and put it right on there like that to help hold that veneer to the outer veneer [Robert tapes the end of the veneer to the end of the guitar side]. Out here on the ends, I've even seen guys come in with a staple and just put a staple on each end here to help hold those veneers so they don't float around [Robert tapes the veneer to the guitar side on the edges all the way around]. But I think the tape ought to be just fine. Now, you don't want to tape this stuff too securely, because if it needs to slide as you're doing your clamping in your vacuum, then it needs to be able to do that. There we go.
Using the Roarockit manual vacuum press system
Now, we're almost ready for the vacuum bag. Before I go there though, I'm worried about getting glue inside my vacuum bag. So I'm just going to place some plastic wrap around this thing to help keep any squeeze out from getting inside the bag. All right, and now we're ready for the Roarockit vacuum bag. And once it's in the bag, you'll notice that it starts to try and flatten out a little bit. No big deal, because now we're going to put it over a form and help it maintain its shape. So once the side is into the bag, you're going to take a piece of this material here. This is just a breather material that goes between the valve and the bottom of the bag, so it doesn't close the seal and stop pulling the vacuum where you need it. So I'm just going to place a piece of that in there, and just tape it in there over that valve.
Next thing we're going to do is close the seal, and I'm just going to peel off this piece of film over the adhesive part. Make sure you save this, so you can put it back on there and reuse that adhesive later. And this is some really sticky stuff, so make sure that you get it to clamp all the way down. Really create a seal there. So with the side into the vacuum bag and the seal made, you need to put it over some type of shape to maintain the shape. And what I've chosen to do is just reuse my LMI bender that I used to bend the outside veneer there. You could also make a male-female form. You can make a camelback type form and clamp it down with clamps and things, but I just found this real convenient just to place it right back inside my bender like that. I'm even going to place a piece of spring steel in there, underneath it to help give it a little bit more support, like so.
And then now I can just go ahead and lower the waist here, take it on home. And it doesn't take a lot of pressure, just something to hold it down, make it take it's shape. Now I'm just going to take a couple of scrap blocks of wood here, and just place my clamps right over the top like this, and just bring it in and help maintain its shape. Make sure that you've got your side clamped in there parallel, and pushed all the way down against your form. Now we're ready to create the vacuum.
And the valve secures the vacuum so I don't have to pump it all the time. However, over the first few minutes I want to make sure it's not leaking. So we'll come in and pump it a few times, make sure you're getting a good vacuum. See how the bags collapsed there? Getting a nice vacuum there. And there you have it. I'm going to let it sit overnight, and we're good to go.
And here's what the sides look like after they come out of the vacuum bag [Robert removes the plastic from the sides], and they're still flexible enough to go right into your form. So Paul, as you can see, there's a little bit more effort involved, but I think the tonal advantage and the structural advantage can far outweigh that.
Advantages to using the Roarockit vacuum press
Now here's a few more advantages to using the thin air press from a Roarockit. There's no expensive equipment to buy like a pump. Just that will set you back several hundred dollars. There's no noise from the pump. It's a manual system. The bags are reusable, flexible enough that if you decide to do bracing on your top of your bag, the bag will mold over your bracing.
Also, there's no uneven clamping from having to use clamps and clamping cauls, if you decide to do that system. Also, if you tried to do a male-female mold, that's darn near impossible to get those to match. So this system, you don't have to have a male-female mold. You can use either an external or an internal mold. And the best thing about this is it's just as strong, gives you as good results as using an electric veneering system. So Paul, if you're wanting to get into laminating your sides, perhaps this is a way for you to do it, so happy building.
[on-screen text reads: More Luthier Tips and online courses available at www.obrienguitars.com. Private and small group guitar building and finishing instruction available.]
