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Pros and cons?

How does the mismatch between outside and inside look?

I have seen it done, looks pretty involved with the forms and vac bags. But once they were dried, they were solid as plywood. That sounds funny..
The guitars that I have seen used similar wood inside and out. So much so I couldn't tell the difference.

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Lance@LuthiersForum.com

I use forms with fitted cauls and LOTS of clamps.
Pros:
-Very rigid sides that are a joy to work with.
-Mass. With the added mass in the sides (and maybe the rigidity?) I think you loose less energy to the sides. I honestly think my instruments with double sides sound better than my first few without...though that could be due to other factors as well.
-Since each lam is thinner than a typical solid side bending is a breeze...and doesn't have to be quite as precise.

Cons:
-Time.
-The forms take up Space.
-Mass. It's easy to build a heavy guitar when using double sides. I think a touch of extra mass in the sides helps the sound but I hate picking up a heavy instrument. So I try to keep all of my sides close to the same mass: just slightly over what solid EIR sides would be. To do this I use cypress or yellow cedar for the inner lam for heavy sides and rosewood (or similar) for the inner lam on lighter sides and I don't go too thick. I'm also very conscious about mass in other areas and do what I can to drop mass where I can (so long as I don't think it will be a detriment).

I think it looks fine.

EIR w/Cypress


Bocote w/yellow cedar


Same


Curly Spanish Cedar w/EIR

I think it looks fine too. Just curious why the side braces. I wouldn't think it necessary. Nice work.

Thanks,
Danny

I only use 2 lams. Both have the grain running the same direction which doesn't do much to stop a crack.
I've considered going with a third, cross-grain lam in between and losing the cross-grain reinforcements but I think it'd end up heavier than I'd like.

I have been doing double sides for about four years. Same species, lower grade on the inside. Bend together in the bender. Solid forms with fitted cauls and clamps. Unibond 800.

I love what they do for the sound and so do most of the good players that have tried them. They have been a plus for sales. Count me as a believer.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

It strikes me that what everyone is talking about here is laminated sides not double sides. We build a model we call the double body which has two sets of sides locked together by spacers made of rosewood and two backs that do not touch each other. In effect it is a sort of resonator like on a banjo and it produces a very interesting and positive effect on the voice of the guitar. The sides do become very stiff even though they are held together by spacers rather than being laminated.

I use a three part laminate in an MDF form I also use an aluminum half side overholtzer bending jig. e.g. 1/4 sawn walnut .070and 2 laminates .022 for a .110 set of sides .Have used epoxy, UF glue titebond and plain elmers white glue or HF,Going to test a new white PVA glue from G. wade which gives abt 13min of setup time. Titebond IMHO sets too fast . to get the clamps on. The rigid sides have more pros than cons.

Same here. I've used PVA and Epoxy-and they're ok-but Unibond is now my go-to for this. There's not a close second.

I would echo Danny's question regarding the side reinforcement braces. Granted your grain is all running the same direction, but it's not like you'd have a split in one of the laminates duplicating a split in the other. I just wouldn't expect it to be as much of an issue. (I could, of course, be wrong.)

I can't imagine that weight is an issue, compared to some of the things that go on in the classical world (internal plywood frames in Smallman guitars, etc.) But I do like light guitars myself as well. I'm building a Torres-style guitar right now with 3mm EIR sides (just cuz the stuff bends so easily) and the body feels like a tank to me, but I'm curious how it will sound in the end.

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Jim Kirby
kirby@udel.edu

"Pros and cons?
How does the mismatch between outside and inside look?"


I glue up flitch matched veneers with the leaves aligned. This method seems to make the back and sides appear and behave much as solid wood. During times of extreme low humidity or abuse the pieces will crack, just like solid wood. I use side reinforcements and build with it the same as when I use solid wood.
The advantage to the method is that low cost "waste" materials from the veneer industry can be recycled into beautiful and functional end products. Fragile veneers (burls, crotches, pomelle, etc.) can have carbon fiber cloth interleaved to give strength and toughness to the construction. With longer pieces harp guitar sets can be created.
The down side is that it is more work. As an amateur this is not a big deal, but for the professional it might be a deal breaker.

If the grain is running the same direction then it acts much like a solid piece of wood so far as cracking is concerned. Really, all it would take, though, to have crack prevention built in would be to skew the grain on the inner lam a touch...But I've always gone with really straight-grained stuff.

Oh, and I wouldn't really call the cross-grain reinforcements "braces." They're only about 1mm thick. And they take practically no time to install.

There is no reason the doubled sides have to be thicker- My 2 piece sides are thinner than a single bent side.

I do skew the grain slightly. I almost always use mahogany on the inside. no one has complained or asked for something different.

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Burton
http://www.legeytinstruments.com
Brookline, MA.

Did you do some with same species Burton? If so any discernible tonal difference?

Any issues with sand through using laminates that thin?

Thanks

Terry

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It's not what you don't know that hurts you, it's what you do know that's wrong.

Very true.
I personally do go a touch thicker: my sides end up right around 2.5mm after glue-up, before any sanding and regardless what the b/s material is I try to keep the mass of my sides relatively similar for all my builds, probably about the same as typical solid cocobolo or abw solid sides.

Hi Terry,

Except for guitars that are already mahogany on the outside I haven't done same species. I don't think I would hear a difference but I can't say for sure.
I've never sanded through, as long as the forms are accurately made the sides don't need a lot of attention.

I'm usually about .3-.35 for the inner and .35-.4 for the outer.

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Burton
http://www.legeytinstruments.com
Brookline, MA.