Acoustic Guitar Construction

John - I have used different woods in the lamination, and in fact it is a common practice among laminators. Brian Burns for instance will use Cypress on his Flamenco guitars, with the sides being .045" Cypress, .025" neutral axis wood, and .025" mahogany for the inside layer. This yields the benefits you mentioned.

I'm going the 2 x .045" route as I think it retains most of the advantages of the 3-ply - resistance to cracks, great stiffness - and eliminates the third ply. I think you're right in that the inside layer does not matter that much, the sides functioning as you pointed out.

As to cost - I buy thick veneers - 1/16" (.060") or 1/18" (.055) - those are very easy to thickness down to .045", hardly any waste - and use between 8 and 11 square feet for back and sides. I can purchase, for instance, some very nice Sapele for - get this - under $3 a square foot. Simple math - at the most, around $30. There are more expensive woods, but even outrageously figured vanity woods, at $6 sq ft are huge cost savers.

Unlike some 'double side' luthiers, I don't pre-bend the individual layers on a pipe or in a form/blanket and then laminate them - at .045" there is no need for that - just glue together and place in a vacuum bag and press into your mold. The vacuum takes care of the laminating clamp force, the mold is just to give shape to the sides.

Yesterday I finished making a double mold and a wider vacuum bag, so I can do both sides at once, and this afternoon I will be using it to bend some maple sides for the Terz-shaped guitar.

Nice explanation Dave. How about a picture of that new mold?

I am in the process of deciding what type of molds to build myself. Female versus male, for instance.

Davy,
To me Sapele is a real nice tonewood. I used it twice and the guitars sound really great. Also I used Honduras mahogany. The sapele was harder to work on, in fact it was the thoughest wood I ever bent. But it could be just that difficult piece I got. Maybe other samples are easier. I agree with Ken that Sapele has more bottom sound than Honduras mahogany. Plus it has beautiful ribbon figure. Over here Sapele is one of the cheapest tonewoods available. Guitarplayers do not seek it, but as a builder I would say: Nothing wrong with it.
Herman

Nice wood, Herman ;-)

John - one good thing about the outside molds that are used for the construction process is - the two halves can be separated, turned up, and used as molds for laminating the sides in a large vacuum bag; or, as I do, use a small vacuum bag that just fits the sides and some breather mesh, push into the outside mold, and clamp to shape.
I know that Michael Collins uses the outside of a mold to clamp to. That's a good idea as well.

John - the first pic is my outside mold - actually a 00-12 mold from KMG that I reworked for the Terz shape - that I spread out to the width of two sides with some 1/4-20" rods and 1" lengths of some old hose. It's important to remember that the clamping of the lams is done by the vacuum bag - the only reason we need a form is for the shaping.
I could use the expanded form as is by laying the sides in the vacuum bag and pressing into the form, and clamping it all to the form.
I could also as in the second pic, load the form and bag onto the inner mold I made out of some scrap fiberboard and copper pipe - the shape is .1" smaller than the outside mold to allow for the bag and the laminates. Both ways work well, as long as the middle of the waist is in the right place and the waist area in general is really attended to.

I really like these Dave. Doing two sides at once helps ensure the raw grain of each side is laid out in proper relationship to the other. The first mold (female) looks like it would be easier to clamp to.