Pickinbob: Yes it does make a difference what you use for bracing. I recommend spruce because of the strenght to weight ratio. In other words the highest strenght for the least weight. Assuming this is your first guitar I suggest you get the Stew-Mac dreadnaught plan.Also a book on construction such as the Cumpiano book. If after that you want to continue building get the Gore-Gilet books as others have suggested. Good luck and have fun.
Tom

Tom,

Thanks for you time and patience answering my questions. I will check into the StewMac braces. I was initially going to use mahogany or basswood. I have several books on guitar construction that have been helpful. However, as in any endeavor, there are lots of ways to do things. Talking to persons who have experience and skills simply adds to the vast field of information to consider for folks like me.

Again, thanks for you help.

FWIW, stika spruce was used for WWII fighter planes due to its high (highest?) strength to weight ratio.

http://www.woodmagazine.com/material.../sitka-spruce/

Also, I have read that the speed of sound travelling through sitka spruce is fastest of all spruces.

Steel string with Sitka top, I'd use Sitka, Lutz or Adi bracing for the top. Back braces can be Spruce, Mahogany, or Spanish Cedar. No problem with any of those that I know of.

As to plans, check around I'm sure there are some Martin plans around that you can get your hands on.

I'm resurrecting this thread because it has some valuable and timeless information... And because it raised some questions in my mind.

After taking some scrap pine and getting my fingers into the process in hopes of learning something about making the soundboard and braces, I've moved to actually trying to build that first acoustic.

I have two plans, both based on the Martin OM. One plan comes from Jonathan Kincaid's book, the other from LMI. They are noticeably different. I also picked up a plexiglas pattern from LMI which is supposed to match their plan.

The Kincaid bracing pattern opens the bass area a bit from the LMI, which has those braces parallel. The Kincaid bottom braces not in parallel. The X brace on the Kincaid is at 98 degrees, the LMI at 94. Overall, the size of the Kincaid braces have more mass than the LMI version. Kincaid's is designed for scalloping, LMI for tapering.

I'm starting with the LMI version but from what I've read here I'm having doubts about running the bottom braces parallel. While I am far more mechanical than artistic, something is telling me parallel braces won't sound as good as non-parallel. FWIW, I prefer picking when I play.

Again, keep in mind that the bracing is primarily structural, although it does affect the sound, of course.

" While I am far more mechanical than artistic, something is telling me parallel braces won't sound as good as non-parallel."

'Good sound' is, of course, in the ear of the beholder. All of those slight variations alter the tone in some way, probably, but there are so many variables in the equation that it's hard to say just what any given feature really does. In theory, maybe, there's an ideal brace layout for any particular top that would vary depending on the properties of the wood and what sound you're going for. You might, for example, alter the X-brace angle depending on the long to cross grain stiffness ratio of the wood. In practice I don't think anybody really knows how to find that 'ideal' layout for sure . I suspect there are a number of people who believe they do... ;) for the most part, most makers just try something and see if they can tweak it later if it's not exactly what they wanted.

Even if you knew what the ideal layout was, it wouldn't work well if it was not made well. Good glue joints and neat cuts are part of it, but there's also the need to profile the braces so that they work right in context. Other things, like the bridge size and material and the height of the strings off the top get in there too.

All you can do in the beginning is to pick a design you like, for whatever reason, and make it as well as you can. After you've made a few you'll start to see what's going on, and get ideas about how to tweak the design to make it work better in a given case. Some of those ideas will even be right!

Stay with traditional specs/designs to start if you want a guitar not firewood.