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Good Morning!

This is my first post here on this forum, but I've been a lurking for quite a long time and can't tell you how grateful I am for all the great advice that is offered up in this place

I'm working on my second guitar which will be a 13 fret OM and I've laid out the symetric bracing pattern based on Jean Larrivee's guitars and William Laskin's old article that appeared in Fine Wood Working quite some time ago.

I would really appreciate any advice that I can get but I do have some specific questions/concerns.
- The x-braces will be 7mm x 15 mm. Is this too heavy or too light for an OM size guitar

- finger braces. William Laskin's article shows that they go from the x-brace right to the edge of the soundboard. I'm not sure if I should stick with this or if I should taper the braces down to nothing well before the edge of the sound board (as is shown in William Cumpiano's book).

- Upper Transverse Brace - I would like to use a low and wide brace 12mm high x 18mm wide so that there will be somewhat better access to the truss rod but now I'm second guessing myself and am thinking that a taller brace with an access hole drilled into the brace would be better.

- Bridge plate. Is it too large? The plate is just over 2mm thick and 42mm wide. The bridge I will be using is 26 mm wide.

- The symmetrical tone brace behind the bridge plate....I really have no idea if this one is in the right place (I'll attempt to attach a picture). I've placed it about 5mm behind the bridge plate. Might it be better to butt it up against the bridge plate either by moving the brace up or by making the bridge plate larger?

Any advice would be greatly appreciated!

Thanks

Gary

I can't seem to get my photos to post. I'll try to figure out what I'm doing wrong.

Gary: So hard to answer this question. But just a few thoughts. Think your X braces will be OK.Make sure you use stiff material,test it.The bridge plate at 1"+is a bit too narrow for my liking. I like to have the plate wider then the bridge so that there is over run on front and back. I use a bridge about 1.125" or so wide,so my bridge plate is at least 1.5" wide and generally wider. I think the UTB should be as your second guess . I like about .375" wide by .750" high with a through hole for rod adjustment.I'll let others jump in on some of the other bits.I have used tapered braces as per Larrivee but use normal lightly scalloped tone bars.I have had fair success with this but have dropped the tapered braces for more traditional lightly scalloped ones. I find this works better for me. Have never used the totally symeterical bracing. Good luck and have fun.
Tom

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A person who has never made a mistake has never made anything!!!

I think you should be fine except for the UTB. I would make that taller and drill for the truss rod. Although FYI Larrivee 6 string x's are 8mm.

Still haven't been able to figure out how to post photos so that all of you would have an easier time making comments.

Thanks for the advice!
I'm using Lutz spruce bracing from Shane it does seem to be really stiff...I'll read up on how to test them.
My planned bridge plate is 42mm so I hope that is okay given that I'll be using a 26mm bridge.
I'll take the advice on the UTB for sure!
and thanks for letting me know Larrivee braces are 8 mm

I'm having a blast!

Re photos. The most usual problem is size. They need to be re-sized to less than 200 KB. Depending on your system, Windows XP, 7, Vista, or Mac, as to the software solution to accomplish the re-sizing. If you are using Windows XP, there is a resizer HERE. There is an aftermarket version for Windows 7, Vista, and 2000, HERE

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Waddy

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Sound Clips of most of my guitars

This is a top for a grand concert sized guitar, which is 15" wide. (I'm all in inches, so you'll have to translate) the X is 1/4" thk x 9/16. The plate is .100 x 1-1/8" My bridge is 1" wide, so the plate is slightly wider than the bridge, as Tom describes. The #1 brace is 3/8" and has an arch like a little bridge. I don't think it matters much about the finger braces, just taper them down to nothing at the linings.

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I would love to read the Grit Laskin article, what issue was it in.

Fred

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Fred Tellier
http://www.fetellierguitars.com
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Waddy thanks for the picture resizing tip! I've got a mac so I'll try to find out how to resize the picture.

Dave thanks for the providing the picture the dimensions you use!

Thanks!!!

Gary

Hi Fred,

I found the three articles on line (I'll see if I can find the link) so I don't actually have the issue numbers but the articles were published in the November/December 1987, March/April 1988 and May/June 1990.

Gary: Sorry,I mistook your bridge size for the bridgeplate. In my mind both your dimensions for the bridge and bridgeplate should be fine. Take care and good luck with project.
Tom

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A person who has never made a mistake has never made anything!!!

Fred : If it's any help the issue #s were 67, 69 and 82. Plans are included in one of the articles but if I remember correctly there was a lot of missing info when compared to some of the more recent building books.Plans were complete,but missing written how to. But still a worthwhile read in my opinion. Fine Woodworking has downloads but you have to have a membership.....Not sure what that means.
Tom

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A person who has never made a mistake has never made anything!!!

Fingers: Most builders taper the braces to ~nothing, but the effective 'end point' is hard to define since the taper often goes so thin. Most end them between the kerfing and ~1/2" inboard of that. Keep in mind that once the brace height tapers to be less than the top thickness, it's not doing much for stiffness.

UTB: A taller brace is much more common, as stiffness is proportional to the height cubed. A 12mm h x 18mm w brace has an "I" of 2592 mm^4 ("I" = (1/12)*b*h^3, a measure of stiffness). A typical UTB would be 5/8" h x 1/2" w, which has an I of about 4000 mm^4.

Lower braces: A symmetric-lateral layout of 2 tone bars is unusual (Larrivee excepted). A lateral brace butted to the bridge plate is often called a PMTE, but this usually has additional braces below it.

Here's a common OM layout, if useful: http://www.grellier.fr/plans.php?lang=en

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David Malicky

Gary,
I built an OM using those plans a few years back and it still sounds and plays great. As I recall the braces were lightened up a bit due to the smaller body size but otherwise fairly consistent. That article is like Colonel Sanders publishing the 11 secret spices. I suggest following closely on this build to use as a baseline, then make mods to your next one (there's always a next one!).