My #4, a BRW and Adi spruce OM

[enalnitram]

Thanks! I showed you guys how I pieced together the center strip, so all of the pieces were very tight. but while I was gluing brace number two, I had it just a little bit crooked, as the glue was beginning to tack. so I had to force it a little bit with both hands, and it came loose a little hard, denting and making a gap in the center strip, the one that is directly under the sound hole! oh well, it doesn't look nearly as bad as it sounds, it is just a fraction of a mm. but my center strip is no longer gapless.

[Darryl Young]

even though I am building this guitar like a 32 OM, I opted for modern-style dimensions of the braces across the lower bout.

Martin, I'm sure you've thought about this before choosing this option. Is there a benefit you see to using the thinner and taller braces in the lower bout vs using the old school wide and low braces? I've only used the old school low/wide braces so I can't comment on how the taller/thinner lower bout braces change things......but I sorta thought the extra mass made it a little easier to get the main resonant frequency of the back down where I wanted it (close to the main top frequency). Thoughts?

[enalnitram]

I hadn't thought about it that way, Darryl. and thanks for bringing that up! it's why i'm posting the progress. I'm not aware of how it might be easier to tune with one or the other. The main things I were thinking about were (and i may be wrong):

1. it seems to me like height will make the braces stiffer than width, and i want them stiffer
2. my first guitar was a 000 with taller lower bout back braces and it coincidentally had the "right" resonant frequencies without me having to even tune anything.
3. (an almost different issue, but...) my second guitar had the wider old style braces and went completely concave on me when we had a long cold snap last january. i hated that.

[Darryl Young]

All valid points Martin.

On the back whose frequency came out about right where you wanted it, what wood did you use and do you remember about what thickness that back was?

I was using EIR back at 0.10" thick and I sanded the wide/low braces pretty good on the sides and made a nice roundover to the top. I actually wen t a bit too far on the upper wide brace.

[Ken Hundley]

I am using all taller, thinner back braces on mine....I think I use 5 for each back. I just like em better. How is that for scientific reasoning?

[enalnitram]

sounds good Ken!

Darryl, on my first, the 000, I handed it to Bryan Galloup back in Feb, and he tapped it in front of a mic plugged into his laptop, and he had audacity going. he looked at it and played it for a sec, and then handed it back to me, and said, "this is right where a 000 should be, and you should have your own table next time." I was so enormously floored, that my eyes kinda glazed over, and the rest of what he said accumulated into a hazy silver orb and kinda floated right past me. but I remember he did say something about (I think) the tops on old martins were a whole step lower than the back, and (I think) my top was a 'g' and the back was an 'a'.

the back on that guitar was also EIR 0.100".

I guess I should be embarrassed, though, that I didn't engineer the end result. I just like the guitar. I hadn't figured out if I cared at that point about tuning to resonant frequences, but now I do.

[enalnitram]

I told you guys all about how I made that crazy sanding wheel thing to put a curve in my brace ends, as well as to use for other things. well, the motor attached to the wheel spins pretty fast. which makes it pretty darn aggressive. i need to figure out variable speed on that.

in the meantime i used my battery powered drill with a handy little drum attachment and 60 grit. it worked real good.

[Kevin Sjostrand]

You are making progress Martin. Looking good. Do you like carving the braces as much as I do?

Kevin

[enalnitram]

I like carving a lot! I haven't been able to get a chisel to easily make a consistent, good looking, subtle curve on the brace ends though, even since I've started working on using scary sharp. i would wind up sanding it smooth. so now i just sand the whole curve with the drill. overall i use a variety of tools, hand and power to work on bracing.

there has been a few new pics this year of 30's guitars in the UMGF bracing library thread. I save those and have a big folder of them on my pc. I try to make mine look a lot like those.

[enalnitram]

no problem. but will a flapper wheel rip a piece of spruce out of your hands, and fling it across a garage like an arrow? because once you get over the shock and surprise of it suddenly happening, it's actually kind of cool.