|
estebanana -> RE: J. McGuire playing S. Faulk Maple cutaway (May 12 2013 2:22:05)
|
quote:
nteresting bracing pattern mystery
Looks like you were thinking about that open woody sound you get with fewer braces.
You wanted more control of the doming then 3 fan braces would give, so you went with the flat braces.
You didn't want the guitar to be over powered by the basses so you added the closing bars, but inverted them to keep with the open theme
Anyway, where were we? Oh yes bracing.
Sean your idea is close, but I was not thinking totally about arching. When Jason Mc Guire went to Australia last summer he met Jim Redgate and looked at a flamenco guitar he had made. Jason explained to me that Redgate intentionally reverse arches a section of the top in his classical guitars. I was thinking about this idea and thought that the old flamenco guitars I've seen that sounded good can often have a very flat if not dished out top between the bridge and sound hole. I don't know if that has anything to do with the sound, I say that because there is always a guy who has an opinion on these things. But Jason explained Redgate's idea, whether I understood it correctly or not I used what I thought was the idea. I may have gotten it wrong, but if so I ended up with a interesting idea as a result of listening to the explanation.
I used the flat braces and made then shorter so the area behind the bridge would be more open, but the braces where glued on to be flat a make that section of the top flat. Under tension I hoped it would actually pull the top between the bridge and sound hole into a negative arch.
The bridge strap was put in with a bit of arching on the solera and thinned carefully to a taper by flexing the top as I planed it. The judgement of how flexible to leave the top in the cross grain direction was just subjective flex and plane. When it felt 'right' I stopped.
I then cut the strap and layed in the flat braces and the normal fan braces, but I did them so they are pretty much flat, not pressed into an arch. Then I added the fishbone/peace sign braces in near the tail block to support that area and stiffen it.
I saw a 'line' between the outer fan brace and the where the normal cut off bars would go and I figured I could get away with indirectly bracing that area by the stiffness of the rim and the fish bone brace.
What I was intending to do is keep cross grain stiffness under the bridge, keep the areas of below the waist stiff and move the most cross grain flexibility of the top to the area behind the bridge, lower into the lower bout and in the center behind the bridge. The reasoning was the top pulls the bridge up under tension and drives the front of the bridge down while lifting the back of the bridge. The old guitars which beak down under that stress show the lower area of the bout behind the bridge in full arch, while the front of the bridge is flat and slightly concave. Basically I just built that structure into the guitar in such a way that it won't collapse. I've always had good luck making that area behind the bridge a bit more loose, so this time I accentuated the looseness while keeping the other areas cross grain stiffness tight.
So I'm curious if anyone has ever experimented with these ideas? Mind you I did not make this a radical departure from the a normal five fan flamenco guitar, but just made it easier for the guitar to settle into this structure. I'm going to try it again just to see if it was a fluke of luck, or if there is something to it.
In addition to that the Black Acacia bridge has fairly thin wings and it was glued on flat by pressing it into the top with braces from the outside. After the braces came off the top was slightly deformed flat, but sprung back overnight. Under tension the top pulled up a 1/32" and it gained about that much neck relief. The top is not super thin it is quite varied in thickness due to the differences in stiffness of each of the two panels.
|
|
|
|
