GoodWood Posted November 19, 2006 Report Share Posted November 19, 2006 Ok, Im trying 2 for 1 here. I have a 21" guitar in the making. Is there a mathmatical formula for determining the X brace center position? Also, can someone go over the basic sizes of the guitar for me? My body form is based on my Tacoma DM-9, which I then enlarged here and there to fit the tops I got. I thought it was dreadnaught size, but I keep looking at wood, and it seems dread would be larger?? Thanks Quote Link to comment Share on other sites More sharing options...
fryovanni Posted November 19, 2006 Report Share Posted November 19, 2006 If this is your first acoustic. Get a set of plans for a standard model or a good book with a set of plans. After you have a couple acoustics under your belt and fair understanding of the process. Then tackle your own design. You don't want to wing it on an acoustic. There is no absolute formula for the placement of your bracing, but it's location will relate to your bridge location. "Also, can someone go over the basic sizes of the guitar for me? My body form is based on my Tacoma DM-9, which I then enlarged here and there to fit the tops I got. I thought it was dreadnaught size, but I keep looking at wood, and it seems dread would be larger?? " I have no idea what you are asking, but I recomend you find a set of plans to build to. Peace,Rich Quote Link to comment Share on other sites More sharing options...
Joe-Of-Fortyseconds Posted November 19, 2006 Report Share Posted November 19, 2006 You have to make sure that either side of the bridge lie on the X brace, so the centre of the X will be slightly higher than the bridge, if you get me. Definaltey get a mplan, but you dont want the bridge to be off the X brace or else the string tension will ruin the guitar by pushing the soundhole area down. Joe Quote Link to comment Share on other sites More sharing options...
jammy Posted November 19, 2006 Report Share Posted November 19, 2006 You have to make sure that either side of the bridge lie on the X brace, so the centre of the X will be slightly higher than the bridge, if you get me. Definaltey get a mplan, but you dont want the bridge to be off the X brace or else the string tension will ruin the guitar by pushing the soundhole area down. Joe Indeed, compensation can be made though... Shifting the X brace toward the tail block tightens up/reduces the size of the main active area of the sound board so if your bridge position is quite a way back, you may need to find another way to support it without shifting the X a long way. A large/thick bridge plate can help as it transfers the forces on the bridge to the x braces even if very little of the bridge is actually over them... Quote Link to comment Share on other sites More sharing options...
fryovanni Posted November 19, 2006 Report Share Posted November 19, 2006 You have to make sure that either side of the bridge lie on the X brace, so the centre of the X will be slightly higher than the bridge, if you get me. Definaltey get a mplan, but you dont want the bridge to be off the X brace or else the string tension will ruin the guitar by pushing the soundhole area down. Joe Indeed, compensation can be made though... Shifting the X brace toward the tail block tightens up/reduces the size of the main active area of the sound board so if your bridge position is quite a way back, you may need to find another way to support it without shifting the X a long way. A large/thick bridge plate can help as it transfers the forces on the bridge to the x braces even if very little of the bridge is actually over them... Interesting, I had thought about how you were dealing with your Baratone's bridge position. Did you leave the X-brace close to a traditional location, and span the braces with a heavy backing block? Also did your bridge actually span the brace arms or does it set between the braces? You seemed to be happy with the results. Backing plate and the bridge are bracing. Actually the heaviest bracing on the soundboard. As a general rule of thumb you would want to keep the bridge weight down as much as possible. Weight reductiion without sacrificing strength is the goal on a soundboard. Typically bridge weight is in the 35 to 25 gram range. Leaning to the heavy side of that range may afford a bit more control for heavy play. Lighter is going to allow the board to be more responcive and dynamic. The soundboard thickness, bracing, and bridge weight all have to be adjusted to work well as a unit. Light bracing, thin soundboard and heavy bridge is going to be bad. Taking note of weights to help achive the right balance of stiffness, weight and brace shape is really important(if you use similar materials and design style). This is how you develop a high efficiency soundboard. If you use a traditional design you are going to have a good starting point. If you use a radical design you are going to be starting from scratch, and need to pay even more attension to the information you have from past builds. Using what your experience tells you in conjuction with your best guess based on how you believe the new system will respond will help get you in the ballpark, but it will take several attempts to refine it. Peace,Rich Quote Link to comment Share on other sites More sharing options...
jammy Posted November 19, 2006 Report Share Posted November 19, 2006 You have to make sure that either side of the bridge lie on the X brace, so the centre of the X will be slightly higher than the bridge, if you get me. Definaltey get a mplan, but you dont want the bridge to be off the X brace or else the string tension will ruin the guitar by pushing the soundhole area down. Joe Indeed, compensation can be made though... Shifting the X brace toward the tail block tightens up/reduces the size of the main active area of the sound board so if your bridge position is quite a way back, you may need to find another way to support it without shifting the X a long way. A large/thick bridge plate can help as it transfers the forces on the bridge to the x braces even if very little of the bridge is actually over them... Interesting, I had thought about how you were dealing with your Baratone's bridge position. Did you leave the X-brace close to a traditional location, and span the braces with a heavy backing block? Also did your bridge actually span the brace arms or does it set between the braces? You seemed to be happy with the results. There was a number of things I did to try and stop my baritone folding in half/sounding rubbish For a start, to get the brigde closer to normal position I used a 15 fret neck joint, shifting it up a cm or so. Next, the X was shifted slightly (about a cm) and finally the bigger, thicker bridge plate helped to transfer the stresses to the X. The bridge's wings just intersect with the X, but it's only the corners. I relyed on the bridge plate doing most of the work. It's interesting what you mention about the bridge and it's plate. The baritone sounds great to me, and I'm really happy with it, but it is a little quiet - something to do with the extra weight around the bridge area I wonder? Quote Link to comment Share on other sites More sharing options...
fryovanni Posted November 19, 2006 Report Share Posted November 19, 2006 It's interesting what you mention about the bridge and it's plate. The baritone sounds great to me, and I'm really happy with it, but it is a little quiet - something to do with the extra weight around the bridge area I wonder? Oh that is hard to say. It is about all the factors coming into play. A taller bridge would increase volume, but would stress the top more. Did you have to keep the bridge height down to help accomodate the bridge position? What radius did you use on the top? Flat is more efficient, but with larger soundboards the radius improves strength. Really all these factors and more play into the equation. I guess it just brings my point to Goodwood home. Even when you have some experience a custom design is a hard thing to develop. It would be easier if you could swap soundboards like pickups . Peace,Rich Quote Link to comment Share on other sites More sharing options...
Mattia Posted November 19, 2006 Report Share Posted November 19, 2006 X-brace rules of thumb: 95 to 105 degrees is about 'normal', although I've seen plenty of guitars with far tighter and slightly wider angles that work. I think a slightly tighter angle loosens up the cross-wise stiffness, but increases the lengthwise. What that does for sound...dunno. In my way of thinking, a forward shifted X (towards the neck) with a wider angle will 'open' the lower bout up more, make it a touch bassier, less focussed/tight. I think. And make sure you have the wings of your bridge overlap the lower legs of the X-brace. Other than that...go for it. Quote Link to comment Share on other sites More sharing options...
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