Over the weekend, I managed to bang out the compound radius dish that I mentioned in my last post. I figure I'd share the fruits of my labor, with ya in the form of a few pics. Originally I had planned to put up more, but the pics I had taken, didn't seem all that great. Plus I am a little lazy right now and its a bit late. For that reason, I'll keep it simple for now and when I have the gumption to add more elaborate images. I'll do so.
So Finally I get to put to use the go bar deck I made (aside from being a table stand for my scroll saw). The construction of this dish is pretty straight forward. Its an oppostie form of what the sound board and back shapes are. That in consideration, instead of convex braces, concave radius braces that share the same radius as the braces that will be used in the guitar are used to form the shape of the dish. I used standard 23/32" sanded plywood as the brace material, and two 1/8" hardboard(masonite)cutouts to form the dish. I used my 3d skills to figure out a more accurate sloping transition from brace to brace using mesurments that I had made off the plans. So instead of using the standard 7' and 12' radiused braces as what was called for in the Selmer book, I figured out my radiuses by find a radius where points at the edge of the sound board where brace ends are located and a center point of the brace all reside on the radiuses circle. May sound confusing, and maybe I am a little exhausted to coherently explain it properly, but in math if your given 3 points in space, you can typically find a circle that will fit them, giing you your radius. Once I had those all figured out, I printed out cut-out guides and placed them on the plywood using contact cement. I also created a brace that runs down the center of the the dish, which also helps form the "pliage" of the soundboard. All the other braces would cross this brace to give the deck its compound curves. This is where the go-bars came into play. I used them to conform the hardboard to the curves of the braces. In the picture shown, is the final step of the gluing process where I am adding the second cutout of hardboard to reinforce the board that was glued to the braces. Also notice I came up with a nifty trick of using some of the left over plywood stock and created some cantilever style go bar that are pressing in the radiused cauls near the apex of the pliage. Its actually a pretty nifty clamping system and i might actually make some proper cantilever bars for other clamping jobs.
So here is the end result, its kinda hard to see the actual radius of the dish from this pic, so I'll take a few with a ruler so that you can see the arch that is created and how that arch changes over the length of the body of the guitar. Also I have my centerline and pliage line marked out on the face of the dish, so that when I go to use the dish for shaping braces or what not, I have a good idea where everything is placed withing the contours of the dish using the templates I made a while ago. I also made sure there was a bit of a lip on the dish so that there is a ledge for the guitar mould to rest on when doing jobs that require both.
Lastly here is a pic of the backside of the dish, here you can see what I mean't as far as the cross bracing to create the complex radius of this dish. If you notice the spacing of the cross braces, they aren't even. What I did was placed each brace where each brace on the sound board would be placed. that way I have extra support in that area when it comes time to glue the braces to the soundboard. I thought about adding additional braces to cover the back braces when I was designing this dish on the computer, but figured it would be overkill and with the braces that it already has should supply ample support. Anyhow thats it for now, gotta get me some sleep!
So Finally I get to put to use the go bar deck I made (aside from being a table stand for my scroll saw). The construction of this dish is pretty straight forward. Its an oppostie form of what the sound board and back shapes are. That in consideration, instead of convex braces, concave radius braces that share the same radius as the braces that will be used in the guitar are used to form the shape of the dish. I used standard 23/32" sanded plywood as the brace material, and two 1/8" hardboard(masonite)cutouts to form the dish. I used my 3d skills to figure out a more accurate sloping transition from brace to brace using mesurments that I had made off the plans. So instead of using the standard 7' and 12' radiused braces as what was called for in the Selmer book, I figured out my radiuses by find a radius where points at the edge of the sound board where brace ends are located and a center point of the brace all reside on the radiuses circle. May sound confusing, and maybe I am a little exhausted to coherently explain it properly, but in math if your given 3 points in space, you can typically find a circle that will fit them, giing you your radius. Once I had those all figured out, I printed out cut-out guides and placed them on the plywood using contact cement. I also created a brace that runs down the center of the the dish, which also helps form the "pliage" of the soundboard. All the other braces would cross this brace to give the deck its compound curves. This is where the go-bars came into play. I used them to conform the hardboard to the curves of the braces. In the picture shown, is the final step of the gluing process where I am adding the second cutout of hardboard to reinforce the board that was glued to the braces. Also notice I came up with a nifty trick of using some of the left over plywood stock and created some cantilever style go bar that are pressing in the radiused cauls near the apex of the pliage. Its actually a pretty nifty clamping system and i might actually make some proper cantilever bars for other clamping jobs. 
So here is the end result, its kinda hard to see the actual radius of the dish from this pic, so I'll take a few with a ruler so that you can see the arch that is created and how that arch changes over the length of the body of the guitar. Also I have my centerline and pliage line marked out on the face of the dish, so that when I go to use the dish for shaping braces or what not, I have a good idea where everything is placed withing the contours of the dish using the templates I made a while ago. I also made sure there was a bit of a lip on the dish so that there is a ledge for the guitar mould to rest on when doing jobs that require both. 
Lastly here is a pic of the backside of the dish, here you can see what I mean't as far as the cross bracing to create the complex radius of this dish. If you notice the spacing of the cross braces, they aren't even. What I did was placed each brace where each brace on the sound board would be placed. that way I have extra support in that area when it comes time to glue the braces to the soundboard. I thought about adding additional braces to cover the back braces when I was designing this dish on the computer, but figured it would be overkill and with the braces that it already has should supply ample support. Anyhow thats it for now, gotta get me some sleep!
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