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| Adding brace to top of closed guitar http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=43717 |
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| Author: | MaxBishop [ Wed Jun 25, 2014 6:03 pm ] |
| Post subject: | Adding brace to top of closed guitar |
Hi all, Does anyone have a clever trick for gluing braces to the top of a closed up guitar? I'd like to add stiffness to a few key areas of the top of my latest guitar. The guitar has fan bracing and the points are at the outside edge below the bridge. I've tried reaching in through the soundhole with my hand and I just can't make the reach. I also can't see what I'm doing because my arm's in the way. Any ideas? Thanks, Max |
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| Author: | DennisK [ Wed Jun 25, 2014 6:21 pm ] |
| Post subject: | Re: Adding brace to top of closed guitar |
MaxBishop wrote: I've tried reaching in through the soundhole with my hand and I just can't make the reach. How about gluing the brace to a cam clamp, oriented so when you put it through the soundhole, you can use the outer jaw as a visual reference to position it? |
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| Author: | Michael [ Wed Jun 25, 2014 7:32 pm ] |
| Post subject: | Re: Adding brace to top of closed guitar |
Very smart!! Michael |
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| Author: | Ben-Had [ Wed Jun 25, 2014 7:42 pm ] |
| Post subject: | Re: Adding brace to top of closed guitar |
I locate the brace position with magnets, then position it with a magnet caul (you can see that caul on the bridge under the center clamp. Then I use the internal clamps to clamp it in place. I also use outside cauls not shown in the pics, these were just pics of my mock up clamping to be sure everything was going into place so there was little pressure used. |
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| Author: | MaxBishop [ Thu Jun 26, 2014 6:24 am ] |
| Post subject: | Re: Adding brace to top of closed guitar |
Thanks for the tips, guys. Dennis, the distance from the edge of the soundhole to the brace location is about 10" so my cam clamps are too short. Tim, I'm a bit confused about function of the magnet caul on the bridge in your clamping set up. Could you say a bit more about it? More clarification: my braces are a bit like finger braces on a steel string. They're about 1.5" long, gabled and scolloped. Any other tips? Thanks, Max |
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| Author: | Ben-Had [ Thu Jun 26, 2014 9:02 am ] |
| Post subject: | Re: Adding brace to top of closed guitar |
MaxBishop wrote: Thanks for the tips, guys. Dennis, the distance from the edge of the soundhole to the brace location is about 10" so my cam clamps are too short. Tim, I'm a bit confused about function of the magnet caul on the bridge in your clamping set up. Could you say a bit more about it? More clarification: my braces are a bit like finger braces on a steel string. They're about 1.5" long, gabled and scolloped. Any other tips? Thanks, Max I'm a bit confused about function of the magnet caul on the bridge in your clamping set up. - I first use that caul to position the brace "inside" the body, the magnets are used on the caul to hold it in place, the other magnets position the edge of the brace. Once it is clamped in place, I take the caul out and in this case just used it to help clamp to the top. I usually have to custom make the caul to fit the brace and I use rare earth magnets (very strong), sometimes need more than one or two. |
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| Author: | jfmckenna [ Thu Jun 26, 2014 10:16 am ] |
| Post subject: | Re: Adding brace to top of closed guitar |
+1 on the use of magnets to position. You can also get very small and good quality cameras these days. Just set up a lap top on your work bench and you can watch what you are doing inside. |
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| Author: | RusRob [ Thu Jun 26, 2014 11:07 am ] |
| Post subject: | Re: Adding brace to top of closed guitar |
Max, If I understand your problem it is that you can not reach far enough in to even place the brace let alone clamp it? I have run into this situation a few times when repairing loose braces and it can be a problem even trying to get a caul or a brace jack in place. I have a variety of tools that I have made. One is a piece of heavy stainless steel rod with a bulldog clip attached to the end so I can clamp different tools such as a chisel point X-acto blade for scraping or brushes for applying glue. The bulldog clip is pretty strong so I can hold a brace firmly enough to position it with glue on the brace and then use blocks to hold the whole rod and brace while the glue sets. In your case if you can not get clamps or cauls down far enough you can use Hot Hide Glue with no clamps as long as you have a perfect fit between your soundboard and the brace. One way I have done this is to use stick-it sandpaper on the outside where your brace will go. Then take another piece of brace material and sand the radius of the top of the guitar to that piece. When it fits perfectly then put your stick-it paper on the bottom of that piece and sand the shape into your brace. Now you have a brace with the exact shape you need. By using HHG you can glue the brace in without clamping as long as you can hold it in position for a few minutes without moving it. The HHG is actually self clamping as it dries so it will literally pull the pieces together providing you have a perfect fit and you don't move it when you set it in place. In the past I have cut 1/2" plywood into different shapes to use as tools to position and hold braces in place. You can cut them in a way that they make a fulcrum off of one of the back braces to hold it in the position you need. I also have a couple of 3" X 5" mirrors taped together so I can fold them together and slip them in through the sound hole and then unfold them in side the box. This will give you a good view (although backwards) of what you are doing. A couple of those little closet LED lights work great for lighting up the inside and can be tucked out of your way. Another thing I will do when trying to hold loose braces where I can't get a clamp in is to first lay a few scraps of thin wood like 1/8" plywood inside the guitar so you bridge the horizontal braces on the back of the box. This will give you a good platform to use as the fulcrum since sometimes the braces are not quite in the right spot. The only other thing I would suggest is before you start, measure the hight of your soundboard with the strings on and then reproduce that hight with some kind of jack inside (I have a couple of small turnbuckles I epoxied wood cauls on the end). That way when you shape your braces they will be correct for the radius with strings on. It isn't an easy job, so before you glue anything do a few dry runs to be positive you know exactly what you plan is. Ideally you should clamp the brace in place but if you just can't get anything in there then HHG is the way to go since it sets up pretty fast and will draw the pieces together as it sets. Hope this helps, Bob One last thing, You may want to make a caul for the outside of the guitar so as you apply pressure to the brace you are not deforming the top which will create gaps between the brace and the top. You need a perfect fit for HHG to work without clamping. |
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| Author: | jfmckenna [ Thu Jun 26, 2014 1:42 pm ] |
| Post subject: | Re: Adding brace to top of closed guitar |
I just had a thought. You could use tuning machine clamps. One at each end would position it perfectly then you would just need one deep throat clamp for the middle. I use this technique for crack repairs. Use an 8 or 9 gauge guitar wire and it would be easy to hide the holes especially if you aim for a darker annular ring line. You could probably just push the wire through the spruce, no drilling necessary. Here is a pic to show how they are used on a crack repair. 
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