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| X brace positioning http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=43978 |
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| Author: | Beth Mayer [ Tue Aug 12, 2014 4:17 pm ] |
| Post subject: | X brace positioning |
I've been tooling right along on my newest guitar, which is a cutaway version of a slope shouldered dreadnaught. Plans I'm using are the Gibson J45 plans. The plans call for 24.75" scale length, but on this one, I wanted to use 25.34", and that's what the fretboard is. I located the new bridge position and everything else is done. Made and glued the x brace today and realized as I was making the bridge patch that I glued it according to the plans (for the 24.75"). I'm guessing this will not allow for a suitable amount of overlap of the bridge footprint with the lower legs of the x-brace. Looks like the upper corners of the bridge will just cross the legs completely. HOpe that makes sense. Can I proceed or is it too far forward for 25.34"? I don't want to remove the brace, so if this is too forward-braced to support the bridge and top properly, I will change the scale length back to 24.75 and use a different FB. Thanks! Beth |
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| Author: | timoM [ Tue Aug 12, 2014 4:42 pm ] |
| Post subject: | Re: X brace positioning |
Draw the 25.34 scale on your plan and see what you get. May have to lower your bridge patch or possibly make wider/ longer bridge. In the future it's a good idea if working from an existing plan to redraw the changes in red. Don't ask how I know this! 
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| Author: | Ben-Had [ Tue Aug 12, 2014 4:43 pm ] |
| Post subject: | Re: X brace positioning |
There is about a 0.30" difference in the 2 locations. Depending on where you placed that bridge plate you could be OK. You should be able measure that out by using the distance from the 14th fret to the saddle location to check. |
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| Author: | Beth Mayer [ Tue Aug 12, 2014 5:06 pm ] |
| Post subject: | Re: X brace positioning |
So I haven't placed the bridge patch yet. I was making it based on the 25.34" placement of the saddle, and realized it was larger than usual. That's when I realized what I had done. The upper corners of the bridge will be on top of the legs of the X, but the corners will not go past the legs, as they do in the plans. The bridge plate will be placed properly for the 25.34" scale length. So I''m wondering if this X is too far forward to be structurally and tonally acceptable. |
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| Author: | DennisK [ Tue Aug 12, 2014 5:11 pm ] |
| Post subject: | Re: X brace positioning |
I'd go with the shorter scale, or a wider bridge. |
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| Author: | meddlingfool [ Tue Aug 12, 2014 6:37 pm ] |
| Post subject: | Re: X brace positioning |
How much overhangdid you leave when cutting out the top? Can you push the top back physically on the rims to account for your .030? Or at least most of it? I've done stuff like that lots of times without issue. Just watch that the FB is long enough to hit the soundhole... |
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| Author: | Clay S. [ Tue Aug 12, 2014 7:35 pm ] |
| Post subject: | Re: X brace positioning |
" Looks like the upper corners of the bridge will just cross the legs completely. HOpe that makes sense. " That is the way I usually build them. If you want more coverage make your bridge slightly longer, as Tim mentioned. You may need to move the bridge patch down to make sure the pin holes land on it. |
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| Author: | Beth Mayer [ Tue Aug 12, 2014 8:07 pm ] |
| Post subject: | Re: X brace positioning |
Dennis, I'm glad to hear that you think either option would be okay. I'd rather not start a new fretboard so I think I will just make the bridge a tad longer. Hopefully it won't look weird or unexpected. Meddling, I do have a little leeway, but the soundhole being enough lower to compensate for this mistake might be more noticeable than the slightly longer bridge. Great idea though! Clay, the bridge patch will be right where it should be for the longer scale length. Thanks everyone! |
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| Author: | DennisK [ Tue Aug 12, 2014 8:51 pm ] |
| Post subject: | Re: X brace positioning |
Beth Mayer wrote: Dennis, I'm glad to hear that you think either option would be okay. I'd rather not start a new fretboard so I think I will just make the bridge a tad longer. Hopefully it won't look weird or unexpected. It might, if you're going for authentic Gibson styling on everything else. I was thinking more than a tad... like 1/2 to 1" longer, going for more Somogyi style. Notching the bridge plate under the X would be another good way to make the structural link, but I suppose it's too late for that now  Quote: Meddling, I do have a little leeway, but the soundhole being enough lower to compensate for this mistake might be more noticeable than the slightly longer bridge. Great idea though! Could do half of each. Move the soundhole 1/8" south, and make the bridge 1/4 to 1/2" longer. That's usually the best way to deal with positional mistakes... make as many different small nudges as you can. Another one would be to lengthen the neck a touch, moving the joining fret just a bit outside the body outline, and the bridge up with it. |
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| Author: | uvh sam [ Tue Aug 12, 2014 10:24 pm ] |
| Post subject: | Re: X brace positioning |
Why not just take the braces off and start over? It's super easy to do, I do it any time I have a brace issue whatsoever. A top and the intended design of the instrument do not have to be compromised for this minor oversight. I use my ground fret cutters to chomp off most of the brace, then finish with a chisel and scraper. Revalue the new braces and bobs your uncle |
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| Author: | meddlingfool [ Tue Aug 12, 2014 10:43 pm ] |
| Post subject: | Re: X brace positioning |
Believe me, no one will notice a shift in the soundhole. It's arbitrary anyway, based off of slicing the FB at the 21st fret and covering the rosette gap, or whatever model it would be. Look at a l-OO, a nick Lucas, an AJ, and a j45. Soundhole small over the place and they all look right. .030 will go unnoticed IMO.. |
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| Author: | Ruby50 [ Wed Aug 13, 2014 4:06 am ] |
| Post subject: | Re: X brace positioning |
You wouldn't be the first - here is a beautiful Banner Gibson that never got played because the top bowed so badly. It is very easy to remove the bridge plate at this stage. Ed Minch |
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| Author: | Beth Mayer [ Wed Aug 13, 2014 9:51 am ] |
| Post subject: | Re: X brace positioning |
Jeez, Ed...that's one pitiful bridge plate! Mine will be positioned correctly and the bridge pins will go through about the middle of the plate. These are all really good points. Sam, I believe I can use what I have without re-bracing, and still have a sound guitar. Dennis and Meddling, I like the idea of doing a little of both of those tweaks to be sure everything's in place, and that nothing looks too unexpected. Thanks, guys! |
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| Author: | Beth Mayer [ Wed Aug 13, 2014 2:05 pm ] |
| Post subject: | Re: X brace positioning |
So, I got the bridge off today, and there were a few things that contributed to the failure. First, the finished area was significantly far under the lower left corner, where the lifting began. Next, that same corner of the mating surface on the bridge was not precisely level with the rest of the glue surface, thus compounding the problem in that corner. As mentioned in my OP I had not rabbeted the bridge edges. Finally, the glue on both surfaces seemed to be a little thicker in one central spot, leading me to believe that there was a gap at that location. I have scribed the finish all the way to the bridge edges and scraped it and the glue residue from both surfaces. I re-radiused the bridge on the 30' sanding board I made for this purpose, but from now on will perfect the fit using the top itself as the sanding surface. Because the owner has not been humidifying the guitar, I am going to let it humidify in my shop for a week before re-gluing the bridge. I'll do the final sanding of the mating surfaces just before the gluing. It has been a great learning experience, from removing the piezo and bridge, to trouble shooting. Thanks for all the advice! I hope this will be my one and only bridge lift! |
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| Author: | Clay S. [ Thu Aug 14, 2014 7:16 am ] |
| Post subject: | Re: X brace positioning |
Greg B. wrote in another discussion: "The way I see it: the X arms crossing the upper corners of the bridge and exiting the sides is forward shifted, X arms exiting across the lower corners of the bridge is standard, and X arms crossing the back of the bridge is rear shifted." From your description, Beth, forward shifted bracing is what you have, which is what some of us prefer. |
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| Author: | Darryl Young [ Mon Aug 18, 2014 4:43 pm ] |
| Post subject: | Re: X brace positioning |
On the Martin Norman Blake edition (a 000 body), only the front corners of the bridge are over the X-brace legs. So with tha tin mind, you will likely be ok. |
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| Author: | bobgramann [ Mon Aug 18, 2014 9:18 pm ] |
| Post subject: | Re: X brace positioning |
I have made many dozens of guitars where the X crosses the very top corners of the bridge and touch it nowhere else. They have all worked just fine. |
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| Author: | Beth Mayer [ Sat Aug 23, 2014 5:07 pm ] |
| Post subject: | Re: X brace positioning |
Beth Mayer wrote: So, I got the bridge off today, and there were a few things that contributed to the failure. First, the finished area was significantly far under the lower left corner, where the lifting began. Next, that same corner of the mating surface on the bridge was not precisely level with the rest of the glue surface, thus compounding the problem in that corner. As mentioned in my OP I had not rabbeted the bridge edges. Finally, the glue on both surfaces seemed to be a little thicker in one central spot, leading me to believe that there was a gap at that location. I have scribed the finish all the way to the bridge edges and scraped it and the glue residue from both surfaces. I re-radiused the bridge on the 30' sanding board I made for this purpose, but from now on will perfect the fit using the top itself as the sanding surface. Because the owner has not been humidifying the guitar, I am going to let it humidify in my shop for a week before re-gluing the bridge. I'll do the final sanding of the mating surfaces just before the gluing. It has been a great learning experience, from removing the piezo and bridge, to trouble shooting. Thanks for all the advice! I hope this will be my one and only bridge lift! Oops! This was meant for another thread I had going about a bridge lifting failure. Sorry about any confusion! |
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