That's way I fine tune my fit except I don't have the fancy countertop, only plywood
I tape an appropriate height spacer at the saddle location. It helps get everything tuned up nice and level.
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| 1st Potential Fatal Flaw... http://www-.luthiersforum.com/forum/viewtopic.php?f=10101&t=45810 |
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| Author: | sdsollod [ Sun May 31, 2015 11:19 am ] |
| Post subject: | 1st Potential Fatal Flaw... |
I may have made my first potentially fatal flaw (after 10 successful builds). I failed to sand the rim of the upper bout of the top to accommodate the appropriate geometry for the neck. I have always done this but forgot this time. I noticed that Robbie O'Brien doesn't appear to do this step in his online course... I've been puzzled by that. I don't want the 14 fret hump (...in this case 12fret). If I continue the build without fixing this will I have a hump where the fingerboard meets the body? I would really hate to remove the top... Any recommendations would be welcome. |
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| Author: | johnparchem [ Sun May 31, 2015 11:46 am ] |
| Post subject: | Re: 1st Potential Fatal Flaw... |
Have you put a straight edge on the top to see where you are at the saddle? Hard to evaluate your question without knowing that gap. There are options without removing the top. |
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| Author: | meddlingfool [ Sun May 31, 2015 12:24 pm ] |
| Post subject: | Re: 1st Potential Fatal Flaw... |
Geometry is complex. I plunk a 28' radius top onto flat rims and get it right every time with no upper bout modifications. Point being, mock up your neck and see where you're at. Tape the bridge in place. Pinch clamp the fingerboard to your neck blank. Run a straightedge down the FB to the bridge. Adjust your back and forth angle (forget side to side presently). When the straightedge kisses the top of the bridge (or a hair under as I like to do in order to leave a smidge for flossing after paint) check you fall away. And if this one time it drops more than you like, so what? It's a 000, good for 14 frets at best. If it goes up, that might be a different story. But then I'd concentrate on grinding some fall away into the FB and forget about the upper bout. IMO, proceed... |
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| Author: | DennisK [ Sun May 31, 2015 1:08 pm ] |
| Post subject: | Re: 1st Potential Fatal Flaw... |
How much do you normally sand away? If it's not too much (like 1/16" or less), I think you could create the same geometry by reducing the fingerboard thickness by that amount, and adding a thin tapered wedge underneath the fingerboard extension. And of course with a thinner fingerboard, you'll want to make the neck itself a little thicker to get the total neck thickness back up to normal. Alternatively, you could use a thicker fingerboard, and less neck angle. As Ed says, geometry is complex. But as long as the fret plane projects to a bit higher than the bridge, you're good to go. |
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| Author: | Colin North [ Sun May 31, 2015 1:43 pm ] |
| Post subject: | Re: 1st Potential Fatal Flaw... |
If your top radius is 25/28' you can flatten the top from the soundhole to the neck area by drilling a small hole in the middle of the bridge area and using a sanding board with a 1/8" spacer pinned with a small dowel/pin dowel though that hole. 1/8" + (FB+fret height) thickness at 1/4" (total) lines up your top bout/neck to give a FB/frets projection of 3/8" above the soundboard at the bridge, which should be just about right for 1/2" string height off the soundboard. This lines up the top of the neck and upper bout, allowing an even thickness of FB. In my case (14th fret neck/body joint) plenty top thickness was still left in the upper bout. For a 12 fret join, you would take off slightly more, so check for your top thickness, and if you want some fall-off after the neck/body join you can do that by milling it into the upper frets. That's the way I did it before starting to use a 60' radius UTB. |
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| Author: | sdsollod [ Sun May 31, 2015 1:51 pm ] |
| Post subject: | Re: 1st Potential Fatal Flaw... |
John, The brake angle with a straight edge is after the bridge location. Essentially, there is no space at the bridge location. Ed - I absolutely hate the "hump". That's why I typically sand the top's upper bout up to the sound hole with the lower bout elevated with a 1/8" shim. That will result in the proper gap at the saddle. Dennis - I had thought of placing a wedge under the fretboard extension, but it seems like that might be an obvious fix... |
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| Author: | sdsollod [ Sun May 31, 2015 2:26 pm ] |
| Post subject: | Re: 1st Potential Fatal Flaw... |
Okay. I think I fixed it. I sanded the fretboard location with a piece of granite counter top with the rear elevated by 3 mm and achieved a 3mm gap. Yes I thinned the top but it's reinforced by the upper transverse brace and neck block. I can live with that... |
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| Author: | kencierp [ Sun May 31, 2015 2:41 pm ] |
| Post subject: | Re: 1st Potential Fatal Flaw... |
I am with you on the hump -- ugly!!! Just an opinion. Your solution is great, I was looking for a tool/jig that one of the prominent makers had posted on their website much fancier (had a center bearing etc.) than the counter top sanding block but did exactly the same thing -- way to go. |
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| Author: | Rod True [ Sun May 31, 2015 3:39 pm ] |
| Post subject: | Re: 1st Potential Fatal Flaw... |
Good job Steve. You did exactly what I was going to suggest. |
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| Author: | sdsollod [ Sun May 31, 2015 7:46 pm ] |
| Post subject: | Re: 1st Potential Fatal Flaw... |
I didn't mean to be so dramatic... Sometimes you get a holy sh** moment and then you figure out some way to do a fix. As much as I think I know the sequence of events, I probably should post the basic steps somewhere in my shop, just so I don't forget something... Thanks for all of the responses. |
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| Author: | Robbie_McD [ Sun May 31, 2015 8:01 pm ] |
| Post subject: | Re: 1st Potential Fatal Flaw... |
Nice save! |
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| Author: | johnparchem [ Mon Jun 01, 2015 7:44 am ] |
| Post subject: | Re: 1st Potential Fatal Flaw... |
I like your way of fixing it, I may incorporate it into my standard process to fine tune the angle. I would put the neck on first and sand until I had contact at both the shim and the neck joint. |
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| Author: | SteveSmith [ Mon Jun 01, 2015 9:44 am ] |
| Post subject: | Re: 1st Potential Fatal Flaw... |
That's way I fine tune my fit except I don't have the fancy countertop, only plywood I tape an appropriate height spacer at the saddle location. It helps get everything tuned up nice and level.
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| Author: | sdsollod [ Mon Jun 01, 2015 6:57 pm ] |
| Post subject: | Re: 1st Potential Fatal Flaw... |
Steve - I got the scrap piece of counter top at Habitat for Humanity for a few bucks. It is (and stays) very flat. I find many uses for it. Normaly, I sand the upper bout (top) with sand paper stuck to the back of one of my radius dishes (flat) with an 1/8" shim at the end block BEFORE GLUING ON THE TOP. I sand until chalk comes off lateral to where the sound hole begins. This is after the rim is trued first of course. I learned this from a guy that spent time with Frank Finnoccio (I also have Franks DVDs). This will give you the necessary gap at the bridge location. This discussion is for thoses that aren't familiar with the technique. |
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| Author: | Don Williams [ Mon Jun 01, 2015 8:34 pm ] |
| Post subject: | Re: 1st Potential Fatal Flaw... |
Great save! |
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| Author: | SteveSmith [ Mon Jun 01, 2015 9:33 pm ] |
| Post subject: | Re: 1st Potential Fatal Flaw... |
sdsollod wrote: Steve - I got the scrap piece of counter top at Habitat for Humanity for a few bucks. It is (and stays) very flat. I find many uses for it. Normaly, I sand the upper bout (top) with sand paper stuck to the back of one of my radius dishes (flat) with an 1/8" shim at the end block BEFORE GLUING ON THE TOP. I sand until chalk comes off lateral to where the sound hole begins. This is after the rim is trued first of course. I learned this from a guy that spent time with Frank Finnoccio (I also have Franks DVDs). This will give you the necessary gap at the bridge location. This discussion is for thoses that aren't familiar with the technique. Hadn't thought of that - I'll have to stop by the local Habitat store and scope it out every once in a while. |
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| Author: | phavriluk [ Fri Jun 05, 2015 10:36 pm ] |
| Post subject: | Re: 1st Potential Fatal Flaw... |
I think any vendor of stone countertops will have literally tons of scrap pieces up until they all jump into the dumpster. Stuff gets trimmed to length/width all the time, and sink cutouts get made all the time. |
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| Author: | Mike OMelia [ Sun Jun 14, 2015 10:30 am ] |
| Post subject: | Re: 1st Potential Fatal Flaw... |
Just so I understand, how do you avoid putting a gouge in the edge of the guitar at the neck joint? |
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| Author: | Mike OMelia [ Sun Jun 14, 2015 9:46 pm ] |
| Post subject: | Re: 1st Potential Fatal Flaw... |
Well, I bought s marble threshold I will cut to size. Very nice and flat. I get the concept, just guessing I need to control sanding to not reach neck joint. |
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